miri: normalize struct tail in ABI compat check

Author: Lukas Markeffsky

compiler/rustc_const_eval/src/interpret/terminator.rs

@@ -372,7 +372,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         };
         if let (Some(caller), Some(callee)) = (pointee_ty(caller.ty)?, pointee_ty(callee.ty)?) {
             // This is okay if they have the same metadata type.
-            let meta_ty = |ty: Ty<'tcx>| ty.ptr_metadata_ty(*self.tcx, |ty| ty);
+            let normalize = |ty: Ty<'tcx>| self.tcx.normalize_erasing_regions(self.param_env, ty);
+            let meta_ty = |ty: Ty<'tcx>| ty.ptr_metadata_ty(*self.tcx, normalize);
             return Ok(meta_ty(caller) == meta_ty(callee));
         }
 

src/tools/miri/tests/pass/function_calls/abi_compat_normalize.rs

@@ -0,0 +1,20 @@
+// regression test for an ICE: https://github.com/rust-lang/miri/issues/3282
+
+trait Id {
+    type Assoc: ?Sized;
+}
+
+impl<T: ?Sized> Id for T {
+    type Assoc = T;
+}
+
+#[repr(transparent)]
+struct Foo<T: ?Sized> {
+    field: <T as Id>::Assoc,
+}
+
+fn main() {
+    let x = unsafe { std::mem::transmute::<fn(&str), fn(&Foo<str>)>(|_| ()) };
+    let foo: &Foo<str> = unsafe { &*("uwu" as *const str as *const Foo<str>) };
+    x(foo);
+}