Allow raw path-segment kw but not suggest escaping them

Author: mu001999

compiler/rustc_attr_parsing/src/parser.rs

@@ -435,7 +435,7 @@ impl<'a, 'sess> MetaItemListParserContext<'a, 'sess> {
 
         let path = if self.parser.parse_cfg_pred {
             self.parser.parse_cfg_pred = false;
-            Path::from_ident(self.parser.parse_ident()?)
+            self.parser.parse_path(PathStyle::SingleIdent)?
         } else {
             self.parser.parse_path(PathStyle::Mod)?
         };

compiler/rustc_parse/src/parser/attr.rs

@@ -1,7 +1,7 @@
 use rustc_ast as ast;
 use rustc_ast::token::{self, MetaVarKind};
 use rustc_ast::tokenstream::ParserRange;
-use rustc_ast::{Attribute, Path, attr};
+use rustc_ast::{Attribute, attr};
 use rustc_errors::codes::*;
 use rustc_errors::{Diag, PResult};
 use rustc_span::{BytePos, Span};
@@ -452,7 +452,7 @@ impl<'a> Parser<'a> {
 
         let path = if self.parse_cfg_pred {
             self.parse_cfg_pred = false;
-            Path::from_ident(self.parse_ident()?)
+            self.parse_path(PathStyle::SingleIdent)?
         } else {
             self.parse_path(PathStyle::Mod)?
         };

compiler/rustc_parse/src/parser/path.rs

@@ -57,6 +57,8 @@ pub enum PathStyle {
     /// anyway, due to macros), but it is used to avoid weird suggestions about expected
     /// tokens when something goes wrong.
     Mod,
+    /// Disallow path segment keywords when parsing cfg preds
+    SingleIdent,
 }
 
 impl PathStyle {
@@ -299,7 +301,12 @@ impl<'a> Parser<'a> {
         style: PathStyle,
         ty_generics: Option<&Generics>,
     ) -> PResult<'a, PathSegment> {
-        let ident = self.parse_path_segment_ident()?;
+        let ident = if style == PathStyle::SingleIdent {
+            self.parse_ident()?
+        } else {
+            self.parse_path_segment_ident()?
+        };
+
         let is_args_start = |token: &Token| {
             matches!(token.kind, token::Lt | token::Shl | token::OpenParen | token::LArrow)
         };

compiler/rustc_span/src/symbol.rs

@@ -3082,7 +3082,7 @@ impl Ident {
     /// We see this identifier in a normal identifier position, like variable name or a type.
     /// How was it written originally? Did it use the raw form? Let's try to guess.
     pub fn is_raw_guess(self) -> bool {
-        self.name.can_be_raw() && self.is_reserved()
+        self.name.can_be_raw() && !self.is_path_segment_keyword() && self.is_reserved()
     }
 
     /// Given the name of a lifetime without the first quote (`'`),
@@ -3095,6 +3095,7 @@ impl Ident {
         let name_without_apostrophe = self.without_first_quote();
         name_without_apostrophe.name != self.name
             && name_without_apostrophe.name.can_be_raw()
+            && !name_without_apostrophe.name.is_path_segment_keyword()
             && name_without_apostrophe.is_reserved_lifetime()
     }
 

tests/ui/cfg/path-kw-as-pred.stderr

@@ -27,44 +27,24 @@ error: expected identifier, found keyword `crate`
    |
 LL | #[cfg_attr(crate, path = "foo")]
    |            ^^^^^ expected identifier, found keyword
-   |
-help: escape `crate` to use it as an identifier
-   |
-LL | #[cfg_attr(r#crate, path = "foo")]
-   |            ++
 
 error: expected identifier, found keyword `super`
   --> $DIR/path-kw-as-pred.rs:28:12
    |
 LL | #[cfg_attr(super, path = "foo")]
    |            ^^^^^ expected identifier, found keyword
-   |
-help: escape `super` to use it as an identifier
-   |
-LL | #[cfg_attr(r#super, path = "foo")]
-   |            ++
 
 error: expected identifier, found keyword `self`
   --> $DIR/path-kw-as-pred.rs:30:12
    |
 LL | #[cfg_attr(self, path = "foo")]
    |            ^^^^ expected identifier, found keyword
-   |
-help: escape `self` to use it as an identifier
-   |
-LL | #[cfg_attr(r#self, path = "foo")]
-   |            ++
 
 error: expected identifier, found keyword `Self`
   --> $DIR/path-kw-as-pred.rs:32:12
    |
 LL | #[cfg_attr(Self, path = "foo")]
    |            ^^^^ expected identifier, found keyword
-   |
-help: escape `Self` to use it as an identifier
-   |
-LL | #[cfg_attr(r#Self, path = "foo")]
-   |            ++
 
 error: expected identifier, found keyword `crate`
   --> $DIR/path-kw-as-pred.rs:34:22