use correct feature flag for impl-block-level trait bounds on const fn

compiler/rustc_mir/src/transform/check_consts/validation.rs

@@ -426,7 +426,7 @@ impl Validator<'mir, 'tcx> {
                     ty::PredicateKind::Subtype(_) => {
                         bug!("subtype predicate on function: {:#?}", predicate)
                     }
-                    ty::PredicateKind::Trait(pred, constness) => {
+                    ty::PredicateKind::Trait(pred, _constness) => {
                         if Some(pred.def_id()) == tcx.lang_items().sized_trait() {
                             continue;
                         }
@@ -440,16 +440,7 @@ impl Validator<'mir, 'tcx> {
                                 // arguments when determining importance.
                                 let kind = LocalKind::Arg;
 
-                                if constness == hir::Constness::Const {
-                                    self.check_op_spanned(ops::ty::TraitBound(kind), span);
-                                } else if !tcx.features().const_fn
-                                    || self.ccx.is_const_stable_const_fn()
-                                {
-                                    // HACK: We shouldn't need the conditional above, but trait
-                                    // bounds on containing impl blocks are wrongly being marked as
-                                    // "not-const".
-                                    self.check_op_spanned(ops::ty::TraitBound(kind), span);
-                                }
+                                self.check_op_spanned(ops::ty::TraitBound(kind), span);
                             }
                             // other kinds of bounds are either tautologies
                             // or cause errors in other passes

library/proc_macro/src/lib.rs

@@ -21,7 +21,8 @@
 #![feature(rustc_allow_const_fn_unstable)]
 #![feature(nll)]
 #![feature(staged_api)]
-#![feature(const_fn)]
+#![cfg_attr(bootstrap, feature(const_fn))]
+#![cfg_attr(not(bootstrap), feature(const_fn_trait_bound))]
 #![feature(const_fn_fn_ptr_basics)]
 #![feature(allow_internal_unstable)]
 #![feature(decl_macro)]

src/test/ui/array-slice-vec/subslice-patterns-const-eval-match.rs

@@ -2,8 +2,6 @@
 
 // run-pass
 
-#![feature(const_fn)]
-
 #[derive(PartialEq, Debug, Clone)]
 struct N(u8);
 

src/test/ui/associated-consts/associated-const-in-trait.rs

@@ -1,6 +1,6 @@
 // #29924
 
-#![feature(const_fn, associated_consts)]
+#![feature(associated_consts)]
 
 trait Trait {
     const N: usize;

src/test/ui/consts/const-eval/auxiliary/stability.rs

@@ -3,7 +3,6 @@
 #![crate_type="rlib"]
 #![stable(feature = "rust1", since = "1.0.0")]
 
-#![feature(const_fn)]
 #![feature(staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]

src/test/ui/consts/const-eval/const_fn_ptr.rs

@@ -1,6 +1,5 @@
 // run-pass
 // compile-flags: -Zunleash-the-miri-inside-of-you
-#![feature(const_fn)]
 
 fn double(x: usize) -> usize { x * 2 }
 const fn double_const(x: usize) -> usize { x * 2 }

src/test/ui/consts/const-eval/const_fn_ptr.stderr

@@ -1,27 +1,27 @@
 warning: skipping const checks
    |
 help: skipping check that does not even have a feature gate
-  --> $DIR/const_fn_ptr.rs:12:5
+  --> $DIR/const_fn_ptr.rs:11:5
    |
 LL |     X(x)
    |     ^^^^
 help: skipping check that does not even have a feature gate
-  --> $DIR/const_fn_ptr.rs:16:5
+  --> $DIR/const_fn_ptr.rs:15:5
    |
 LL |     X_CONST(x)
    |     ^^^^^^^^^^
 help: skipping check for `const_fn_fn_ptr_basics` feature
-  --> $DIR/const_fn_ptr.rs:19:14
+  --> $DIR/const_fn_ptr.rs:18:14
    |
 LL | const fn foo(x: fn(usize) -> usize, y: usize)  -> usize {
    |              ^
 help: skipping check for `const_fn_fn_ptr_basics` feature
-  --> $DIR/const_fn_ptr.rs:20:5
+  --> $DIR/const_fn_ptr.rs:19:5
    |
 LL |     x(y)
    |     ^
 help: skipping check that does not even have a feature gate
-  --> $DIR/const_fn_ptr.rs:20:5
+  --> $DIR/const_fn_ptr.rs:19:5
    |
 LL |     x(y)
    |     ^^^^

