Allow passing expr metavariable to cfg

Jules-Bertholet · Jules-Bertholet · commit 1cd49c10bdfd · 2025-09-24T01:08:31.000-04:00
diff --git a/compiler/rustc_ast/src/attr/mod.rs b/compiler/rustc_ast/src/attr/mod.rs
@@ -424,7 +424,7 @@ impl MetaItem {
                 _span,
                 _spacing,
                 Delimiter::Invisible(InvisibleOrigin::MetaVar(
-                    MetaVarKind::Meta { .. } | MetaVarKind::Path,
+                    MetaVarKind::Meta | MetaVarKind::Path,
                 )),
                 _stream,
             )) => {
diff --git a/compiler/rustc_ast/src/token.rs b/compiler/rustc_ast/src/token.rs
@@ -64,10 +64,7 @@ pub enum MetaVarKind {
     Ident,
     Lifetime,
     Literal,
-    Meta {
-        /// Will `AttrItem::meta` succeed on this, if reparsed?
-        has_meta_form: bool,
-    },
+    Meta,
     Path,
     Vis,
     TT,
@@ -87,7 +84,7 @@ impl fmt::Display for MetaVarKind {
             MetaVarKind::Ident => sym::ident,
             MetaVarKind::Lifetime => sym::lifetime,
             MetaVarKind::Literal => sym::literal,
-            MetaVarKind::Meta { .. } => sym::meta,
+            MetaVarKind::Meta => sym::meta,
             MetaVarKind::Path => sym::path,
             MetaVarKind::Vis => sym::vis,
             MetaVarKind::TT => sym::tt,
@@ -693,7 +690,7 @@ impl Token {
             OpenInvisible(InvisibleOrigin::MetaVar(
                 MetaVarKind::Expr { .. } |
                 MetaVarKind::Literal |
-                MetaVarKind::Meta { .. } |
+                MetaVarKind::Meta |
                 MetaVarKind::Pat(_) |
                 MetaVarKind::Path |
                 MetaVarKind::Ty { .. }
diff --git a/compiler/rustc_attr_parsing/src/parser.rs b/compiler/rustc_attr_parsing/src/parser.rs
@@ -410,19 +410,18 @@ impl<'a, 'sess> MetaItemListParserContext<'a, 'sess> {
     }
 
     fn parse_attr_item(&mut self) -> PResult<'sess, MetaItemParser<'static>> {
-        if let Some(MetaVarKind::Meta { has_meta_form }) = self.parser.token.is_metavar_seq() {
-            return if has_meta_form {
-                let attr_item = self
-                    .parser
-                    .eat_metavar_seq(MetaVarKind::Meta { has_meta_form: true }, |this| {
-                        MetaItemListParserContext { parser: this, should_emit: self.should_emit }
-                            .parse_attr_item()
-                    })
-                    .unwrap();
-                Ok(attr_item)
-            } else {
-                self.parser.unexpected_any()
-            };
+        if let Some(mv_kind @ (MetaVarKind::Meta | MetaVarKind::Expr { .. })) =
+            self.parser.token.is_metavar_seq()
+        {
+            return self
+                .parser
+                .eat_metavar_seq(mv_kind, |this| {
+                    MetaItemListParserContext { parser: this, should_emit: self.should_emit }
+                        .parse_attr_item()
+                })
+                .ok_or_else(|| {
+                    self.parser.unexpected_any::<core::convert::Infallible>().unwrap_err()
+                });
         }
 
