Stabilize anonymous_lifetime_in_impl_trait

compiler/rustc_feature/src/accepted.rs

@@ -57,6 +57,8 @@ declare_features! (
     (accepted, abi_thiscall, "1.73.0", None, None),
     /// Allows using ADX intrinsics from `core::arch::{x86, x86_64}`.
     (accepted, adx_target_feature, "1.61.0", Some(44839), None),
+    /// Allows using anonymous lifetimes in argument-position impl-trait.
+    (accepted, anonymous_lifetime_in_impl_trait, "CURRENT_RUSTC_VERSION", None, None),
     /// Allows explicit discriminants on non-unit enum variants.
     (accepted, arbitrary_enum_discriminant, "1.66.0", Some(60553), None),
     /// Allows using `sym` operands in inline assembly.

compiler/rustc_feature/src/active.rs

@@ -172,8 +172,6 @@ declare_features! (
     /// below (it has to be checked before expansion possibly makes
     /// macros disappear).
     (internal, allow_internal_unstable, "1.0.0", None, None),
-    /// Allows using anonymous lifetimes in argument-position impl-trait.
-    (active, anonymous_lifetime_in_impl_trait, "1.63.0", None, None),
     /// Allows identifying the `compiler_builtins` crate.
     (internal, compiler_builtins, "1.13.0", None, None),
     /// Allows writing custom MIR

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -21,7 +21,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, TyCtxt, TypeSuperVisitable, TypeVisitor};
 use rustc_session::lint;
 use rustc_span::def_id::DefId;
-use rustc_span::symbol::{sym, Ident};
+use rustc_span::symbol::Ident;
 use rustc_span::{Span, DUMMY_SP};
 use std::fmt;
 
@@ -1197,68 +1197,14 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                     break None;
                 }
 
-                Scope::Binder { ref bound_vars, scope_type, s, where_bound_origin, .. } => {
+                Scope::Binder { ref bound_vars, scope_type, s, .. } => {
                     if let Some(&def) = bound_vars.get(&region_def_id) {
                         break Some(def.shifted(late_depth));
                     }
                     match scope_type {
                         BinderScopeType::Normal => late_depth += 1,
                         BinderScopeType::Concatenating => {}
                     }
-                    // Fresh lifetimes in APIT used to be allowed in async fns and forbidden in
-                    // regular fns.
-                    if let Some(hir::PredicateOrigin::ImplTrait) = where_bound_origin
-                        && let hir::LifetimeName::Param(param_id) = lifetime_ref.res
-                        && let Some(generics) = self.tcx.hir().get_generics(self.tcx.local_parent(param_id))
-                        && let Some(param) = generics.params.iter().find(|p| p.def_id == param_id)
-                        && param.is_elided_lifetime()
-                        && !self.tcx.asyncness(lifetime_ref.hir_id.owner.def_id).is_async()
-                        && !self.tcx.features().anonymous_lifetime_in_impl_trait
-                    {
-                        let mut diag =  rustc_session::parse::feature_err(
-                            &self.tcx.sess.parse_sess,
-                            sym::anonymous_lifetime_in_impl_trait,
-                            lifetime_ref.ident.span,
-                            "anonymous lifetimes in `impl Trait` are unstable",
-                        );
-
-                        if let Some(generics) =
-                            self.tcx.hir().get_generics(lifetime_ref.hir_id.owner.def_id)
-                        {
-                            let new_param_sugg = if let Some(span) =
-                                generics.span_for_lifetime_suggestion()
-                            {
-                                (span, "'a, ".to_owned())
-                            } else {
-                                (generics.span, "<'a>".to_owned())
-                            };
-
-                            let lifetime_sugg = match lifetime_ref.suggestion_position() {
-                                (hir::LifetimeSuggestionPosition::Normal, span) => (span, "'a".to_owned()),
-                                (hir::LifetimeSuggestionPosition::Ampersand, span) => (span, "'a ".to_owned()),
-                                (hir::LifetimeSuggestionPosition::ElidedPath, span) => (span, "<'a>".to_owned()),
-                                (hir::LifetimeSuggestionPosition::ElidedPathArgument, span) => (span, "'a, ".to_owned()),
-                                (hir::LifetimeSuggestionPosition::ObjectDefault, span) => (span, "+ 'a".to_owned()),
-                            };
-                            let suggestions = vec![
-                                lifetime_sugg,
-                                new_param_sugg,
-                            ];
-
-                            diag.span_label(
-                                lifetime_ref.ident.span,
-                                "expected named lifetime parameter",
-                            );
-                            diag.multipart_suggestion(
-                                "consider introducing a named lifetime parameter",
-                                suggestions,
-                                rustc_errors::Applicability::MaybeIncorrect,
-                            );
-                        }
-
-                        diag.emit();
-                        return;
-                    }
                     scope = s;
                 }
 

tests/ui/associated-type-bounds/elision.rs

@@ -1,5 +1,4 @@
 #![feature(associated_type_bounds)]
-#![feature(anonymous_lifetime_in_impl_trait)]
 
