Rollup merge of #132357 - m-ou-se:explicit-abi, r=compiler-errors

Improve missing_abi lint

This is for the migration lint for https://github.com/rust-lang/rfcs/pull/3722

It is not yet marked as an edition migration lint, because `Edition2027` doesn't exist yet.

The lint now includes a machine applicable suggestion:

```
warning: extern declarations without an explicit ABI are deprecated
 --> src/main.rs:3:1
  |
3 | extern fn a() {}
  | ^^^^^^ help: explicitly specify the C ABI: `extern "C"`
  |
```

1 files changed, 2 insertions, 0 deletions

diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 36733726564..6b4e2d0f4e2 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -1194,6 +1194,7 @@ impl<'a> Parser<'a> {
         attrs: &mut AttrVec,
         mut safety: Safety,
     ) -> PResult<'a, ItemInfo> {
+        let extern_span = self.prev_token.uninterpolated_span();
         let abi = self.parse_abi(); // ABI?
         // FIXME: This recovery should be tested better.
         if safety == Safety::Default
@@ -1205,6 +1206,7 @@ impl<'a> Parser<'a> {
             let _ = self.eat_keyword(kw::Unsafe);
         }
         let module = ast::ForeignMod {
+            extern_span,
             safety,
             abi,
             items: self.parse_item_list(attrs, |p| p.parse_foreign_item(ForceCollect::No))?,