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.

2 files changed, 5 insertions, 3 deletions

diff --git a/src/test/rustdoc-ui/check-doc-alias-attr-location.rs b/src/test/rustdoc-ui/check-doc-alias-attr-location.rs
index 7de2caa189d..6de1960e2e2 100644
--- a/src/test/rustdoc-ui/check-doc-alias-attr-location.rs
+++ b/src/test/rustdoc-ui/check-doc-alias-attr-location.rs
@@ -5,7 +5,7 @@ pub trait Foo {
 }
 
 #[doc(alias = "foo")] //~ ERROR
-extern {}
+extern "C" {}
 
 #[doc(alias = "bar")] //~ ERROR
 impl Bar {
@@ -17,5 +17,7 @@ impl Bar {
 impl Foo for Bar {
     #[doc(alias = "assoc")] //~ ERROR
     type X = i32;
-    fn foo() -> Self::X { 0 }
+    fn foo() -> Self::X {
+        0
+    }
 }
diff --git a/src/test/rustdoc-ui/coverage/basic.rs b/src/test/rustdoc-ui/coverage/basic.rs
index 98507f99e8d..6c26b751c5e 100644
--- a/src/test/rustdoc-ui/coverage/basic.rs
+++ b/src/test/rustdoc-ui/coverage/basic.rs
@@ -45,6 +45,6 @@ macro_rules! some_macro {
     () => {};
 }
 
-extern {
+extern "C" {
     pub type ExternType;
 }