 // The same thing should happen for constraints in dyn trait.
 fn f(x: &mut dyn Iterator<Item: Iterator<Item = &'_ ()>>) -> Option<&'_ ()> { x.next() }

tests/ui/associated-type-bounds/elision.stderr

@@ -1,5 +1,5 @@
 error[E0106]: missing lifetime specifier
-  --> $DIR/elision.rs:5:70
+  --> $DIR/elision.rs:4:70
    |
 LL | fn f(x: &mut dyn Iterator<Item: Iterator<Item = &'_ ()>>) -> Option<&'_ ()> { x.next() }
    |         ------------------------------------------------             ^^ expected named lifetime parameter
@@ -11,7 +11,7 @@ LL | fn f<'a>(x: &'a mut dyn Iterator<Item: Iterator<Item = &'a ()>>) -> Option<
    |     ++++     ++                                         ~~                  ~~
 
 error[E0308]: mismatched types
-  --> $DIR/elision.rs:5:79
+  --> $DIR/elision.rs:4:79
    |
 LL | fn f(x: &mut dyn Iterator<Item: Iterator<Item = &'_ ()>>) -> Option<&'_ ()> { x.next() }
    |                           -----------------------------      --------------   ^^^^^^^^ expected `Option<&()>`, found `Option<impl Iterator<Item = &'_ ()>>`

tests/ui/borrowck/anonymous-region-in-apit.rs

@@ -1,5 +1,3 @@
-#![feature(anonymous_lifetime_in_impl_trait)]
-
 trait Foo<T> {
     fn bar(self, baz: T);
 }

tests/ui/borrowck/anonymous-region-in-apit.stderr

@@ -1,5 +1,5 @@
 error[E0521]: borrowed data escapes outside of closure
-  --> $DIR/anonymous-region-in-apit.rs:8:17
+  --> $DIR/anonymous-region-in-apit.rs:6:17
    |
 LL | fn qux(foo: impl Foo<&str>) {
    |        --- lifetime `'2` appears in the type of `foo`

tests/ui/generic-associated-types/issue-95305.rs

@@ -2,7 +2,6 @@
 // Forbid it for now but proper support might be added
 // at some point in the future.
 
-#![feature(anonymous_lifetime_in_impl_trait)]
 trait Foo {
     type Item<'a>;
 }

tests/ui/generic-associated-types/issue-95305.stderr

@@ -1,5 +1,5 @@
 error[E0637]: `'_` cannot be used here
-  --> $DIR/issue-95305.rs:10:26
+  --> $DIR/issue-95305.rs:9:26
    |
 LL | fn foo(x: &impl Foo<Item<'_> = u32>) { }
    |                          ^^ `'_` is a reserved lifetime name

tests/ui/impl-trait/impl-trait-lifetimes.rs

@@ -0,0 +1,47 @@
+trait Foo<T> {
+    fn foo(&self, _: T) { }
+}
+
+mod foo {
+    fn fun(t: impl crate::Foo<&u32>, n: u32) {
+        t.foo(&n);
+        //~^ ERROR `n` does not live long enough
+    }
+}
+
+mod fun {
+    fn fun(t: impl Fn(&u32), n: u32) {
+        t(&n);
+    }
+}
+
+mod iterator_fun {
+    fn fun(t: impl Iterator<Item = impl Fn(&u32)>, n: u32) {
+        for elem in t {
+            elem(&n);
+        }
+    }
+}
+
+mod iterator_foo {
+    fn fun(t: impl Iterator<Item = impl crate::Foo<&u32>>, n: u32) {
+        for elem in t {
+            elem.foo(&n);
+            //~^ ERROR `n` does not live long enough
+        }
+    }
+}
+
+mod placeholder {
+    trait Placeholder<'a> {
+        fn foo(&self, _: &'a u32) {}
+    }
+
+    fn fun(t: impl Placeholder<'_>, n: u32) {
+        t.foo(&n);
+        //~^ ERROR `n` does not live long enough
+    }
+}
+
+fn main() {
+}

