review comments

src/libfmt_macros/lib.rs

@@ -627,7 +627,7 @@ mod tests {
     use super::*;
 
     fn same(fmt: &'static str, p: &[Piece<'static>]) {
-        let parser = Parser::new(fmt, None, vec![], false, None);
+        let parser = Parser::new(fmt, None, vec![], false);
         assert!(parser.collect::<Vec<Piece<'static>>>() == p);
     }
 
@@ -643,7 +643,7 @@ mod tests {
     }
 
     fn musterr(s: &str) {
-        let mut p = Parser::new(s, None, vec![], false, None);
+        let mut p = Parser::new(s, None, vec![], false);
         p.next();
         assert!(!p.errors.is_empty());
     }

src/libsyntax/config.rs

@@ -98,7 +98,7 @@ impl<'a> StripUnconfigured<'a> {
             self.sess.span_diagnostic.struct_span_err(attr.span, "bad `cfg_attr` attribute")
                 .span_label(attr.span, "missing condition and attribute")
                 .note("`cfg_attr` must be of the form: \
-                       `#[cfg_attr(condition, attribute)]`")
+                       `#[cfg_attr(condition, attribute, other_attribute, ...)]`")
                 .note("for more information, visit \
                        <https://doc.rust-lang.org/reference/conditional-compilation.html\
                        #the-cfg_attr-attribute>")

src/libsyntax/ext/base.rs

@@ -11,7 +11,7 @@ use crate::parse::{self, parser, DirectoryOwnership};
 use crate::parse::token;
 use crate::ptr::P;
 use crate::symbol::{kw, sym, Ident, Symbol};
-use crate::ThinVec;
+use crate::{ThinVec, MACRO_ARGUMENTS};
 use crate::tokenstream::{self, TokenStream};
 
 use errors::{DiagnosticBuilder, DiagnosticId};
@@ -850,11 +850,7 @@ impl<'a> ExtCtxt<'a> {
     }
 
     pub fn new_parser_from_tts(&self, tts: &[tokenstream::TokenTree]) -> parser::Parser<'a> {
-        parse::stream_to_parser(
-            self.parse_sess,
-            tts.iter().cloned().collect(),
-            Some("macro arguments"),
-        )
+        parse::stream_to_parser(self.parse_sess, tts.iter().cloned().collect(), MACRO_ARGUMENTS)
     }
     pub fn source_map(&self) -> &'a SourceMap { self.parse_sess.source_map() }
     pub fn parse_sess(&self) -> &'a parse::ParseSess { self.parse_sess }

src/libsyntax/ext/tt/macro_parser.rs

@@ -664,7 +664,7 @@ pub fn parse(
         directory,
         recurse_into_modules,
         true,
-        Some("macro arguments"),
+        crate::MACRO_ARGUMENTS,
     );
 
     // A queue of possible matcher positions. We initialize it with the matcher position in which

src/libsyntax/lib.rs

@@ -31,6 +31,8 @@ pub use rustc_data_structures::thin_vec::ThinVec;
 use ast::AttrId;
 use syntax_pos::edition::Edition;
 
+const MACRO_ARGUMENTS: Option<&'static str> = Some("macro arguments");
+
 // A variant of 'try!' that panics on an Err. This is used as a crutch on the
 // way towards a non-panic!-prone parser. It should be used for fatal parsing
 // errors; eventually we plan to convert all code using panictry to just use

src/libsyntax/parse/diagnostics.rs

@@ -13,7 +13,7 @@ use crate::symbol::kw;
 use crate::ThinVec;
 use errors::{Applicability, DiagnosticBuilder};
 use log::debug;
-use syntax_pos::Span;
+use syntax_pos::{Span, DUMMY_SP};
 
 pub trait RecoverQPath: Sized + 'static {
     const PATH_STYLE: PathStyle = PathStyle::Expr;
@@ -201,7 +201,7 @@ impl<'a> Parser<'a> {
 
