Use ConstArgKind::Path for all paths

Like in the previous commit, (most of) these changes to error output are
not desired. They are merely committed temporarily to make it easier to
see what's changed.

compiler/rustc_ast_lowering/src/lib.rs

@@ -2396,9 +2396,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let maybe_res =
             self.resolver.get_partial_res(expr.id).and_then(|partial_res| partial_res.full_res());
         debug!("res={:?}", maybe_res);
-        // FIXME(min_generic_const_args): for now we only lower params to ConstArgKind::Path
         if let Some(res) = maybe_res
-            && let Res::Def(DefKind::ConstParam, _) = res
+            && let Res::Def(DefKind::ConstParam | DefKind::Const, _) = res
             && let ExprKind::Path(qself, path) = &expr.kind
         {
             let qpath = self.lower_qpath(

tests/ui/const-generics/bad-generic-in-copy-impl.stderr

@@ -1,17 +1,36 @@
-error[E0308]: mismatched types
-  --> $DIR/bad-generic-in-copy-impl.rs:3:13
+error: the constant `1` is not of type `usize`
+  --> $DIR/bad-generic-in-copy-impl.rs:3:8
    |
 LL |     x: [u8; SIZE],
-   |             ^^^^ expected `usize`, found `u32`
+   |        ^^^^^^^^^^ expected `usize`, found `u32`
 
-error[E0308]: mismatched types
-  --> $DIR/bad-generic-in-copy-impl.rs:3:13
+error[E0204]: the trait `Copy` cannot be implemented for this type
+  --> $DIR/bad-generic-in-copy-impl.rs:1:10
    |
+LL | #[derive(Copy, Clone)]
+   |          ^^^^
+LL | pub struct Foo {
 LL |     x: [u8; SIZE],
-   |             ^^^^ expected `usize`, found `u32`
+   |     ------------- this field does not implement `Copy`
    |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+note: the `Copy` impl for `[u8; 1]` requires that `the constant `1` has type `usize``
+  --> $DIR/bad-generic-in-copy-impl.rs:3:8
+   |
+LL |     x: [u8; SIZE],
+   |        ^^^^^^^^^^
+   = note: this error originates in the derive macro `Copy` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: the constant `1` is not of type `usize`
+  --> $DIR/bad-generic-in-copy-impl.rs:3:5
+   |
+LL | #[derive(Copy, Clone)]
+   |                ----- in this derive macro expansion
+LL | pub struct Foo {
+LL |     x: [u8; SIZE],
+   |     ^^^^^^^^^^^^^ expected `usize`, found `u32`
+   |
+   = note: this error originates in the derive macro `Clone` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0204`.

tests/ui/const-generics/generic_const_exprs/type-alias-bounds.neg.stderr

@@ -1,15 +1,3 @@
-error[E0277]: the trait bound `String: Copy` is not satisfied
-  --> $DIR/type-alias-bounds.rs:23:12
-   |
-LL |     let _: AliasConstUnused<String>;
-   |            ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `String`
-   |
-note: required by a bound in `ct_unused_0::AliasConstUnused`
-  --> $DIR/type-alias-bounds.rs:20:30
-   |
-LL |     type AliasConstUnused<T: Copy> = (T, I32<{ DATA }>);
-   |                              ^^^^ required by this bound in `AliasConstUnused`
-
 error[E0277]: the trait bound `String: Copy` is not satisfied
   --> $DIR/type-alias-bounds.rs:31:12
    |
@@ -58,6 +46,6 @@ note: required by a bound in `AliasFnUsed`
 LL |     type AliasFnUsed<T: Trait + Copy> = I32<{ code::<T>() }>;
    |                                 ^^^^ required by this bound in `AliasFnUsed`
 
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/consts/const-len-underflow-separate-spans.old.stderr

@@ -4,12 +4,6 @@ error[E0080]: evaluation of constant value failed
 LL | const LEN: usize = ONE - TWO;
    |                    ^^^^^^^^^ attempt to compute `1_usize - 2_usize`, which would overflow
 
-note: erroneous constant encountered
-  --> $DIR/const-len-underflow-separate-spans.rs:14:17
-   |
-LL |     let a: [i8; LEN] = unimplemented!();
-   |                 ^^^
-
 error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0080`.

tests/ui/consts/issue-39974.stderr

@@ -9,12 +9,6 @@ help: use a float literal
 LL | const LENGTH: f64 = 2.0;
    |                      ++
 
-error[E0308]: mismatched types
-  --> $DIR/issue-39974.rs:5:19
-   |
-LL |     f: [[f64; 2]; LENGTH],
-   |                   ^^^^^^ expected `usize`, found `f64`
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0308`.