         let path = self.parser.parse_path(PathStyle::Mod)?;
diff --git a/compiler/rustc_expand/src/mbe/transcribe.rs b/compiler/rustc_expand/src/mbe/transcribe.rs
@@ -481,12 +481,7 @@ fn transcribe_pnr<'tx>(
             mk_delimited(ty.span, MetaVarKind::Ty { is_path }, TokenStream::from_ast(ty))
         }
         ParseNtResult::Meta(attr_item) => {
-            let has_meta_form = attr_item.meta_kind().is_some();
-            mk_delimited(
-                attr_item.span(),
-                MetaVarKind::Meta { has_meta_form },
-                TokenStream::from_ast(attr_item),
-            )
+            mk_delimited(attr_item.span(), MetaVarKind::Meta, TokenStream::from_ast(attr_item))
         }
         ParseNtResult::Path(path) => {
             mk_delimited(path.span, MetaVarKind::Path, TokenStream::from_ast(path))
diff --git a/compiler/rustc_parse/src/parser/attr.rs b/compiler/rustc_parse/src/parser/attr.rs
@@ -290,7 +290,7 @@ impl<'a> Parser<'a> {
     /// The delimiters or `=` are still put into the resulting token stream.
     pub fn parse_attr_item(&mut self, force_collect: ForceCollect) -> PResult<'a, ast::AttrItem> {
         if let Some(item) = self.eat_metavar_seq_with_matcher(
-            |mv_kind| matches!(mv_kind, MetaVarKind::Meta { .. }),
+            |mv_kind| matches!(mv_kind, MetaVarKind::Meta),
             |this| this.parse_attr_item(force_collect),
         ) {
             return Ok(item);
@@ -421,17 +421,13 @@ impl<'a> Parser<'a> {
         &mut self,
         unsafe_allowed: AllowLeadingUnsafe,
     ) -> PResult<'a, ast::MetaItem> {
-        if let Some(MetaVarKind::Meta { has_meta_form }) = self.token.is_metavar_seq() {
-            return if has_meta_form {
-                let attr_item = self
-                    .eat_metavar_seq(MetaVarKind::Meta { has_meta_form: true }, |this| {
-                        this.parse_attr_item(ForceCollect::No)
-                    })
-                    .unwrap();
-                Ok(attr_item.meta(attr_item.path.span).unwrap())
-            } else {
-                self.unexpected_any()
-            };
+        if let Some(mv_kind @ (MetaVarKind::Meta | MetaVarKind::Expr { .. })) =
+            self.token.is_metavar_seq()
+        {
+            return self
+                .eat_metavar_seq(mv_kind, |this| this.parse_attr_item(ForceCollect::No))
+                .map(|attr_item| attr_item.meta(attr_item.path.span).unwrap())
+                .ok_or_else(|| self.unexpected_any::<core::convert::Infallible>().unwrap_err());
         }
 
         let lo = self.token.span;
diff --git a/compiler/rustc_parse/src/parser/nonterminal.rs b/compiler/rustc_parse/src/parser/nonterminal.rs
@@ -24,7 +24,7 @@ impl<'a> Parser<'a> {
                 | MetaVarKind::Expr { .. }
                 | MetaVarKind::Ty { .. }
                 | MetaVarKind::Literal // `true`, `false`
-                | MetaVarKind::Meta { .. }
+                | MetaVarKind::Meta
                 | MetaVarKind::Path => true,
 
                 MetaVarKind::Item
@@ -82,7 +82,7 @@ impl<'a> Parser<'a> {
                     MetaVarKind::Item
                     | MetaVarKind::Pat(_)
                     | MetaVarKind::Ty { .. }
-                    | MetaVarKind::Meta { .. }
+                    | MetaVarKind::Meta
                     | MetaVarKind::Path
                     | MetaVarKind::Vis => false,
                     MetaVarKind::Lifetime | MetaVarKind::Ident | MetaVarKind::TT => {
diff --git a/tests/ui/attributes/nonterminal-expansion.rs b/tests/ui/attributes/nonterminal-expansion.rs
@@ -5,8 +5,7 @@
 macro_rules! pass_nonterminal {
     ($n:expr) => {
         #[repr(align($n))]
-        //~^ ERROR expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found `expr` metavariable
-        struct S;
+        fn foo() {}
     };
 }
 
