Auto merge of #125915 - camelid:const-arg-refactor, r=BoxyUwU

Represent type-level consts with new-and-improved `hir::ConstArg`

### Summary

This is a step toward `min_generic_const_exprs`. We now represent all const
generic arguments using an enum that differentiates between const *paths*
(temporarily just bare const params) and arbitrary anon consts that may perform
computations. This will enable us to cleanly implement the `min_generic_const_args`
plan of allowing the use of generics in paths used as const args, while
disallowing their use in arbitrary anon consts. Here is a summary of the salient
aspects of this change:

- Add `current_def_id_parent` to `LoweringContext`

  This is needed to track anon const parents properly once we implement
  `ConstArgKind::Path` (which requires moving anon const def-creation
  outside of `DefCollector`).

- Create `hir::ConstArgKind` enum with `Path` and `Anon` variants. Use it in the
  existing `hir::ConstArg` struct, replacing the previous `hir::AnonConst` field.

- Use `ConstArg` for all instances of const args. Specifically, use it instead
  of `AnonConst` for assoc item constraints, array lengths, and const param
  defaults.

- Some `ast::AnonConst`s now have their `DefId`s created in
  rustc_ast_lowering rather than `DefCollector`. This is because in some
  cases they will end up becoming a `ConstArgKind::Path` instead, which
  has no `DefId`. We have to solve this in a hacky way where we guess
  whether the `AnonConst` could end up as a path const since we can't
  know for sure until after name resolution (`N` could refer to a free
  const or a nullary struct). If it has no chance as being a const
  param, then we create a `DefId` in `DefCollector` -- otherwise we
  decide during ast_lowering. This will have to be updated once all path
  consts use `ConstArgKind::Path`.

- We explicitly use `ConstArgHasType` for array lengths, rather than
  implicitly relying on anon const type feeding -- this is due to the
  addition of `ConstArgKind::Path`.

- Some tests have their outputs changed, but the changes are for the
  most part minor (including removing duplicate or almost-duplicate
  errors). One test now ICEs, but it is for an incomplete, unstable
  feature and is now tracked at https://github.com/rust-lang/rust/issues/127009.

### Followup items post-merge

- Use `ConstArgKind::Path` for all const paths, not just const params.
- Fix (no github dont close this issue) #127009
- If a path in generic args doesn't resolve as a type, try to resolve as a const
  instead (do this in rustc_resolve). Then remove the special-casing from
  `rustc_ast_lowering`, so that all params will automatically be lowered as
  `ConstArgKind::Path`.
- (?) Consider making `const_evaluatable_unchecked` a hard error, or at least
  trying it in crater

r? `@BoxyUwU`

34 files changed, 126 insertions, 217 deletions

diff --git a/tests/crashes/127009.rs b/tests/crashes/127009.rs
new file mode 100644
index 00000000000..74ca14393e4
--- /dev/null
+++ b/tests/crashes/127009.rs
@@ -0,0 +1,11 @@
+//@ known-bug: #127009
+
+#![feature(non_lifetime_binders)]
+
+fn b()
+where
+    for<const C: usize> [(); C]: Copy,
+{
+}
+
+fn main() {}
diff --git a/tests/ui-fulldeps/stable-mir/check_instance.rs b/tests/ui-fulldeps/stable-mir/check_instance.rs
index f971426723f..5e3f2557566 100644
--- a/tests/ui-fulldeps/stable-mir/check_instance.rs
+++ b/tests/ui-fulldeps/stable-mir/check_instance.rs
@@ -33,7 +33,7 @@ fn test_stable_mir() -> ControlFlow<()> {
     // Get all items and split generic vs monomorphic items.
     let (generic, mono): (Vec<_>, Vec<_>) =
         items.into_iter().partition(|item| item.requires_monomorphization());
-    assert_eq!(mono.len(), 4, "Expected 2 mono functions and one constant");
+    assert_eq!(mono.len(), 3, "Expected 3 mono functions");
     assert_eq!(generic.len(), 2, "Expected 2 generic functions");
 
     // For all monomorphic items, get the correspondent instances.
diff --git a/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.rs b/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.rs
index fa0b0fdc136..e07fa78463c 100644
--- a/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.rs
+++ b/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.rs
@@ -5,9 +5,7 @@
 #![feature(with_negative_coherence)]
 trait Trait {}
 impl<const N: u8> Trait for [(); N] {}
-//~^ ERROR: mismatched types
 impl<const N: i8> Trait for [(); N] {}
-//~^ ERROR: mismatched types
-//~| ERROR: conflicting implementations of trait `Trait`
+//~^ ERROR: conflicting implementations of trait `Trait`
 
 fn main() {}
diff --git a/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.stderr b/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.stderr
index d65450845bc..2087be8e711 100644
--- a/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.stderr
+++ b/tests/ui/coherence/negative-coherence/generic_const_type_mismatch.stderr
@@ -1,25 +1,11 @@
 error[E0119]: conflicting implementations of trait `Trait` for type `[(); _]`
-  --> $DIR/generic_const_type_mismatch.rs:9:1
+  --> $DIR/generic_const_type_mismatch.rs:8:1
    |
 LL | impl<const N: u8> Trait for [(); N] {}
    | ----------------------------------- first implementation here
-LL |
 LL | impl<const N: i8> Trait for [(); N] {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `[(); _]`
 
