Rollup merge of #96868 - nrc:turbo-stable, r=jhpratt,nbdd0121,nagisa

Stabilize explicit_generic_args_with_impl_trait

This is a stabilisation PR for `explicit_generic_args_with_impl_trait`.

* [tracking issue](https://github.com/rust-lang/rust/issues/83701)
  - [Stabilisation report](https://github.com/rust-lang/rust/issues/83701#issuecomment-1109949897)
  - [FCP entered](https://github.com/rust-lang/rust/issues/83701#issuecomment-1120285703)
* [implementation PR](https://github.com/rust-lang/rust/pull/86176)
* [Reference PR](https://github.com/rust-lang/reference/pull/1212)
* There is no mention of using the turbofish operator in the book (other than an entry in the operator list in the appendix), so there is no documentation to change/add there, unless we felt like we should add a section on using turbofish, but that seems orthogonal to `explicit_generic_args_with_impl_trait`

compiler/rustc_error_codes/src/error_codes/E0632.md

@@ -1,9 +1,11 @@
+#### Note: this error code is no longer emitted by the compiler.
+
 An explicit generic argument was provided when calling a function that
 uses `impl Trait` in argument position.
 
 Erroneous code example:
 
-```compile_fail,E0632
+```ignore (no longer an error)
 fn foo<T: Copy>(a: T, b: impl Clone) {}
 
 foo::<i32>(0i32, "abc".to_string());

compiler/rustc_error_messages/locales/en-US/typeck.ftl

@@ -95,12 +95,6 @@ typeck-expected-return-type = expected `{$expected}` because of return type
 typeck-unconstrained-opaque-type = unconstrained opaque type
     .note = `{$name}` must be used in combination with a concrete type within the same module
 
-typeck-explicit-generic-args-with-impl-trait =
-    cannot provide explicit generic arguments when `impl Trait` is used in argument position
-    .label = 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
-
 typeck-missing-type-params =
     the type {$parameterCount ->
         [one] parameter

compiler/rustc_feature/src/accepted.rs

@@ -142,6 +142,8 @@ declare_features! (
     (accepted, dyn_trait, "1.27.0", Some(44662), None),
     /// Allows integer match exhaustiveness checking (RFC 2591).
     (accepted, exhaustive_integer_patterns, "1.33.0", Some(50907), None),
+    /// Allows explicit generic arguments specification with `impl Trait` present.
+    (accepted, explicit_generic_args_with_impl_trait, "1.63.0", Some(83701), None),
     /// Allows arbitrary expressions in key-value attributes at parse time.
     (accepted, extended_key_value_attributes, "1.54.0", Some(78835), None),
     /// Allows resolving absolute paths as paths from other crates.

compiler/rustc_feature/src/active.rs

@@ -383,8 +383,6 @@ declare_features! (
     (active, exclusive_range_pattern, "1.11.0", Some(37854), None),
     /// Allows exhaustive pattern matching on types that contain uninhabited types.
     (active, exhaustive_patterns, "1.13.0", Some(51085), None),
-    /// Allows explicit generic arguments specification with `impl Trait` present.
-    (active, explicit_generic_args_with_impl_trait, "1.56.0", Some(83701), None),
     /// Allows defining `extern type`s.
     (active, extern_types, "1.23.0", Some(43467), None),
     /// Allows the use of `#[ffi_const]` on foreign functions.

compiler/rustc_typeck/src/astconv/generics.rs

@@ -3,7 +3,7 @@ use crate::astconv::{
     AstConv, CreateSubstsForGenericArgsCtxt, ExplicitLateBound, GenericArgCountMismatch,
     GenericArgCountResult, GenericArgPosition,
 };
-use crate::errors::{AssocTypeBindingNotAllowed, ExplicitGenericArgsWithImplTrait};
+use crate::errors::AssocTypeBindingNotAllowed;
 use crate::structured_errors::{GenericArgsInfo, StructuredDiagnostic, WrongNumberOfGenericArgs};
 use rustc_ast::ast::ParamKindOrd;
 use rustc_errors::{struct_span_err, Applicability, Diagnostic, MultiSpan};
@@ -397,8 +397,6 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         is_method_call: IsMethodCall,
     ) -> GenericArgCountResult {
         let empty_args = hir::GenericArgs::none();
-        let suppress_mismatch = Self::check_impl_trait(tcx, seg, generics);
-
         let gen_args = seg.args.unwrap_or(&empty_args);
         let gen_pos = if is_method_call == IsMethodCall::Yes {
             GenericArgPosition::MethodCall
@@ -406,10 +404,17 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             GenericArgPosition::Value
         };
         let has_self = generics.parent.is_none() && generics.has_self;
-        let infer_args = seg.infer_args || suppress_mismatch;
 
