Auto merge of #150380 - Kivooeo:add-match-for-constkidn, r=BoxyUwU

avoid recreating field_const vec

r? BoxyUwU

fixes #150354
fixes #150355

Author: bors

compiler/rustc_ty_utils/src/consts.rs

@@ -39,25 +39,16 @@ fn destructure_const<'tcx>(
             (field_consts, None)
         }
         ty::Adt(def, _) if def.variants().is_empty() => bug!("unreachable"),
-        ty::Adt(def, args) => {
-            let (variant_idx, branches) = if def.is_enum() {
+        ty::Adt(def, _) => {
+            let (variant_idx, field_consts) = if def.is_enum() {
                 let (head, rest) = branches.split_first().unwrap();
                 (VariantIdx::from_u32(head.to_leaf().to_u32()), rest)
             } else {
                 (FIRST_VARIANT, branches)
             };
-            let fields = &def.variant(variant_idx).fields;
-            let mut field_consts = Vec::with_capacity(fields.len());
-
-            for (field, field_valtree) in iter::zip(fields, branches) {
-                let field_ty = field.ty(tcx, args);
-                let field_const =
-                    ty::Const::new_value(tcx, field_valtree.to_value().valtree, field_ty);
-                field_consts.push(field_const);
-            }
             debug!(?field_consts);
 
-            (field_consts, Some(variant_idx))
+            (field_consts.to_vec(), Some(variant_idx))
         }
         ty::Tuple(elem_tys) => {
             let fields = iter::zip(*elem_tys, branches)

tests/ui/const-generics/mgca/printing_valtrees_supports_non_values.rs

@@ -0,0 +1,27 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/150354>
+//@ edition 2024
+
+#![allow(incomplete_features)]
+#![feature(min_generic_const_args, adt_const_params)]
+
+#[derive(Eq, PartialEq, core::marker::ConstParamTy)]
+struct Foo;
+
+trait Trait {
+    #[type_const]
+    const ASSOC: usize;
+}
+
+fn foo<const N: Foo>() {}
+
+fn bar<T, const N: u32>() {
+    foo::<{ Option::Some::<u32> { 0: N } }>;
+    //~^ ERROR the constant `Option::<u32>::Some(N)` is not of type `Foo`
+}
+
+fn baz<T: Trait>() {
+    foo::<{ Option::Some::<u32> { 0: <T as Trait>::ASSOC } }>();
+    //~^ ERROR the constant `Option::<u32>::Some(<T as Trait>::ASSOC)` is not of type `Foo`
+}
+
+fn main() {}

tests/ui/const-generics/mgca/printing_valtrees_supports_non_values.stderr

@@ -0,0 +1,26 @@
+error: the constant `Option::<u32>::Some(N)` is not of type `Foo`
+  --> $DIR/printing_valtrees_supports_non_values.rs:18:13
+   |
+LL |     foo::<{ Option::Some::<u32> { 0: N } }>;
+   |             ^^^^^^^^^^^^^^^^^^^ expected `Foo`, found `Option<u32>`
+   |
+note: required by a const generic parameter in `foo`
+  --> $DIR/printing_valtrees_supports_non_values.rs:15:8
+   |
+LL | fn foo<const N: Foo>() {}
+   |        ^^^^^^^^^^^^ required by this const generic parameter in `foo`
+
+error: the constant `Option::<u32>::Some(<T as Trait>::ASSOC)` is not of type `Foo`
+  --> $DIR/printing_valtrees_supports_non_values.rs:23:13
+   |
+LL |     foo::<{ Option::Some::<u32> { 0: <T as Trait>::ASSOC } }>();
+   |             ^^^^^^^^^^^^^^^^^^^ expected `Foo`, found `Option<u32>`
+   |
+note: required by a const generic parameter in `foo`
+  --> $DIR/printing_valtrees_supports_non_values.rs:15:8
+   |
+LL | fn foo<const N: Foo>() {}
+   |        ^^^^^^^^^^^^ required by this const generic parameter in `foo`
+
+error: aborting due to 2 previous errors
+