FIx ICE on wf check for foreign fns

Author: JohnTitor

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -153,6 +153,7 @@ fn msg_span_from_early_bound_and_free_regions(
         Some(Node::Item(it)) => item_scope_tag(&it),
         Some(Node::TraitItem(it)) => trait_item_scope_tag(&it),
         Some(Node::ImplItem(it)) => impl_item_scope_tag(&it),
+        Some(Node::ForeignItem(it)) => foreign_item_scope_tag(&it),
         _ => unreachable!(),
     };
     let (prefix, span) = match *region {
@@ -233,6 +234,13 @@ fn impl_item_scope_tag(item: &hir::ImplItem<'_>) -> &'static str {
     }
 }
 
+fn foreign_item_scope_tag(item: &hir::ForeignItem<'_>) -> &'static str {
+    match item.kind {
+        hir::ForeignItemKind::Fn(..) => "method body",
+        hir::ForeignItemKind::Static(..) | hir::ForeignItemKind::Type => "associated item",
+    }
+}
+
 fn explain_span(tcx: TyCtxt<'tcx>, heading: &str, span: Span) -> (String, Option<Span>) {
     let lo = tcx.sess.source_map().lookup_char_pos(span.lo());
     (format!("the {} at {}:{}", heading, lo.line, lo.col.to_usize() + 1), Some(span))

compiler/rustc_typeck/src/check/wfcheck.rs

@@ -51,7 +51,7 @@ impl<'tcx> CheckWfFcxBuilder<'tcx> {
             let fcx = FnCtxt::new(&inh, param_env, id);
             if !inh.tcx.features().trivial_bounds {
                 // As predicates are cached rather than obligations, this
-                // needsto be called first so that they are checked with an
+                // needs to be called first so that they are checked with an
                 // empty `param_env`.
                 check_false_global_bounds(&fcx, span, id);
             }

src/test/ui/wf/wf-in-foreign-fn-decls-issue-80468.rs

@@ -0,0 +1,17 @@
+// Regression test for #80468.
+
+#![crate_type = "lib"]
+
+pub trait Trait {}
+
+#[repr(transparent)]
+pub struct Wrapper<T: Trait>(T);
+
+#[repr(transparent)]
+pub struct Ref<'a>(&'a u8);
+
+impl Trait for Ref {} //~ ERROR:  implicit elided lifetime not allowed here
+
+extern "C" {
+    pub fn repro(_: Wrapper<Ref>); //~ ERROR: mismatched types
+}

src/test/ui/wf/wf-in-foreign-fn-decls-issue-80468.stderr

@@ -0,0 +1,24 @@
+error[E0726]: implicit elided lifetime not allowed here
+  --> $DIR/wf-in-foreign-fn-decls-issue-80468.rs:13:16
+   |
+LL | impl Trait for Ref {}
+   |                ^^^- help: indicate the anonymous lifetime: `<'_>`
+
+error[E0308]: mismatched types
+  --> $DIR/wf-in-foreign-fn-decls-issue-80468.rs:16:21
+   |
+LL |     pub fn repro(_: Wrapper<Ref>);
+   |                     ^^^^^^^^^^^^ lifetime mismatch
+   |
+   = note: expected trait `Trait`
+              found trait `Trait`
+note: the anonymous lifetime #1 defined on the method body at 16:5...
+  --> $DIR/wf-in-foreign-fn-decls-issue-80468.rs:16:5
+   |
+LL |     pub fn repro(_: Wrapper<Ref>);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: ...does not necessarily outlive the static lifetime
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.