         let mut path = ast::Path {
             segments: Vec::new(),
-            span: syntax_pos::DUMMY_SP,
+            span: DUMMY_SP,
         };
         self.parse_path_segments(&mut path.segments, T::PATH_STYLE)?;
         path.span = ty_span.to(self.prev_span);
@@ -267,6 +267,58 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// Create a `DiagnosticBuilder` for an unexpected token `t` and try to recover if it is a
+    /// closing delimiter.
+    pub fn unexpected_try_recover(
+        &mut self,
+        t: &token::Token,
+    ) -> PResult<'a, bool /* recovered */> {
+        let token_str = pprust::token_to_string(t);
+        let this_token_str = self.this_token_descr();
+        let (prev_sp, sp) = match (&self.token, self.subparser_name) {
+            // Point at the end of the macro call when reaching end of macro arguments.
+            (token::Token::Eof, Some(_)) => {
+                let sp = self.sess.source_map().next_point(self.span);
+                (sp, sp)
+            }
+            // We don't want to point at the following span after DUMMY_SP.
+            // This happens when the parser finds an empty TokenStream.
+            _ if self.prev_span == DUMMY_SP => (self.span, self.span),
+            // EOF, don't want to point at the following char, but rather the last token.
+            (token::Token::Eof, None) => (self.prev_span, self.span),
+            _ => (self.sess.source_map().next_point(self.prev_span), self.span),
+        };
+        let msg = format!(
+            "expected `{}`, found {}",
+            token_str,
+            match (&self.token, self.subparser_name) {
+                (token::Token::Eof, Some(origin)) => format!("end of {}", origin),
+                _ => this_token_str,
+            },
+        );
+        let mut err = self.struct_span_err(sp, &msg);
+        let label_exp = format!("expected `{}`", token_str);
+        match self.recover_closing_delimiter(&[t.clone()], err) {
+            Err(e) => err = e,
+            Ok(recovered) => {
+                return Ok(recovered);
+            }
+        }
+        let cm = self.sess.source_map();
+        match (cm.lookup_line(prev_sp.lo()), cm.lookup_line(sp.lo())) {
+            (Ok(ref a), Ok(ref b)) if a.line == b.line => {
+                // When the spans are in the same line, it means that the only content
+                // between them is whitespace, point only at the found token.
+                err.span_label(sp, label_exp);
+            }
+            _ => {
+                err.span_label(prev_sp, label_exp);
+                err.span_label(sp, "unexpected token");
+            }
+        }
+        Err(err)
+    }
+
     /// Consume alternative await syntaxes like `await <expr>`, `await? <expr>`, `await(<expr>)`
     /// and `await { <expr> }`.
     crate fn parse_incorrect_await_syntax(

src/libsyntax/parse/mod.rs

@@ -248,7 +248,7 @@ fn maybe_source_file_to_parser(
 // must preserve old name for now, because quote! from the *existing*
 // compiler expands into it
 pub fn new_parser_from_tts(sess: &ParseSess, tts: Vec<TokenTree>) -> Parser<'_> {
-    stream_to_parser(sess, tts.into_iter().collect(), Some("macro arguments"))
+    stream_to_parser(sess, tts.into_iter().collect(), crate::MACRO_ARGUMENTS)
 }
 
 
@@ -331,9 +331,9 @@ pub fn maybe_file_to_stream(
 pub fn stream_to_parser<'a>(
     sess: &'a ParseSess,
     stream: TokenStream,
-    is_subparser: Option<&'static str>,
+    subparser_name: Option<&'static str>,
 ) -> Parser<'a> {
-    Parser::new(sess, stream, None, true, false, is_subparser)
+    Parser::new(sess, stream, None, true, false, subparser_name)
 }
 
 /// Given stream, the `ParseSess` and the base directory, produces a parser.

src/libsyntax/parse/parser.rs

@@ -233,8 +233,8 @@ pub struct Parser<'a> {
     /// error.
     crate unclosed_delims: Vec<UnmatchedBrace>,
     last_unexpected_token_span: Option<Span>,
-    /// If `true`, this `Parser` is not parsing Rust code but rather a macro call.
-    is_subparser: Option<&'static str>,
+    /// If present, this `Parser` is not parsing Rust code but rather a macro call.
+    crate subparser_name: Option<&'static str>,
 }
 