-error[E0308]: mismatched types
-  --> $DIR/generic_const_type_mismatch.rs:7:34
-   |
-LL | impl<const N: u8> Trait for [(); N] {}
-   |                                  ^ expected `usize`, found `u8`
-
-error[E0308]: mismatched types
-  --> $DIR/generic_const_type_mismatch.rs:9:34
-   |
-LL | impl<const N: i8> Trait for [(); N] {}
-   |                                  ^ expected `usize`, found `i8`
-
-error: aborting due to 3 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0119, E0308.
-For more information about an error, try `rustc --explain E0119`.
+For more information about this error, try `rustc --explain E0119`.
diff --git a/tests/ui/const-generics/bad-subst-const-kind.rs b/tests/ui/const-generics/bad-subst-const-kind.rs
index d5913879191..cc2ff9b8dea 100644
--- a/tests/ui/const-generics/bad-subst-const-kind.rs
+++ b/tests/ui/const-generics/bad-subst-const-kind.rs
@@ -6,7 +6,7 @@ trait Q {
 }
 
 impl<const N: u64> Q for [u8; N] {
-    //~^ ERROR mismatched types
+    //~^ ERROR: the constant `N` is not of type `usize`
     const ASSOC: usize = 1;
 }
 
diff --git a/tests/ui/const-generics/bad-subst-const-kind.stderr b/tests/ui/const-generics/bad-subst-const-kind.stderr
index 6725f6762e4..5c8d9c90363 100644
--- a/tests/ui/const-generics/bad-subst-const-kind.stderr
+++ b/tests/ui/const-generics/bad-subst-const-kind.stderr
@@ -1,3 +1,9 @@
+error: the constant `N` is not of type `usize`
+  --> $DIR/bad-subst-const-kind.rs:8:26
+   |
+LL | impl<const N: u64> Q for [u8; N] {
+   |                          ^^^^^^^ expected `usize`, found `u64`
+
 error: the constant `13` is not of type `u64`
   --> $DIR/bad-subst-const-kind.rs:13:24
    |
@@ -12,12 +18,5 @@ LL | impl<const N: u64> Q for [u8; N] {
    |      |
    |      unsatisfied trait bound introduced here
 
-error[E0308]: mismatched types
-  --> $DIR/bad-subst-const-kind.rs:8:31
-   |
-LL | impl<const N: u64> Q for [u8; N] {
-   |                               ^ expected `usize`, found `u64`
-
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/const-generics/generic_const_exprs/type_mismatch.rs b/tests/ui/const-generics/generic_const_exprs/type_mismatch.rs
index 6b0d9e047db..8e5e23b2337 100644
--- a/tests/ui/const-generics/generic_const_exprs/type_mismatch.rs
+++ b/tests/ui/const-generics/generic_const_exprs/type_mismatch.rs
@@ -7,7 +7,7 @@ trait Q {
 
 impl<const N: u64> Q for [u8; N] {}
 //~^ ERROR not all trait items implemented
-//~| ERROR mismatched types
+//~| ERROR the constant `N` is not of type `usize`
 
 pub fn q_user() -> [u8; <[u8; 13] as Q>::ASSOC] {}
 //~^ ERROR the constant `13` is not of type `u64`
diff --git a/tests/ui/const-generics/generic_const_exprs/type_mismatch.stderr b/tests/ui/const-generics/generic_const_exprs/type_mismatch.stderr
index bb6d650b7ab..e03580ec007 100644
--- a/tests/ui/const-generics/generic_const_exprs/type_mismatch.stderr
+++ b/tests/ui/const-generics/generic_const_exprs/type_mismatch.stderr
@@ -1,3 +1,9 @@
+error: the constant `N` is not of type `usize`
+  --> $DIR/type_mismatch.rs:8:26
+   |
+LL | impl<const N: u64> Q for [u8; N] {}
+   |                          ^^^^^^^ expected `usize`, found `u64`
+
 error[E0046]: not all trait items implemented, missing: `ASSOC`
   --> $DIR/type_mismatch.rs:8:1
    |
@@ -29,12 +35,6 @@ LL | pub fn q_user() -> [u8; <[u8; 13] as Q>::ASSOC] {}
    |        |
    |        implicitly returns `()` as its body has no tail or `return` expression
 
-error[E0308]: mismatched types
-  --> $DIR/type_mismatch.rs:8:31
-   |
-LL | impl<const N: u64> Q for [u8; N] {}
-   |                               ^ expected `usize`, found `u64`
-
 error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0046, E0308.
diff --git a/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.rs b/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.rs
index 51cae20df84..8b7ee577569 100644
--- a/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.rs
+++ b/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.rs
@@ -25,8 +25,8 @@ mod v20 {
     }
 
     impl<const v10: usize> v17<v10, v2> {
-    //~^ ERROR maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#1}
-    //~| ERROR maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#1}
+    //~^ ERROR maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
+    //~| ERROR maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
         pub const fn v21() -> v18 {
         //~^ ERROR cannot find type `v18` in this scope
             v18 { _p: () }
diff --git a/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.stderr b/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.stderr
index 39f022fbee9..15d3c472585 100644
--- a/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.stderr
+++ b/tests/ui/const-generics/generic_const_exprs/unevaluated-const-ice-119731.stderr
@@ -72,13 +72,13 @@ help: add `#![feature(adt_const_params)]` to the crate attributes to enable more
 LL + #![feature(adt_const_params)]
    |
 