         Self::check_generic_arg_count(
-            tcx, span, def_id, seg, generics, gen_args, gen_pos, has_self, infer_args,
+            tcx,
+            span,
+            def_id,
+            seg,
+            generics,
+            gen_args,
+            gen_pos,
+            has_self,
+            seg.infer_args,
         )
     }
 
@@ -431,19 +436,14 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         let param_counts = gen_params.own_counts();
 
         // Subtracting from param count to ensure type params synthesized from `impl Trait`
-        // cannot be explicitly specified even with `explicit_generic_args_with_impl_trait`
+        // cannot be explicitly specified.
-        // feature enabled.
+        let synth_type_param_count = gen_params
-        let synth_type_param_count = if tcx.features().explicit_generic_args_with_impl_trait {
+            .params
-            gen_params
+            .iter()
-                .params
+            .filter(|param| {
-                .iter()
+                matches!(param.kind, ty::GenericParamDefKind::Type { synthetic: true, .. })
-                .filter(|param| {
+            })
-                    matches!(param.kind, ty::GenericParamDefKind::Type { synthetic: true, .. })
+            .count();
-                })
-                .count()
-        } else {
-            0
-        };
         let named_type_param_count =
             param_counts.types - has_self as usize - synth_type_param_count;
         let infer_lifetimes =
@@ -611,40 +611,6 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         }
     }
 
-    /// Report error if there is an explicit type parameter when using `impl Trait`.
-    pub(crate) fn check_impl_trait(
-        tcx: TyCtxt<'_>,
-        seg: &hir::PathSegment<'_>,
-        generics: &ty::Generics,
-    ) -> bool {
-        if seg.infer_args || tcx.features().explicit_generic_args_with_impl_trait {
-            return false;
-        }
-
-        let impl_trait = generics.has_impl_trait();
-
-        if impl_trait {
-            let spans = seg
-                .args()
-                .args
-                .iter()
-                .filter_map(|arg| match arg {
-                    GenericArg::Infer(_) | GenericArg::Type(_) | GenericArg::Const(_) => {
-                        Some(arg.span())
-                    }
-                    _ => None,
-                })
-                .collect::<Vec<_>>();
-
-            tcx.sess.emit_err(ExplicitGenericArgsWithImplTrait {
-                spans,
-                is_nightly_build: tcx.sess.is_nightly_build().then_some(()),
-            });
-        }
-
-        impl_trait
-    }
-
     /// Emits an error regarding forbidden type binding associations
     pub fn prohibit_assoc_ty_binding(tcx: TyCtxt<'_>, span: Span) {
         tcx.sess.emit_err(AssocTypeBindingNotAllowed { span });

compiler/rustc_typeck/src/errors.rs

@@ -241,17 +241,6 @@ pub struct UnconstrainedOpaqueType {
     pub name: Symbol,
 }
 
-#[derive(SessionDiagnostic)]
-#[error(code = "E0632", slug = "typeck-explicit-generic-args-with-impl-trait")]
-#[note]
-pub struct ExplicitGenericArgsWithImplTrait {
-    #[primary_span]
-    #[label]
-    pub spans: Vec<Span>,
-    #[help]
-    pub is_nightly_build: Option<()>,
-}
-
 pub struct MissingTypeParams {
     pub span: Span,
     pub def_span: Span,

src/doc/unstable-book/src/language-features/explicit-generic-args-with-impl-trait.md

