Add a note about feature(explicit_generic_args_with_impl_trait) to the relevant error message

Author: meithecatte

compiler/rustc_typeck/src/astconv/generics.rs

@@ -672,6 +672,17 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 err.span_label(span, "explicit generic argument not allowed");
             }
 
+            err.note(
+                "see issue #83701 <https://github.com/rust-lang/rust/issues/83701> \
+                 for more information",
+            );
+            if tcx.sess.is_nightly_build() {
+                err.help(
+                    "add `#![feature(explicit_generic_args_with_impl_trait)]` \
+                     to the crate attributes to enable",
+                );
+            }
+
             err.emit();
         }
 

src/test/ui/const-generics/impl-trait-with-const-arguments.stderr

@@ -3,6 +3,9 @@ error[E0632]: cannot provide explicit generic arguments when `impl Trait` is use
    |
 LL |     assert_eq!(f::<4usize>(Usizable), 20usize);
    |                    ^^^^^^ explicit generic argument not allowed
+   |
+   = note: see issue #83701 <https://github.com/rust-lang/rust/issues/83701> for more information
+   = help: add `#![feature(explicit_generic_args_with_impl_trait)]` to the crate attributes to enable
 
 error: aborting due to previous error
 

src/test/ui/impl-trait/explicit-generic-args-with-impl-trait/feature-gate.stderr

@@ -3,6 +3,9 @@ error[E0632]: cannot provide explicit generic arguments when `impl Trait` is use
    |
 LL |     foo::<str>("".to_string());
    |           ^^^ explicit generic argument not allowed
+   |
+   = note: see issue #83701 <https://github.com/rust-lang/rust/issues/83701> for more information
+   = help: add `#![feature(explicit_generic_args_with_impl_trait)]` to the crate attributes to enable
 
 error: aborting due to previous error
 

src/test/ui/impl-trait/issues/universal-issue-48703.stderr

@@ -3,6 +3,9 @@ error[E0632]: cannot provide explicit generic arguments when `impl Trait` is use
    |
 LL |     foo::<String>('a');
    |           ^^^^^^ explicit generic argument not allowed
+   |
+   = note: see issue #83701 <https://github.com/rust-lang/rust/issues/83701> for more information
+   = help: add `#![feature(explicit_generic_args_with_impl_trait)]` to the crate attributes to enable
 
 error: aborting due to previous error
 

src/test/ui/impl-trait/issues/universal-turbofish-in-method-issue-50950.stderr

@@ -5,6 +5,9 @@ LL |     evt.handle_event::<TestEvent, fn(TestEvent)>(|_evt| {
    |                        ^^^^^^^^^  ^^^^^^^^^^^^^ explicit generic argument not allowed
    |                        |
    |                        explicit generic argument not allowed
+   |
+   = note: see issue #83701 <https://github.com/rust-lang/rust/issues/83701> for more information
+   = help: add `#![feature(explicit_generic_args_with_impl_trait)]` to the crate attributes to enable
 
 error: aborting due to previous error
 

src/test/ui/synthetic-param.stderr

@@ -3,18 +3,27 @@ error[E0632]: cannot provide explicit generic arguments when `impl Trait` is use
    |
 LL |     func::<u8>(42);
    |            ^^ explicit generic argument not allowed
+   |
+   = note: see issue #83701 <https://github.com/rust-lang/rust/issues/83701> for more information
+   = help: add `#![feature(explicit_generic_args_with_impl_trait)]` to the crate attributes to enable
 
 error[E0632]: cannot provide explicit generic arguments when `impl Trait` is used in argument position
   --> $DIR/synthetic-param.rs:23:17
    |
 LL |     Foo::func::<u8>(42);
    |                 ^^ explicit generic argument not allowed
+   |
+   = note: see issue #83701 <https://github.com/rust-lang/rust/issues/83701> for more information
+   = help: add `#![feature(explicit_generic_args_with_impl_trait)]` to the crate attributes to enable
 
 error[E0632]: cannot provide explicit generic arguments when `impl Trait` is used in argument position
   --> $DIR/synthetic-param.rs:26:23
    |
 LL |     Bar::<i8>::func::<u8>(42);
    |                       ^^ explicit generic argument not allowed
+   |
+   = note: see issue #83701 <https://github.com/rust-lang/rust/issues/83701> for more information
+   = help: add `#![feature(explicit_generic_args_with_impl_trait)]` to the crate attributes to enable
 
 error: aborting due to 3 previous errors