Merge #2657

2657: Omit closure parameters in closure type display strings r=flodiebold a=SomeoneToIgnore

Part of https://github.com/rust-analyzer/rust-analyzer/issues/1946

I wonder, should we display the the closure trait (Fn/FnMut/FnOnce) in inlay hints instead of `|...|` at all?

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>

crates/ra_hir_ty/src/display.rs

@@ -10,7 +10,7 @@ pub struct HirFormatter<'a, 'b, DB> {
     buf: String,
     curr_size: usize,
     max_size: Option<usize>,
-    should_display_default_types: bool,
+    omit_verbose_types: bool,
 }
 
 pub trait HirDisplay {
@@ -20,7 +20,7 @@ pub trait HirDisplay {
     where
         Self: Sized,
     {
-        HirDisplayWrapper(db, self, None, true)
+        HirDisplayWrapper(db, self, None, false)
     }
 
     fn display_truncated<'a, DB>(
@@ -31,7 +31,7 @@ pub trait HirDisplay {
     where
         Self: Sized,
     {
-        HirDisplayWrapper(db, self, max_size, false)
+        HirDisplayWrapper(db, self, max_size, true)
     }
 }
 
@@ -74,8 +74,8 @@ where
         }
     }
 
-    pub fn should_display_default_types(&self) -> bool {
+    pub fn omit_verbose_types(&self) -> bool {
-        self.should_display_default_types
+        self.omit_verbose_types
     }
 }
 
@@ -93,7 +93,7 @@ where
             buf: String::with_capacity(20),
             curr_size: 0,
             max_size: self.2,
-            should_display_default_types: self.3,
+            omit_verbose_types: self.3,
         })
     }
 }

crates/ra_hir_ty/src/lib.rs

@@ -821,6 +821,8 @@ impl TypeWalk for Ty {
     }
 }
 
+const TYPE_HINT_TRUNCATION: &str = "…";
+
 impl HirDisplay for &Ty {
     fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
         HirDisplay::hir_fmt(*self, f)
@@ -830,7 +832,7 @@ impl HirDisplay for &Ty {
 impl HirDisplay for ApplicationTy {
     fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
         if f.should_truncate() {
-            return write!(f, "…");
+            return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
 
         match self.ctor {
@@ -908,9 +910,7 @@ impl HirDisplay for ApplicationTy {
                     write!(f, "<")?;
 
                     let mut non_default_parameters = Vec::with_capacity(self.parameters.len());
-                    let parameters_to_write = if f.should_display_default_types() {
+                    let parameters_to_write = if f.omit_verbose_types() {
-                        self.parameters.0.as_ref()
-                    } else {
                         match self
                             .ctor
                             .as_generic_def()
@@ -935,6 +935,8 @@ impl HirDisplay for ApplicationTy {
                                 &non_default_parameters
                             }
                         }
+                    } else {
+                        self.parameters.0.as_ref()
                     };
 
                     f.write_joined(parameters_to_write, ", ")?;
@@ -959,9 +961,16 @@ impl HirDisplay for ApplicationTy {
                 let sig = self.parameters[0]
                     .callable_sig(f.db)
                     .expect("first closure parameter should contain signature");
-                write!(f, "|")?;
+                let return_type_hint = sig.ret().display(f.db);
-                f.write_joined(sig.params(), ", ")?;
+                if sig.params().is_empty() {
-                write!(f, "| -> {}", sig.ret().display(f.db))?;
+                    write!(f, "|| -> {}", return_type_hint)?;
+                } else if f.omit_verbose_types() {
+                    write!(f, "|{}| -> {}", TYPE_HINT_TRUNCATION, return_type_hint)?;
+                } else {
+                    write!(f, "|")?;
+                    f.write_joined(sig.params(), ", ")?;
+                    write!(f, "| -> {}", return_type_hint)?;
+                };
             }
         }
         Ok(())
@@ -971,7 +980,7 @@ impl HirDisplay for ApplicationTy {
 impl HirDisplay for ProjectionTy {
     fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
         if f.should_truncate() {
-            return write!(f, "…");
+            return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
 
         let trait_name = f.db.trait_data(self.trait_(f.db)).name.clone();
@@ -989,7 +998,7 @@ impl HirDisplay for ProjectionTy {
 impl HirDisplay for Ty {
     fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
         if f.should_truncate() {
-            return write!(f, "…");
+            return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
 
         match self {
@@ -1074,7 +1083,7 @@ impl HirDisplay for Ty {
 impl TraitRef {
     fn hir_fmt_ext(&self, f: &mut HirFormatter<impl HirDatabase>, use_as: bool) -> fmt::Result {
         if f.should_truncate() {
-            return write!(f, "…");
+            return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
 
         self.substs[0].hir_fmt(f)?;
@@ -1108,7 +1117,7 @@ impl HirDisplay for &GenericPredicate {
 impl HirDisplay for GenericPredicate {
     fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
         if f.should_truncate() {
-            return write!(f, "…");
+            return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
 
         match self {

crates/ra_ide/src/inlay_hints.rs

@@ -293,7 +293,7 @@ fn main() {
     }
 
     #[test]
-    fn closure_parameter() {
+    fn closure_parameters() {
         let (analysis, file_id) = single_file(
             r#"
 fn main() {
@@ -301,6 +301,11 @@ fn main() {
     (0..2).for_each(|increment| {
         start += increment;
     })
+
+    let multiply = |a, b, c, d| a * b * c * d;
+    let _: i32 = multiply(1, 2, 3, 4);
+
+    let return_42 = || 42;
 }"#,
         );
 
@@ -316,6 +321,36 @@ fn main() {
                 kind: TypeHint,
                 label: "i32",
             },
+            InlayHint {
+                range: [114; 122),
+                kind: TypeHint,
+                label: "|…| -> i32",
+            },
+            InlayHint {
+                range: [126; 127),
+                kind: TypeHint,
+                label: "i32",
+            },
+            InlayHint {
+                range: [129; 130),
+                kind: TypeHint,
+                label: "i32",
+            },
+            InlayHint {
+                range: [132; 133),
+                kind: TypeHint,
+                label: "i32",
+            },
+            InlayHint {
+                range: [135; 136),
+                kind: TypeHint,
+                label: "i32",
+            },
+            InlayHint {
+                range: [201; 210),
+                kind: TypeHint,
+                label: "|| -> i32",
+            },
         ]
         "###
         );