Rollup merge of rust-lang#63931 - petrochenkov:stabmac, r=Centril

Stabilize macros in some more positions

- Fn-like macros and attribute macros in `extern` blocks
- Fn-like procedural macros in type positions
- ~Attribute macros on inline modules~ (moved to rust-lang#64273)

Stabilization report: rust-lang#63931 (comment).

Closes rust-lang#49476
cc rust-lang#54727

src/librustc_macros/src/lib.rs

@@ -1,4 +1,3 @@
-#![feature(proc_macro_hygiene)]
 #![allow(rustc::default_hash_types)]
 
 #![recursion_limit="128"]

src/libsyntax/ext/expand.rs

@@ -555,15 +555,6 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
     }
 
     fn expand_invoc(&mut self, invoc: Invocation, ext: &SyntaxExtensionKind) -> AstFragment {
-        let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
-        if fragment_kind == AstFragmentKind::ForeignItems && !self.cx.ecfg.macros_in_extern() {
-            if let SyntaxExtensionKind::NonMacroAttr { .. } = ext {} else {
-                emit_feature_err(&self.cx.parse_sess, sym::macros_in_extern,
-                                 span, GateIssue::Language,
-                                 "macro invocations in `extern {}` blocks are experimental");
-            }
-        }
-
         if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit {
             let expn_data = self.cx.current_expansion.id.expn_data();
             let suggested_limit = self.cx.ecfg.recursion_limit * 2;
@@ -578,6 +569,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             FatalError.raise();
         }
 
+        let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
         match invoc.kind {
             InvocationKind::Bang { mac, .. } => match ext {
                 SyntaxExtensionKind::Bang(expander) => {
@@ -758,14 +750,14 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
 
     fn gate_proc_macro_expansion_kind(&self, span: Span, kind: AstFragmentKind) {
         let kind = match kind {
-            AstFragmentKind::Expr => "expressions",
+            AstFragmentKind::Expr |
             AstFragmentKind::OptExpr => "expressions",
             AstFragmentKind::Pat => "patterns",
-            AstFragmentKind::Ty => "types",
             AstFragmentKind::Stmts => "statements",
-            AstFragmentKind::Items => return,
-            AstFragmentKind::TraitItems => return,
-            AstFragmentKind::ImplItems => return,
+            AstFragmentKind::Ty |
+            AstFragmentKind::Items |
+            AstFragmentKind::TraitItems |
+            AstFragmentKind::ImplItems |
             AstFragmentKind::ForeignItems => return,
             AstFragmentKind::Arms
             | AstFragmentKind::Fields
@@ -1578,9 +1570,6 @@ impl<'feat> ExpansionConfig<'feat> {
         }
     }
 
-    fn macros_in_extern(&self) -> bool {
-        self.features.map_or(false, |features| features.macros_in_extern)
-    }
     fn proc_macro_hygiene(&self) -> bool {
         self.features.map_or(false, |features| features.proc_macro_hygiene)
     }

src/libsyntax/feature_gate/accepted.rs

@@ -245,6 +245,8 @@ declare_features! (
     (accepted, bind_by_move_pattern_guards, "1.39.0", Some(15287), None),
     /// Allows attributes in formal function parameters.
     (accepted, param_attrs, "1.39.0", Some(60406), None),
+    // Allows macro invocations in `extern {}` blocks.
+    (accepted, macros_in_extern, "1.40.0", Some(49476), None),
 
     // -------------------------------------------------------------------------
     // feature-group-end: accepted features

src/libsyntax/feature_gate/active.rs

@@ -402,9 +402,6 @@ declare_features! (
     /// Allows infering `'static` outlives requirements (RFC 2093).
     (active, infer_static_outlives_requirements, "1.26.0", Some(54185), None),
 
-    /// Allows macro invocations in `extern {}` blocks.
-    (active, macros_in_extern, "1.27.0", Some(49476), None),
-
     /// Allows accessing fields of unions inside `const` functions.
     (active, const_fn_union, "1.27.0", Some(51909), None),
 

src/test/ui/macros/issue-54441.rs

@@ -1,5 +1,3 @@
-#![feature(macros_in_extern)]
-
 macro_rules! m {
     () => {
         let //~ ERROR expected

src/test/ui/macros/issue-54441.stderr

@@ -1,5 +1,5 @@
 error: expected one of `crate`, `fn`, `pub`, `static`, or `type`, found `let`
-  --> $DIR/issue-54441.rs:5:9
+  --> $DIR/issue-54441.rs:3:9
    |
 LL |         let
    |         ^^^ unexpected token

src/test/ui/abi/macros/macros-in-extern.rs → src/test/ui/macros/macros-in-extern.rs

@@ -1,3 +1,4 @@
+// run-pass
 // ignore-wasm32
 
 #![feature(decl_macro)]
@@ -16,17 +17,29 @@ macro_rules! emits_nothing(
     () => ()
 );
 
+macro_rules! emits_multiple(
+    () => {
+        fn f1() -> u32;
+        fn f2() -> u32;
+    }
+);
+
+mod defs {
+    #[no_mangle] extern fn f1() -> u32 { 1 }
+    #[no_mangle] extern fn f2() -> u32 { 2 }
+}
+
 fn main() {
-    assert_eq!(unsafe { rust_get_test_int() }, 0isize);
+    assert_eq!(unsafe { rust_get_test_int() }, 1);
     assert_eq!(unsafe { rust_dbg_extern_identity_u32(0xDEADBEEF) }, 0xDEADBEEFu32);
+    assert_eq!(unsafe { f1() }, 1);
+    assert_eq!(unsafe { f2() }, 2);
 }
 
 #[link(name = "rust_test_helpers", kind = "static")]
 extern {
     returns_isize!(rust_get_test_int);
-    //~^ ERROR macro invocations in `extern {}` blocks are experimental
     takes_u32_returns_u32!(rust_dbg_extern_identity_u32);
-    //~^ ERROR macro invocations in `extern {}` blocks are experimental
     emits_nothing!();
-    //~^ ERROR macro invocations in `extern {}` blocks are experimental
+    emits_multiple!();
 }