@@ -15,5 +14,6 @@ macro_rules! n {
 }
 
 pass_nonterminal!(n!());
+//~^ ERROR expected one of `(`, `::`, or `=`, found `!`
 
 fn main() {}
diff --git a/tests/ui/attributes/nonterminal-expansion.stderr b/tests/ui/attributes/nonterminal-expansion.stderr
@@ -1,13 +1,8 @@
-error: expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found `expr` metavariable
-  --> $DIR/nonterminal-expansion.rs:7:22
+error: expected one of `(`, `::`, or `=`, found `!`
+  --> $DIR/nonterminal-expansion.rs:16:20
    |
-LL |         #[repr(align($n))]
-   |                      ^^
-...
 LL | pass_nonterminal!(n!());
-   | ----------------------- in this macro invocation
-   |
-   = note: this error originates in the macro `pass_nonterminal` (in Nightly builds, run with -Z macro-backtrace for more info)
+   |                    ^ expected one of `(`, `::`, or `=`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/macros/attr-expr.rs b/tests/ui/macros/attr-expr.rs
@@ -0,0 +1,11 @@
+macro_rules! foo {
+    ($e:expr) => {
+        #[$e]
+        //~^ ERROR expected identifier, found metavariable
+        fn foo() {}
+    }
+}
+
+foo!(inline);
+
+fn main() {}
diff --git a/tests/ui/macros/attr-expr.stderr b/tests/ui/macros/attr-expr.stderr
@@ -0,0 +1,13 @@
+error: expected identifier, found metavariable
+  --> $DIR/attr-expr.rs:3:11
+   |
+LL |         #[$e]
+   |           ^^ expected identifier, found metavariable
+...
+LL | foo!(inline);
+   | ------------ in this macro invocation
+   |
+   = note: this error originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/macros/cfg_attr-expr.rs b/tests/ui/macros/cfg_attr-expr.rs
@@ -0,0 +1,11 @@
+macro_rules! foo {
+    ($e:expr) => {
+        #[cfg_attr(true, $e)]
+        //~^ ERROR expected identifier, found metavariable
+        fn foo() {}
+    }
+}
+
+foo!(inline);
+
+fn main() {}
diff --git a/tests/ui/macros/cfg_attr-expr.stderr b/tests/ui/macros/cfg_attr-expr.stderr
@@ -0,0 +1,15 @@
+error: expected identifier, found metavariable
+  --> $DIR/cfg_attr-expr.rs:3:26
+   |
+LL |         #[cfg_attr(true, $e)]
+   |                          ^^ expected identifier, found metavariable
+...
+LL | foo!(inline);
+   | ------------ in this macro invocation
+   |
+   = help: the valid syntax is `#[cfg_attr(condition, attribute, other_attribute, ...)]`
+   = note: for more information, visit <https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg_attr-attribute>
+   = note: this error originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/macros/cfg_expr.rs b/tests/ui/macros/cfg_expr.rs
@@ -0,0 +1,25 @@
+//@ run-pass
+
+macro_rules! foo {
+    ($e:expr, $n:ident) => {
+        #[cfg_attr($e, allow(non_snake_case))]
+        #[cfg($e)]
+        fn $n() {}
+
+        #[cfg(not($e))]
+        fn $n() {
+            panic!()
+        }
+    }
+}
+
+foo!(true, BAR);
+foo!(any(true, unix, target_pointer_width = "64"), baz);
+foo!(target_pointer_width = "64", quux);
+
+fn main() {
+    BAR();
+    baz();
+    #[cfg(target_pointer_width = "64")]
+    quux();
+}
diff --git a/tests/ui/parser/attribute/attr-bad-meta-4.rs b/tests/ui/parser/attribute/attr-bad-meta-4.rs
@@ -1,12 +1,14 @@
 macro_rules! mac {
     ($attr_item: meta) => {
         #[cfg($attr_item)]
-        //~^ ERROR expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found `meta` metavariable
         struct S;
     }
 }
 
 mac!(an(arbitrary token stream));
+//~^ ERROR expected one of `(`, `)`, `,`, `::`, or `=`, found `token`
+//~| ERROR expected one of `(`, `)`, `,`, `::`, or `=`, found `stream`
+//~| ERROR [E0537]
 
