diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/append.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/append.rs
index 3774751ffb..ac079d43a4 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/append.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/append.rs
@@ -23,8 +23,10 @@ impl Command for AppendDF {
         Signature::build(self.name())
             .required("other", SyntaxShape::Any, "dataframe to be appended")
             .switch("col", "appends in col orientation", Some('c'))
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/columns.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/columns.rs
index cdf97de7ef..0a7dccfb98 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/columns.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/columns.rs
@@ -19,8 +19,7 @@ impl Command for ColumnsDF {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Any)
+            .input_output_type(Type::Custom("dataframe".into()), Type::Any)
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/drop.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/drop.rs
index 56bbc31925..dbf36d6fe2 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/drop.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/drop.rs
@@ -23,8 +23,10 @@ impl Command for DropDF {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .rest("rest", SyntaxShape::Any, "column names to be dropped")
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/drop_duplicates.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/drop_duplicates.rs
index ac8786049f..80b1ab61de 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/drop_duplicates.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/drop_duplicates.rs
@@ -34,8 +34,10 @@ impl Command for DropDuplicates {
                 "keeps last duplicate value (by default keeps first)",
                 Some('l'),
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/drop_nulls.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/drop_nulls.rs
index 0397e358d6..071db45ca9 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/drop_nulls.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/drop_nulls.rs
@@ -27,8 +27,10 @@ impl Command for DropNulls {
                 SyntaxShape::Table,
                 "subset of columns to drop nulls",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/dtypes.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/dtypes.rs
index a38ba440cb..c7e2a8299c 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/dtypes.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/dtypes.rs
@@ -19,8 +19,10 @@ impl Command for DataTypes {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/dummies.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/dummies.rs
index a1c673a3cc..c0194ea305 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/dummies.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/dummies.rs
@@ -20,8 +20,10 @@ impl Command for Dummies {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/filter_with.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/filter_with.rs
index 733385ca52..88c40e336c 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/filter_with.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/filter_with.rs
@@ -29,8 +29,10 @@ impl Command for FilterWith {
                 SyntaxShape::Any,
                 "boolean mask used to filter data",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe or lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/first.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/first.rs
index 458ecec525..839aaa7527 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/first.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/first.rs
@@ -25,8 +25,10 @@ impl Command for FirstDF {
                 SyntaxShape::Int,
                 "starting from the front, the number of rows to return",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/get.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/get.rs
index 74174de789..e763974cb5 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/get.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/get.rs
@@ -24,8 +24,10 @@ impl Command for GetDF {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .rest("rest", SyntaxShape::Any, "column names to sort dataframe")
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/last.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/last.rs
index 0d7428a3c2..fe8a2b5e06 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/last.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/last.rs
@@ -21,8 +21,10 @@ impl Command for LastDF {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .optional("rows", SyntaxShape::Int, "Number of rows for tail")
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/melt.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/melt.rs
index 6ecff9120b..39a908fcfb 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/melt.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/melt.rs
@@ -48,8 +48,10 @@ impl Command for MeltDF {
                 "optional name for value column",
                 Some('l'),
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/open.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/open.rs
index e3aaffa375..45a906d656 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/open.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/open.rs
@@ -68,8 +68,7 @@ impl Command for OpenDataFrame {
                 "Columns to be selected from csv file. CSV and Parquet file",
                 None,
             )
-            .input_type(Type::Any)
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(Type::Any, Type::Custom("dataframe".into()))
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/query_df.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/query_df.rs
index 275f23da5e..1d76e0ae12 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/query_df.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/query_df.rs
@@ -28,8 +28,10 @@ impl Command for QueryDf {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .required("sql", SyntaxShape::String, "sql query")
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/rename.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/rename.rs
index ffe02d5c34..67cd8649f3 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/rename.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/rename.rs
@@ -33,8 +33,10 @@ impl Command for RenameDF {
                 SyntaxShape::Any,
                 "New names for the selected column(s). A string or list of strings",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe or lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/sample.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/sample.rs
index 7bd8833bf1..4730ec09ec 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/sample.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/sample.rs
@@ -41,8 +41,10 @@ impl Command for SampleDF {
             )
             .switch("replace", "sample with replace", Some('e'))
             .switch("shuffle", "shuffle sample", Some('u'))
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/shape.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/shape.rs
index a121bf4b7a..71ca997767 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/shape.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/shape.rs
@@ -22,8 +22,10 @@ impl Command for ShapeDF {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/slice.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/slice.rs
index 67b3939bf9..21be93094b 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/slice.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/slice.rs
@@ -25,8 +25,10 @@ impl Command for SliceDF {
         Signature::build(self.name())
             .required("offset", SyntaxShape::Int, "start of slice")
             .required("size", SyntaxShape::Int, "size of slice")
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/summary.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/summary.rs
index 29bb740e38..9d2e0197f9 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/summary.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/summary.rs
@@ -29,8 +29,10 @@ impl Command for Summary {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .category(Category::Custom("dataframe".into()))
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .named(
                 "quantiles",
                 SyntaxShape::Table,
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/take.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/take.rs
index 114c77fe1a..4d2a4681fa 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/take.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/take.rs
@@ -29,8 +29,10 @@ impl Command for TakeDF {
                 SyntaxShape::Any,
                 "list of indices used to take data",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/to_arrow.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/to_arrow.rs
index 7d0dc0960b..b4b4848042 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/to_arrow.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/to_arrow.rs
@@ -25,8 +25,7 @@ impl Command for ToArrow {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .required("file", SyntaxShape::Filepath, "file path to save dataframe")
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Any)
+            .input_output_type(Type::Custom("dataframe".into()), Type::Any)
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/to_csv.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/to_csv.rs
index fc08520190..26d36f119e 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/to_csv.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/to_csv.rs
@@ -32,8 +32,7 @@ impl Command for ToCSV {
                 Some('d'),
             )
             .switch("no-header", "Indicates if file doesn't have header", None)
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Any)
+            .input_output_type(Type::Custom("dataframe".into()), Type::Any)
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/to_df.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/to_df.rs
index fb452968c7..45bf5ea42b 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/to_df.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/to_df.rs
@@ -20,8 +20,7 @@ impl Command for ToDataFrame {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Any)
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(Type::Any, Type::Custom("dataframe".into()))
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/to_json_lines.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/to_json_lines.rs
index e255385102..976af7e585 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/to_json_lines.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/to_json_lines.rs
@@ -25,8 +25,7 @@ impl Command for ToJsonLines {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .required("file", SyntaxShape::Filepath, "file path to save dataframe")
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Any)
+            .input_output_type(Type::Custom("dataframe".into()), Type::Any)
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/to_nu.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/to_nu.rs
index f0db9ef7f5..40c5f92a0d 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/to_nu.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/to_nu.rs
@@ -28,8 +28,7 @@ impl Command for ToNu {
                 Some('n'),
             )
             .switch("tail", "shows tail rows", Some('t'))
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Any)
+            .input_output_type(Type::Custom("dataframe".into()), Type::Any)
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/to_parquet.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/to_parquet.rs
index 2f9bcb2133..ab2421fbd0 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/to_parquet.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/to_parquet.rs
@@ -25,8 +25,7 @@ impl Command for ToParquet {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .required("file", SyntaxShape::Filepath, "file path to save dataframe")
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Any)
+            .input_output_type(Type::Custom("dataframe".into()), Type::Any)
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/eager/with_column.rs b/crates/nu-cmd-dataframe/src/dataframe/eager/with_column.rs
index 09a7c977e0..17b195ec5f 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/eager/with_column.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/eager/with_column.rs
@@ -27,8 +27,10 @@ impl Command for WithColumn {
                 SyntaxShape::Any,
                 "series to be added or expressions used to define the new columns",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe or lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/alias.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/alias.rs
index d03fc4f0eb..c672b18343 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/alias.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/alias.rs
@@ -26,8 +26,10 @@ impl Command for ExprAlias {
                 SyntaxShape::String,
                 "Alias name for the expression",
             )
-            .input_type(Type::Custom("expression".into()))
-            .output_type(Type::Custom("expression".into()))
+            .input_output_type(
+                Type::Custom("expression".into()),
+                Type::Custom("expression".into()),
+            )
             .category(Category::Custom("expression".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/arg_where.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/arg_where.rs
index aa8cb2dbe3..f04be2511e 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/arg_where.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/arg_where.rs
@@ -22,8 +22,7 @@ impl Command for ExprArgWhere {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .required("column name", SyntaxShape::Any, "Expression to evaluate")
-            .input_type(Type::Any)
-            .output_type(Type::Custom("expression".into()))
+            .input_output_type(Type::Any, Type::Custom("expression".into()))
             .category(Category::Custom("expression".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/as_nu.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/as_nu.rs
index 322e6958a0..8cd893ae45 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/as_nu.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/as_nu.rs
@@ -20,8 +20,7 @@ impl Command for ExprAsNu {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("expression".into()))
-            .output_type(Type::Any)
+            .input_output_type(Type::Custom("expression".into()), Type::Any)
             .category(Category::Custom("expression".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/col.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/col.rs
index 76f1c30a0f..8ff5ec5a74 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/col.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/col.rs
@@ -26,8 +26,7 @@ impl Command for ExprCol {
                 SyntaxShape::String,
                 "Name of column to be used",
             )
-            .input_type(Type::Any)
-            .output_type(Type::Custom("expression".into()))
+            .input_output_type(Type::Any, Type::Custom("expression".into()))
             .category(Category::Custom("expression".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/concat_str.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/concat_str.rs
index 6a0f52c2de..789142c463 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/concat_str.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/concat_str.rs
@@ -31,8 +31,7 @@ impl Command for ExprConcatStr {
                 SyntaxShape::List(Box::new(SyntaxShape::Any)),
                 "Expression(s) that define the string concatenation",
             )
-            .input_type(Type::Any)
-            .output_type(Type::Custom("expression".into()))
+            .input_output_type(Type::Any, Type::Custom("expression".into()))
             .category(Category::Custom("expression".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/datepart.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/datepart.rs
index bdecd50913..4cc157aaec 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/datepart.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/datepart.rs
@@ -29,8 +29,10 @@ impl Command for ExprDatePart {
                 SyntaxShape::String,
                 "Part of the date to capture.  Possible values are year, quarter, month, week, weekday, day, hour, minute, second, millisecond, microsecond, nanosecond",
             )
-            .input_type(Type::Custom("expression".into()))
-            .output_type(Type::Custom("expression".into()))
+            .input_output_type(
+                Type::Custom("expression".into()),
+                Type::Custom("expression".into()),
+            )
             .category(Category::Custom("expression".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/expressions_macro.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/expressions_macro.rs
index fcb4695773..6ab69b27b3 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/expressions_macro.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/expressions_macro.rs
@@ -26,8 +26,10 @@ macro_rules! expr_command {
 
             fn signature(&self) -> Signature {
                 Signature::build(self.name())
-                    .input_type(Type::Custom("expression".into()))
-                    .output_type(Type::Custom("expression".into()))
+                    .input_output_type(
+                        Type::Custom("expression".into()),
+                        Type::Custom("expression".into()),
+                    )
                     .category(Category::Custom("expression".into()))
             }
 
