mgca: fix issue with mismatched array valtree/valtree tys

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -2492,8 +2492,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     ) -> Const<'tcx> {
         let tcx = self.tcx();
 
-        let (elem_ty, len) = match ty.kind() {
-            ty::Array(elem_ty, len) => (elem_ty, len),
+        let elem_ty = match ty.kind() {
+            ty::Array(elem_ty, _) => elem_ty,
             ty::Error(e) => return Const::new_error(tcx, *e),
             _ => {
                 let e = tcx
@@ -2509,28 +2509,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             .map(|elem| self.lower_const_arg(elem, *elem_ty))
             .collect::<Vec<_>>();
 
-        let len = tcx
-            .try_normalize_erasing_regions(
-                ty::TypingEnv::new(ty::ParamEnv::empty(), TypingMode::non_body_analysis()),
-                Unnormalized::new_wip(*len),
-            )
-            .unwrap_or(*len);
-        if let Some(expected_len) = len.try_to_target_usize(tcx)
-            && expected_len != elems.len() as u64
-        {
-            let e = tcx.dcx().span_err(
-                array_expr.span,
-                format!(
-                    "expected array with {expected_len} elements, found {} elements",
-                    array_expr.elems.len()
-                ),
-            );
-            return Const::new_error(tcx, e);
-        }
-
+        // The array len passed in the type might be an infer var, or a const param, or it could
+        // just be an incorrect constant. So, construct the resulting valtree's type based on the
+        // provided syntax rather than the expected type. The surrounding typeck will catch any
+        // mismatches.
+        let valtree_ty = Ty::new_array(tcx, *elem_ty, elems.len() as u64);
         let valtree = ty::ValTree::from_branches(tcx, elems);
-
-        ty::Const::new_value(tcx, valtree, ty)
+        ty::Const::new_value(tcx, valtree, valtree_ty)
     }
 
     fn try_recover_misrepresented_function_call(

tests/ui/const-generics/mgca/array-const-arg-len-mismatch.rs

@@ -28,13 +28,13 @@ fn baz<const A: [u8; <S as Trait>::LEN]>() {}
 
 fn main() {
     foo::<u8, 2, { [] }>();
-    //~^ ERROR: expected array with 2 elements, found 0 elements
+    //~^ ERROR: the constant `*b""` is not of type `[u8; 2]`
     foo::<u8, 2, { [0, 0, 0] }>();
-    //~^ ERROR: expected array with 2 elements, found 3 elements
+    //~^ ERROR: the constant `*b"\x00\x00\x00"` is not of type `[u8; 2]`
     bar::<{ [] }>();
-    //~^ ERROR: expected array with 2 elements, found 0 elements
+    //~^ ERROR: the constant `*b""` is not of type `[u8; 2]`
     bar::<{ [1, 2, 3] }>();
-    //~^ ERROR: expected array with 2 elements, found 3 elements
+    //~^ ERROR: the constant `*b"\x01\x02\x03"` is not of type `[u8; 2]`
     baz::<{ [42] }>();
-    //~^ ERROR: expected array with 3 elements, found 1 elements
+    //~^ ERROR: the constant `*b"*"` is not of type `[u8; 3]`
 }

tests/ui/const-generics/mgca/array-const-arg-len-mismatch.stderr

@@ -1,32 +1,62 @@
-error: expected array with 2 elements, found 0 elements
-  --> $DIR/array-const-arg-len-mismatch.rs:30:20
+error: the constant `*b""` is not of type `[u8; 2]`
+  --> $DIR/array-const-arg-len-mismatch.rs:30:11
    |
 LL |     foo::<u8, 2, { [] }>();
-   |                    ^^
+   |           ^^ expected `[u8; 2]`, found `[u8; 0]`
+   |
+note: required by a const generic parameter in `foo`
+  --> $DIR/array-const-arg-len-mismatch.rs:11:42
+   |
+LL | fn foo<T: ConstParamTy_, const N: usize, const M: [T; N]>() -> [T; N] {
+   |                                          ^^^^^^^^^^^^^^^ required by this const generic parameter in `foo`
 
-error: expected array with 2 elements, found 3 elements
-  --> $DIR/array-const-arg-len-mismatch.rs:32:20
+error: the constant `*b"\x00\x00\x00"` is not of type `[u8; 2]`
+  --> $DIR/array-const-arg-len-mismatch.rs:32:11
    |
 LL |     foo::<u8, 2, { [0, 0, 0] }>();
-   |                    ^^^^^^^^^
+   |           ^^ expected `[u8; 2]`, found `[u8; 3]`
+   |
+note: required by a const generic parameter in `foo`
+  --> $DIR/array-const-arg-len-mismatch.rs:11:42
+   |
+LL | fn foo<T: ConstParamTy_, const N: usize, const M: [T; N]>() -> [T; N] {
+   |                                          ^^^^^^^^^^^^^^^ required by this const generic parameter in `foo`
 