 #[cfg(feature = -1)]
 //~^ ERROR expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found `-`
diff --git a/tests/ui/parser/attribute/attr-bad-meta-4.stderr b/tests/ui/parser/attribute/attr-bad-meta-4.stderr
@@ -1,5 +1,5 @@
 error: expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found `-`
-  --> $DIR/attr-bad-meta-4.rs:11:17
+  --> $DIR/attr-bad-meta-4.rs:13:17
    |
 LL | #[cfg(feature = -1)]
    |                 ^
@@ -10,16 +10,28 @@ LL - #[cfg(feature = -1)]
 LL + #[cfg(feature = 1)]
    |
 
-error: expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found `meta` metavariable
-  --> $DIR/attr-bad-meta-4.rs:3:15
+error: expected one of `(`, `)`, `,`, `::`, or `=`, found `token`
+  --> $DIR/attr-bad-meta-4.rs:8:19
    |
-LL |         #[cfg($attr_item)]
-   |               ^^^^^^^^^^
-...
 LL | mac!(an(arbitrary token stream));
-   | -------------------------------- in this macro invocation
+   |                  -^^^^^ expected one of `(`, `)`, `,`, `::`, or `=`
+   |                  |
+   |                  help: missing `,`
+
+error: expected one of `(`, `)`, `,`, `::`, or `=`, found `stream`
+  --> $DIR/attr-bad-meta-4.rs:8:25
    |
-   = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
+LL | mac!(an(arbitrary token stream));
+   |                        -^^^^^^ expected one of `(`, `)`, `,`, `::`, or `=`
+   |                        |
+   |                        help: missing `,`
+
+error[E0537]: invalid predicate `an`
+  --> $DIR/attr-bad-meta-4.rs:8:6
+   |
+LL | mac!(an(arbitrary token stream));
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to 4 previous errors
 
+For more information about this error, try `rustc --explain E0537`.

Original file line number	Diff line number	Diff line change
`@@ -481,12 +481,7 @@ fn transcribe_pnr<'tx>(`
`481`	`481`	`mk_delimited(ty.span, MetaVarKind::Ty { is_path }, TokenStream::from_ast(ty))`
`482`	`482`	`}`
`483`	`483`	`ParseNtResult::Meta(attr_item) => {`
`484`		`- let has_meta_form = attr_item.meta_kind().is_some();`
`485`		`- mk_delimited(`
`486`		`- attr_item.span(),`
`487`		`- MetaVarKind::Meta { has_meta_form },`
`488`		`- TokenStream::from_ast(attr_item),`
`489`		`- )`
	`484`	`+ mk_delimited(attr_item.span(), MetaVarKind::Meta, TokenStream::from_ast(attr_item))`
`490`	`485`	`}`
`491`	`486`	`ParseNtResult::Path(path) => {`
`492`	`487`	`mk_delimited(path.span, MetaVarKind::Path, TokenStream::from_ast(path))`
Original file line number	Diff line number	Diff line change
`@@ -5,8 +5,7 @@`
`5`	`5`	`macro_rules! pass_nonterminal {`
`6`	`6`	`($n:expr) => {`
`7`	`7`	`#[repr(align($n))]`
`8`		- //~^ ERROR expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found `expr` metavariable
`9`		`- struct S;`
	`8`	`+ fn foo() {}`
`10`	`9`	`};`
`11`	`10`	`}`
`12`	`11`
`@@ -15,5 +14,6 @@ macro_rules! n {`
`15`	`14`	`}`
`16`	`15`
`17`	`16`	`pass_nonterminal!(n!());`
	`17`	+//~^ ERROR expected one of `(`, `::`, or `=`, found `!`
`18`	`18`
`19`	`19`	`fn main() {}`