src/test/ui/consts/const-eval/const_fn_ptr_fail.rs

@@ -1,6 +1,5 @@
 // run-pass
 // compile-flags: -Zunleash-the-miri-inside-of-you
-#![feature(const_fn)]
 #![allow(unused)]
 
 fn double(x: usize) -> usize { x * 2 }

src/test/ui/consts/const-eval/const_fn_ptr_fail.stderr

@@ -1,7 +1,7 @@
 warning: skipping const checks
    |
 help: skipping check that does not even have a feature gate
-  --> $DIR/const_fn_ptr_fail.rs:10:5
+  --> $DIR/const_fn_ptr_fail.rs:9:5
    |
 LL |     X(x) // FIXME: this should error someday
    |     ^^^^

src/test/ui/consts/const-eval/const_fn_ptr_fail2.rs

@@ -1,7 +1,6 @@
 // build-fail
 // compile-flags: -Zunleash-the-miri-inside-of-you
 
-#![feature(const_fn)]
 #![allow(const_err)]
 
 fn double(x: usize) -> usize {

src/test/ui/consts/const-eval/const_fn_ptr_fail2.stderr

@@ -1,29 +1,29 @@
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_fn_ptr_fail2.rs:20:16
+  --> $DIR/const_fn_ptr_fail2.rs:19:16
    |
 LL |     assert_eq!(Y, 4);
    |                ^ referenced constant has errors
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const_fn_ptr_fail2.rs:22:16
+  --> $DIR/const_fn_ptr_fail2.rs:21:16
    |
 LL |     assert_eq!(Z, 4);
    |                ^ referenced constant has errors
 
 warning: skipping const checks
    |
 help: skipping check for `const_fn_fn_ptr_basics` feature
-  --> $DIR/const_fn_ptr_fail2.rs:12:14
+  --> $DIR/const_fn_ptr_fail2.rs:11:14
    |
 LL | const fn bar(x: fn(usize) -> usize, y: usize) -> usize {
    |              ^
 help: skipping check for `const_fn_fn_ptr_basics` feature
-  --> $DIR/const_fn_ptr_fail2.rs:13:5
+  --> $DIR/const_fn_ptr_fail2.rs:12:5
    |
 LL |     x(y)
    |     ^
 help: skipping check that does not even have a feature gate
-  --> $DIR/const_fn_ptr_fail2.rs:13:5
+  --> $DIR/const_fn_ptr_fail2.rs:12:5
    |
 LL |     x(y)
    |     ^^^^

src/test/ui/consts/const-eval/dont_promote_unstable_const_fn.rs

@@ -3,7 +3,6 @@
             we're apparently really bad at it",
             issue = "none")]
 
-#![feature(const_fn)]
 #![feature(staged_api)]
 
 #[stable(feature = "rust1", since = "1.0.0")]

src/test/ui/consts/const-eval/dont_promote_unstable_const_fn.stderr

@@ -1,13 +1,13 @@
 error: `foo` is not yet stable as a const fn
-  --> $DIR/dont_promote_unstable_const_fn.rs:15:25
+  --> $DIR/dont_promote_unstable_const_fn.rs:14:25
    |
 LL | const fn bar() -> u32 { foo() }
    |                         ^^^^^
    |
    = help: add `#![feature(foo)]` to the crate attributes to enable
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/dont_promote_unstable_const_fn.rs:18:28
+  --> $DIR/dont_promote_unstable_const_fn.rs:17:28
    |
 LL |     let _: &'static u32 = &foo();
    |            ------------    ^^^^^ creates a temporary which is freed while still in use
@@ -17,7 +17,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/dont_promote_unstable_const_fn.rs:22:28
+  --> $DIR/dont_promote_unstable_const_fn.rs:21:28
    |
 LL |     let _: &'static u32 = &meh();
    |            ------------    ^^^^^ creates a temporary which is freed while still in use
@@ -28,7 +28,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/dont_promote_unstable_const_fn.rs:23:26
+  --> $DIR/dont_promote_unstable_const_fn.rs:22:26
    |
 LL |     let x: &'static _ = &std::time::Duration::from_millis(42).subsec_millis();
    |            ----------    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ creates a temporary which is freed while still in use

src/test/ui/consts/const-eval/double_promotion.rs

@@ -1,6 +1,6 @@
 // check-pass
 
-#![feature(const_fn, rustc_attrs)]
+#![feature(rustc_attrs)]
 