 impl<'a> Drop for Parser<'a> {
@@ -541,7 +541,7 @@ impl<'a> Parser<'a> {
         directory: Option<Directory<'a>>,
         recurse_into_file_modules: bool,
         desugar_doc_comments: bool,
-        is_subparser: Option<&'static str>,
+        subparser_name: Option<&'static str>,
     ) -> Self {
         let mut parser = Parser {
             sess,
@@ -572,7 +572,7 @@ impl<'a> Parser<'a> {
             max_angle_bracket_count: 0,
             unclosed_delims: Vec::new(),
             last_unexpected_token_span: None,
-            is_subparser,
+            subparser_name,
         };
 
         let tok = parser.next_tok();
@@ -636,56 +636,13 @@ impl<'a> Parser<'a> {
     }
 
     /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
-    pub fn expect(&mut self, t: &token::Token) -> PResult<'a,  bool /* recovered */> {
+    pub fn expect(&mut self, t: &token::Token) -> PResult<'a, bool /* recovered */> {
         if self.expected_tokens.is_empty() {
             if self.token == *t {
                 self.bump();
                 Ok(false)
             } else {
-                let token_str = pprust::token_to_string(t);
-                let this_token_str = self.this_token_descr();
-                let (prev_sp, sp) = match (&self.token, self.is_subparser) {
-                    // Point at the end of the macro call when reaching end of macro arguments.
-                    (token::Token::Eof, Some(_)) => {
-                        let sp = self.sess.source_map().next_point(self.span);
-                        (sp, sp)
-                    }
-                    // We don't want to point at the following span after DUMMY_SP.
-                    // This happens when the parser finds an empty TokenStream.
-                    _ if self.prev_span == DUMMY_SP => (self.span, self.span),
-                    // EOF, don't want to point at the following char, but rather the last token.
-                    (token::Token::Eof, None) => (self.prev_span, self.span),
-                    _ => (self.sess.source_map().next_point(self.prev_span), self.span),
-                };
-                let msg = format!(
-                    "expected `{}`, found {}",
-                    token_str,
-                    match (&self.token, self.is_subparser) {
-                        (token::Token::Eof, Some(origin)) => format!("end of {}", origin),
-                        _ => this_token_str,
-                    },
-                );
-                let mut err = self.struct_span_err(sp, &msg);
-                let label_exp = format!("expected `{}`", token_str);
-                match self.recover_closing_delimiter(&[t.clone()], err) {
-                    Err(e) => err = e,
-                    Ok(recovered) => {
-                        return Ok(recovered);
-                    }
-                }
-                let cm = self.sess.source_map();
-                match (cm.lookup_line(prev_sp.lo()), cm.lookup_line(sp.lo())) {
-                    (Ok(ref a), Ok(ref b)) if a.line == b.line => {
-                        // When the spans are in the same line, it means that the only content
-                        // between them is whitespace, point only at the found token.
-                        err.span_label(sp, label_exp);
-                    }
-                    _ => {
-                        err.span_label(prev_sp, label_exp);
-                        err.span_label(sp, "unexpected token");
-                    }
-                }
-                Err(err)
+                self.unexpected_try_recover(t)
             }
         } else {
             self.expect_one_of(slice::from_ref(t), &[])
@@ -2644,7 +2601,7 @@ impl<'a> Parser<'a> {
                         }
                         Err(mut err) => {
                             self.cancel(&mut err);
-                            let (span, msg) = match (&self.token, self.is_subparser) {
+                            let (span, msg) = match (&self.token, self.subparser_name) {
                                 (&token::Token::Eof, Some(origin)) => {
                                     let sp = self.sess.source_map().next_point(self.span);
                                     (sp, format!( "expected expression, found end of {}", origin))

src/test/ui/malformed/malformed-special-attrs.stderr

@@ -4,7 +4,7 @@ error: bad `cfg_attr` attribute
 LL | #[cfg_attr]
    | ^^^^^^^^^^^ missing condition and attribute
    |
-   = note: `cfg_attr` must be of the form: `#[cfg_attr(condition, attribute)]`
+   = note: `cfg_attr` must be of the form: `#[cfg_attr(condition, attribute, other_attribute, ...)]`
    = note: for more information, visit <https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg_attr-attribute>
 
 error: expected `(`, found `=`