-error: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#1}
+error: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
   --> $DIR/unevaluated-const-ice-119731.rs:27:37
    |
 LL |     impl<const v10: usize> v17<v10, v2> {
    |                                     ^^
 
-error: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#1}
+error: maximum number of nodes exceeded in constant v20::v17::<v10, v2>::{constant#0}
   --> $DIR/unevaluated-const-ice-119731.rs:27:37
    |
 LL |     impl<const v10: usize> v17<v10, v2> {
diff --git a/tests/ui/const-generics/issues/issue-88119.stderr b/tests/ui/const-generics/issues/issue-88119.stderr
index c17a7d5d9fa..b5eec3046fd 100644
--- a/tests/ui/const-generics/issues/issue-88119.stderr
+++ b/tests/ui/const-generics/issues/issue-88119.stderr
@@ -1,26 +1,32 @@
-error[E0284]: type annotations needed: cannot satisfy `the constant `name_len::<T>()` can be evaluated`
-  --> $DIR/issue-88119.rs:21:5
+error[E0284]: type annotations needed: cannot normalize `<&T as ConstName>::{constant#0}`
+  --> $DIR/issue-88119.rs:19:49
    |
-LL |     [(); name_len::<T>()]:,
-   |     ^^^^^^^^^^^^^^^^^^^^^ cannot satisfy `the constant `name_len::<T>()` can be evaluated`
+LL | impl<T: ?Sized + ConstName> const ConstName for &T
+   |                                                 ^^ cannot normalize `<&T as ConstName>::{constant#0}`
    |
-note: required by a bound in `<&T as ConstName>`
-  --> $DIR/issue-88119.rs:21:10
+note: required for `&T` to implement `ConstName`
+  --> $DIR/issue-88119.rs:19:35
    |
+LL | impl<T: ?Sized + ConstName> const ConstName for &T
+   |                                   ^^^^^^^^^     ^^
+LL | where
 LL |     [(); name_len::<T>()]:,
-   |          ^^^^^^^^^^^^^^^ required by this bound in `<&T as ConstName>`
+   |     --------------------- unsatisfied trait bound introduced here
 
-error[E0284]: type annotations needed: cannot satisfy `the constant `name_len::<T>()` can be evaluated`
-  --> $DIR/issue-88119.rs:28:5
+error[E0284]: type annotations needed: cannot normalize `<&mut T as ConstName>::{constant#0}`
+  --> $DIR/issue-88119.rs:26:49
    |
-LL |     [(); name_len::<T>()]:,
-   |     ^^^^^^^^^^^^^^^^^^^^^ cannot satisfy `the constant `name_len::<T>()` can be evaluated`
+LL | impl<T: ?Sized + ConstName> const ConstName for &mut T
+   |                                                 ^^^^^^ cannot normalize `<&mut T as ConstName>::{constant#0}`
    |
-note: required by a bound in `<&mut T as ConstName>`
-  --> $DIR/issue-88119.rs:28:10
+note: required for `&mut T` to implement `ConstName`
+  --> $DIR/issue-88119.rs:26:35
    |
+LL | impl<T: ?Sized + ConstName> const ConstName for &mut T
+   |                                   ^^^^^^^^^     ^^^^^^
+LL | where
 LL |     [(); name_len::<T>()]:,
-   |          ^^^^^^^^^^^^^^^ required by this bound in `<&mut T as ConstName>`
+   |     --------------------- unsatisfied trait bound introduced here
 
 error: aborting due to 2 previous errors
 
diff --git a/tests/ui/const-generics/repeat_expr_hack_gives_right_generics.rs b/tests/ui/const-generics/repeat_expr_hack_gives_right_generics.rs
index e7ae2ea1d5a..def4611f94b 100644
--- a/tests/ui/const-generics/repeat_expr_hack_gives_right_generics.rs
+++ b/tests/ui/const-generics/repeat_expr_hack_gives_right_generics.rs
@@ -19,6 +19,8 @@ fn bar<const N: usize>() {}
 fn foo<const N: usize>() {
     bar::<{ [1; N] }>();
     //~^ ERROR: generic parameters may not be used in const operations
+    bar::<{ [1; { N + 1 }] }>();
+    //~^ ERROR: generic parameters may not be used in const operations
 }
 
 fn main() {}
diff --git a/tests/ui/const-generics/repeat_expr_hack_gives_right_generics.stderr b/tests/ui/const-generics/repeat_expr_hack_gives_right_generics.stderr
index 72a6e6977f5..ead6c621d60 100644
--- a/tests/ui/const-generics/repeat_expr_hack_gives_right_generics.stderr
+++ b/tests/ui/const-generics/repeat_expr_hack_gives_right_generics.stderr
@@ -7,5 +7,14 @@ LL |     bar::<{ [1; N] }>();
    = help: const parameters may only be used as standalone arguments, i.e. `N`
    = help: add `#![feature(generic_const_exprs)]` to allow generic const expressions
 
