Auto merge of #87648 - JulianKnodt:const_eq_constrain, r=oli-obk

allow eq constraints on associated constants

Updates #70256

(cc `@varkor,` `@Centril)`

4 files changed, 52 insertions, 16 deletions

diff --git a/src/test/ui/const-generics/parser-error-recovery/issue-89013-no-kw.rs b/src/test/ui/const-generics/parser-error-recovery/issue-89013-no-kw.rs
index 19e0f38d320..b126b24853f 100644
--- a/src/test/ui/const-generics/parser-error-recovery/issue-89013-no-kw.rs
+++ b/src/test/ui/const-generics/parser-error-recovery/issue-89013-no-kw.rs
@@ -7,8 +7,9 @@ struct Bar;
 const T: usize = 42;
 
 impl Foo<N = 3> for Bar {
-//~^ ERROR cannot constrain an associated constant to a value
+//~^ ERROR this trait takes 1 generic argument but 0 generic arguments were supplied
 //~| ERROR associated type bindings are not allowed here
+//~| ERROR associated const equality is incomplete
     fn do_x(&self) -> [u8; 3] {
         [0u8; 3]
     }
diff --git a/src/test/ui/const-generics/parser-error-recovery/issue-89013-no-kw.stderr b/src/test/ui/const-generics/parser-error-recovery/issue-89013-no-kw.stderr
index bbca92ad63a..59ba054aa11 100644
--- a/src/test/ui/const-generics/parser-error-recovery/issue-89013-no-kw.stderr
+++ b/src/test/ui/const-generics/parser-error-recovery/issue-89013-no-kw.stderr
@@ -1,11 +1,27 @@
-error: cannot constrain an associated constant to a value
+error[E0658]: associated const equality is incomplete
   --> $DIR/issue-89013-no-kw.rs:9:10
    |
 LL | impl Foo<N = 3> for Bar {
-   |          -^^^-
-   |          |   |
-   |          |   ...cannot be constrained to this value
-   |          this associated constant...
+   |          ^^^^^
+   |
+   = note: see issue #92827 <https://github.com/rust-lang/rust/issues/92827> for more information
+   = help: add `#![feature(associated_const_equality)]` to the crate attributes to enable
+
+error[E0107]: this trait takes 1 generic argument but 0 generic arguments were supplied
+  --> $DIR/issue-89013-no-kw.rs:9:6
+   |
+LL | impl Foo<N = 3> for Bar {
+   |      ^^^ expected 1 generic argument
+   |
+note: trait defined here, with 1 generic parameter: `N`
+  --> $DIR/issue-89013-no-kw.rs:1:7
+   |
+LL | trait Foo<const N: usize> {
+   |       ^^^       -
+help: add missing generic argument
+   |
+LL | impl Foo<N, N = 3> for Bar {
+   |          ++
 
 error[E0229]: associated type bindings are not allowed here
   --> $DIR/issue-89013-no-kw.rs:9:10
@@ -13,6 +29,7 @@ error[E0229]: associated type bindings are not allowed here
 LL | impl Foo<N = 3> for Bar {
    |          ^^^^^ associated type not allowed here
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0229`.
+Some errors have detailed explanations: E0107, E0229, E0658.
+For more information about an error, try `rustc --explain E0107`.
diff --git a/src/test/ui/const-generics/parser-error-recovery/issue-89013.rs b/src/test/ui/const-generics/parser-error-recovery/issue-89013.rs
index ca1158a2f6d..9431779faf8 100644
--- a/src/test/ui/const-generics/parser-error-recovery/issue-89013.rs
+++ b/src/test/ui/const-generics/parser-error-recovery/issue-89013.rs
@@ -8,8 +8,9 @@ const T: usize = 42;
 
 impl Foo<N = const 3> for Bar {
 //~^ ERROR expected lifetime, type, or constant, found keyword `const`
-//~| ERROR cannot constrain an associated constant to a value
+//~| ERROR this trait takes 1 generic
 //~| ERROR associated type bindings are not allowed here
+//~| ERROR associated const equality is incomplete
     fn do_x(&self) -> [u8; 3] {
         [0u8; 3]
     }
diff --git a/src/test/ui/const-generics/parser-error-recovery/issue-89013.stderr b/src/test/ui/const-generics/parser-error-recovery/issue-89013.stderr
index 85379d3f06e..9d473992670 100644
--- a/src/test/ui/const-generics/parser-error-recovery/issue-89013.stderr
+++ b/src/test/ui/const-generics/parser-error-recovery/issue-89013.stderr
@@ -10,14 +10,30 @@ LL - impl Foo<N = const 3> for Bar {
 LL + impl Foo<N = 3> for Bar {
    | 
 
-error: cannot constrain an associated constant to a value
+error[E0658]: associated const equality is incomplete
   --> $DIR/issue-89013.rs:9:10
    |
 LL | impl Foo<N = const 3> for Bar {
-   |          -^^^^^^^^^-
-   |          |         |
-   |          |         ...cannot be constrained to this value
-   |          this associated constant...
+   |          ^^^^^^^^^^^
+   |
+   = note: see issue #92827 <https://github.com/rust-lang/rust/issues/92827> for more information
+   = help: add `#![feature(associated_const_equality)]` to the crate attributes to enable
+
+error[E0107]: this trait takes 1 generic argument but 0 generic arguments were supplied
+  --> $DIR/issue-89013.rs:9:6
+   |
+LL | impl Foo<N = const 3> for Bar {
+   |      ^^^ expected 1 generic argument
+   |
+note: trait defined here, with 1 generic parameter: `N`
+  --> $DIR/issue-89013.rs:1:7
+   |
+LL | trait Foo<const N: usize> {
+   |       ^^^       -
+help: add missing generic argument
+   |
+LL | impl Foo<N, N = const 3> for Bar {
+   |          ++
 
 error[E0229]: associated type bindings are not allowed here
   --> $DIR/issue-89013.rs:9:10
@@ -25,6 +41,7 @@ error[E0229]: associated type bindings are not allowed here
 LL | impl Foo<N = const 3> for Bar {
    |          ^^^^^^^^^^^ associated type not allowed here
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
-For more information about this error, try `rustc --explain E0229`.
+Some errors have detailed explanations: E0107, E0229, E0658.
+For more information about an error, try `rustc --explain E0107`.