syntax: Support modern attribute syntax in the `meta` matcher

src/libsyntax/attr/mod.rs

@@ -255,9 +255,8 @@ impl MetaItem {
     }
 }
 
-impl Attribute {
-    /// Extracts the `MetaItem` from inside this `Attribute`.
-    pub fn meta(&self) -> Option<MetaItem> {
+impl AttrItem {
+    crate fn meta(&self, span: Span) -> Option<MetaItem> {
         let mut tokens = self.tokens.trees().peekable();
         Some(MetaItem {
             path: self.path.clone(),
@@ -269,9 +268,16 @@ impl Attribute {
             } else {
                 return None;
             },
-            span: self.span,
+            span,
         })
     }
+}
+
+impl Attribute {
+    /// Extracts the MetaItem from inside this Attribute.
+    pub fn meta(&self) -> Option<MetaItem> {
+        self.item.meta(self.span)
+    }
 
     pub fn parse<'a, T, F>(&self, sess: &'a ParseSess, mut f: F) -> PResult<'a, T>
         where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
@@ -524,7 +530,7 @@ impl MetaItem {
             }
             Some(TokenTree::Token(Token { kind: token::Interpolated(nt), .. })) => match *nt {
                 token::Nonterminal::NtIdent(ident, _) => Path::from_ident(ident),
-                token::Nonterminal::NtMeta(ref meta) => return Some(meta.clone()),
+                token::Nonterminal::NtMeta(ref item) => return item.meta(item.path.span),
                 token::Nonterminal::NtPath(ref path) => path.clone(),
                 _ => return None,
             },

src/libsyntax/config.rs

@@ -122,8 +122,8 @@ impl<'a> StripUnconfigured<'a> {
 
             while !parser.check(&token::CloseDelim(token::Paren)) {
                 let lo = parser.token.span.lo();
-                let (path, tokens) = parser.parse_meta_item_unrestricted()?;
-                expanded_attrs.push((path, tokens, parser.prev_span.with_lo(lo)));
+                let item = parser.parse_attr_item()?;
+                expanded_attrs.push((item, parser.prev_span.with_lo(lo)));
                 parser.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Paren)])?;
             }
 
@@ -150,8 +150,8 @@ impl<'a> StripUnconfigured<'a> {
             // `cfg_attr` inside of another `cfg_attr`. E.g.
             //  `#[cfg_attr(false, cfg_attr(true, some_attr))]`.
             expanded_attrs.into_iter()
-            .flat_map(|(path, tokens, span)| self.process_cfg_attr(ast::Attribute {
-                item: ast::AttrItem { path, tokens },
+            .flat_map(|(item, span)| self.process_cfg_attr(ast::Attribute {
+                item,
                 id: attr::mk_attr_id(),
                 style: attr.style,
                 is_sugared_doc: false,

src/libsyntax/ext/mbe/macro_parser.rs

@@ -924,7 +924,7 @@ fn parse_nt(p: &mut Parser<'_>, sp: Span, name: Symbol) -> Nonterminal {
             FatalError.raise()
         }
         sym::path => token::NtPath(panictry!(p.parse_path(PathStyle::Type))),
-        sym::meta => token::NtMeta(panictry!(p.parse_meta_item())),
+        sym::meta => token::NtMeta(panictry!(p.parse_attr_item())),
         sym::vis => token::NtVis(panictry!(p.parse_visibility(true))),
         sym::lifetime => if p.check_lifetime() {
             token::NtLifetime(p.expect_lifetime().ident)

src/libsyntax/mut_visit.rs

@@ -682,7 +682,10 @@ pub fn noop_visit_interpolated<T: MutVisitor>(nt: &mut token::Nonterminal, vis:
         token::NtIdent(ident, _is_raw) => vis.visit_ident(ident),
         token::NtLifetime(ident) => vis.visit_ident(ident),
         token::NtLiteral(expr) => vis.visit_expr(expr),
-        token::NtMeta(meta) => vis.visit_meta_item(meta),
+        token::NtMeta(AttrItem { path, tokens }) => {
+            vis.visit_path(path);
+            vis.visit_tts(tokens);
+        }
         token::NtPath(path) => vis.visit_path(path),
         token::NtTT(tt) => vis.visit_tt(tt),
         token::NtImplItem(item) =>