-error: aborting due to 1 previous error
+error: generic parameters may not be used in const operations
+  --> $DIR/repeat_expr_hack_gives_right_generics.rs:22:19
+   |
+LL |     bar::<{ [1; { N + 1 }] }>();
+   |                   ^ cannot perform const operation using `N`
+   |
+   = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = help: add `#![feature(generic_const_exprs)]` to allow generic const expressions
+
+error: aborting due to 2 previous errors
 
diff --git a/tests/ui/const-generics/transmute-fail.rs b/tests/ui/const-generics/transmute-fail.rs
index 90afd232534..59b77c678e8 100644
--- a/tests/ui/const-generics/transmute-fail.rs
+++ b/tests/ui/const-generics/transmute-fail.rs
@@ -10,11 +10,10 @@ fn foo<const W: usize, const H: usize>(v: [[u32;H+1]; W]) -> [[u32; W+1]; H] {
 }
 
 fn bar<const W: bool, const H: usize>(v: [[u32; H]; W]) -> [[u32; W]; H] {
-  //~^ ERROR mismatched types
-  //~| ERROR mismatched types
+  //~^ ERROR the constant `W` is not of type `usize`
   unsafe {
     std::mem::transmute(v)
-    //~^ ERROR cannot transmute between types
+    //~^ ERROR the constant `W` is not of type `usize`
   }
 }
 
diff --git a/tests/ui/const-generics/transmute-fail.stderr b/tests/ui/const-generics/transmute-fail.stderr
index b76ec10bd3f..b40fb23c331 100644
--- a/tests/ui/const-generics/transmute-fail.stderr
+++ b/tests/ui/const-generics/transmute-fail.stderr
@@ -1,3 +1,9 @@
+error: the constant `W` is not of type `usize`
+  --> $DIR/transmute-fail.rs:12:42
+   |
+LL | fn bar<const W: bool, const H: usize>(v: [[u32; H]; W]) -> [[u32; W]; H] {
+   |                                          ^^^^^^^^^^^^^ expected `usize`, found `bool`
+
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
   --> $DIR/transmute-fail.rs:7:5
    |
@@ -7,17 +13,14 @@ LL |     std::mem::transmute(v)
    = note: source type: `[[u32; H+1]; W]` (size can vary because of [u32; H+1])
    = note: target type: `[[u32; W+1]; H]` (size can vary because of [u32; W+1])
 
-error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:16:5
+error: the constant `W` is not of type `usize`
+  --> $DIR/transmute-fail.rs:15:5
    |
 LL |     std::mem::transmute(v)
-   |     ^^^^^^^^^^^^^^^^^^^
-   |
-   = note: source type: `[[u32; H]; W]` (size can vary because of [u32; H])
-   = note: target type: `[[u32; W]; H]` (size can vary because of [u32; W])
+   |     ^^^^^^^^^^^^^^^^^^^ expected `usize`, found `bool`
 
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:23:5
+  --> $DIR/transmute-fail.rs:22:5
    |
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
@@ -26,7 +29,7 @@ LL |     std::mem::transmute(v)
    = note: target type: `[u32; W * H * H]` (this type does not have a fixed size)
 
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:30:5
+  --> $DIR/transmute-fail.rs:29:5
    |
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
@@ -35,7 +38,7 @@ LL |     std::mem::transmute(v)
    = note: target type: `[[[u32; 9999999]; 777777777]; 8888888]` (values of the type `[[u32; 9999999]; 777777777]` are too big for the current architecture)
 
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:37:5
+  --> $DIR/transmute-fail.rs:36:5
    |
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
@@ -44,7 +47,7 @@ LL |     std::mem::transmute(v)
    = note: target type: `[[u32; W]; H]` (size can vary because of [u32; W])
 
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:50:5
+  --> $DIR/transmute-fail.rs:49:5
    |
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
@@ -53,7 +56,7 @@ LL |     std::mem::transmute(v)
    = note: target type: `[u32; W * H]` (this type does not have a fixed size)
 
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:57:5
+  --> $DIR/transmute-fail.rs:56:5
    |
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
@@ -62,7 +65,7 @@ LL |     std::mem::transmute(v)
    = note: target type: `[[u32; W]; H]` (size can vary because of [u32; W])
 
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:66:5
+  --> $DIR/transmute-fail.rs:65:5
    |
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
@@ -71,7 +74,7 @@ LL |     std::mem::transmute(v)
    = note: target type: `[u32; D * W * H]` (this type does not have a fixed size)
 
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:75:5
+  --> $DIR/transmute-fail.rs:74:5
    |
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
@@ -80,7 +83,7 @@ LL |     std::mem::transmute(v)
    = note: target type: `[[u32; D * W]; H]` (size can vary because of [u32; D * W])
 
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:82:5
+  --> $DIR/transmute-fail.rs:81:5
    |
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
@@ -89,7 +92,7 @@ LL |     std::mem::transmute(v)
    = note: target type: `[u8; L * 2]` (this type does not have a fixed size)
 
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:89:5
+  --> $DIR/transmute-fail.rs:88:5
    |
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
@@ -98,7 +101,7 @@ LL |     std::mem::transmute(v)
    = note: target type: `[u16; L]` (this type does not have a fixed size)
 