@@ -85,8 +87,10 @@ macro_rules! expr_command {
 
             fn signature(&self) -> Signature {
                 Signature::build(self.name())
-                    .input_type(Type::Custom("expression".into()))
-                    .output_type(Type::Custom("expression".into()))
+                    .input_output_type(
+                        Type::Custom("expression".into()),
+                        Type::Custom("expression".into()),
+                    )
                     .category(Category::Custom("expression".into()))
             }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/is_in.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/is_in.rs
index 42d77b50a5..587dd21bad 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/is_in.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/is_in.rs
@@ -26,8 +26,10 @@ impl Command for ExprIsIn {
                 SyntaxShape::List(Box::new(SyntaxShape::Any)),
                 "List to check if values are in",
             )
-            .input_type(Type::Custom("expression".into()))
-            .output_type(Type::Custom("expression".into()))
+            .input_output_type(
+                Type::Custom("expression".into()),
+                Type::Custom("expression".into()),
+            )
             .category(Category::Custom("expression".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/lit.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/lit.rs
index a69e18cc6c..2f964e72c3 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/lit.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/lit.rs
@@ -25,8 +25,7 @@ impl Command for ExprLit {
                 SyntaxShape::Any,
                 "literal to construct the expression",
             )
-            .input_type(Type::Any)
-            .output_type(Type::Custom("expression".into()))
+            .input_output_type(Type::Any, Type::Custom("expression".into()))
             .category(Category::Custom("expression".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/otherwise.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/otherwise.rs
index 0cad793bf9..d1b4479af3 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/otherwise.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/otherwise.rs
@@ -25,8 +25,7 @@ impl Command for ExprOtherwise {
                 SyntaxShape::Any,
                 "expression to apply when no when predicate matches",
             )
-            .input_type(Type::Any)
-            .output_type(Type::Custom("expression".into()))
+            .input_output_type(Type::Any, Type::Custom("expression".into()))
             .category(Category::Custom("expression".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/quantile.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/quantile.rs
index f88bc2340b..6952c27e68 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/quantile.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/quantile.rs
@@ -26,8 +26,10 @@ impl Command for ExprQuantile {
                 SyntaxShape::Number,
                 "quantile value for quantile operation",
             )
-            .input_type(Type::Custom("expression".into()))
-            .output_type(Type::Custom("expression".into()))
+            .input_output_type(
+                Type::Custom("expression".into()),
+                Type::Custom("expression".into()),
+            )
             .category(Category::Custom("expression".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/expressions/when.rs b/crates/nu-cmd-dataframe/src/dataframe/expressions/when.rs
index b90950cf02..26f358120f 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/expressions/when.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/expressions/when.rs
@@ -31,8 +31,10 @@ impl Command for ExprWhen {
                 SyntaxShape::Any,
                 "expression that will be applied when predicate is true",
             )
-            .input_type(Type::Custom("expression".into()))
-            .output_type(Type::Custom("expression".into()))
+            .input_output_type(
+                Type::Custom("expression".into()),
+                Type::Custom("expression".into()),
+            )
             .category(Category::Custom("expression".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/aggregate.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/aggregate.rs
index 44e005df8c..2e5e913ba9 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/aggregate.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/aggregate.rs
@@ -27,8 +27,10 @@ impl Command for LazyAggregate {
                 SyntaxShape::Any,
                 "Expression(s) that define the aggregations to be applied",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("lazyframe".into()))
     }
 
@@ -121,7 +123,7 @@ impl Command for LazyAggregate {
         let group_by = NuLazyGroupBy::try_from_pipeline(input, call.head)?;
 
         if let Some(schema) = &group_by.schema {
-            for expr in &expressions {
+            for expr in expressions.iter() {
                 if let Some(name) = get_col_name(expr) {
                     let dtype = schema.get(name.as_str());
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/collect.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/collect.rs
index 208869f2cb..55b13f3047 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/collect.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/collect.rs
@@ -21,8 +21,10 @@ impl Command for LazyCollect {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/fetch.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/fetch.rs
index f1c7585470..2b9b417192 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/fetch.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/fetch.rs
@@ -26,8 +26,10 @@ impl Command for LazyFetch {
                 SyntaxShape::Int,
                 "number of rows to be fetched from lazyframe",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/fill_nan.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/fill_nan.rs
index 82eb7dfbb4..9406fe3443 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/fill_nan.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/fill_nan.rs
@@ -25,8 +25,10 @@ impl Command for LazyFillNA {
                 SyntaxShape::Any,
                 "Expression to use to fill the NAN values",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/fill_null.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/fill_null.rs
index 32fff5460d..445d5366e7 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/fill_null.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/fill_null.rs
@@ -25,8 +25,10 @@ impl Command for LazyFillNull {
                 SyntaxShape::Any,
                 "Expression to use to fill the null values",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/filter.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/filter.rs
index b150b9d8a5..5250c8beed 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/filter.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/filter.rs
@@ -26,8 +26,10 @@ impl Command for LazyFilter {
                 SyntaxShape::Any,
                 "Expression that define the column selection",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/groupby.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/groupby.rs
index 9a9337eb5c..99d4897819 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/groupby.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/groupby.rs
@@ -26,8 +26,10 @@ impl Command for ToLazyGroupBy {
                 SyntaxShape::Any,
                 "Expression(s) that define the lazy group-by",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/join.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/join.rs
index 1689009982..58f4d6be86 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/join.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/join.rs
@@ -38,8 +38,10 @@ impl Command for LazyJoin {
                 "Suffix to use on columns with same name",
                 Some('s'),
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/macro_commands.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/macro_commands.rs
index 913fd87a2e..1765861c99 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/macro_commands.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/macro_commands.rs
@@ -24,8 +24,10 @@ macro_rules! lazy_command {
 
             fn signature(&self) -> Signature {
                 Signature::build(self.name())
-                    .input_type(Type::Custom("dataframe".into()))
-                    .output_type(Type::Custom("dataframe".into()))
+                    .input_output_type(
+                        Type::Custom("dataframe".into()),
+                        Type::Custom("dataframe".into()),
+                    )
                     .category(Category::Custom("lazyframe".into()))
             }
 
@@ -74,8 +76,10 @@ macro_rules! lazy_command {
 
             fn signature(&self) -> Signature {
                 Signature::build(self.name())
-                    .input_type(Type::Custom("dataframe".into()))
-                    .output_type(Type::Custom("dataframe".into()))
+                    .input_output_type(
+                        Type::Custom("dataframe".into()),
+                        Type::Custom("dataframe".into()),
+                    )
                     .category(Category::Custom("lazyframe".into()))
             }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/quantile.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/quantile.rs
index 055f792f4c..8b42b3cec1 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/quantile.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/quantile.rs
@@ -26,8 +26,10 @@ impl Command for LazyQuantile {
                 SyntaxShape::Number,
                 "quantile value for quantile operation",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/select.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/select.rs
index 2d67cfc2e7..18c9206e3f 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/select.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/select.rs
@@ -25,8 +25,10 @@ impl Command for LazySelect {
                 SyntaxShape::Any,
                 "Expression(s) that define the column selection",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/sort_by_expr.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/sort_by_expr.rs
index 0ac9fc687b..5a3ca4e150 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/sort_by_expr.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/sort_by_expr.rs
@@ -37,8 +37,10 @@ impl Command for LazySortBy {
                 "nulls are shown last in the dataframe",
                 Some('n'),
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/lazy/to_lazy.rs b/crates/nu-cmd-dataframe/src/dataframe/lazy/to_lazy.rs
index 99aabc9f60..cfbcaf32b0 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/lazy/to_lazy.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/lazy/to_lazy.rs
@@ -20,8 +20,7 @@ impl Command for ToLazyFrame {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Any)
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(Type::Any, Type::Custom("dataframe".into()))
             .category(Category::Custom("lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/all_false.rs b/crates/nu-cmd-dataframe/src/dataframe/series/all_false.rs
index 391534245b..8f10398dc6 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/all_false.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/all_false.rs
@@ -20,8 +20,10 @@ impl Command for AllFalse {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/all_true.rs b/crates/nu-cmd-dataframe/src/dataframe/series/all_true.rs
index ac8dbf03aa..2f07567db1 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/all_true.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/all_true.rs
@@ -20,8 +20,10 @@ impl Command for AllTrue {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/arg_max.rs b/crates/nu-cmd-dataframe/src/dataframe/series/arg_max.rs
index aaec16f747..c517eb2acb 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/arg_max.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/arg_max.rs
@@ -25,8 +25,10 @@ impl Command for ArgMax {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/arg_min.rs b/crates/nu-cmd-dataframe/src/dataframe/series/arg_min.rs
index 953f7baf0e..fd7df8f5d2 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/arg_min.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/arg_min.rs
@@ -25,8 +25,10 @@ impl Command for ArgMin {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/cumulative.rs b/crates/nu-cmd-dataframe/src/dataframe/series/cumulative.rs
index 761da4eb7b..920ac8ef72 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/cumulative.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/cumulative.rs
@@ -56,8 +56,10 @@ impl Command for Cumulative {
         Signature::build(self.name())
             .required("type", SyntaxShape::String, "rolling operation")
             .switch("reverse", "Reverse cumulative calculation", Some('r'))
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/as_date.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/as_date.rs
index 83eeb5f2d9..2f24d4c4d7 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/as_date.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/as_date.rs
@@ -31,9 +31,11 @@ impl Command for AsDate {
         Signature::build(self.name())
             .required("format", SyntaxShape::String, "formatting date string")
             .switch("not-exact", "the format string may be contained in the date (e.g. foo-2021-01-01-bar could match 2021-01-01)", Some('n'))
-                        .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
-.category(Category::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
+            .category(Category::Custom("dataframe".into()))
     }
 
     fn examples(&self) -> Vec<Example> {
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/as_datetime.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/as_datetime.rs
index 49a1edd5ea..efa7df2d89 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/as_datetime.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/as_datetime.rs
@@ -40,9 +40,11 @@ impl Command for AsDateTime {
         Signature::build(self.name())
             .required("format", SyntaxShape::String, "formatting date time string")
             .switch("not-exact", "the format string may be contained in the date (e.g. foo-2021-01-01-bar could match 2021-01-01)", Some('n'))
-                        .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
-.category(Category::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
+            .category(Category::Custom("dataframe".into()))
     }
 