tests/ui/impl-trait/impl-trait-lifetimes.stderr

@@ -0,0 +1,43 @@
+error[E0597]: `n` does not live long enough
+  --> $DIR/impl-trait-lifetimes.rs:7:15
+   |
+LL |     fn fun(t: impl crate::Foo<&u32>, n: u32) {
+   |            - has type `t`            - binding `n` declared here
+LL |         t.foo(&n);
+   |         ------^^-
+   |         |     |
+   |         |     borrowed value does not live long enough
+   |         argument requires that `n` is borrowed for `'1`
+LL |
+LL |     }
+   |      - `n` dropped here while still borrowed
+
+error[E0597]: `n` does not live long enough
+  --> $DIR/impl-trait-lifetimes.rs:29:22
+   |
+LL |     fn fun(t: impl Iterator<Item = impl crate::Foo<&u32>>, n: u32) {
+   |                                                            - binding `n` declared here
+LL |         for elem in t {
+LL |             elem.foo(&n);
+   |                      ^^ borrowed value does not live long enough
+...
+LL |     }
+   |      - `n` dropped here while still borrowed
+
+error[E0597]: `n` does not live long enough
+  --> $DIR/impl-trait-lifetimes.rs:41:15
+   |
+LL |     fn fun(t: impl Placeholder<'_>, n: u32) {
+   |            - has type `t`           - binding `n` declared here
+LL |         t.foo(&n);
+   |         ------^^-
+   |         |     |
+   |         |     borrowed value does not live long enough
+   |         argument requires that `n` is borrowed for `'1`
+LL |
+LL |     }
+   |      - `n` dropped here while still borrowed
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0597`.

tests/ui/suggestions/impl-trait-missing-lifetime-gated.rs → tests/ui/impl-trait/impl-trait-missing-lifetime-gated.rs

@@ -4,11 +4,9 @@
 
 mod elided {
     fn f(_: impl Iterator<Item = &()>) {}
-    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
 
     fn g(mut x: impl Iterator<Item = &()>) -> Option<&()> { x.next() }
-    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
-    //~| ERROR missing lifetime specifier
+    //~^ ERROR missing lifetime specifier
 
     // Anonymous lifetimes in async fn are already allowed.
     // This is understood as `fn foo<'_1>(_: impl Iterator<Item = &'_1 ()>) {}`.
@@ -17,16 +15,15 @@ mod elided {
     // Anonymous lifetimes in async fn are already allowed.
     // But that lifetime does not participate in resolution.
     async fn i(mut x: impl Iterator<Item = &()>) -> Option<&()> { x.next() }
-    //~^ ERROR missing lifetime specifier
+    //~^ ERROR lifetime may not live long
+    //~| ERROR missing lifetime specifier
 }
 
 mod underscore {
     fn f(_: impl Iterator<Item = &'_ ()>) {}
-    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
 
     fn g(mut x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
-    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
-    //~| ERROR missing lifetime specifier
+    //~^ ERROR missing lifetime specifier
 
     // Anonymous lifetimes in async fn are already allowed.
     // This is understood as `fn foo<'_1>(_: impl Iterator<Item = &'_1 ()>) {}`.
@@ -35,34 +32,31 @@ mod underscore {
     // Anonymous lifetimes in async fn are already allowed.
     // But that lifetime does not participate in resolution.
     async fn i(mut x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
-    //~^ ERROR missing lifetime specifier
+    //~^ ERROR lifetime may not live long
+    //~| ERROR missing lifetime specifier
 }
 
 mod alone_in_path {
     trait Foo<'a> { fn next(&mut self) -> Option<&'a ()>; }
 
     fn f(_: impl Foo) {}
-    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
 
     fn g(mut x: impl Foo) -> Option<&()> { x.next() }
-    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
-    //~| ERROR missing lifetime specifier
+    //~^ ERROR missing lifetime specifier
 }
 
 mod in_path {
     trait Foo<'a, T> { fn next(&mut self) -> Option<&'a T>; }
 
     fn f(_: impl Foo<()>) {}
-    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
 
     fn g(mut x: impl Foo<()>) -> Option<&()> { x.next() }
-    //~^ ERROR anonymous lifetimes in `impl Trait` are unstable
-    //~| ERROR missing lifetime specifier
+    //~^ ERROR missing lifetime specifier
 }
 
 // This must not err, as the `&` actually resolves to `'a`.
-fn resolved_anonymous<'a, T>(f: impl Fn(&'a str) -> &T) {
-    f("f")
+fn resolved_anonymous<'a, T: 'a>(f: impl Fn(&'a str) -> &T) {
+    f("f");
 }
 
 fn main() {}