@@ -1,53 +0,0 @@
-# `explicit_generic_args_with_impl_trait`
-
-The tracking issue for this feature is: [#83701]
-
-[#83701]: https://github.com/rust-lang/rust/issues/83701
-
-------------------------
-
-The `explicit_generic_args_with_impl_trait` feature gate lets you specify generic arguments even
-when `impl Trait` is used in argument position.
-
-A simple example is:
-
-```rust
-#![feature(explicit_generic_args_with_impl_trait)]
-
-fn foo<T: ?Sized>(_f: impl AsRef<T>) {}
-
-fn main() {
-    foo::<str>("".to_string());
-}
-```
-
-This is currently rejected:
-
-```text
-error[E0632]: cannot provide explicit generic arguments when `impl Trait` is used in argument position
- --> src/main.rs:6:11
-  |
-6 |     foo::<str>("".to_string());
-  |           ^^^ explicit generic argument not allowed
-
-```
-
-However it would compile if `explicit_generic_args_with_impl_trait` is enabled.
-
-Note that the synthetic type parameters from `impl Trait` are still implicit and you
-cannot explicitly specify these:
-
-```rust,compile_fail
-#![feature(explicit_generic_args_with_impl_trait)]
-
-fn foo<T: ?Sized>(_f: impl AsRef<T>) {}
-fn bar<T: ?Sized, F: AsRef<T>>(_f: F) {}
-
-fn main() {
-    bar::<str, _>("".to_string()); // Okay
-    bar::<str, String>("".to_string()); // Okay
-
-    foo::<str>("".to_string()); // Okay
-    foo::<str, String>("".to_string()); // Error, you cannot specify `impl Trait` explicitly
-}
-```

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

@@ -1,12 +0,0 @@
-error[E0632]: cannot provide explicit generic arguments when `impl Trait` is used in argument position
-  --> $DIR/impl-trait-with-const-arguments.rs:18:20
-   |
-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
-
-For more information about this error, try `rustc --explain E0632`.

src/test/ui/impl-trait/explicit-generic-args-with-impl-trait/const-args.rs

@@ -1,3 +1,5 @@
+// check-pass
+
 trait Usizer {
     fn m(self) -> usize;
 }
@@ -16,5 +18,4 @@ impl Usizer for Usizable {
 
 fn main() {
     assert_eq!(f::<4usize>(Usizable), 20usize);
-//~^ ERROR cannot provide explicit generic arguments when `impl Trait` is used in argument position
 }

src/test/ui/impl-trait/explicit-generic-args-with-impl-trait/explicit-generic-args-for-impl.rs

@@ -1,5 +1,3 @@
-#![feature(explicit_generic_args_with_impl_trait)]
-
 fn foo<T: ?Sized>(_f: impl AsRef<T>) {}
 
 fn main() {

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

@@ -1,5 +1,5 @@
 error[E0107]: this function takes 1 generic argument but 2 generic arguments were supplied
-  --> $DIR/explicit-generic-args-for-impl.rs:6:5
+  --> $DIR/explicit-generic-args-for-impl.rs:4:5
    |
 LL |     foo::<str, String>("".to_string());
    |     ^^^        ------ help: remove this generic argument
@@ -7,7 +7,7 @@ LL |     foo::<str, String>("".to_string());
    |     expected 1 generic argument
    |
 note: function defined here, with 1 generic parameter: `T`
-  --> $DIR/explicit-generic-args-for-impl.rs:3:4
+  --> $DIR/explicit-generic-args-for-impl.rs:1:4
    |
 LL | fn foo<T: ?Sized>(_f: impl AsRef<T>) {}
    |    ^^^ -

src/test/ui/impl-trait/explicit-generic-args-with-impl-trait/explicit-generic-args.rs

@@ -1,7 +1,5 @@
 // check-pass
 
-#![feature(explicit_generic_args_with_impl_trait)]
-
 fn foo<T: ?Sized>(_f: impl AsRef<T>) {}
 
 fn main() {

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

@@ -1,7 +0,0 @@
-// gate-test-explicit_generic_args_with_impl_trait
-
-fn foo<T: ?Sized>(_f: impl AsRef<T>) {}
-
-fn main() {
-    foo::<str>("".to_string()); //~ ERROR E0632
-}

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

@@ -1,12 +0,0 @@
-error[E0632]: cannot provide explicit generic arguments when `impl Trait` is used in argument position
-  --> $DIR/feature-gate.rs:6:11
-   |
-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
-
-For more information about this error, try `rustc --explain E0632`.

