Auto merge of #115699 - RalfJung:interpret-abi-compat, r=oli-obk

interpret: change ABI-compat test to be type-based

This makes the test consistent across targets. Otherwise the chances are very high that ABI mismatches get accepted on x86_64 but still fail on many other targets with more complicated ABIs.

This implements (most of) the rules described in https://github.com/rust-lang/rust/pull/115476.

compiler/rustc_middle/src/mir/interpret/error.rs

@@ -255,9 +255,16 @@ impl_into_diagnostic_arg_through_debug! {
 
 /// Error information for when the program caused Undefined Behavior.
 #[derive(Debug)]
-pub enum UndefinedBehaviorInfo<'a> {
+pub enum UndefinedBehaviorInfo<'tcx> {
     /// Free-form case. Only for errors that are never caught! Used by miri
     Ub(String),
+    // FIXME(fee1-dead) these should all be actual variants of the enum instead of dynamically
+    // dispatched
+    /// A custom (free-form) fluent-translated error, created by `err_ub_custom!`.
+    Custom(crate::error::CustomSubdiagnostic<'tcx>),
+    /// Validation error.
+    ValidationError(ValidationErrorInfo<'tcx>),
+
     /// Unreachable code was executed.
     Unreachable,
     /// A slice/array index projection went out-of-bounds.
@@ -319,12 +326,10 @@ pub enum UndefinedBehaviorInfo<'a> {
     UninhabitedEnumVariantWritten(VariantIdx),
     /// An uninhabited enum variant is projected.
     UninhabitedEnumVariantRead(VariantIdx),
-    /// Validation error.
-    ValidationError(ValidationErrorInfo<'a>),
-    // FIXME(fee1-dead) these should all be actual variants of the enum instead of dynamically
-    // dispatched
-    /// A custom (free-form) error, created by `err_ub_custom!`.
-    Custom(crate::error::CustomSubdiagnostic<'a>),
+    /// ABI-incompatible argument types.
+    AbiMismatchArgument { caller_ty: Ty<'tcx>, callee_ty: Ty<'tcx> },
+    /// ABI-incompatible return types.
+    AbiMismatchReturn { caller_ty: Ty<'tcx>, callee_ty: Ty<'tcx> },
 }
 
 #[derive(Debug, Clone, Copy)]

compiler/rustc_middle/src/ty/sty.rs

@@ -2749,6 +2749,8 @@ impl<'tcx> Ty<'tcx> {
             | ty::Error(_)
             // Extern types have metadata = ().
             | ty::Foreign(..)
+            // `dyn*` has no metadata
+            | ty::Dynamic(_, _, DynKind::DynStar)
             // If returned by `struct_tail_without_normalization` this is a unit struct
             // without any fields, or not a struct, and therefore is Sized.
             | ty::Adt(..)
@@ -2757,7 +2759,7 @@ impl<'tcx> Ty<'tcx> {
             | ty::Tuple(..) => (tcx.types.unit, false),
 
             ty::Str | ty::Slice(_) => (tcx.types.usize, false),
-            ty::Dynamic(..) => {
+            ty::Dynamic(_, _, DynKind::Dyn) => {
                 let dyn_metadata = tcx.require_lang_item(LangItem::DynMetadata, None);
                 (tcx.type_of(dyn_metadata).instantiate(tcx, &[tail.into()]), false)
             },