src/libsyntax/parse/attr.rs

@@ -90,7 +90,7 @@ impl<'a> Parser<'a> {
         debug!("parse_attribute_with_inner_parse_policy: inner_parse_policy={:?} self.token={:?}",
                inner_parse_policy,
                self.token);
-        let (span, path, tokens, style) = match self.token.kind {
+        let (span, item, style) = match self.token.kind {
             token::Pound => {
                 let lo = self.token.span;
                 self.bump();
@@ -107,7 +107,7 @@ impl<'a> Parser<'a> {
                 };
 
                 self.expect(&token::OpenDelim(token::Bracket))?;
-                let (path, tokens) = self.parse_meta_item_unrestricted()?;
+                let item = self.parse_attr_item()?;
                 self.expect(&token::CloseDelim(token::Bracket))?;
                 let hi = self.prev_span;
 
@@ -142,7 +142,7 @@ impl<'a> Parser<'a> {
                     }
                 }
 
-                (attr_sp, path, tokens, style)
+                (attr_sp, item, style)
             }
             _ => {
                 let token_str = self.this_token_to_string();
@@ -151,7 +151,7 @@ impl<'a> Parser<'a> {
         };
 
         Ok(ast::Attribute {
-            item: ast::AttrItem { path, tokens },
+            item,
             id: attr::mk_attr_id(),
             style,
             is_sugared_doc: false,
@@ -168,17 +168,17 @@ impl<'a> Parser<'a> {
     ///     PATH
     ///     PATH `=` TOKEN_TREE
     /// The delimiters or `=` are still put into the resulting token stream.
-    pub fn parse_meta_item_unrestricted(&mut self) -> PResult<'a, (ast::Path, TokenStream)> {
-        let meta = match self.token.kind {
+    pub fn parse_attr_item(&mut self) -> PResult<'a, ast::AttrItem> {
+        let item = match self.token.kind {
             token::Interpolated(ref nt) => match **nt {
-                Nonterminal::NtMeta(ref meta) => Some(meta.clone()),
+                Nonterminal::NtMeta(ref item) => Some(item.clone()),
                 _ => None,
             },
             _ => None,
         };
-        Ok(if let Some(meta) = meta {
+        Ok(if let Some(item) = item {
             self.bump();
-            (meta.path, meta.kind.tokens(meta.span))
+            item
         } else {
             let path = self.parse_path(PathStyle::Mod)?;
             let tokens = if self.check(&token::OpenDelim(DelimToken::Paren)) ||
@@ -205,7 +205,7 @@ impl<'a> Parser<'a> {
             } else {
                 TokenStream::empty()
             };
-            (path, tokens)
+            ast::AttrItem { path, tokens }
         })
     }
 
@@ -273,9 +273,14 @@ impl<'a> Parser<'a> {
             _ => None,
         };
 
-        if let Some(meta) = nt_meta {
-            self.bump();
-            return Ok(meta);
+        if let Some(item) = nt_meta {
+            return match item.meta(item.path.span) {
+                Some(meta) => {
+                    self.bump();
+                    Ok(meta)
+                }
+                None => self.unexpected(),
+            }
         }
 
         let lo = self.token.span;

src/libsyntax/parse/parser/path.rs

@@ -114,9 +114,9 @@ impl<'a> Parser<'a> {
     pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, Path> {
         let meta_ident = match self.token.kind {
             token::Interpolated(ref nt) => match **nt {
-                token::NtMeta(ref meta) => match meta.kind {
-                    ast::MetaItemKind::Word => Some(meta.path.clone()),
-                    _ => None,
+                token::NtMeta(ref item) => match item.tokens.is_empty() {
+                    true => Some(item.path.clone()),
+                    false => None,
                 },
                 _ => None,
             },

src/libsyntax/parse/token.rs

@@ -687,7 +687,7 @@ pub enum Nonterminal {
     NtLifetime(ast::Ident),
     NtLiteral(P<ast::Expr>),
     /// Stuff inside brackets for attributes
-    NtMeta(ast::MetaItem),
+    NtMeta(ast::AttrItem),
     NtPath(ast::Path),
     NtVis(ast::Visibility),
     NtTT(TokenTree),

src/libsyntax/print/pprust.rs

@@ -324,7 +324,7 @@ fn token_to_string_ext(token: &Token, convert_dollar_crate: bool) -> String {
 crate fn nonterminal_to_string(nt: &Nonterminal) -> String {
     match *nt {
         token::NtExpr(ref e)        => expr_to_string(e),
-        token::NtMeta(ref e)        => meta_item_to_string(e),
+        token::NtMeta(ref e)        => attr_item_to_string(e),
         token::NtTy(ref e)          => ty_to_string(e),
         token::NtPath(ref e)        => path_to_string(e),
         token::NtItem(ref e)        => item_to_string(e),
@@ -412,8 +412,8 @@ pub fn meta_list_item_to_string(li: &ast::NestedMetaItem) -> String {
     to_string(|s| s.print_meta_list_item(li))
 }
 