src/test/ui/impl-trait/explicit-generic-args-with-impl-trait/issue-87718.rs

@@ -1,7 +1,5 @@
 // check-pass
 
-#![feature(explicit_generic_args_with_impl_trait)]
-
 fn f<T: ?Sized>(_: impl AsRef<T>, _: impl AsRef<T>) {}
 
 fn main() {

src/test/ui/impl-trait/explicit-generic-args-with-impl-trait/not-enough-args.rs

@@ -1,5 +1,3 @@
-#![feature(explicit_generic_args_with_impl_trait)]
-
 fn f<T: ?Sized, U: ?Sized>(_: impl AsRef<T>, _: impl AsRef<U>) {}
 
 fn main() {

src/test/ui/impl-trait/explicit-generic-args-with-impl-trait/not-enough-args.stderr

@@ -1,5 +1,5 @@
 error[E0107]: this function takes 2 generic arguments but 1 generic argument was supplied
-  --> $DIR/not-enough-args.rs:6:5
+  --> $DIR/not-enough-args.rs:4:5
    |
 LL |     f::<[u8]>("a", b"a");
    |     ^   ---- supplied 1 generic argument
@@ -7,7 +7,7 @@ LL |     f::<[u8]>("a", b"a");
    |     expected 2 generic arguments
    |
 note: function defined here, with 2 generic parameters: `T`, `U`
-  --> $DIR/not-enough-args.rs:3:4
+  --> $DIR/not-enough-args.rs:1:4
    |
 LL | fn f<T: ?Sized, U: ?Sized>(_: impl AsRef<T>, _: impl AsRef<U>) {}
    |    ^ -          -

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

@@ -1,7 +0,0 @@
-use std::fmt::Debug;
-
-fn foo<T>(x: impl Debug) { }
-
-fn main() {
-    foo::<String>('a'); //~ ERROR cannot provide explicit generic arguments
-}

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

@@ -1,12 +0,0 @@
-error[E0632]: cannot provide explicit generic arguments when `impl Trait` is used in argument position
-  --> $DIR/universal-issue-48703.rs:6:11
-   |
-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
-
-For more information about this error, try `rustc --explain E0632`.

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

@@ -1,17 +0,0 @@
-use std::any::Any;
-pub struct EventHandler {
-}
-
-impl EventHandler
-{
-    pub fn handle_event<T: Any>(&mut self, _efunc: impl FnMut(T)) {}
-}
-
-struct TestEvent(i32);
-
-fn main() {
-    let mut evt = EventHandler {};
-    evt.handle_event::<TestEvent, fn(TestEvent)>(|_evt| {
-        //~^ ERROR cannot provide explicit generic arguments
-    });
-}

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

@@ -1,14 +0,0 @@
-error[E0632]: cannot provide explicit generic arguments when `impl Trait` is used in argument position
-  --> $DIR/universal-turbofish-in-method-issue-50950.rs:14:24
-   |
-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
-
-For more information about this error, try `rustc --explain E0632`.

src/test/ui/inference/issue-83606.rs

@@ -5,6 +5,6 @@ fn foo<const N: usize>(_: impl std::fmt::Display) -> [usize; N] {
 }
 
 fn main() {
-    let _ = foo("foo"); //<- Do not suggest `foo::<N>("foo");`!
+    let _ = foo("foo");
     //~^ ERROR: type annotations needed for `[usize; _]`
 }

src/test/ui/inference/issue-83606.stderr

@@ -1,12 +1,12 @@
 error[E0282]: type annotations needed for `[usize; _]`
   --> $DIR/issue-83606.rs:8:9
    |
-LL |     let _ = foo("foo"); //<- Do not suggest `foo::<N>("foo");`!
+LL |     let _ = foo("foo");
    |         ^
    |
 help: consider giving this pattern a type, where the the value of const parameter `N` is specified
    |
-LL |     let _: [usize; _] = foo("foo"); //<- Do not suggest `foo::<N>("foo");`!
+LL |     let _: [usize; _] = foo("foo");
    |          ++++++++++++
 
 error: aborting due to previous error