Apply changes as per @fee1-dead's comments in rust-lang#116210.

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -52,10 +52,8 @@ struct AstValidator<'a> {
     /// Are we inside a trait impl?
     in_trait_impl: bool,
 
-    in_const_trait_impl: bool,
-
-    /// Are we inside a const trait defn?
-    in_const_trait_defn: bool,
+    /// Are we inside a const trait defn or impl?
+    in_const_trait: bool,
 
     has_proc_macro_decls: bool,
 
@@ -82,16 +80,16 @@ impl<'a> AstValidator<'a> {
     ) {
         let old = mem::replace(&mut self.in_trait_impl, is_in);
         let old_const =
-            mem::replace(&mut self.in_const_trait_impl, matches!(constness, Some(Const::Yes(_))));
+            mem::replace(&mut self.in_const_trait, matches!(constness, Some(Const::Yes(_))));
         f(self);
         self.in_trait_impl = old;
-        self.in_const_trait_impl = old_const;
+        self.in_const_trait = old_const;
     }
 
     fn with_in_trait(&mut self, is_const: bool, f: impl FnOnce(&mut Self)) {
-        let old = mem::replace(&mut self.in_const_trait_defn, is_const);
+        let old = mem::replace(&mut self.in_const_trait, is_const);
         f(self);
-        self.in_const_trait_defn = old;
+        self.in_const_trait = old;
     }
 
     fn with_banned_impl_trait(&mut self, f: impl FnOnce(&mut Self)) {
@@ -1289,16 +1287,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         }
 
         let tilde_const_allowed =
-            if matches!(fk.header(), Some(FnHeader { constness: ast::Const::Yes(_), .. })) {
-                true
-            } else if let Some(FnCtxt::Assoc(ctxt)) = fk.ctxt() {
-                match ctxt {
-                    AssocCtxt::Trait => self.in_const_trait_defn,
-                    AssocCtxt::Impl => self.in_const_trait_impl,
-                }
-            } else {
-                false
-            };
+            matches!(fk.header(), Some(FnHeader { constness: ast::Const::Yes(_), .. }))
+                || (matches!(fk.ctxt(), Some(FnCtxt::Assoc(_))) && self.in_const_trait);
 
         let disallowed = (!tilde_const_allowed).then(|| DisallowTildeConstContext::Fn(fk));
 
@@ -1383,7 +1373,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 walk_list!(self, visit_ty, ty);
             }
             AssocItemKind::Fn(box Fn { sig, generics, body, .. })
-                if self.in_const_trait_impl
+                if self.in_const_trait
                     || ctxt == AssocCtxt::Trait
                     || matches!(sig.header.constness, Const::Yes(_)) =>
             {
@@ -1530,8 +1520,7 @@ pub fn check_crate(
         features,
         extern_mod: None,
         in_trait_impl: false,
-        in_const_trait_impl: false,
-        in_const_trait_defn: false,
+        in_const_trait: false,
         has_proc_macro_decls: false,
         outer_impl_trait: None,
         disallow_tilde_const: None,

tests/ui/rfcs/rfc-2632-const-trait-impl/effects/const-bound-on-not-const-associated-fn.rs

@@ -6,9 +6,7 @@ trait MyTrait {
 }
 
 trait OtherTrait {
-    fn do_something_else()
-    where
-        Self: ~const MyTrait;
+    fn do_something_else() where Self: ~const MyTrait;
     //~^ ERROR `~const` is not allowed here
 }
 
@@ -19,11 +17,8 @@ impl const MyTrait for u32 {
 }
 
 impl<T> MyStruct<T> {
-    pub fn foo(&self)
-    where
-        T: ~const MyTrait,
+    pub fn foo(&self) where T: ~const MyTrait {
         //~^ ERROR `~const` is not allowed here
-    {
         self.0.do_something();
     }
 }

tests/ui/rfcs/rfc-2632-const-trait-impl/effects/const-bound-on-not-const-associated-fn.stderr

