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, 1 deletions

diff --git a/library/std/src/keyword_docs.rs b/library/std/src/keyword_docs.rs
index 417a54e9dff..6b06539a094 100644
--- a/library/std/src/keyword_docs.rs
+++ b/library/std/src/keyword_docs.rs
@@ -401,7 +401,7 @@ mod enum_keyword {}
 ///
 /// ```rust
 /// #[no_mangle]
-/// pub extern fn callable_from_c(x: i32) -> bool {
+/// pub extern "C" fn callable_from_c(x: i32) -> bool {
 ///     x % 3 == 0
 /// }
 /// ```