 #[rustc_args_required_const(0)]
 pub const fn a(value: u8) -> u8 {

src/test/ui/consts/const-eval/feature-gate-const_fn_union.rs

@@ -1,5 +1,3 @@
-#![feature(const_fn)]
-
 fn main() {}
 
 #[repr(C)]

src/test/ui/consts/const-eval/feature-gate-const_fn_union.stderr

@@ -1,5 +1,5 @@
 error[E0658]: unions in const fn are unstable
-  --> $DIR/feature-gate-const_fn_union.rs:12:5
+  --> $DIR/feature-gate-const_fn_union.rs:10:5
    |
 LL |     Foo { u }.i
    |     ^^^^^^^^^^^

src/test/ui/consts/const-eval/promoted_const_fn_fail.rs

@@ -1,4 +1,4 @@
-#![feature(const_fn, const_fn_union)]
+#![feature(const_fn_union)]
 
 #![allow(const_err)]
 

src/test/ui/consts/const-eval/promoted_const_fn_fail_deny_const_err.rs

@@ -1,4 +1,4 @@
-#![feature(const_fn, const_fn_union)]
+#![feature(const_fn_union)]
 
 #![deny(const_err)]
 

src/test/ui/consts/const-eval/simd/insert_extract.rs

@@ -1,5 +1,4 @@
 // run-pass
-#![feature(const_fn)]
 #![feature(repr_simd)]
 #![feature(platform_intrinsics)]
 #![feature(staged_api)]

src/test/ui/consts/const-eval/union-const-eval-field.rs

@@ -1,5 +1,4 @@
 // only-x86_64
-#![feature(const_fn)]
 
 type Field1 = i32;
 type Field2 = f32;

src/test/ui/consts/const-eval/union-const-eval-field.stderr

@@ -1,5 +1,5 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/union-const-eval-field.rs:29:5
+  --> $DIR/union-const-eval-field.rs:28:5
    |
 LL |     const FIELD3: Field3 = unsafe { UNION.field3 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected initialized plain (non-pointer) bytes

src/test/ui/consts/const-eval/union-ice.rs

@@ -1,5 +1,4 @@
 // only-x86_64
-#![feature(const_fn)]
 
 type Field1 = i32;
 type Field3 = i64;

src/test/ui/consts/const-eval/union-ice.stderr

@@ -1,5 +1,5 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/union-ice.rs:15:1
+  --> $DIR/union-ice.rs:14:1
    |
 LL | const FIELD3: Field3 = unsafe { UNION.field3 };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected initialized plain (non-pointer) bytes
@@ -10,7 +10,7 @@ LL | const FIELD3: Field3 = unsafe { UNION.field3 };
            }
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/union-ice.rs:17:1
+  --> $DIR/union-ice.rs:16:1
    |
 LL | / const FIELD_PATH: Struct = Struct {
 LL | |     a: 42,
@@ -24,7 +24,7 @@ LL | | };
            }
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/union-ice.rs:27:1
+  --> $DIR/union-ice.rs:26:1
    |
 LL | / const FIELD_PATH2: Struct2 = Struct2 {
 LL | |     b: [

src/test/ui/consts/const-eval/validate_uninhabited_zsts.32bit.stderr

@@ -1,26 +1,26 @@
 warning: any use of this value will cause an error
-  --> $DIR/validate_uninhabited_zsts.rs:6:14
+  --> $DIR/validate_uninhabited_zsts.rs:5:14
    |
 LL |     unsafe { std::mem::transmute(()) }
    |              ^^^^^^^^^^^^^^^^^^^^^^^
    |              |
    |              transmuting to uninhabited type
-   |              inside `foo` at $DIR/validate_uninhabited_zsts.rs:6:14
-   |              inside `FOO` at $DIR/validate_uninhabited_zsts.rs:16:26
+   |              inside `foo` at $DIR/validate_uninhabited_zsts.rs:5:14
+   |              inside `FOO` at $DIR/validate_uninhabited_zsts.rs:15:26
 ...
 LL | const FOO: [Empty; 3] = [foo(); 3];
    | -----------------------------------
    |
 note: the lint level is defined here
-  --> $DIR/validate_uninhabited_zsts.rs:15:8
+  --> $DIR/validate_uninhabited_zsts.rs:14:8
    |
 LL | #[warn(const_err)]
    |        ^^^^^^^^^
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/validate_uninhabited_zsts.rs:19:1
+  --> $DIR/validate_uninhabited_zsts.rs:18:1
    |
 LL | const BAR: [Empty; 3] = [unsafe { std::mem::transmute(()) }; 3];
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type Empty at [0]
@@ -29,7 +29,7 @@ LL | const BAR: [Empty; 3] = [unsafe { std::mem::transmute(()) }; 3];
    = note: the raw bytes of the constant (size: 0, align: 1) {}
 