     fn examples(&self) -> Vec<Example> {
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_day.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_day.rs
index f7af95ec77..51ded86e08 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_day.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_day.rs
@@ -21,8 +21,10 @@ impl Command for GetDay {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_hour.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_hour.rs
index 2731f582af..548edb4267 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_hour.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_hour.rs
@@ -21,8 +21,10 @@ impl Command for GetHour {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_minute.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_minute.rs
index 86d3867d51..de5dd9d5cf 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_minute.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_minute.rs
@@ -21,8 +21,10 @@ impl Command for GetMinute {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_month.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_month.rs
index d26afb2a40..58d0cba227 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_month.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_month.rs
@@ -21,8 +21,10 @@ impl Command for GetMonth {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_nanosecond.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_nanosecond.rs
index 8a3b074284..f36e4c7af4 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_nanosecond.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_nanosecond.rs
@@ -21,8 +21,10 @@ impl Command for GetNanosecond {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_ordinal.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_ordinal.rs
index 399685c1e9..40d245121e 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_ordinal.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_ordinal.rs
@@ -21,8 +21,10 @@ impl Command for GetOrdinal {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_second.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_second.rs
index 7a77ee4ae9..74b7fa8909 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_second.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_second.rs
@@ -21,8 +21,10 @@ impl Command for GetSecond {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_week.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_week.rs
index 115a027c26..ba39d18634 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_week.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_week.rs
@@ -21,8 +21,10 @@ impl Command for GetWeek {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_weekday.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_weekday.rs
index 906c812de0..668c32c640 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_weekday.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_weekday.rs
@@ -21,8 +21,10 @@ impl Command for GetWeekDay {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_year.rs b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_year.rs
index b31e949c09..991d347c71 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/date/get_year.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/date/get_year.rs
@@ -21,8 +21,10 @@ impl Command for GetYear {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_sort.rs b/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_sort.rs
index 38e01b46d3..9ac9314a25 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_sort.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_sort.rs
@@ -27,8 +27,10 @@ impl Command for ArgSort {
         Signature::build(self.name())
             .switch("reverse", "reverse order", Some('r'))
             .switch("nulls-last", "nulls ordered last", Some('n'))
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_true.rs b/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_true.rs
index 2a067c4297..63947b96f6 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_true.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_true.rs
@@ -25,8 +25,10 @@ impl Command for ArgTrue {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_unique.rs b/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_unique.rs
index 5824c59ecf..d8ca33c34f 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_unique.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/indexes/arg_unique.rs
@@ -25,8 +25,10 @@ impl Command for ArgUnique {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/indexes/set_with_idx.rs b/crates/nu-cmd-dataframe/src/dataframe/series/indexes/set_with_idx.rs
index 0146b6c4c3..575111534e 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/indexes/set_with_idx.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/indexes/set_with_idx.rs
@@ -29,8 +29,10 @@ impl Command for SetWithIndex {
                 "list of indices indicating where to set the value",
                 Some('i'),
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_duplicated.rs b/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_duplicated.rs
index 5311e63a0b..a9d6d88656 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_duplicated.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_duplicated.rs
@@ -21,8 +21,10 @@ impl Command for IsDuplicated {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_in.rs b/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_in.rs
index 1edb98e59f..687b5e78d2 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_in.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_in.rs
@@ -23,8 +23,10 @@ impl Command for IsIn {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .required("other", SyntaxShape::Any, "right series")
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_not_null.rs b/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_not_null.rs
index d58bd13d21..652d9cccdb 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_not_null.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_not_null.rs
@@ -20,8 +20,10 @@ impl Command for IsNotNull {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_null.rs b/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_null.rs
index be2d653e88..4f3f5962ff 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_null.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_null.rs
@@ -20,8 +20,10 @@ impl Command for IsNull {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_unique.rs b/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_unique.rs
index 84ca8b737a..e903048245 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_unique.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/masks/is_unique.rs
@@ -21,8 +21,10 @@ impl Command for IsUnique {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/masks/not.rs b/crates/nu-cmd-dataframe/src/dataframe/series/masks/not.rs
index 990c7935dc..3bb627597d 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/masks/not.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/masks/not.rs
@@ -22,8 +22,10 @@ impl Command for NotSeries {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/masks/set.rs b/crates/nu-cmd-dataframe/src/dataframe/series/masks/set.rs
index 87fe242930..2d2ed72061 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/masks/set.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/masks/set.rs
@@ -29,8 +29,10 @@ impl Command for SetSeries {
                 "mask indicating insertions",
                 Some('m'),
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/n_null.rs b/crates/nu-cmd-dataframe/src/dataframe/series/n_null.rs
index bd9b2c8cd8..52f61a0a15 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/n_null.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/n_null.rs
@@ -20,8 +20,10 @@ impl Command for NNull {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/n_unique.rs b/crates/nu-cmd-dataframe/src/dataframe/series/n_unique.rs
index b80dac305a..657790c5a5 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/n_unique.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/n_unique.rs
@@ -19,8 +19,10 @@ impl Command for NUnique {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/rolling.rs b/crates/nu-cmd-dataframe/src/dataframe/series/rolling.rs
index 1f5641ccb8..9e5a568339 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/rolling.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/rolling.rs
@@ -59,8 +59,10 @@ impl Command for Rolling {
         Signature::build(self.name())
             .required("type", SyntaxShape::String, "rolling operation")
             .required("window", SyntaxShape::Int, "Window size for rolling")
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/shift.rs b/crates/nu-cmd-dataframe/src/dataframe/series/shift.rs
index e04d607f9a..caebd173a1 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/shift.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/shift.rs
@@ -30,8 +30,10 @@ impl Command for Shift {
                 "Expression used to fill the null values (lazy df)",
                 Some('f'),
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe or lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/string/concatenate.rs b/crates/nu-cmd-dataframe/src/dataframe/series/string/concatenate.rs
index 4e12f867df..1152bcad63 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/string/concatenate.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/string/concatenate.rs
@@ -27,8 +27,10 @@ impl Command for Concatenate {
                 SyntaxShape::Any,
                 "Other array with string to be concatenated",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/string/contains.rs b/crates/nu-cmd-dataframe/src/dataframe/series/string/contains.rs
index 48e30048ba..d82a7c526a 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/string/contains.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/string/contains.rs
@@ -27,8 +27,10 @@ impl Command for Contains {
                 SyntaxShape::String,
                 "Regex pattern to be searched",
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/string/replace.rs b/crates/nu-cmd-dataframe/src/dataframe/series/string/replace.rs
index 0a68761237..f0b36ddb24 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/string/replace.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/string/replace.rs
@@ -34,8 +34,10 @@ impl Command for Replace {
                 "replacing string",
                 Some('r'),
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/string/replace_all.rs b/crates/nu-cmd-dataframe/src/dataframe/series/string/replace_all.rs
index 9e1125568c..02532e4091 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/string/replace_all.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/string/replace_all.rs
@@ -34,8 +34,10 @@ impl Command for ReplaceAll {
                 "replacing string",
                 Some('r'),
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/string/str_lengths.rs b/crates/nu-cmd-dataframe/src/dataframe/series/string/str_lengths.rs
index b90c48f3bb..d33f81dc29 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/string/str_lengths.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/string/str_lengths.rs
@@ -21,8 +21,10 @@ impl Command for StrLengths {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/string/str_slice.rs b/crates/nu-cmd-dataframe/src/dataframe/series/string/str_slice.rs
index 8bfca0eed8..3c8ec85324 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/string/str_slice.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/string/str_slice.rs
@@ -24,8 +24,10 @@ impl Command for StrSlice {
         Signature::build(self.name())
             .required("start", SyntaxShape::Int, "start of slice")
             .named("length", SyntaxShape::Int, "optional length", Some('l'))
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/string/strftime.rs b/crates/nu-cmd-dataframe/src/dataframe/series/string/strftime.rs
index eeece66c5f..530770a608 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/string/strftime.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/string/strftime.rs
@@ -23,8 +23,10 @@ impl Command for StrFTime {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .required("fmt", SyntaxShape::String, "Format rule")
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/string/to_lowercase.rs b/crates/nu-cmd-dataframe/src/dataframe/series/string/to_lowercase.rs
index 26d0931c0d..954b4a3d95 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/string/to_lowercase.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/string/to_lowercase.rs
@@ -21,8 +21,10 @@ impl Command for ToLowerCase {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/string/to_uppercase.rs b/crates/nu-cmd-dataframe/src/dataframe/series/string/to_uppercase.rs
index 13c7702f84..92a2d713e2 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/string/to_uppercase.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/string/to_uppercase.rs
@@ -25,8 +25,10 @@ impl Command for ToUpperCase {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/unique.rs b/crates/nu-cmd-dataframe/src/dataframe/series/unique.rs
index b6794d9ab8..4f463ac2b0 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/unique.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/unique.rs
@@ -40,8 +40,10 @@ impl Command for Unique {
                 "Keep the same order as the original DataFrame (lazy df)",
                 Some('k'),
             )
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe or lazyframe".into()))
     }
 
diff --git a/crates/nu-cmd-dataframe/src/dataframe/series/value_counts.rs b/crates/nu-cmd-dataframe/src/dataframe/series/value_counts.rs
index 6fcbe522b8..391f5130bc 100644
--- a/crates/nu-cmd-dataframe/src/dataframe/series/value_counts.rs
+++ b/crates/nu-cmd-dataframe/src/dataframe/series/value_counts.rs
@@ -22,8 +22,10 @@ impl Command for ValueCount {
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .input_type(Type::Custom("dataframe".into()))
-            .output_type(Type::Custom("dataframe".into()))
+            .input_output_type(
+                Type::Custom("dataframe".into()),
+                Type::Custom("dataframe".into()),
+            )
             .category(Category::Custom("dataframe".into()))
     }
 
diff --git a/crates/nu-command/src/database/commands/query_db.rs b/crates/nu-command/src/database/commands/query_db.rs
index c068bc1090..a0779d33c2 100644
--- a/crates/nu-command/src/database/commands/query_db.rs
+++ b/crates/nu-command/src/database/commands/query_db.rs
@@ -24,8 +24,6 @@ impl Command for QueryDb {
                 SyntaxShape::String,
                 "SQL to execute against the database",
             )
-            .input_type(Type::Any)
-            .output_type(Type::Any)
             .category(Category::Custom("database".into()))
     }
 
