diff --git a/Cargo.toml b/Cargo.toml
index f49593db5f..8d861f2a18 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -181,7 +181,6 @@ non_canonical_partial_ord_impl = "allow"
 self_named_constructors = "allow"
 too_many_arguments = "allow"
 type_complexity = "allow"
-unnecessary_cast = "allow"
 unnecessary_filter_map = "allow"
 unnecessary_lazy_evaluations = "allow"
 unnecessary_mut_passed = "allow"
diff --git a/crates/hir-def/src/import_map.rs b/crates/hir-def/src/import_map.rs
index 5d096c7a5e..c698510ca9 100644
--- a/crates/hir-def/src/import_map.rs
+++ b/crates/hir-def/src/import_map.rs
@@ -297,7 +297,7 @@ impl SearchMode {
             SearchMode::Exact => candidate.eq_ignore_ascii_case(query),
             SearchMode::Prefix => {
                 query.len() <= candidate.len() && {
-                    let prefix = &candidate[..query.len() as usize];
+                    let prefix = &candidate[..query.len()];
                     if case_sensitive {
                         prefix == query
                     } else {
@@ -446,7 +446,7 @@ fn search_maps(
             let end = (value & 0xFFFF_FFFF) as usize;
             let start = (value >> 32) as usize;
             let ImportMap { item_to_info_map, importables, .. } = &*import_maps[import_map_idx];
-            let importables = &importables[start as usize..end];
+            let importables = &importables[start..end];
 
             let iter = importables
                 .iter()
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 2c5474c5c8..1e21045e98 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -903,7 +903,7 @@ fn emit_def_diagnostic_(
         }
         DefDiagnosticKind::InvalidDeriveTarget { ast, id } => {
             let node = ast.to_node(db.upcast());
-            let derive = node.attrs().nth(*id as usize);
+            let derive = node.attrs().nth(*id);
             match derive {
                 Some(derive) => {
                     acc.push(
@@ -918,7 +918,7 @@ fn emit_def_diagnostic_(
         }
         DefDiagnosticKind::MalformedDerive { ast, id } => {
             let node = ast.to_node(db.upcast());
-            let derive = node.attrs().nth(*id as usize);
+            let derive = node.attrs().nth(*id);
             match derive {
                 Some(derive) => {
                     acc.push(