Auto merge of #76219 - Mark-Simulacrum:extern-require-abi, r=estebank

Add allow-by-default lint on implicit ABI in extern function pointers and items

This adds a new lint, missing_abi, which lints on omitted ABIs on extern blocks, function declarations, and function pointers.

It is currently not emitting the best possible diagnostics -- we need to track the span of "extern" at least or do some heuristic searching based on the available spans -- but seems good enough for an initial pass than can be expanded in future PRs.

This is a pretty large PR, but mostly due to updating a large number of tests to include ABIs; I can split that into a separate PR if it would be helpful, but test updates are already in dedicated commits.

1 files changed, 1 insertions, 2 deletions

diff --git a/src/test/ui/empty/empty-linkname.rs b/src/test/ui/empty/empty-linkname.rs
index 79895ab5834..b64123389c2 100644
--- a/src/test/ui/empty/empty-linkname.rs
+++ b/src/test/ui/empty/empty-linkname.rs
@@ -1,5 +1,4 @@
 #[link(name = "")] //~ ERROR: given with empty name
-extern {
-}
+extern "C" {}
 
 fn main() {}