diff --git a/crates/nu-command/src/database/commands/schema.rs b/crates/nu-command/src/database/commands/schema.rs
index a27c8328e4..1ce80294f8 100644
--- a/crates/nu-command/src/database/commands/schema.rs
+++ b/crates/nu-command/src/database/commands/schema.rs
@@ -17,8 +17,6 @@ impl Command for SchemaDb {
     fn signature(&self) -> Signature {
         Signature::build(self.name())
             .input_output_types(vec![(Type::Any, Type::Any)])
-            .input_type(Type::Any)
-            .output_type(Type::Any)
             .category(Category::Custom("database".into()))
     }
 
diff --git a/crates/nu-command/src/filters/lines.rs b/crates/nu-command/src/filters/lines.rs
index 61bddcab70..31fbcf2c25 100644
--- a/crates/nu-command/src/filters/lines.rs
+++ b/crates/nu-command/src/filters/lines.rs
@@ -23,7 +23,7 @@ impl Command for Lines {
 
     fn signature(&self) -> nu_protocol::Signature {
         Signature::build("lines")
-            .input_output_types(vec![(Type::String, Type::List(Box::new(Type::String)))])
+            .input_output_types(vec![(Type::Any, Type::List(Box::new(Type::String)))])
             .switch("skip-empty", "skip empty lines", Some('s'))
             .category(Category::Filters)
     }
diff --git a/crates/nu-command/src/strings/encode_decode/encode_base64.rs b/crates/nu-command/src/strings/encode_decode/encode_base64.rs
index 65e390aa58..6ba4d5b59a 100644
--- a/crates/nu-command/src/strings/encode_decode/encode_base64.rs
+++ b/crates/nu-command/src/strings/encode_decode/encode_base64.rs
@@ -31,7 +31,6 @@ impl Command for EncodeBase64 {
                 SyntaxShape::CellPath,
                 "For a data structure input, encode data at the given cell paths",
             )
-            .output_type(Type::String)
             .category(Category::Hash)
     }
 
diff --git a/crates/nu-command/src/strings/encode_decode/encode_hex.rs b/crates/nu-command/src/strings/encode_decode/encode_hex.rs
index cb9f350bc2..d4974ea83f 100644
--- a/crates/nu-command/src/strings/encode_decode/encode_hex.rs
+++ b/crates/nu-command/src/strings/encode_decode/encode_hex.rs
@@ -22,7 +22,6 @@ impl Command for EncodeHex {
                 SyntaxShape::CellPath,
                 "For a data structure input, encode data at the given cell paths",
             )
-            .output_type(Type::String)
             .category(Category::Formats)
     }
 
diff --git a/crates/nu-parser/src/parse_keywords.rs b/crates/nu-parser/src/parse_keywords.rs
index eeb8611263..19a1e64495 100644
--- a/crates/nu-parser/src/parse_keywords.rs
+++ b/crates/nu-parser/src/parse_keywords.rs
@@ -1,4 +1,4 @@
-use crate::parser_path::ParserPath;
+use crate::{parser_path::ParserPath, type_check::type_compatible};
 use itertools::Itertools;
 use log::trace;
 use nu_path::canonicalize_with;
@@ -235,7 +235,7 @@ pub fn parse_for(working_set: &mut StateWorkingSet, spans: &[Span]) -> Expressio
     // Parsing the spans and checking that they match the register signature
     // Using a parsed call makes more sense than checking for how many spans are in the call
     // Also, by creating a call, it can be checked if it matches the declaration signature
-    let (call, call_span) = match working_set.find_decl(b"for", &Type::Any) {
+    let (call, call_span) = match working_set.find_decl(b"for", &Type::Nothing) {
         None => {
             working_set.error(ParseError::UnknownState(
                 "internal error: for declaration not found".into(),
@@ -290,9 +290,21 @@ pub fn parse_for(working_set: &mut StateWorkingSet, spans: &[Span]) -> Expressio
 
     // All positional arguments must be in the call positional vector by this point
     let var_decl = call.positional_nth(0).expect("for call already checked");
+    let iteration_expr = call.positional_nth(1).expect("for call already checked");
     let block = call.positional_nth(2).expect("for call already checked");
 
+    let iteration_expr_ty = iteration_expr.ty.clone();
+
+    // Figure out the type of the variable the `for` uses for iteration
+    let var_type = match iteration_expr_ty {
+        Type::List(x) => *x,
+        Type::Table(x) => Type::Record(x),
+        x => x,
+    };
+
     if let (Some(var_id), Some(block_id)) = (&var_decl.as_var(), block.as_block()) {
+        working_set.set_variable_type(*var_id, var_type.clone());
+
         let block = working_set.get_block_mut(block_id);
 
         block.signature.required_positional.insert(
@@ -300,7 +312,7 @@ pub fn parse_for(working_set: &mut StateWorkingSet, spans: &[Span]) -> Expressio
             PositionalArg {
                 name: String::new(),
                 desc: String::new(),
-                shape: SyntaxShape::Any,
+                shape: var_type.to_shape(),
                 var_id: Some(*var_id),
                 default_value: None,
             },
@@ -310,7 +322,7 @@ pub fn parse_for(working_set: &mut StateWorkingSet, spans: &[Span]) -> Expressio
     Expression {
         expr: Expr::Call(call),
         span: call_span,
-        ty: Type::Any,
+        ty: Type::Nothing,
         custom_completion: None,
     }
 }
@@ -347,7 +359,7 @@ pub fn parse_def(
     // Parsing the spans and checking that they match the register signature
     // Using a parsed call makes more sense than checking for how many spans are in the call
     // Also, by creating a call, it can be checked if it matches the declaration signature
-    let (call, call_span) = match working_set.find_decl(&def_call, &Type::Any) {
+    let (call, call_span) = match working_set.find_decl(&def_call, &Type::Nothing) {
         None => {
             working_set.error(ParseError::UnknownState(
                 "internal error: def declaration not found".into(),
@@ -391,12 +403,15 @@ pub fn parse_def(
                         expr: Expr::Block(block_id),
                         ..
                     }
+                    | Expression {
+                        expr: Expr::Closure(block_id),
+                        ..
+                    }
                     | Expression {
                         expr: Expr::RowCondition(block_id),
                         ..
                     } => {
                         let block = working_set.get_block_mut(*block_id);
-
                         block.signature = Box::new(sig.clone());
                     }
                     _ => {}
@@ -469,6 +484,20 @@ pub fn parse_def(
             block.recursive = Some(calls_itself);
             block.signature = signature;
             block.redirect_env = def_call == b"def-env";
+
+            // Sadly we can't use this here as the inference would have to happen before
+            // all the definitions had been fully parsed.
+
+            // infer the return type based on the output of the block
+            // let block = working_set.get_block(block_id);
+
+            // let input_type = block.input_type(working_set);
+            // let output_type = block.output_type();
+            // block.signature.input_output_types = vec![(input_type, output_type)];
+            block
+                .signature
+                .input_output_types
+                .push((Type::Any, Type::Any));
         } else {
             working_set.error(ParseError::InternalError(
                 "Predeclaration failed to add declaration".into(),
@@ -519,7 +548,7 @@ pub fn parse_extern(
     // Parsing the spans and checking that they match the register signature
     // Using a parsed call makes more sense than checking for how many spans are in the call
     // Also, by creating a call, it can be checked if it matches the declaration signature
-    let (call, call_span) = match working_set.find_decl(&extern_call, &Type::Any) {
+    let (call, call_span) = match working_set.find_decl(&extern_call, &Type::Nothing) {
         None => {
             working_set.error(ParseError::UnknownState(
                 "internal error: def declaration not found".into(),
@@ -710,7 +739,7 @@ pub fn parse_alias(
         return Pipeline::from_vec(vec![garbage(*span)]);
     }
 
-    if let Some(decl_id) = working_set.find_decl(b"alias", &Type::Any) {
+    if let Some(decl_id) = working_set.find_decl(b"alias", &Type::Nothing) {
         let (command_spans, rest_spans) = spans.split_at(split_id);
 
         let original_starting_error_count = working_set.parse_errors.len();
@@ -912,7 +941,7 @@ pub fn parse_export_in_block(
         b"export".to_vec()
     };
 
-    if let Some(decl_id) = working_set.find_decl(&full_name, &Type::Any) {
+    if let Some(decl_id) = working_set.find_decl(&full_name, &Type::Nothing) {
         let ParsedInternalCall { call, output, .. } = parse_internal_call(
             working_set,
             if full_name == b"export" {
@@ -1006,7 +1035,7 @@ pub fn parse_export_in_module(
         return (garbage_pipeline(spans), vec![]);
     };
 
-    let export_decl_id = if let Some(id) = working_set.find_decl(b"export", &Type::Any) {
+    let export_decl_id = if let Some(id) = working_set.find_decl(b"export", &Type::Nothing) {
         id
     } else {
         working_set.error(ParseError::InternalError(
@@ -1036,7 +1065,7 @@ pub fn parse_export_in_module(
                 let pipeline = parse_def(working_set, &lite_command, Some(module_name));
 
                 let export_def_decl_id =
-                    if let Some(id) = working_set.find_decl(b"export def", &Type::Any) {
+                    if let Some(id) = working_set.find_decl(b"export def", &Type::Nothing) {
                         id
                     } else {
                         working_set.error(ParseError::InternalError(
@@ -1072,7 +1101,7 @@ pub fn parse_export_in_module(
                     let decl_name = working_set.get_span_contents(*decl_name_span);
                     let decl_name = trim_quotes(decl_name);
 
-                    if let Some(decl_id) = working_set.find_decl(decl_name, &Type::Any) {
+                    if let Some(decl_id) = working_set.find_decl(decl_name, &Type::Nothing) {
                         result.push(Exportable::Decl {
                             name: decl_name.to_vec(),
                             id: decl_id,
@@ -1095,7 +1124,7 @@ pub fn parse_export_in_module(
                 let pipeline = parse_def(working_set, &lite_command, Some(module_name));
 
                 let export_def_decl_id =
-                    if let Some(id) = working_set.find_decl(b"export def-env", &Type::Any) {
+                    if let Some(id) = working_set.find_decl(b"export def-env", &Type::Nothing) {
                         id
                     } else {
                         working_set.error(ParseError::InternalError(
@@ -1133,7 +1162,7 @@ pub fn parse_export_in_module(
                 };
                 let decl_name = trim_quotes(decl_name);
 