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:96:5
+  --> $DIR/transmute-fail.rs:95:5
    |
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
@@ -107,7 +110,7 @@ LL |     std::mem::transmute(v)
    = note: target type: `[[u8; 1]; L]` (this type does not have a fixed size)
 
 error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
-  --> $DIR/transmute-fail.rs:105:5
+  --> $DIR/transmute-fail.rs:104:5
    |
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
@@ -115,19 +118,6 @@ LL |     std::mem::transmute(v)
    = note: source type: `[[u32; 2 * H]; W + W]` (size can vary because of [u32; 2 * H])
    = note: target type: `[[u32; W + W]; 2 * H]` (size can vary because of [u32; W + W])
 
-error[E0308]: mismatched types
-  --> $DIR/transmute-fail.rs:12:53
-   |
-LL | fn bar<const W: bool, const H: usize>(v: [[u32; H]; W]) -> [[u32; W]; H] {
-   |                                                     ^ expected `usize`, found `bool`
-
-error[E0308]: mismatched types
-  --> $DIR/transmute-fail.rs:12:67
-   |
-LL | fn bar<const W: bool, const H: usize>(v: [[u32; H]; W]) -> [[u32; W]; H] {
-   |                                                                   ^ expected `usize`, found `bool`
-
-error: aborting due to 15 previous errors
+error: aborting due to 14 previous errors
 
-Some errors have detailed explanations: E0308, E0512.
-For more information about an error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0512`.
diff --git a/tests/ui/const-generics/type_mismatch.rs b/tests/ui/const-generics/type_mismatch.rs
index daa13277be0..8187c785cd1 100644
--- a/tests/ui/const-generics/type_mismatch.rs
+++ b/tests/ui/const-generics/type_mismatch.rs
@@ -1,10 +1,10 @@
 fn foo<const N: usize>() -> [u8; N] {
-    bar::<N>() //~ ERROR mismatched types
+    bar::<N>()
     //~^ ERROR the constant `N` is not of type `u8`
 }
 
 fn bar<const N: u8>() -> [u8; N] {}
-//~^ ERROR mismatched types
+//~^ ERROR the constant `N` is not of type `usize`
 //~| ERROR mismatched types
 
 fn main() {}
diff --git a/tests/ui/const-generics/type_mismatch.stderr b/tests/ui/const-generics/type_mismatch.stderr
index 026999827c0..d1bb5c1242f 100644
--- a/tests/ui/const-generics/type_mismatch.stderr
+++ b/tests/ui/const-generics/type_mismatch.stderr
@@ -1,3 +1,9 @@
+error: the constant `N` is not of type `usize`
+  --> $DIR/type_mismatch.rs:6:26
+   |
+LL | fn bar<const N: u8>() -> [u8; N] {}
+   |                          ^^^^^^^ expected `usize`, found `u8`
+
 error: the constant `N` is not of type `u8`
   --> $DIR/type_mismatch.rs:2:11
    |
@@ -18,18 +24,6 @@ LL | fn bar<const N: u8>() -> [u8; N] {}
    |    |
    |    implicitly returns `()` as its body has no tail or `return` expression
 
-error[E0308]: mismatched types
-  --> $DIR/type_mismatch.rs:2:11
-   |
-LL |     bar::<N>()
-   |           ^ expected `u8`, found `usize`
-
-error[E0308]: mismatched types
-  --> $DIR/type_mismatch.rs:6:31
-   |
-LL | fn bar<const N: u8>() -> [u8; N] {}
-   |                               ^ expected `usize`, found `u8`
-
-error: aborting due to 4 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/consts/issue-36163.stderr b/tests/ui/consts/issue-36163.stderr
index 8a7a0981f41..52d3e003f0a 100644
--- a/tests/ui/consts/issue-36163.stderr
+++ b/tests/ui/consts/issue-36163.stderr
@@ -1,10 +1,10 @@
-error[E0391]: cycle detected when simplifying constant for the type system `Foo::B::{constant#0}`
+error[E0391]: cycle detected when simplifying constant for the type system `Foo::{constant#0}`
   --> $DIR/issue-36163.rs:4:9
    |
 LL |     B = A,
    |         ^
    |
-note: ...which requires const-evaluating + checking `Foo::B::{constant#0}`...
+note: ...which requires const-evaluating + checking `Foo::{constant#0}`...
   --> $DIR/issue-36163.rs:4:9
    |
 LL |     B = A,
@@ -19,7 +19,7 @@ note: ...which requires const-evaluating + checking `A`...
    |
 LL | const A: isize = Foo::B as isize;
    |                  ^^^^^^^^^^^^^^^
-   = note: ...which again requires simplifying constant for the type system `Foo::B::{constant#0}`, completing the cycle
+   = note: ...which again requires simplifying constant for the type system `Foo::{constant#0}`, completing the cycle
 note: cycle used when checking that `Foo` is well-formed
   --> $DIR/issue-36163.rs:3:1
    |
diff --git a/tests/ui/lifetimes/issue-95023.rs b/tests/ui/lifetimes/issue-95023.rs
index 7a67297c763..bcacd01474f 100644
--- a/tests/ui/lifetimes/issue-95023.rs
+++ b/tests/ui/lifetimes/issue-95023.rs
@@ -9,6 +9,5 @@ impl Fn(&isize) for Error {
     //~^ ERROR associated function in `impl` without body
     //~^^ ERROR method `foo` is not a member of trait `Fn` [E0407]
     //~^^^ ERROR associated type `B` not found for `Self` [E0220]
-    //~| ERROR associated type `B` not found for `Self` [E0220]
 }
 fn main() {}
diff --git a/tests/ui/lifetimes/issue-95023.stderr b/tests/ui/lifetimes/issue-95023.stderr
index 310dee51406..cbc0eeebee1 100644
--- a/tests/ui/lifetimes/issue-95023.stderr
+++ b/tests/ui/lifetimes/issue-95023.stderr
@@ -56,15 +56,7 @@ error[E0220]: associated type `B` not found for `Self`
 LL |     fn foo<const N: usize>(&self) -> Self::B<{ N }>;
    |                                            ^ help: `Self` has the following associated type: `Output`
 