@@ -1,25 +1,25 @@
 error: `~const` is not allowed here
-  --> $DIR/const-bound-on-not-const-associated-fn.rs:11:15
+  --> $DIR/const-bound-on-not-const-associated-fn.rs:9:40
    |
-LL |         Self: ~const MyTrait;
-   |               ^^^^^^^^^^^^^^
+LL |     fn do_something_else() where Self: ~const MyTrait;
+   |                                        ^^^^^^^^^^^^^^
    |
 note: this function is not `const`, so it cannot have `~const` trait bounds
   --> $DIR/const-bound-on-not-const-associated-fn.rs:9:8
    |
-LL |     fn do_something_else()
+LL |     fn do_something_else() where Self: ~const MyTrait;
    |        ^^^^^^^^^^^^^^^^^
 
 error: `~const` is not allowed here
-  --> $DIR/const-bound-on-not-const-associated-fn.rs:24:12
+  --> $DIR/const-bound-on-not-const-associated-fn.rs:20:32
    |
-LL |         T: ~const MyTrait,
-   |            ^^^^^^^^^^^^^^
+LL |     pub fn foo(&self) where T: ~const MyTrait {
+   |                                ^^^^^^^^^^^^^^
    |
 note: this function is not `const`, so it cannot have `~const` trait bounds
-  --> $DIR/const-bound-on-not-const-associated-fn.rs:22:12
+  --> $DIR/const-bound-on-not-const-associated-fn.rs:20:12
    |
-LL |     pub fn foo(&self)
+LL |     pub fn foo(&self) where T: ~const MyTrait {
    |            ^^^
 
 error: aborting due to 2 previous errors

tests/ui/rfcs/rfc-2632-const-trait-impl/trait-where-clause.rs

@@ -5,9 +5,7 @@ trait Bar {}
 
 trait Foo {
     fn a();
-    fn b()
-    where
-        Self: ~const Bar;
+    fn b() where Self: ~const Bar;
     //~^ ERROR `~const` is not allowed here
     fn c<T: ~const Bar>();
     //~^ ERROR `~const` is not allowed here

tests/ui/rfcs/rfc-2632-const-trait-impl/trait-where-clause.stderr

@@ -1,54 +1,51 @@
 error: `~const` is not allowed here
-  --> $DIR/trait-where-clause.rs:10:15
+  --> $DIR/trait-where-clause.rs:8:24
    |
-LL |         Self: ~const Bar;
-   |               ^^^^^^^^^^
+LL |     fn b() where Self: ~const Bar;
+   |                        ^^^^^^^^^^
    |
 note: this function is not `const`, so it cannot have `~const` trait bounds
   --> $DIR/trait-where-clause.rs:8:8
    |
-LL |     fn b()
+LL |     fn b() where Self: ~const Bar;
    |        ^
 
 error: `~const` is not allowed here
-  --> $DIR/trait-where-clause.rs:12:13
+  --> $DIR/trait-where-clause.rs:10:13
    |
 LL |     fn c<T: ~const Bar>();
    |             ^^^^^^^^^^
    |
 note: this function is not `const`, so it cannot have `~const` trait bounds
-  --> $DIR/trait-where-clause.rs:12:8
+  --> $DIR/trait-where-clause.rs:10:8
    |
 LL |     fn c<T: ~const Bar>();
    |        ^
 
 error[E0277]: the trait bound `T: Bar` is not satisfied
-  --> $DIR/trait-where-clause.rs:18:5
+  --> $DIR/trait-where-clause.rs:16:5
    |
 LL |     T::b();
    |     ^ the trait `Bar` is not implemented for `T`
    |
 note: required by a bound in `Foo::b`
-  --> $DIR/trait-where-clause.rs:10:15
+  --> $DIR/trait-where-clause.rs:8:24
    |
-LL |     fn b()
-   |        - required by a bound in this associated function
-LL |     where
-LL |         Self: ~const Bar;
-   |               ^^^^^^^^^^ required by this bound in `Foo::b`
+LL |     fn b() where Self: ~const Bar;
+   |                        ^^^^^^^^^^ required by this bound in `Foo::b`
 help: consider further restricting this bound
    |
 LL | fn test1<T: Foo + Bar>() {
    |                 +++++
 
 error[E0277]: the trait bound `T: Bar` is not satisfied
-  --> $DIR/trait-where-clause.rs:20:12
+  --> $DIR/trait-where-clause.rs:18:12
    |
 LL |     T::c::<T>();
    |            ^ the trait `Bar` is not implemented for `T`
    |
 note: required by a bound in `Foo::c`
-  --> $DIR/trait-where-clause.rs:12:13
+  --> $DIR/trait-where-clause.rs:10:13
    |
 LL |     fn c<T: ~const Bar>();
    |             ^^^^^^^^^^ required by this bound in `Foo::c`