-                if let Some(decl_id) = working_set.find_decl(decl_name, &Type::Any) {
+                if let Some(decl_id) = working_set.find_decl(decl_name, &Type::Nothing) {
                     result.push(Exportable::Decl {
                         name: decl_name.to_vec(),
                         id: decl_id,
@@ -1155,7 +1184,7 @@ pub fn parse_export_in_module(
                 let pipeline = parse_extern(working_set, &lite_command, Some(module_name));
 
                 let export_def_decl_id =
-                    if let Some(id) = working_set.find_decl(b"export extern", &Type::Any) {
+                    if let Some(id) = working_set.find_decl(b"export extern", &Type::Nothing) {
                         id
                     } else {
                         working_set.error(ParseError::InternalError(
@@ -1193,7 +1222,7 @@ pub fn parse_export_in_module(
                 };
                 let decl_name = trim_quotes(decl_name);
 
-                if let Some(decl_id) = working_set.find_decl(decl_name, &Type::Any) {
+                if let Some(decl_id) = working_set.find_decl(decl_name, &Type::Nothing) {
                     result.push(Exportable::Decl {
                         name: decl_name.to_vec(),
                         id: decl_id,
@@ -1215,7 +1244,7 @@ pub fn parse_export_in_module(
                 let pipeline = parse_alias(working_set, &lite_command, Some(module_name));
 
                 let export_alias_decl_id =
-                    if let Some(id) = working_set.find_decl(b"export alias", &Type::Any) {
+                    if let Some(id) = working_set.find_decl(b"export alias", &Type::Nothing) {
                         id
                     } else {
                         working_set.error(ParseError::InternalError(
@@ -1253,7 +1282,7 @@ pub fn parse_export_in_module(
                 };
                 let alias_name = trim_quotes(alias_name);
 
-                if let Some(alias_id) = working_set.find_decl(alias_name, &Type::Any) {
+                if let Some(alias_id) = working_set.find_decl(alias_name, &Type::Nothing) {
                     result.push(Exportable::Decl {
                         name: alias_name.to_vec(),
                         id: alias_id,
@@ -1275,7 +1304,7 @@ pub fn parse_export_in_module(
                 let (pipeline, exportables) = parse_use(working_set, &lite_command.parts);
 
                 let export_use_decl_id =
-                    if let Some(id) = working_set.find_decl(b"export use", &Type::Any) {
+                    if let Some(id) = working_set.find_decl(b"export use", &Type::Nothing) {
                         id
                     } else {
                         working_set.error(ParseError::InternalError(
@@ -1312,7 +1341,7 @@ pub fn parse_export_in_module(
                     parse_module(working_set, lite_command, Some(module_name));
 
                 let export_module_decl_id =
-                    if let Some(id) = working_set.find_decl(b"export module", &Type::Any) {
+                    if let Some(id) = working_set.find_decl(b"export module", &Type::Nothing) {
                         id
                     } else {
                         working_set.error(ParseError::InternalError(
@@ -1417,7 +1446,7 @@ pub fn parse_export_env(
         return (garbage_pipeline(spans), None);
     }
 
-    let call = match working_set.find_decl(b"export-env", &Type::Any) {
+    let call = match working_set.find_decl(b"export-env", &Type::Nothing) {
         Some(decl_id) => {
             let ParsedInternalCall { call, output } =
                 parse_internal_call(working_set, spans[0], &[spans[1]], decl_id);
@@ -1929,7 +1958,7 @@ pub fn parse_module(
         1
     };
 
-    let (call, call_span) = match working_set.find_decl(b"module", &Type::Any) {
+    let (call, call_span) = match working_set.find_decl(b"module", &Type::Nothing) {
         Some(decl_id) => {
             let (command_spans, rest_spans) = spans.split_at(split_id);
 
@@ -2070,7 +2099,7 @@ pub fn parse_module(
     };
 
     let module_decl_id = working_set
-        .find_decl(b"module", &Type::Any)
+        .find_decl(b"module", &Type::Nothing)
         .expect("internal error: missing module command");
 
     let call = Box::new(Call {
@@ -2121,7 +2150,7 @@ pub fn parse_use(working_set: &mut StateWorkingSet, spans: &[Span]) -> (Pipeline
         return (garbage_pipeline(spans), vec![]);
     }
 
-    let (call, call_span, args_spans) = match working_set.find_decl(b"use", &Type::Any) {
+    let (call, call_span, args_spans) = match working_set.find_decl(b"use", &Type::Nothing) {
         Some(decl_id) => {
             let (command_spans, rest_spans) = spans.split_at(split_id);
 
@@ -2277,7 +2306,7 @@ pub fn parse_hide(working_set: &mut StateWorkingSet, spans: &[Span]) -> Pipeline
         return garbage_pipeline(spans);
     }
 
-    let (call, args_spans) = match working_set.find_decl(b"hide", &Type::Any) {
+    let (call, args_spans) = match working_set.find_decl(b"hide", &Type::Nothing) {
         Some(decl_id) => {
             let ParsedInternalCall { call, output } =
                 parse_internal_call(working_set, spans[0], &spans[1..], decl_id);
@@ -2336,7 +2365,7 @@ pub fn parse_hide(working_set: &mut StateWorkingSet, spans: &[Span]) -> Pipeline
                 (true, working_set.get_module(module_id).clone())
             } else if import_pattern.members.is_empty() {
                 // The pattern head can be:
-                if let Some(id) = working_set.find_decl(&import_pattern.head.name, &Type::Any) {
+                if let Some(id) = working_set.find_decl(&import_pattern.head.name, &Type::Nothing) {
                     // a custom command,
                     let mut module = Module::new(b"tmp".to_vec());
                     module.add_decl(import_pattern.head.name.clone(), id);
@@ -2767,17 +2796,19 @@ pub fn parse_overlay_hide(working_set: &mut StateWorkingSet, call: Box<Call>) ->
 }
 
 pub fn parse_let_or_const(working_set: &mut StateWorkingSet, spans: &[Span]) -> Pipeline {
+    trace!("parsing: let");
     let name = working_set.get_span_contents(spans[0]);
 
     if name == b"let" || name == b"const" {
         let is_const = &name == b"const";
 
-        if let Some(span) = check_name(working_set, spans) {
-            return Pipeline::from_vec(vec![garbage(*span)]);
-        }
+        // JT: Disabling check_name because it doesn't work with optional types in the declaration
+        // if let Some(span) = check_name(working_set, spans) {
+        //     return Pipeline::from_vec(vec![garbage(*span)]);
+        // }
 
         if let Some(decl_id) =
-            working_set.find_decl(if is_const { b"const" } else { b"let" }, &Type::Any)
+            working_set.find_decl(if is_const { b"const" } else { b"let" }, &Type::Nothing)
         {
             let cmd = working_set.get_decl(decl_id);
             let call_signature = cmd.signature().call_signature();
@@ -2805,7 +2836,8 @@ pub fn parse_let_or_const(working_set: &mut StateWorkingSet, spans: &[Span]) ->
                         }
 
                         let mut idx = 0;
-                        let lvalue = parse_var_with_opt_type(
+
+                        let (lvalue, explicit_type) = parse_var_with_opt_type(
                             working_set,
                             &spans[1..(span.0)],
                             &mut idx,
@@ -2824,8 +2856,20 @@ pub fn parse_let_or_const(working_set: &mut StateWorkingSet, spans: &[Span]) ->
                         let var_id = lvalue.as_var();
                         let rhs_type = rvalue.ty.clone();
 
+                        if let Some(explicit_type) = &explicit_type {
+                            if !type_compatible(explicit_type, &rhs_type) {
+                                working_set.error(ParseError::TypeMismatch(
+                                    explicit_type.clone(),
+                                    rhs_type.clone(),
+                                    nu_protocol::span(&spans[(span.0 + 1)..]),
+                                ));
+                            }
+                        }
+
                         if let Some(var_id) = var_id {
-                            working_set.set_variable_type(var_id, rhs_type);
+                            if explicit_type.is_none() {
+                                working_set.set_variable_type(var_id, rhs_type);
+                            }
 
                             if is_const {
                                 match eval_constant(working_set, &rvalue) {
@@ -2867,6 +2911,11 @@ pub fn parse_let_or_const(working_set: &mut StateWorkingSet, spans: &[Span]) ->
                 ty: output,
                 custom_completion: None,
             }]);
+        } else {
+            working_set.error(ParseError::UnknownState(
+                "internal error: let or const statements not found in core language".into(),
+                span(spans),
+            ))
         }
     }
 
@@ -2882,11 +2931,11 @@ pub fn parse_mut(working_set: &mut StateWorkingSet, spans: &[Span]) -> Pipeline
     let name = working_set.get_span_contents(spans[0]);
 
     if name == b"mut" {
-        if let Some(span) = check_name(working_set, spans) {
-            return Pipeline::from_vec(vec![garbage(*span)]);
-        }
+        // if let Some(span) = check_name(working_set, spans) {
+        //     return Pipeline::from_vec(vec![garbage(*span)]);
+        // }
 
-        if let Some(decl_id) = working_set.find_decl(b"mut", &Type::Any) {
+        if let Some(decl_id) = working_set.find_decl(b"mut", &Type::Nothing) {
             let cmd = working_set.get_decl(decl_id);
             let call_signature = cmd.signature().call_signature();
 
@@ -2913,7 +2962,7 @@ pub fn parse_mut(working_set: &mut StateWorkingSet, spans: &[Span]) -> Pipeline
                         }
 
                         let mut idx = 0;
-                        let lvalue = parse_var_with_opt_type(
+                        let (lvalue, explicit_type) = parse_var_with_opt_type(
                             working_set,
                             &spans[1..(span.0)],
                             &mut idx,
@@ -2932,8 +2981,20 @@ pub fn parse_mut(working_set: &mut StateWorkingSet, spans: &[Span]) -> Pipeline
                         let var_id = lvalue.as_var();
                         let rhs_type = rvalue.ty.clone();
 
+                        if let Some(explicit_type) = &explicit_type {
+                            if &rhs_type != explicit_type && explicit_type != &Type::Any {
+                                working_set.error(ParseError::TypeMismatch(
+                                    explicit_type.clone(),
+                                    rhs_type.clone(),
+                                    rvalue.span,
+                                ));
+                            }
+                        }
+
                         if let Some(var_id) = var_id {
-                            working_set.set_variable_type(var_id, rhs_type);
+                            if explicit_type.is_none() {
+                                working_set.set_variable_type(var_id, rhs_type);
+                            }
                         }
 
                         let call = Box::new(Call {
@@ -2982,7 +3043,7 @@ pub fn parse_source(working_set: &mut StateWorkingSet, spans: &[Span]) -> Pipeli
     if name == b"source" || name == b"source-env" {
         let scoped = name == b"source-env";
 
-        if let Some(decl_id) = working_set.find_decl(name, &Type::Any) {
+        if let Some(decl_id) = working_set.find_decl(name, &Type::Nothing) {
             let cwd = working_set.get_cwd();
 