-error[E0220]: associated type `B` not found for `Self`
-  --> $DIR/issue-95023.rs:8:44
-   |
-LL |     fn foo<const N: usize>(&self) -> Self::B<{ N }>;
-   |                                            ^ help: `Self` has the following associated type: `Output`
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: aborting due to 8 previous errors
+error: aborting due to 7 previous errors
 
 Some errors have detailed explanations: E0046, E0183, E0220, E0229, E0277, E0407.
 For more information about an error, try `rustc --explain E0046`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-trait-bounds.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-trait-bounds.stderr
index 4d543f6a155..7db6a77c77b 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-trait-bounds.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-trait-bounds.stderr
@@ -4,20 +4,11 @@ error[E0284]: type annotations needed: cannot normalize `process<T>::{constant#0
 LL | fn process<T: const Trait>(input: [(); T::make(2)]) -> [(); T::make(2)] {
    |                                   ^^^^^^^^^^^^^^^^ cannot normalize `process<T>::{constant#0}`
 
-error[E0284]: type annotations needed: cannot satisfy `the constant `T::make(P)` can be evaluated`
-  --> $DIR/const-trait-bounds.rs:18:5
+error[E0284]: type annotations needed: cannot normalize `Struct<T, P>::field::{constant#0}`
+  --> $DIR/const-trait-bounds.rs:20:12
    |
-LL |     [u32; T::make(P)]:,
-   |     ^^^^^^^^^^^^^^^^^ cannot satisfy `the constant `T::make(P)` can be evaluated`
-   |
-note: required by a bound in `Struct`
-  --> $DIR/const-trait-bounds.rs:18:11
-   |
-LL | struct Struct<T: const Trait, const P: usize>
-   |        ------ required by a bound in this struct
-LL | where
-LL |     [u32; T::make(P)]:,
-   |           ^^^^^^^^^^ required by this bound in `Struct`
+LL |     field: [u32; T::make(P)],
+   |            ^^^^^^^^^^^^^^^^^ cannot normalize `Struct<T, P>::field::{constant#0}`
 
 error[E0284]: type annotations needed: cannot normalize `process<T>::{constant#1}`
   --> $DIR/const-trait-bounds.rs:13:5
diff --git a/tests/ui/specialization/default-proj-ty-as-type-of-const-issue-125757.rs b/tests/ui/specialization/default-proj-ty-as-type-of-const-issue-125757.rs
index 59a015da84e..fb962ad24bf 100644
--- a/tests/ui/specialization/default-proj-ty-as-type-of-const-issue-125757.rs
+++ b/tests/ui/specialization/default-proj-ty-as-type-of-const-issue-125757.rs
@@ -14,6 +14,5 @@ struct Wrapper<const C: <i32 as Trait>::Type> {}
 
 impl<const C: usize> Wrapper<C> {}
 //~^ ERROR the constant `C` is not of type `<i32 as Trait>::Type`
-//~^^ ERROR mismatched types
 
 fn main() {}
diff --git a/tests/ui/specialization/default-proj-ty-as-type-of-const-issue-125757.stderr b/tests/ui/specialization/default-proj-ty-as-type-of-const-issue-125757.stderr
index 71d4277275f..7094ee8c67c 100644
--- a/tests/ui/specialization/default-proj-ty-as-type-of-const-issue-125757.stderr
+++ b/tests/ui/specialization/default-proj-ty-as-type-of-const-issue-125757.stderr
@@ -20,17 +20,5 @@ note: required by a const generic parameter in `Wrapper`
 LL | struct Wrapper<const C: <i32 as Trait>::Type> {}
    |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this const generic parameter in `Wrapper`
 
-error[E0308]: mismatched types
-  --> $DIR/default-proj-ty-as-type-of-const-issue-125757.rs:15:30
-   |
-LL | impl<const C: usize> Wrapper<C> {}
-   |                              ^ expected associated type, found `usize`
-   |
-   = note: expected associated type `<i32 as Trait>::Type`
-                         found type `usize`
-   = help: consider constraining the associated type `<i32 as Trait>::Type` to `usize`
-   = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.rs b/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.rs
index f89a463bc58..a0ee7714417 100644
--- a/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.rs
+++ b/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.rs
@@ -6,7 +6,6 @@
 struct S<const L: usize>;
 
 impl<const N: i32> Copy for S<N> {}
-//~^ ERROR: mismatched types
 impl<const M: usize> Copy for S<M> {}
 //~^ ERROR: conflicting implementations of trait `Copy` for type `S<_>`
 
diff --git a/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.stderr b/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.stderr
index 1dac58e1f69..2953bc95917 100644
--- a/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.stderr
+++ b/tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.stderr
@@ -1,19 +1,11 @@
 error[E0119]: conflicting implementations of trait `Copy` for type `S<_>`
-  --> $DIR/bad-const-wf-doesnt-specialize.rs:10:1
+  --> $DIR/bad-const-wf-doesnt-specialize.rs:9:1
    |
 LL | impl<const N: i32> Copy for S<N> {}
    | -------------------------------- first implementation here
-LL |
 LL | impl<const M: usize> Copy for S<M> {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `S<_>`
 
