Auto merge of #58899 - petrochenkov:derval2, r=estebank

Do not accidentally treat multi-segment meta-items as single-segment

Fixes https://github.com/rust-lang/rust/issues/55168 and many other regressions from https://github.com/rust-lang/rust/pull/50030

Basically, attributes like `#[any::prefix::foo]` were commonly interpreted as `#[foo]` due to `name()` successfully returning the last segment (this applies to nested things as well `#[attr(any::prefix::foo)]`).

3 files changed, 11 insertions, 20 deletions

diff --git a/src/libsyntax/parse/attr.rs b/src/libsyntax/parse/attr.rs
index e93e15f9012..4211268f33e 100644
--- a/src/libsyntax/parse/attr.rs
+++ b/src/libsyntax/parse/attr.rs
@@ -1,6 +1,5 @@
 use crate::attr;
 use crate::ast;
-use crate::source_map::respan;
 use crate::parse::{SeqSep, PResult};
 use crate::parse::token::{self, Nonterminal, DelimToken};
 use crate::parse::parser::{Parser, TokenType, PathStyle};
@@ -149,7 +148,7 @@ impl<'a> Parser<'a> {
         };
         Ok(if let Some(meta) = meta {
             self.bump();
-            (meta.ident, meta.node.tokens(meta.span))
+            (meta.path, meta.node.tokens(meta.span))
         } else {
             let path = self.parse_path(PathStyle::Mod)?;
             let tokens = if self.check(&token::OpenDelim(DelimToken::Paren)) ||
@@ -250,10 +249,10 @@ impl<'a> Parser<'a> {
         }
 
         let lo = self.span;
-        let ident = self.parse_path(PathStyle::Mod)?;
+        let path = self.parse_path(PathStyle::Mod)?;
         let node = self.parse_meta_item_kind()?;
         let span = lo.to(self.prev_span);
-        Ok(ast::MetaItem { ident, node, span })
+        Ok(ast::MetaItem { path, node, span })
     }
 
     crate fn parse_meta_item_kind(&mut self) -> PResult<'a, ast::MetaItemKind> {
@@ -268,18 +267,16 @@ impl<'a> Parser<'a> {
 
     /// matches meta_item_inner : (meta_item | UNSUFFIXED_LIT) ;
     fn parse_meta_item_inner(&mut self) -> PResult<'a, ast::NestedMetaItem> {
-        let lo = self.span;
-
         match self.parse_unsuffixed_lit() {
             Ok(lit) => {
-                return Ok(respan(lo.to(self.prev_span), ast::NestedMetaItemKind::Literal(lit)))
+                return Ok(ast::NestedMetaItem::Literal(lit))
             }
             Err(ref mut err) => self.diagnostic().cancel(err)
         }
 
         match self.parse_meta_item() {
             Ok(mi) => {
-                return Ok(respan(lo.to(self.prev_span), ast::NestedMetaItemKind::MetaItem(mi)))
+                return Ok(ast::NestedMetaItem::MetaItem(mi))
             }
             Err(ref mut err) => self.diagnostic().cancel(err)
         }
diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index 01e3b292903..bcd53dbfeb2 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/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);
                     }
 
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 22af7d47fd0..aa70c54a1ef 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/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() &&
-                ident.name != keywords::Underscore.name()
-            {
+            if ident.is_raw_guess() {
                 err.span_suggestion(
                     self.span,
                     "you can escape reserved keywords to use them as identifiers",
@@ -2335,7 +2333,7 @@ impl<'a> Parser<'a> {
         let meta_ident = match self.token {
             token::Interpolated(ref nt) => match **nt {
                 token::NtMeta(ref meta) => match meta.node {
-                    ast::MetaItemKind::Word => Some(meta.ident.clone()),
+                    ast::MetaItemKind::Word => Some(meta.path.clone()),
                     _ => None,
                 },
                 _ => None,