             // Is this the right call to be using here?
@@ -3113,7 +3174,7 @@ pub fn parse_where_expr(working_set: &mut StateWorkingSet, spans: &[Span]) -> Ex
         return garbage(span(spans));
     }
 
-    let call = match working_set.find_decl(b"where", &Type::Any) {
+    let call = match working_set.find_decl(b"where", &Type::List(Box::new(Type::Any))) {
         Some(decl_id) => {
             let ParsedInternalCall { call, output } =
                 parse_internal_call(working_set, spans[0], &spans[1..], decl_id);
@@ -3176,7 +3237,7 @@ pub fn parse_register(working_set: &mut StateWorkingSet, spans: &[Span]) -> Pipe
     // Parsing the spans and checking that they match the register signature
     // Using a parsed call makes more sense than checking for how many spans are in the call
     // Also, by creating a call, it can be checked if it matches the declaration signature
-    let (call, call_span) = match working_set.find_decl(b"register", &Type::Any) {
+    let (call, call_span) = match working_set.find_decl(b"register", &Type::Nothing) {
         None => {
             working_set.error(ParseError::UnknownState(
                 "internal error: Register declaration not found".into(),
diff --git a/crates/nu-parser/src/parser.rs b/crates/nu-parser/src/parser.rs
index 8edc4ae677..13d59c5359 100644
--- a/crates/nu-parser/src/parser.rs
+++ b/crates/nu-parser/src/parser.rs
@@ -607,7 +607,7 @@ pub fn parse_multispan_value(
         SyntaxShape::VarWithOptType => {
             trace!("parsing: var with opt type");
 
-            parse_var_with_opt_type(working_set, spans, spans_idx, false)
+            parse_var_with_opt_type(working_set, spans, spans_idx, false).0
         }
         SyntaxShape::RowCondition => {
             trace!("parsing: row condition");
@@ -779,7 +779,7 @@ pub fn parse_internal_call(
 
     let decl = working_set.get_decl(decl_id);
     let signature = decl.signature();
-    let output = signature.output_type.clone();
+    let output = signature.get_output_type();
 
     if decl.is_builtin() {
         attach_parser_info_builtin(working_set, decl.name(), &mut call);
@@ -1172,6 +1172,7 @@ pub fn parse_call(
 }
 
 pub fn parse_binary(working_set: &mut StateWorkingSet, span: Span) -> Expression {
+    trace!("parsing: binary");
     let contents = working_set.get_span_contents(span);
     if contents.starts_with(b"0x[") {
         parse_binary_with_base(working_set, span, 16, 2, b"0x[", b"]")
@@ -2007,25 +2008,7 @@ pub fn parse_full_cell_path(
                 .type_scope
                 .add_type(working_set.type_scope.get_last_output());
 
-            let ty = output
-                .pipelines
-                .last()
-                .and_then(|Pipeline { elements, .. }| elements.last())
-                .map(|element| match element {
-                    PipelineElement::Expression(_, expr)
-                        if matches!(
-                            expr,
-                            Expression {
-                                expr: Expr::BinaryOp(..),
-                                ..
-                            }
-                        ) =>
-                    {
-                        expr.ty.clone()
-                    }
-                    _ => working_set.type_scope.get_last_output(),
-                })
-                .unwrap_or_else(|| working_set.type_scope.get_last_output());
+            let ty = output.output_type();
 
             let block_id = working_set.add_block(output);
             tokens.next();
@@ -3081,7 +3064,7 @@ pub fn parse_var_with_opt_type(
     spans: &[Span],
     spans_idx: &mut usize,
     mutable: bool,
-) -> Expression {
+) -> (Expression, Option<Type>) {
     let bytes = working_set.get_span_contents(spans[*spans_idx]).to_vec();
 
     if bytes.contains(&b' ')
@@ -3090,7 +3073,7 @@ pub fn parse_var_with_opt_type(
         || bytes.contains(&b'`')
     {
         working_set.error(ParseError::VariableNotValid(spans[*spans_idx]));
-        return garbage(spans[*spans_idx]);
+        return (garbage(spans[*spans_idx]), None);
     }
 
     if bytes.ends_with(b":") {
@@ -3108,17 +3091,20 @@ pub fn parse_var_with_opt_type(
                     "valid variable name",
                     spans[*spans_idx],
                 ));
-                return garbage(spans[*spans_idx]);
+                return (garbage(spans[*spans_idx]), None);
             }
 
             let id = working_set.add_variable(var_name, spans[*spans_idx - 1], ty.clone(), mutable);
 
-            Expression {
-                expr: Expr::VarDecl(id),
-                span: span(&spans[*spans_idx - 1..*spans_idx + 1]),
-                ty,
-                custom_completion: None,
-            }
+            (
+                Expression {
+                    expr: Expr::VarDecl(id),
+                    span: span(&spans[*spans_idx - 1..*spans_idx + 1]),
+                    ty: ty.clone(),
+                    custom_completion: None,
+                },
+                Some(ty),
+            )
         } else {
             let var_name = bytes[0..(bytes.len() - 1)].to_vec();
 
@@ -3127,18 +3113,21 @@ pub fn parse_var_with_opt_type(
                     "valid variable name",
                     spans[*spans_idx],
                 ));
-                return garbage(spans[*spans_idx]);
+                return (garbage(spans[*spans_idx]), None);
             }
 
             let id = working_set.add_variable(var_name, spans[*spans_idx], Type::Any, mutable);
 
             working_set.error(ParseError::MissingType(spans[*spans_idx]));
-            Expression {
-                expr: Expr::VarDecl(id),
-                span: spans[*spans_idx],
-                ty: Type::Any,
-                custom_completion: None,
-            }
+            (
+                Expression {
+                    expr: Expr::VarDecl(id),
+                    span: spans[*spans_idx],
+                    ty: Type::Any,
+                    custom_completion: None,
+                },
+                None,
+            )
         }
     } else {
         let var_name = bytes;
@@ -3148,7 +3137,7 @@ pub fn parse_var_with_opt_type(
                 "valid variable name",
                 spans[*spans_idx],
             ));
-            return garbage(spans[*spans_idx]);
+            return (garbage(spans[*spans_idx]), None);
         }
 
         let id = working_set.add_variable(
@@ -3158,12 +3147,15 @@ pub fn parse_var_with_opt_type(
             mutable,
         );
 
-        Expression {
-            expr: Expr::VarDecl(id),
-            span: span(&spans[*spans_idx..*spans_idx + 1]),
-            ty: Type::Any,
-            custom_completion: None,
-        }
+        (
+            Expression {
+                expr: Expr::VarDecl(id),
+                span: span(&spans[*spans_idx..*spans_idx + 1]),
+                ty: Type::Any,
+                custom_completion: None,
+            },
+            None,
+        )
     }
 }
 
@@ -5088,11 +5080,13 @@ pub fn parse_builtin_commands(
     lite_command: &LiteCommand,
     is_subexpression: bool,
 ) -> Pipeline {
+    trace!("parsing: builtin commands");
     if !is_math_expression_like(working_set, lite_command.parts[0])
         && !is_unaliasable_parser_keyword(working_set, &lite_command.parts)
     {
+        trace!("parsing: not math expression or unaliasable parser keyword");
         let name = working_set.get_span_contents(lite_command.parts[0]);
-        if let Some(decl_id) = working_set.find_decl(name, &Type::Any) {
+        if let Some(decl_id) = working_set.find_decl(name, &Type::Nothing) {
             let cmd = working_set.get_decl(decl_id);
             if cmd.is_alias() {
                 // Parse keywords that can be aliased. Note that we check for "unaliasable" keywords
@@ -5122,6 +5116,7 @@ pub fn parse_builtin_commands(
         }
     }
 
+    trace!("parsing: checking for keywords");
     let name = working_set.get_span_contents(lite_command.parts[0]);
 
     match name {
@@ -5347,9 +5342,9 @@ pub fn parse_block(
                         parse_builtin_commands(working_set, command, is_subexpression);
 
                     if idx == 0 {
-                        if let Some(let_decl_id) = working_set.find_decl(b"let", &Type::Any) {
+                        if let Some(let_decl_id) = working_set.find_decl(b"let", &Type::Nothing) {
                             if let Some(let_env_decl_id) =
-                                working_set.find_decl(b"let-env", &Type::Any)
+                                working_set.find_decl(b"let-env", &Type::Nothing)
                             {
                                 for element in pipeline.elements.iter_mut() {
                                     if let PipelineElement::Expression(
@@ -5823,7 +5818,7 @@ fn wrap_element_with_collect(
 fn wrap_expr_with_collect(working_set: &mut StateWorkingSet, expr: &Expression) -> Expression {
     let span = expr.span;
 
-    if let Some(decl_id) = working_set.find_decl(b"collect", &Type::Any) {
+    if let Some(decl_id) = working_set.find_decl(b"collect", &Type::List(Box::new(Type::Any))) {
         let mut output = vec![];
 
         let var_id = IN_VARIABLE_ID;
diff --git a/crates/nu-parser/src/type_check.rs b/crates/nu-parser/src/type_check.rs
index 3ad88e70e5..aa5ffce1b3 100644
--- a/crates/nu-parser/src/type_check.rs
+++ b/crates/nu-parser/src/type_check.rs
@@ -22,8 +22,11 @@ pub fn type_compatible(lhs: &Type, rhs: &Type) -> bool {
 
     match (lhs, rhs) {
         (Type::List(c), Type::List(d)) => type_compatible(c, d),
+        (Type::List(c), Type::Table(_)) => matches!(**c, Type::Any),
         (Type::Number, Type::Int) => true,
+        (Type::Int, Type::Number) => true,
         (Type::Number, Type::Float) => true,
+        (Type::Float, Type::Number) => true,
         (Type::Closure, Type::Block) => true,
         (Type::Any, _) => true,
         (_, Type::Any) => true,
@@ -47,6 +50,11 @@ pub fn math_result_type(
                 (Type::Float, Type::Int) => (Type::Float, None),
                 (Type::Int, Type::Float) => (Type::Float, None),
                 (Type::Float, Type::Float) => (Type::Float, None),
+                (Type::Number, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Int) => (Type::Number, None),
+                (Type::Int, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Float) => (Type::Number, None),
+                (Type::Float, Type::Number) => (Type::Number, None),
                 (Type::String, Type::String) => (Type::String, None),
                 (Type::Date, Type::Duration) => (Type::Date, None),
                 (Type::Duration, Type::Duration) => (Type::Duration, None),
@@ -143,6 +151,11 @@ pub fn math_result_type(
                 (Type::Float, Type::Int) => (Type::Float, None),
                 (Type::Int, Type::Float) => (Type::Float, None),
                 (Type::Float, Type::Float) => (Type::Float, None),
+                (Type::Number, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Int) => (Type::Number, None),
+                (Type::Int, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Float) => (Type::Number, None),
+                (Type::Float, Type::Number) => (Type::Number, None),
                 (Type::Date, Type::Date) => (Type::Duration, None),
                 (Type::Date, Type::Duration) => (Type::Date, None),
                 (Type::Duration, Type::Duration) => (Type::Duration, None),
@@ -185,6 +198,11 @@ pub fn math_result_type(
                 (Type::Float, Type::Int) => (Type::Float, None),
                 (Type::Int, Type::Float) => (Type::Float, None),
                 (Type::Float, Type::Float) => (Type::Float, None),
+                (Type::Number, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Int) => (Type::Number, None),
+                (Type::Int, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Float) => (Type::Number, None),
+                (Type::Float, Type::Number) => (Type::Number, None),
                 (Type::Filesize, Type::Int) => (Type::Filesize, None),
                 (Type::Int, Type::Filesize) => (Type::Filesize, None),
                 (Type::Filesize, Type::Float) => (Type::Filesize, None),
@@ -241,6 +259,11 @@ pub fn math_result_type(
                 (Type::Float, Type::Int) => (Type::Float, None),
                 (Type::Int, Type::Float) => (Type::Float, None),
                 (Type::Float, Type::Float) => (Type::Float, None),
+                (Type::Number, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Int) => (Type::Number, None),
+                (Type::Int, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Float) => (Type::Number, None),
+                (Type::Float, Type::Number) => (Type::Number, None),
 