-error[E0308]: mismatched types
-  --> $DIR/bad-const-wf-doesnt-specialize.rs:8:31
-   |
-LL | impl<const N: i32> Copy for S<N> {}
-   |                               ^ expected `usize`, found `i32`
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0119, E0308.
-For more information about an error, try `rustc --explain E0119`.
+For more information about this error, try `rustc --explain E0119`.
diff --git a/tests/ui/stats/hir-stats.stderr b/tests/ui/stats/hir-stats.stderr
index a7a612a8a9e..b27f769ba34 100644
--- a/tests/ui/stats/hir-stats.stderr
+++ b/tests/ui/stats/hir-stats.stderr
@@ -123,15 +123,15 @@ hir-stats Lifetime                  24 ( 0.3%)             1            24
 hir-stats Mod                       32 ( 0.4%)             1            32
 hir-stats ExprField                 40 ( 0.4%)             1            40
 hir-stats TraitItemRef              56 ( 0.6%)             2            28
+hir-stats GenericArg                64 ( 0.7%)             4            16
+hir-stats - Type                      16 ( 0.2%)             1
+hir-stats - Lifetime                  48 ( 0.5%)             3
 hir-stats Local                     64 ( 0.7%)             1            64
 hir-stats Param                     64 ( 0.7%)             2            32
 hir-stats Body                      72 ( 0.8%)             3            24
 hir-stats InlineAsm                 72 ( 0.8%)             1            72
 hir-stats ImplItemRef               72 ( 0.8%)             2            36
 hir-stats Arm                       80 ( 0.9%)             2            40
-hir-stats GenericArg                96 ( 1.1%)             4            24
-hir-stats - Type                      24 ( 0.3%)             1
-hir-stats - Lifetime                  72 ( 0.8%)             3
 hir-stats FieldDef                  96 ( 1.1%)             2            48
 hir-stats Stmt                      96 ( 1.1%)             3            32
 hir-stats - Let                       32 ( 0.4%)             1
@@ -155,8 +155,8 @@ hir-stats Generics                 560 ( 6.2%)            10            56
 hir-stats Ty                       720 ( 8.0%)            15            48
 hir-stats - Ptr                       48 ( 0.5%)             1
 hir-stats - Ref                       48 ( 0.5%)             1
-hir-stats - Path                     624 ( 6.9%)            13
-hir-stats Expr                     768 ( 8.5%)            12            64
+hir-stats - Path                     624 ( 7.0%)            13
+hir-stats Expr                     768 ( 8.6%)            12            64
 hir-stats - Path                      64 ( 0.7%)             1
 hir-stats - Struct                    64 ( 0.7%)             1
 hir-stats - Match                     64 ( 0.7%)             1
@@ -174,5 +174,5 @@ hir-stats - Use                      352 ( 3.9%)             4
 hir-stats Path                   1_240 (13.8%)            31            40
 hir-stats PathSegment            1_920 (21.4%)            40            48
 hir-stats ----------------------------------------------------------------
-hir-stats Total                  8_992
+hir-stats Total                  8_960
 hir-stats
diff --git a/tests/ui/traits/non_lifetime_binders/capture-late-ct-in-anon.rs b/tests/ui/traits/non_lifetime_binders/capture-late-ct-in-anon.rs
deleted file mode 100644
index bbae67f0bad..00000000000
--- a/tests/ui/traits/non_lifetime_binders/capture-late-ct-in-anon.rs
+++ /dev/null
@@ -1,11 +0,0 @@
-#![feature(non_lifetime_binders)]
-//~^ WARN the feature `non_lifetime_binders` is incomplete
-
-fn b()
-where
-    for<const C: usize> [(); C]: Copy,
-    //~^ ERROR cannot capture late-bound const parameter in constant
-{
-}
-
-fn main() {}
diff --git a/tests/ui/traits/non_lifetime_binders/capture-late-ct-in-anon.stderr b/tests/ui/traits/non_lifetime_binders/capture-late-ct-in-anon.stderr
deleted file mode 100644
index 4e0441c1c7d..00000000000
--- a/tests/ui/traits/non_lifetime_binders/capture-late-ct-in-anon.stderr
+++ /dev/null
@@ -1,19 +0,0 @@
-warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/capture-late-ct-in-anon.rs:1:12
-   |
-LL | #![feature(non_lifetime_binders)]
-   |            ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #108185 <https://github.com/rust-lang/rust/issues/108185> for more information
-   = note: `#[warn(incomplete_features)]` on by default
-
-error: cannot capture late-bound const parameter in constant
-  --> $DIR/capture-late-ct-in-anon.rs:6:30
-   |
-LL |     for<const C: usize> [(); C]: Copy,
-   |         --------------       ^
-   |         |
-   |         parameter defined here
-
-error: aborting due to 1 previous error; 1 warning emitted
-
diff --git a/tests/ui/transmutability/issue-101739-1.rs b/tests/ui/transmutability/issue-101739-1.rs
index 0695d7d409f..20bd7917e53 100644
--- a/tests/ui/transmutability/issue-101739-1.rs
+++ b/tests/ui/transmutability/issue-101739-1.rs
@@ -7,7 +7,6 @@ mod assert {
     where
         Dst: BikeshedIntrinsicFrom<Src, ASSUME_ALIGNMENT>, //~ ERROR cannot find type `Dst` in this scope
         //~^ the constant `ASSUME_ALIGNMENT` is not of type `Assume`
-        //~| ERROR: mismatched types
     {
     }
 }
diff --git a/tests/ui/transmutability/issue-101739-1.stderr b/tests/ui/transmutability/issue-101739-1.stderr
index 6f79bf7b424..ba18a980f4d 100644
--- a/tests/ui/transmutability/issue-101739-1.stderr
+++ b/tests/ui/transmutability/issue-101739-1.stderr
@@ -13,13 +13,6 @@ LL |         Dst: BikeshedIntrinsicFrom<Src, ASSUME_ALIGNMENT>,
 note: required by a const generic parameter in `BikeshedIntrinsicFrom`
   --> $SRC_DIR/core/src/mem/transmutability.rs:LL:COL
 
