[PERF] check if walking the bodies is the expensive part

Author: oli-obk

compiler/rustc_ty_utils/src/opaque_types.rs

@@ -317,7 +317,9 @@ fn opaque_types_defined_by<'tcx>(
         | DefKind::Const
         | DefKind::AssocConst
         | DefKind::AnonConst => {
-            collector.collect_taits_declared_in_body();
+            if tcx.features().type_alias_impl_trait {
+                collector.collect_taits_declared_in_body();
+            }
         }
         DefKind::OpaqueTy
         | DefKind::TyAlias

tests/ui/pattern/usefulness/issue-119493-type-error-ice.rs

@@ -9,5 +9,7 @@ fn foo() {
     type U = impl Copy;
     //~^ ERROR `impl Trait` in type aliases is unstable
     let foo: U = Foo(());
+    //~^ ERROR mismatched types
     let Foo(()) = foo;
+    //~^ ERROR mismatched types
 }

tests/ui/pattern/usefulness/issue-119493-type-error-ice.stderr

@@ -25,7 +25,45 @@ LL |     type U = impl Copy;
    = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error: aborting due to 3 previous errors
+error[E0308]: mismatched types
+  --> $DIR/issue-119493-type-error-ice.rs:11:18
+   |
+LL |     type U = impl Copy;
+   |              --------- the expected opaque type
+LL |
+LL |     let foo: U = Foo(());
+   |              -   ^^^^^^^ expected opaque type, found `Foo`
+   |              |
+   |              expected due to this
+   |
+   = note: expected opaque type `U`
+                   found struct `Foo`
+note: this item must have the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/issue-119493-type-error-ice.rs:3:4
+   |
+LL | fn foo() {
+   |    ^^^
+
+error[E0308]: mismatched types
+  --> $DIR/issue-119493-type-error-ice.rs:13:9
+   |
+LL |     type U = impl Copy;
+   |              --------- the expected opaque type
+...
+LL |     let Foo(()) = foo;
+   |         ^^^^^^^   --- this expression has type `U`
+   |         |
+   |         expected opaque type, found `Foo`
+   |
+   = note: expected opaque type `U`
+                   found struct `Foo`
+note: this item must have the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/issue-119493-type-error-ice.rs:3:4
+   |
+LL | fn foo() {
+   |    ^^^
+
+error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0412, E0658.
-For more information about an error, try `rustc --explain E0412`.
+Some errors have detailed explanations: E0308, E0412, E0658.
+For more information about an error, try `rustc --explain E0308`.

tests/ui/pattern/usefulness/issue-119778-type-error-ice.rs

@@ -9,5 +9,7 @@ fn foo() {
     type U = impl Copy;
     //~^ ERROR `impl Trait` in type aliases is unstable
     let foo: U = Foo(());
+    //~^ ERROR mismatched types
     let Foo(()) = foo;
+    //~^ ERROR mismatched types
 }

tests/ui/pattern/usefulness/issue-119778-type-error-ice.stderr

@@ -30,7 +30,45 @@ LL |     type U = impl Copy;
    = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error: aborting due to 3 previous errors
+error[E0308]: mismatched types
+  --> $DIR/issue-119778-type-error-ice.rs:11:18
+   |
+LL |     type U = impl Copy;
+   |              --------- the expected opaque type
+LL |
+LL |     let foo: U = Foo(());
+   |              -   ^^^^^^^ expected opaque type, found `Foo`
+   |              |
+   |              expected due to this
+   |
+   = note: expected opaque type `U`
+                   found struct `Foo`
+note: this item must have the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/issue-119778-type-error-ice.rs:3:4
+   |
+LL | fn foo() {
+   |    ^^^
+
+error[E0308]: mismatched types
+  --> $DIR/issue-119778-type-error-ice.rs:13:9
+   |
+LL |     type U = impl Copy;
+   |              --------- the expected opaque type
+...
+LL |     let Foo(()) = foo;
+   |         ^^^^^^^   --- this expression has type `U`
+   |         |
+   |         expected opaque type, found `Foo`
+   |
+   = note: expected opaque type `U`
+                   found struct `Foo`
+note: this item must have the opaque type in its signature in order to be able to register hidden types
+  --> $DIR/issue-119778-type-error-ice.rs:3:4
+   |
+LL | fn foo() {
+   |    ^^^
+
+error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0425, E0658.
-For more information about an error, try `rustc --explain E0425`.
+Some errors have detailed explanations: E0308, E0425, E0658.
+For more information about an error, try `rustc --explain E0308`.