                 (Type::Custom(a), Type::Custom(b)) if a == b => (Type::Custom(a.to_string()), None),
                 (Type::Custom(a), _) => (Type::Custom(a.to_string()), None),
@@ -280,6 +303,11 @@ pub fn math_result_type(
                 (Type::Float, Type::Int) => (Type::Float, None),
                 (Type::Int, Type::Float) => (Type::Float, None),
                 (Type::Float, Type::Float) => (Type::Float, None),
+                (Type::Number, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Int) => (Type::Number, None),
+                (Type::Int, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Float) => (Type::Number, None),
+                (Type::Float, Type::Number) => (Type::Number, None),
                 (Type::Filesize, Type::Filesize) => (Type::Float, None),
                 (Type::Filesize, Type::Int) => (Type::Filesize, None),
                 (Type::Filesize, Type::Float) => (Type::Filesize, None),
@@ -324,6 +352,11 @@ pub fn math_result_type(
                 (Type::Float, Type::Int) => (Type::Int, None),
                 (Type::Int, Type::Float) => (Type::Int, None),
                 (Type::Float, Type::Float) => (Type::Int, None),
+                (Type::Number, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Int) => (Type::Number, None),
+                (Type::Int, Type::Number) => (Type::Number, None),
+                (Type::Number, Type::Float) => (Type::Number, None),
+                (Type::Float, Type::Number) => (Type::Number, None),
                 (Type::Filesize, Type::Filesize) => (Type::Int, None),
                 (Type::Filesize, Type::Int) => (Type::Filesize, None),
                 (Type::Filesize, Type::Float) => (Type::Filesize, None),
@@ -410,7 +443,13 @@ pub fn math_result_type(
                 (Type::Float, Type::Int) => (Type::Bool, None),
                 (Type::Int, Type::Float) => (Type::Bool, None),
                 (Type::Float, Type::Float) => (Type::Bool, None),
+                (Type::Number, Type::Number) => (Type::Bool, None),
+                (Type::Number, Type::Int) => (Type::Bool, None),
+                (Type::Int, Type::Number) => (Type::Bool, None),
+                (Type::Number, Type::Float) => (Type::Bool, None),
+                (Type::Float, Type::Number) => (Type::Bool, None),
                 (Type::Duration, Type::Duration) => (Type::Bool, None),
+                (Type::Date, Type::Date) => (Type::Bool, None),
                 (Type::Filesize, Type::Filesize) => (Type::Bool, None),
 
                 (Type::Custom(a), Type::Custom(b)) if a == b => (Type::Custom(a.to_string()), None),
@@ -453,7 +492,13 @@ pub fn math_result_type(
                 (Type::Float, Type::Int) => (Type::Bool, None),
                 (Type::Int, Type::Float) => (Type::Bool, None),
                 (Type::Float, Type::Float) => (Type::Bool, None),
+                (Type::Number, Type::Number) => (Type::Bool, None),
+                (Type::Number, Type::Int) => (Type::Bool, None),
+                (Type::Int, Type::Number) => (Type::Bool, None),
+                (Type::Number, Type::Float) => (Type::Bool, None),
+                (Type::Float, Type::Number) => (Type::Bool, None),
                 (Type::Duration, Type::Duration) => (Type::Bool, None),
+                (Type::Date, Type::Date) => (Type::Bool, None),
                 (Type::Filesize, Type::Filesize) => (Type::Bool, None),
 
                 (Type::Custom(a), Type::Custom(b)) if a == b => (Type::Custom(a.to_string()), None),
@@ -496,7 +541,13 @@ pub fn math_result_type(
                 (Type::Float, Type::Int) => (Type::Bool, None),
                 (Type::Int, Type::Float) => (Type::Bool, None),
                 (Type::Float, Type::Float) => (Type::Bool, None),
+                (Type::Number, Type::Number) => (Type::Bool, None),
+                (Type::Number, Type::Int) => (Type::Bool, None),
+                (Type::Int, Type::Number) => (Type::Bool, None),
+                (Type::Number, Type::Float) => (Type::Bool, None),
+                (Type::Float, Type::Number) => (Type::Bool, None),
                 (Type::Duration, Type::Duration) => (Type::Bool, None),
+                (Type::Date, Type::Date) => (Type::Bool, None),
                 (Type::Filesize, Type::Filesize) => (Type::Bool, None),
 
                 (Type::Custom(a), Type::Custom(b)) if a == b => (Type::Custom(a.to_string()), None),
@@ -539,7 +590,13 @@ pub fn math_result_type(
                 (Type::Float, Type::Int) => (Type::Bool, None),
                 (Type::Int, Type::Float) => (Type::Bool, None),
                 (Type::Float, Type::Float) => (Type::Bool, None),
+                (Type::Number, Type::Number) => (Type::Bool, None),
+                (Type::Number, Type::Int) => (Type::Bool, None),
+                (Type::Int, Type::Number) => (Type::Bool, None),
+                (Type::Number, Type::Float) => (Type::Bool, None),
+                (Type::Float, Type::Number) => (Type::Bool, None),
                 (Type::Duration, Type::Duration) => (Type::Bool, None),
+                (Type::Date, Type::Date) => (Type::Bool, None),
                 (Type::Filesize, Type::Filesize) => (Type::Bool, None),
 
                 (Type::Custom(a), Type::Custom(b)) if a == b => (Type::Custom(a.to_string()), None),
@@ -731,7 +788,7 @@ pub fn math_result_type(
             },
             Operator::Comparison(Comparison::In) => match (&lhs.ty, &rhs.ty) {
                 (t, Type::List(u)) if type_compatible(t, u) => (Type::Bool, None),
-                (Type::Int | Type::Float, Type::Range) => (Type::Bool, None),
+                (Type::Int | Type::Float | Type::Number, Type::Range) => (Type::Bool, None),
                 (Type::String, Type::String) => (Type::Bool, None),
                 (Type::String, Type::Record(_)) => (Type::Bool, None),
 
@@ -769,7 +826,7 @@ pub fn math_result_type(
             },
             Operator::Comparison(Comparison::NotIn) => match (&lhs.ty, &rhs.ty) {
                 (t, Type::List(u)) if type_compatible(t, u) => (Type::Bool, None),
-                (Type::Int | Type::Float, Type::Range) => (Type::Bool, None),
+                (Type::Int | Type::Float | Type::Number, Type::Range) => (Type::Bool, None),
                 (Type::String, Type::String) => (Type::Bool, None),
                 (Type::String, Type::Record(_)) => (Type::Bool, None),
 
diff --git a/crates/nu-parser/tests/test_parser.rs b/crates/nu-parser/tests/test_parser.rs
index 2659460bba..f67f8c04f6 100644
--- a/crates/nu-parser/tests/test_parser.rs
+++ b/crates/nu-parser/tests/test_parser.rs
@@ -1361,8 +1361,7 @@ mod input_types {
 
         fn signature(&self) -> nu_protocol::Signature {
             Signature::build(self.name())
-                .input_type(Type::Any)
-                .output_type(Type::Custom("custom".into()))
+                .input_output_type(Type::Any, Type::Custom("custom".into()))
                 .category(Category::Custom("custom".into()))
         }
 
@@ -1393,8 +1392,7 @@ mod input_types {
             Signature::build(self.name())
                 .required("column", SyntaxShape::String, "column name")
                 .required("other", SyntaxShape::String, "other value")
-                .input_type(Type::Custom("custom".into()))
-                .output_type(Type::Custom("custom".into()))
+                .input_output_type(Type::Custom("custom".into()), Type::Custom("custom".into()))
                 .category(Category::Custom("custom".into()))
         }
 
@@ -1424,7 +1422,7 @@ mod input_types {
         fn signature(&self) -> nu_protocol::Signature {
             Signature::build(self.name())
                 .required("operation", SyntaxShape::String, "operation")
-                .input_type(Type::Custom("custom".into()))
+                .input_output_type(Type::Custom("custom".into()), Type::Custom("custom".into()))
                 .category(Category::Custom("custom".into()))
         }
 
@@ -1481,8 +1479,7 @@ mod input_types {
         fn signature(&self) -> nu_protocol::Signature {
             Signature::build(self.name())
                 .rest("operation", SyntaxShape::Any, "operation")
-                .input_type(Type::Custom("custom".into()))
-                .output_type(Type::Custom("custom".into()))
+                .input_output_type(Type::Custom("custom".into()), Type::Custom("custom".into()))
                 .category(Category::Custom("custom".into()))
         }
 
@@ -1511,8 +1508,7 @@ mod input_types {
 
         fn signature(&self) -> nu_protocol::Signature {
             Signature::build(self.name())
-                .input_type(Type::Custom("custom".into()))
-                .output_type(Type::Custom("custom".into()))
+                .input_output_type(Type::Custom("custom".into()), Type::Custom("custom".into()))
                 .category(Category::Custom("custom".into()))
         }
 
