syntax: Introduce Ident::can_be_raw

src/libsyntax/parse/lexer/mod.rs

@@ -1,7 +1,7 @@
 use crate::ast::{self, Ident};
 use crate::source_map::{SourceMap, FilePathMapping};
 use crate::parse::{token, ParseSess};
-use crate::symbol::{Symbol, keywords};
+use crate::symbol::Symbol;
 
 use errors::{Applicability, FatalError, Diagnostic, DiagnosticBuilder};
 use syntax_pos::{BytePos, CharPos, Pos, Span, NO_EXPANSION};
@@ -1249,15 +1249,11 @@ impl<'a> StringReader<'a> {
                     // FIXME: perform NFKC normalization here. (Issue #2253)
                     let ident = self.mk_ident(string);
 
-                    if is_raw_ident && (ident.is_path_segment_keyword() ||
-                                        ident.name == keywords::Underscore.name()) {
-                        self.fatal_span_(raw_start, self.pos,
-                            &format!("`r#{}` is not currently supported.", ident.name)
-                        ).raise();
-                    }
-
                     if is_raw_ident {
                         let span = self.mk_sp(raw_start, self.pos);
+                        if !ident.can_be_raw() {
+                            self.err_span(span, &format!("`{}` cannot be a raw identifier", ident));
+                        }
                         self.sess.raw_identifier_spans.borrow_mut().push(span);
                     }
 

src/libsyntax/parse/parser.rs

@@ -895,9 +895,7 @@ impl<'a> Parser<'a> {
                                            &format!("expected identifier, found {}",
                                                     self.this_token_descr()));
         if let token::Ident(ident, false) = &self.token {
-            if ident.is_reserved() && !ident.is_path_segment_keyword() &&
+            if ident.is_raw_guess() {
-                ident.name != keywords::Underscore.name()
-            {
                 err.span_suggestion(
                     self.span,
                     "you can escape reserved keywords to use them as identifiers",

src/libsyntax_ext/proc_macro_decls.rs

@@ -128,7 +128,7 @@ impl<'a> CollectProcMacros<'a> {
             }
         };
 
-        if trait_ident.is_path_segment_keyword() {
+        if !trait_ident.can_be_raw() {
             self.handler.span_err(trait_attr.span(),
                                   &format!("`{}` cannot be a name of derive macro", trait_ident));
         }
@@ -162,7 +162,7 @@ impl<'a> CollectProcMacros<'a> {
                         return None;
                     }
                 };
-                if ident.is_path_segment_keyword() {
+                if !ident.can_be_raw() {
                     self.handler.span_err(
                         attr.span(),
                         &format!("`{}` cannot be a name of derive helper attribute", ident),

src/libsyntax_ext/proc_macro_server.rs

@@ -340,12 +340,8 @@ impl Ident {
         if !Self::is_valid(string) {
             panic!("`{:?}` is not a valid identifier", string)
         }
-        if is_raw {
+        if is_raw && !ast::Ident::from_str(string).can_be_raw() {
-            let normalized_sym = Symbol::intern(string);
+            panic!("`{}` cannot be a raw identifier", string);
-            if normalized_sym == keywords::Underscore.name() ||
-               ast::Ident::with_empty_ctxt(normalized_sym).is_path_segment_keyword() {
-                panic!("`{:?}` is not a valid raw identifier", string)
-            }
         }
         Ident { sym, is_raw, span }
     }

src/libsyntax_pos/symbol.rs

@@ -484,11 +484,16 @@ impl Ident {
         self.name == keywords::DollarCrate.name()
     }
 
-    // We see this identifier in a normal identifier position, like variable name or a type.
+    /// This identifier can be a raw identifier.
-    // How was it written originally? Did it use the raw form? Let's try to guess.
+    pub fn can_be_raw(self) -> bool {
-    pub fn is_raw_guess(self) -> bool {
         self.name != keywords::Invalid.name() && self.name != keywords::Underscore.name() &&
-        self.is_reserved() && !self.is_path_segment_keyword()
+        !self.is_path_segment_keyword()
+    }
+
+    /// 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.can_be_raw() && self.is_reserved()
     }
 }
 

src/test/ui/parser/raw/raw-literal-self.rs

@@ -1,3 +1,4 @@
-fn self_test(r#self: u32) {
+fn main() {
-    //~^ ERROR `r#self` is not currently supported.
+    let r#self;
+    //~^ ERROR `self` cannot be a raw identifier
 }

src/test/ui/parser/raw/raw-literal-self.stderr

@@ -1,7 +1,7 @@
-error: `r#self` is not currently supported.
+error: `self` cannot be a raw identifier
-  --> $DIR/raw-literal-self.rs:1:14
+  --> $DIR/raw-literal-self.rs:2:9
    |
-LL | fn self_test(r#self: u32) {
+LL |     let r#self;
    |         ^^^^^^
 
 error: aborting due to previous error

src/test/ui/parser/raw/raw-literal-underscore.rs

@@ -1,3 +1,4 @@
-fn underscore_test(r#_: u32) {
+fn main() {
-    //~^ ERROR `r#_` is not currently supported.
+    let r#_;
+    //~^ ERROR `_` cannot be a raw identifier
 }

src/test/ui/parser/raw/raw-literal-underscore.stderr

@@ -1,7 +1,7 @@
-error: `r#_` is not currently supported.
+error: `_` cannot be a raw identifier
-  --> $DIR/raw-literal-underscore.rs:1:20
+  --> $DIR/raw-literal-underscore.rs:2:9
    |
-LL | fn underscore_test(r#_: u32) {
+LL |     let r#_;
    |         ^^^
 
 error: aborting due to previous error

src/test/ui/proc-macro/invalid-punct-ident-3.stderr

@@ -4,7 +4,7 @@ error: proc macro panicked
 LL | invalid_raw_ident!();
    | ^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: message: `"self"` is not a valid raw identifier
+   = help: message: `self` cannot be a raw identifier
 
 error: aborting due to previous error