Rollup merge of #149210 - ShoyuVanilla:issue-148161, r=jdonszelmann

fix: Do not ICE on normalization failure of an extern static item

Fixes #148161

Author: matthiaskrgr

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1186,14 +1186,21 @@ pub(crate) fn check_static_item<'tcx>(
 ) -> Result<(), ErrorGuaranteed> {
     enter_wf_checking_ctxt(tcx, item_id, |wfcx| {
         let span = tcx.ty_span(item_id);
-        let item_ty = wfcx.deeply_normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
+        let loc = Some(WellFormedLoc::Ty(item_id));
+        let item_ty = wfcx.deeply_normalize(span, loc, ty);
 
         let is_foreign_item = tcx.is_foreign_item(item_id);
+        let is_structurally_foreign_item = || {
+            let tail = tcx.struct_tail_raw(
+                item_ty,
+                &ObligationCause::dummy(),
+                |ty| wfcx.deeply_normalize(span, loc, ty),
+                || {},
+            );
 
-        let forbid_unsized = !is_foreign_item || {
-            let tail = tcx.struct_tail_for_codegen(item_ty, wfcx.infcx.typing_env(wfcx.param_env));
-            !matches!(tail.kind(), ty::Foreign(_))
+            matches!(tail.kind(), ty::Foreign(_))
         };
+        let forbid_unsized = !(is_foreign_item && is_structurally_foreign_item());
 
         wfcx.register_wf_obligation(span, Some(WellFormedLoc::Ty(item_id)), item_ty.into());
         if forbid_unsized {

tests/ui/static/extern-static-normalization-failure-issue-148161.rs

@@ -0,0 +1,21 @@
+// Regression test for https://github.com/rust-lang/rust/issues/148161
+trait Trait {
+    type Assoc;
+}
+
+impl Trait for u8 {
+    type Assoc = i8;
+}
+
+struct Struct<T: Trait> {
+    member: T::Assoc,
+}
+
+unsafe extern "C" {
+    // This used to be an ICE due to normalization failure on `<Struct<i8> as Trait>::Assoc`
+    // while wf checking this static item.
+    static VAR: Struct<i8>;
+    //~^ ERROR: the trait bound `i8: Trait` is not satisfied
+}
+
+fn main() {}

tests/ui/static/extern-static-normalization-failure-issue-148161.stderr

@@ -0,0 +1,20 @@
+error[E0277]: the trait bound `i8: Trait` is not satisfied
+  --> $DIR/extern-static-normalization-failure-issue-148161.rs:17:17
+   |
+LL |     static VAR: Struct<i8>;
+   |                 ^^^^^^^^^^ the trait `Trait` is not implemented for `i8`
+   |
+help: the trait `Trait` is implemented for `u8`
+  --> $DIR/extern-static-normalization-failure-issue-148161.rs:6:1
+   |
+LL | impl Trait for u8 {
+   | ^^^^^^^^^^^^^^^^^
+note: required by a bound in `Struct`
+  --> $DIR/extern-static-normalization-failure-issue-148161.rs:10:18
+   |
+LL | struct Struct<T: Trait> {
+   |                  ^^^^^ required by this bound in `Struct`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.