@@ -1619,7 +1615,7 @@ mod input_types {
                 },
             ) => {
                 let expected_id = working_set
-                    .find_decl(b"ls", &Type::Any)
+                    .find_decl(b"ls", &Type::Nothing)
                     .expect("Error merging delta");
                 assert_eq!(call.decl_id, expected_id)
             }
@@ -1789,7 +1785,7 @@ mod input_types {
                     ..
                 },
             ) => {
-                let expected_id = working_set.find_decl(b"ls", &Type::Any).unwrap();
+                let expected_id = working_set.find_decl(b"ls", &Type::Nothing).unwrap();
                 assert_eq!(call.decl_id, expected_id)
             }
             _ => panic!("Expected expression Call not found"),
diff --git a/crates/nu-plugin/src/plugin/mod.rs b/crates/nu-plugin/src/plugin/mod.rs
index 809b4975b0..5eefb42903 100644
--- a/crates/nu-plugin/src/plugin/mod.rs
+++ b/crates/nu-plugin/src/plugin/mod.rs
@@ -203,7 +203,7 @@ pub fn get_signature(
 /// impl Plugin for HelloPlugin {
 ///     fn signature(&self) -> Vec<PluginSignature> {
 ///         let sig = PluginSignature::build("hello")
-///             .output_type(Type::String);
+///             .input_output_type(Type::Nothing, Type::String);
 ///
 ///         vec![sig]
 ///     }
diff --git a/crates/nu-protocol/src/ast/block.rs b/crates/nu-protocol/src/ast/block.rs
index d725774a8c..e57171db0e 100644
--- a/crates/nu-protocol/src/ast/block.rs
+++ b/crates/nu-protocol/src/ast/block.rs
@@ -1,5 +1,5 @@
-use super::Pipeline;
-use crate::{Signature, Span, VarId};
+use super::{Expr, Expression, Pipeline};
+use crate::{ast::PipelineElement, engine::StateWorkingSet, Signature, Span, Type, VarId};
 use serde::{Deserialize, Serialize};
 use std::ops::{Index, IndexMut};
 
@@ -65,6 +65,56 @@ impl Block {
             recursive: None,
         }
     }
+
+    pub fn input_type(&self, working_set: &StateWorkingSet) -> Type {
+        if let Some(first) = self.pipelines.first() {
+            if let Some(first) = first.elements.first() {
+                match first {
+                    PipelineElement::Expression(
+                        _,
+                        Expression {
+                            expr: Expr::Call(call),
+                            ..
+                        },
+                    ) => {
+                        let decl = working_set.get_decl(call.decl_id);
+
+                        decl.signature().get_input_type()
+                    }
+                    PipelineElement::Expression(
+                        _,
+                        Expression {
+                            expr: Expr::ExternalCall(..),
+                            ..
+                        },
+                    ) => Type::Any,
+                    _ => Type::Nothing,
+                }
+            } else {
+                Type::Nothing
+            }
+        } else {
+            Type::Nothing
+        }
+    }
+    pub fn output_type(&self) -> Type {
+        if let Some(last) = self.pipelines.last() {
+            if let Some(last) = last.elements.last() {
+                match last {
+                    PipelineElement::Expression(_, expr) => expr.ty.clone(),
+                    PipelineElement::Redirection(_, _, _) => Type::Any,
+                    PipelineElement::SeparateRedirection { .. } => Type::Any,
+                    PipelineElement::SameTargetRedirection { .. } => Type::Any,
+                    PipelineElement::And(_, expr) => expr.ty.clone(),
+                    PipelineElement::Or(_, expr) => expr.ty.clone(),
+                }
+            } else {
+                Type::Nothing
+            }
+        } else {
+            Type::Nothing
+        }
+    }
 }
 
 impl<T> From<T> for Block
diff --git a/crates/nu-protocol/src/engine/engine_state.rs b/crates/nu-protocol/src/engine/engine_state.rs
index 5d8ef30288..4dc5e6c905 100644
--- a/crates/nu-protocol/src/engine/engine_state.rs
+++ b/crates/nu-protocol/src/engine/engine_state.rs
@@ -981,7 +981,7 @@ impl TypeScope {
     pub fn get_previous(&self) -> &Type {
         match self.outputs.last().and_then(|v| v.last()) {
             Some(input) => input,
-            None => &Type::Any,
+            None => &Type::Nothing,
         }
     }
 
@@ -1193,7 +1193,7 @@ impl<'a> StateWorkingSet<'a> {
 
     pub fn add_decl(&mut self, decl: Box<dyn Command>) -> DeclId {
         let name = decl.name().as_bytes().to_vec();
-        let input_type = decl.signature().input_type;
+        let input_type = decl.signature().get_input_type();
 
         self.delta.decls.push(decl);
         let decl_id = self.num_decls() - 1;
diff --git a/crates/nu-protocol/src/engine/overlay.rs b/crates/nu-protocol/src/engine/overlay.rs
index 640763bd37..0039cb291e 100644
--- a/crates/nu-protocol/src/engine/overlay.rs
+++ b/crates/nu-protocol/src/engine/overlay.rs
@@ -214,7 +214,23 @@ impl OverlayFrame {
         if let Some(decl) = self.decls.get(&(name, input) as &dyn DeclKey) {
             Some(*decl)
         } else {
-            self.decls.get(&(name, &Type::Any) as &dyn DeclKey).cloned()
+            // then fallback to not using the input type
+            for decl_key in self.decls.keys() {
+                if decl_key.0 == name {
+                    // FIXME: this fallback may give bad type information
+                    // in the case where no matching type is found. But, at
+                    // least we treat it as a found internal command rather
+                    // than an external command, which would cause further issues
+                    return Some(
+                        *self
+                            .decls
+                            .get(decl_key)
+                            .expect("internal error: found decl not actually found"),
+                    );
+                }
+            }
+
+            None
         }
     }
 }
diff --git a/crates/nu-protocol/src/plugin_signature.rs b/crates/nu-protocol/src/plugin_signature.rs
index 0185adefef..5c9dd06996 100644
--- a/crates/nu-protocol/src/plugin_signature.rs
+++ b/crates/nu-protocol/src/plugin_signature.rs
@@ -138,14 +138,8 @@ impl PluginSignature {
     }
 
     /// Changes the input type of the command signature
-    pub fn input_type(mut self, input_type: Type) -> PluginSignature {
-        self.sig = self.sig.input_type(input_type);
-        self
-    }
-
-    /// Changes the output type of the command signature
-    pub fn output_type(mut self, output_type: Type) -> PluginSignature {
-        self.sig = self.sig.output_type(output_type);
+    pub fn input_output_type(mut self, input_type: Type, output_type: Type) -> PluginSignature {
+        self.sig.input_output_types.push((input_type, output_type));
         self
     }
 
diff --git a/crates/nu-protocol/src/signature.rs b/crates/nu-protocol/src/signature.rs
index 071914d6ab..99026397d9 100644
--- a/crates/nu-protocol/src/signature.rs
+++ b/crates/nu-protocol/src/signature.rs
@@ -114,8 +114,6 @@ pub struct Signature {
     pub rest_positional: Option<PositionalArg>,
     pub vectorizes_over_list: bool,
     pub named: Vec<Flag>,
-    pub input_type: Type,
-    pub output_type: Type,
     pub input_output_types: Vec<(Type, Type)>,
     pub allow_variants_without_examples: bool,
     pub is_filter: bool,
@@ -215,8 +213,6 @@ impl Signature {
             optional_positional: vec![],
             rest_positional: None,
             vectorizes_over_list: false,
-            input_type: Type::Any,
-            output_type: Type::Any,
             input_output_types: vec![],
             allow_variants_without_examples: false,
             named: vec![],
@@ -227,6 +223,46 @@ impl Signature {
         }
     }
 
+    // Gets the input type from the signature
+    pub fn get_input_type(&self) -> Type {
+        match self.input_output_types.len() {
+            0 => Type::Any,
+            1 => self.input_output_types[0].0.clone(),
+            _ => {
+                let first = &self.input_output_types[0].0;
+                if self
+                    .input_output_types
+                    .iter()
+                    .all(|(input, _)| input == first)
+                {
+                    first.clone()
+                } else {
+                    Type::Any
+                }
+            }
+        }
+    }
+
+    // Gets the output type from the signature
+    pub fn get_output_type(&self) -> Type {
+        match self.input_output_types.len() {
+            0 => Type::Any,
+            1 => self.input_output_types[0].1.clone(),
+            _ => {
+                let first = &self.input_output_types[0].1;
+                if self
+                    .input_output_types
+                    .iter()
+                    .all(|(_, output)| output == first)
+                {
+                    first.clone()
+                } else {
+                    Type::Any
+                }
+            }
+        }
+    }
+
     // Add a default help option to a signature
     pub fn add_help(mut self) -> Signature {
         // default help flag
@@ -423,14 +459,8 @@ impl Signature {
     }
 
     /// Changes the input type of the command signature
-    pub fn input_type(mut self, input_type: Type) -> Signature {
-        self.input_type = input_type;
-        self
-    }
-
-    /// Changes the output type of the command signature
-    pub fn output_type(mut self, output_type: Type) -> Signature {
-        self.output_type = output_type;
+    pub fn input_output_type(mut self, input_type: Type, output_type: Type) -> Signature {
+        self.input_output_types.push((input_type, output_type));
         self
     }
 
diff --git a/crates/nu-std/std/xml.nu b/crates/nu-std/std/xml.nu
index 83ad08e2dd..b52dbe329b 100644
--- a/crates/nu-std/std/xml.nu
+++ b/crates/nu-std/std/xml.nu
@@ -19,7 +19,7 @@ export def xaccess [
     # In xpath first element in path is applied to root element
     # this way it is possible to apply first step to root element
     # of nu xml without unrolling one step of loop
-    mut values = ()
+    mut values: any = ()
     $values = {content: [ { content: $input } ] }
     for $step in ($path) {
         match ($step | describe) {
@@ -66,7 +66,7 @@ def xupdate-string-step [ step: string rest: list updater: closure ] {
 
     let new_values = ($to_update.item | xupdate-internal $rest $updater)
 
-    mut reenumerated_new_values = ($to_update.index | zip $new_values | each {|x| {index: $x.0 item: $x.1}})
+    mut reenumerated_new_values: any = ($to_update.index | zip $new_values | each {|x| {index: $x.0 item: $x.1}})
 
     mut new_content = []
     for it in ($input.content | enumerate) {
diff --git a/src/tests/test_parser.rs b/src/tests/test_parser.rs
index 3382aa9c7a..2d97406891 100644
--- a/src/tests/test_parser.rs
+++ b/src/tests/test_parser.rs
@@ -576,3 +576,8 @@ fn filesize_with_underscores_3() -> TestResult {
 fn filesize_is_not_hex() -> TestResult {
     run_test("0x42b", "1067")
 }
+
+#[test]
+fn let_variable_type_mismatch() -> TestResult {
+    fail_test(r#"let x: int = "foo""#, "expected int, found string")
+}