-error: expected array with 2 elements, found 0 elements
+error: the constant `*b""` is not of type `[u8; 2]`
   --> $DIR/array-const-arg-len-mismatch.rs:34:13
    |
 LL |     bar::<{ [] }>();
-   |             ^^
+   |             ^^ expected `[u8; 2]`, found `[u8; 0]`
+   |
+note: required by a const generic parameter in `bar`
+  --> $DIR/array-const-arg-len-mismatch.rs:15:8
+   |
+LL | fn bar<const A: [u8; 2]>() {}
+   |        ^^^^^^^^^^^^^^^^ required by this const generic parameter in `bar`
 
-error: expected array with 2 elements, found 3 elements
+error: the constant `*b"\x01\x02\x03"` is not of type `[u8; 2]`
   --> $DIR/array-const-arg-len-mismatch.rs:36:13
    |
 LL |     bar::<{ [1, 2, 3] }>();
-   |             ^^^^^^^^^
+   |             ^^^^^^^^^ expected `[u8; 2]`, found `[u8; 3]`
+   |
+note: required by a const generic parameter in `bar`
+  --> $DIR/array-const-arg-len-mismatch.rs:15:8
+   |
+LL | fn bar<const A: [u8; 2]>() {}
+   |        ^^^^^^^^^^^^^^^^ required by this const generic parameter in `bar`
 
-error: expected array with 3 elements, found 1 elements
+error: the constant `*b"*"` is not of type `[u8; 3]`
   --> $DIR/array-const-arg-len-mismatch.rs:38:13
    |
 LL |     baz::<{ [42] }>();
-   |             ^^^^
+   |             ^^^^ expected `[u8; 3]`, found `[u8; 1]`
+   |
+note: required by a const generic parameter in `baz`
+  --> $DIR/array-const-arg-len-mismatch.rs:27:8
+   |
+LL | fn baz<const A: [u8; <S as Trait>::LEN]>() {}
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this const generic parameter in `baz`
 
 error: aborting due to 5 previous errors
 

tests/crashes/160553.rs → tests/ui/const-generics/mgca/generic_const_items-mismatched-array-len.rs

@@ -1,5 +1,4 @@
-//@ known-bug: #160553
-//@ compile-flags: -Copt-level=0
+//! Regression test for #160553 (used to ICE)
 #![allow(incomplete_features)]
 #![feature(adt_const_params, min_generic_const_args, macroless_generic_const_args)]
 #![feature(generic_const_parameter_types)]
@@ -20,6 +19,7 @@ fn foo<T: Trait, const A: [u8; <T as Trait>::LEN]>() -> [u8; <T as Trait>::LEN]
 
 fn bar<T: Trait>() -> [u8; <T as Trait>::LEN] {
     foo::<T, { [1, 2, 3] }>()
+    //~^ ERROR the constant `*b"\x01\x02\x03"` is not of type `[u8; <T as Trait>::LEN]`
 }
 
 fn main() {

tests/ui/const-generics/mgca/generic_const_items-mismatched-array-len.stderr

@@ -0,0 +1,14 @@
+error: the constant `*b"\x01\x02\x03"` is not of type `[u8; <T as Trait>::LEN]`
+  --> $DIR/generic_const_items-mismatched-array-len.rs:21:11
+   |
+LL |     foo::<T, { [1, 2, 3] }>()
+   |           ^ expected `[u8; <T as Trait>::LEN]`, found `[u8; 3]`
+   |
+note: required by a const generic parameter in `foo`
+  --> $DIR/generic_const_items-mismatched-array-len.rs:16:18
+   |
+LL | fn foo<T: Trait, const A: [u8; <T as Trait>::LEN]>() -> [u8; <T as Trait>::LEN] {
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this const generic parameter in `foo`
+
+error: aborting due to 1 previous error
+

tests/ui/const-generics/mgca/generic_const_parameter_types-inferred-array-len.rs

@@ -0,0 +1,8 @@
+//@ check-pass
+
+#![feature(min_adt_const_params, min_generic_const_args, generic_const_parameter_types)]
+fn foo<const N: usize, const A: [u8; N]>() {}
+
+fn main() {
+    foo::<_, core::direct_const_arg!([0, 1, 2, 3])>();
+}