 warning: the type `!` does not permit zero-initialization
-  --> $DIR/validate_uninhabited_zsts.rs:6:14
+  --> $DIR/validate_uninhabited_zsts.rs:5:14
    |
 LL |     unsafe { std::mem::transmute(()) }
    |              ^^^^^^^^^^^^^^^^^^^^^^^
@@ -41,7 +41,7 @@ LL |     unsafe { std::mem::transmute(()) }
    = note: the `!` type has no valid value
 
 warning: the type `Empty` does not permit zero-initialization
-  --> $DIR/validate_uninhabited_zsts.rs:19:35
+  --> $DIR/validate_uninhabited_zsts.rs:18:35
    |
 LL | const BAR: [Empty; 3] = [unsafe { std::mem::transmute(()) }; 3];
    |                                   ^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/consts/const-eval/validate_uninhabited_zsts.64bit.stderr

@@ -1,26 +1,26 @@
 warning: any use of this value will cause an error
-  --> $DIR/validate_uninhabited_zsts.rs:6:14
+  --> $DIR/validate_uninhabited_zsts.rs:5:14
    |
 LL |     unsafe { std::mem::transmute(()) }
    |              ^^^^^^^^^^^^^^^^^^^^^^^
    |              |
    |              transmuting to uninhabited type
-   |              inside `foo` at $DIR/validate_uninhabited_zsts.rs:6:14
-   |              inside `FOO` at $DIR/validate_uninhabited_zsts.rs:16:26
+   |              inside `foo` at $DIR/validate_uninhabited_zsts.rs:5:14
+   |              inside `FOO` at $DIR/validate_uninhabited_zsts.rs:15:26
 ...
 LL | const FOO: [Empty; 3] = [foo(); 3];
    | -----------------------------------
    |
 note: the lint level is defined here
-  --> $DIR/validate_uninhabited_zsts.rs:15:8
+  --> $DIR/validate_uninhabited_zsts.rs:14:8
    |
 LL | #[warn(const_err)]
    |        ^^^^^^^^^
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/validate_uninhabited_zsts.rs:19:1
+  --> $DIR/validate_uninhabited_zsts.rs:18:1
    |
 LL | const BAR: [Empty; 3] = [unsafe { std::mem::transmute(()) }; 3];
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type Empty at [0]
@@ -29,7 +29,7 @@ LL | const BAR: [Empty; 3] = [unsafe { std::mem::transmute(()) }; 3];
    = note: the raw bytes of the constant (size: 0, align: 1) {}
 
 warning: the type `!` does not permit zero-initialization
-  --> $DIR/validate_uninhabited_zsts.rs:6:14
+  --> $DIR/validate_uninhabited_zsts.rs:5:14
    |
 LL |     unsafe { std::mem::transmute(()) }
    |              ^^^^^^^^^^^^^^^^^^^^^^^
@@ -41,7 +41,7 @@ LL |     unsafe { std::mem::transmute(()) }
    = note: the `!` type has no valid value
 
 warning: the type `Empty` does not permit zero-initialization
-  --> $DIR/validate_uninhabited_zsts.rs:19:35
+  --> $DIR/validate_uninhabited_zsts.rs:18:35
    |
 LL | const BAR: [Empty; 3] = [unsafe { std::mem::transmute(()) }; 3];
    |                                   ^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/consts/const-eval/validate_uninhabited_zsts.rs

@@ -1,5 +1,4 @@
 // stderr-per-bitwidth
-#![feature(const_fn)]
 #![feature(const_fn_transmute)]
 
 const fn foo() -> ! {

src/test/ui/consts/const-fn-error.rs

@@ -1,5 +1,3 @@
-#![feature(const_fn)]
-
 const X : usize = 2;
 
 const fn f(x: usize) -> usize {