-error[E0308]: mismatched types
-  --> $DIR/issue-101739-1.rs:8:41
-   |
-LL |         Dst: BikeshedIntrinsicFrom<Src, ASSUME_ALIGNMENT>,
-   |                                         ^^^^^^^^^^^^^^^^ expected `Assume`, found `bool`
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0308, E0412.
-For more information about an error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0412`.
diff --git a/tests/ui/transmutability/issue-101739-2.rs b/tests/ui/transmutability/issue-101739-2.rs
index 1c0bd29d707..8b36bf3dcb1 100644
--- a/tests/ui/transmutability/issue-101739-2.rs
+++ b/tests/ui/transmutability/issue-101739-2.rs
@@ -16,7 +16,7 @@ mod assert {
     where
         Dst: BikeshedIntrinsicFrom< //~ ERROR trait takes at most 2 generic arguments but 5 generic arguments were supplied
             Src,
-            ASSUME_ALIGNMENT, //~ ERROR: mismatched types
+            ASSUME_ALIGNMENT,
             ASSUME_LIFETIMES,
             ASSUME_VALIDITY,
             ASSUME_VISIBILITY,
diff --git a/tests/ui/transmutability/issue-101739-2.stderr b/tests/ui/transmutability/issue-101739-2.stderr
index 38912696c18..519a374dc22 100644
--- a/tests/ui/transmutability/issue-101739-2.stderr
+++ b/tests/ui/transmutability/issue-101739-2.stderr
@@ -9,13 +9,6 @@ LL | |             ASSUME_VALIDITY,
 LL | |             ASSUME_VISIBILITY,
    | |_____________________________- help: remove these generic arguments
 
-error[E0308]: mismatched types
-  --> $DIR/issue-101739-2.rs:19:13
-   |
-LL |             ASSUME_ALIGNMENT,
-   |             ^^^^^^^^^^^^^^^^ expected `Assume`, found `bool`
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0107, E0308.
-For more information about an error, try `rustc --explain E0107`.
+For more information about this error, try `rustc --explain E0107`.
diff --git a/tests/ui/typeck/issue-114918/const-in-impl-fn-return-type.rs b/tests/ui/typeck/issue-114918/const-in-impl-fn-return-type.rs
index 193544ebd3f..9fc249198d0 100644
--- a/tests/ui/typeck/issue-114918/const-in-impl-fn-return-type.rs
+++ b/tests/ui/typeck/issue-114918/const-in-impl-fn-return-type.rs
@@ -5,7 +5,7 @@
 
 
 trait Trait {
-    fn func<const N: u32>() -> [ (); N ]; //~ ERROR mismatched types
+    fn func<const N: u32>() -> [ (); N ]; //~ ERROR the constant `N` is not of type `usize`
 }
 
 struct S {}
diff --git a/tests/ui/typeck/issue-114918/const-in-impl-fn-return-type.stderr b/tests/ui/typeck/issue-114918/const-in-impl-fn-return-type.stderr
index 16aaf0615ed..bff926a2081 100644
--- a/tests/ui/typeck/issue-114918/const-in-impl-fn-return-type.stderr
+++ b/tests/ui/typeck/issue-114918/const-in-impl-fn-return-type.stderr
@@ -4,11 +4,11 @@ error[E0308]: mismatched types
 LL |     fn func<const N: u32>() -> [ (); { () }] {
    |                                        ^^ expected `usize`, found `()`
 
-error[E0308]: mismatched types
-  --> $DIR/const-in-impl-fn-return-type.rs:8:38
+error: the constant `N` is not of type `usize`
+  --> $DIR/const-in-impl-fn-return-type.rs:8:32
    |
 LL |     fn func<const N: u32>() -> [ (); N ];
-   |                                      ^ expected `usize`, found `u32`
+   |                                ^^^^^^^^^ expected `usize`, found `u32`
 
 error: aborting due to 2 previous errors