Add a regression test and fix it.

Author: oli-obk

compiler/rustc_codegen_ssa/src/mir/place.rs

@@ -463,7 +463,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 mir::ProjectionElem::Field(ref field, _) => {
                     cg_base.project_field(bx, field.index())
                 }
-                mir::ProjectionElem::OpaqueCast(ty) => cg_base.project_type(bx, ty),
+                mir::ProjectionElem::OpaqueCast(ty) => {
+                    cg_base.project_type(bx, self.monomorphize(ty))
+                }
                 mir::ProjectionElem::Index(index) => {
                     let index = &mir::Operand::Copy(mir::Place::from(index));
                     let index = self.codegen_operand(bx, index);

tests/ui/type-alias-impl-trait/destructure_tait-layout_of-ice-113594.rs

@@ -0,0 +1,14 @@
+// build-pass
+// edition: 2021
+
+#![feature(type_alias_impl_trait)]
+
+fn foo<T>(x: T) {
+    type Opaque<T> = impl Sized;
+    let foo: Opaque<T> = (x,);
+    let (a,): (T,) = foo;
+}
+
+fn main() {
+    foo::<u32>(1);
+}