Auto merge of #68717 - petrochenkov:stabexpat, r=varkor

Stabilize fn-like proc macros in expression, pattern and statement positions

I.e. all the positions in which stable `macro_rules` macros are supported.

Depends on #68716 ("Stabilize `Span::mixed_site`").

cc #54727
cc #54727 (comment)

Stabilization report: #68717 (comment).

Author: bors

src/librustc_expand/expand.rs

@@ -679,7 +679,6 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         ExpandResult::Ready(match invoc.kind {
             InvocationKind::Bang { mac, .. } => match ext {
                 SyntaxExtensionKind::Bang(expander) => {
-                    self.gate_proc_macro_expansion_kind(span, fragment_kind);
                     let tok_result = match expander.expand(self.cx, span, mac.args.inner_tokens()) {
                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
                         Ok(ts) => ts,
@@ -846,36 +845,6 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         }
     }
 
-    fn gate_proc_macro_expansion_kind(&self, span: Span, kind: AstFragmentKind) {
-        let kind = match kind {
-            AstFragmentKind::Expr | AstFragmentKind::OptExpr => "expressions",
-            AstFragmentKind::Pat => "patterns",
-            AstFragmentKind::Stmts => "statements",
-            AstFragmentKind::Ty
-            | AstFragmentKind::Items
-            | AstFragmentKind::TraitItems
-            | AstFragmentKind::ImplItems
-            | AstFragmentKind::ForeignItems => return,
-            AstFragmentKind::Arms
-            | AstFragmentKind::Fields
-            | AstFragmentKind::FieldPats
-            | AstFragmentKind::GenericParams
-            | AstFragmentKind::Params
-            | AstFragmentKind::StructFields
-            | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
-        };
-        if self.cx.ecfg.proc_macro_hygiene() {
-            return;
-        }
-        feature_err(
-            self.cx.parse_sess,
-            sym::proc_macro_hygiene,
-            span,
-            &format!("procedural macros cannot be expanded to {}", kind),
-        )
-        .emit();
-    }
-
     fn parse_ast_fragment(
         &mut self,
         toks: TokenStream,

src/librustc_feature/active.rs

@@ -430,8 +430,7 @@ declare_features! (
     /// Allows `#[marker]` on certain traits allowing overlapping implementations.
     (active, marker_trait_attr, "1.30.0", Some(29864), None),
 
-    /// Allows macro invocations on modules expressions and statements and
-    /// procedural macros to expand to non-items.
+    /// Allows macro attributes on expressions, statements and non-inline modules.
     (active, proc_macro_hygiene, "1.30.0", Some(54727), None),
 
     /// Allows unsized rvalues at arguments and parameters.

src/test/ui/auxiliary/cond_plugin.rs

@@ -2,7 +2,6 @@
 // no-prefer-dynamic
 
 #![crate_type = "proc-macro"]
-#![feature(proc_macro_hygiene)]
 #![feature(proc_macro_quote)]
 
 extern crate proc_macro;

src/test/ui/auxiliary/hello_macro.rs

@@ -2,7 +2,7 @@
 // no-prefer-dynamic
 
 #![crate_type = "proc-macro"]
-#![feature(proc_macro_hygiene, proc_macro_quote)]
+#![feature(proc_macro_quote)]
 
 extern crate proc_macro;
 

src/test/ui/auxiliary/proc_macro_def.rs

@@ -2,7 +2,6 @@
 // no-prefer-dynamic
 
 #![crate_type = "proc-macro"]
-#![feature(proc_macro_hygiene)]
 #![feature(proc_macro_quote)]
 
 extern crate proc_macro;

src/test/ui/macro-quote-cond.rs

@@ -1,9 +1,7 @@
 // run-pass
-
-#![allow(unused_parens)]
 // aux-build:cond_plugin.rs
 
-#![feature(proc_macro_hygiene)]
+#![allow(unused_parens)]
 
 extern crate cond_plugin;
 

src/test/ui/macro-quote-test.rs

@@ -1,10 +1,8 @@
-// run-pass
 // Test that a macro can emit delimiters with nothing inside - `()`, `{}`
 
+// run-pass
 // aux-build:hello_macro.rs
 
-#![feature(proc_macro_hygiene)]
-
 extern crate hello_macro;
 
 fn main() {

src/test/ui/macros/auxiliary/proc_macro_sequence.rs

@@ -2,7 +2,7 @@
 // no-prefer-dynamic
 
 #![crate_type = "proc-macro"]
-#![feature(proc_macro_span, proc_macro_hygiene, proc_macro_quote)]
+#![feature(proc_macro_span, proc_macro_quote)]
 
 extern crate proc_macro;
 

src/test/ui/proc-macro/attr-invalid-exprs.rs

@@ -1,8 +1,9 @@
-// aux-build:attr-stmt-expr.rs
-
 //! Attributes producing expressions in invalid locations
 
-#![feature(stmt_expr_attributes, proc_macro_hygiene)]
+// aux-build:attr-stmt-expr.rs
+
+#![feature(proc_macro_hygiene)]
+#![feature(stmt_expr_attributes)]
 
 extern crate attr_stmt_expr;
 use attr_stmt_expr::{duplicate, no_output};

src/test/ui/proc-macro/attr-invalid-exprs.stderr

@@ -1,11 +1,11 @@
 error: expected expression, found end of macro arguments
-  --> $DIR/attr-invalid-exprs.rs:11:13
+  --> $DIR/attr-invalid-exprs.rs:12:13
    |
 LL |     let _ = #[no_output] "Hello, world!";
    |             ^^^^^^^^^^^^
 
 error: macro expansion ignores token `,` and any following
-  --> $DIR/attr-invalid-exprs.rs:14:13
+  --> $DIR/attr-invalid-exprs.rs:15:13
    |
 LL |     let _ = #[duplicate] "Hello, world!";
    |             ^^^^^^^^^^^^- help: you might be missing a semicolon here: `;`
@@ -15,7 +15,7 @@ LL |     let _ = #[duplicate] "Hello, world!";
    = note: the usage of `duplicate!` is likely invalid in expression context
 
 error: macro expansion ignores token `,` and any following
-  --> $DIR/attr-invalid-exprs.rs:23:9
+  --> $DIR/attr-invalid-exprs.rs:24:9
    |
 LL |         #[duplicate]
    |         ^^^^^^^^^^^^- help: you might be missing a semicolon here: `;`