-pub fn meta_item_to_string(mi: &ast::MetaItem) -> String {
-    to_string(|s| s.print_meta_item(mi))
+fn attr_item_to_string(ai: &ast::AttrItem) -> String {
+    to_string(|s| s.print_attr_item(ai, ai.path.span))
 }
 
 pub fn attribute_to_string(attr: &ast::Attribute) -> String {
@@ -629,26 +629,30 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
                 ast::AttrStyle::Inner => self.word("#!["),
                 ast::AttrStyle::Outer => self.word("#["),
             }
-            self.ibox(0);
-            match attr.tokens.trees().next() {
-                Some(TokenTree::Delimited(_, delim, tts)) => {
-                    self.print_mac_common(
-                        Some(MacHeader::Path(&attr.path)), false, None, delim, tts, true, attr.span
-                    );
-                }
-                tree => {
-                    self.print_path(&attr.path, false, 0);
-                    if tree.is_some() {
-                        self.space();
-                        self.print_tts(attr.tokens.clone(), true);
-                    }
-                }
-            }
-            self.end();
+            self.print_attr_item(&attr.item, attr.span);
             self.word("]");
         }
     }
 
+    fn print_attr_item(&mut self, item: &ast::AttrItem, span: Span) {
+        self.ibox(0);
+        match item.tokens.trees().next() {
+            Some(TokenTree::Delimited(_, delim, tts)) => {
+                self.print_mac_common(
+                    Some(MacHeader::Path(&item.path)), false, None, delim, tts, true, span
+                );
+            }
+            tree => {
+                self.print_path(&item.path, false, 0);
+                if tree.is_some() {
+                    self.space();
+                    self.print_tts(item.tokens.clone(), true);
+                }
+            }
+        }
+        self.end();
+    }
+
     fn print_meta_list_item(&mut self, item: &ast::NestedMetaItem) {
         match item {
             ast::NestedMetaItem::MetaItem(ref mi) => {

src/libsyntax_ext/cmdline_attrs.rs

@@ -1,6 +1,6 @@
 //! Attributes injected into the crate root from command line using `-Z crate-attr`.
 
-use syntax::ast::{self, AttrStyle};
+use syntax::ast::{self, AttrItem, AttrStyle};
 use syntax::attr::mk_attr;
 use syntax::panictry;
 use syntax::parse::{self, token, ParseSess};
@@ -15,7 +15,7 @@ pub fn inject(mut krate: ast::Crate, parse_sess: &ParseSess, attrs: &[String]) -
         );
 
         let start_span = parser.token.span;
-        let (path, tokens) = panictry!(parser.parse_meta_item_unrestricted());
+        let AttrItem { path, tokens } = panictry!(parser.parse_attr_item());
         let end_span = parser.token.span;
         if parser.token != token::Eof {
             parse_sess.span_diagnostic

src/test/ui/cfg/cfg_stmt_expr.rs

@@ -57,7 +57,7 @@ fn main() {
     // check that macro expanded code works
 
     macro_rules! if_cfg {
-        ($cfg:meta $ib:block else $eb:block) => {
+        ($cfg:meta? $ib:block else $eb:block) => {
             {
                 let r;
                 #[cfg($cfg)]
@@ -69,7 +69,7 @@ fn main() {
         }
     }
 
-    let n = if_cfg!(unset {
+    let n = if_cfg!(unset? {
         413
     } else {
         612

src/test/ui/macros/macro-first-set.rs

@@ -252,12 +252,6 @@ test_path!(::std);
 test_path!(std::u8,);
 test_path!(any, super, super::super::self::path, X<Y>::Z<'a, T=U>);
 
-macro_rules! test_meta_block {
-    ($($m:meta)* $b:block) => {};
-}
-
-test_meta_block!(windows {});
-
 macro_rules! test_lifetime {
     (1. $($l:lifetime)* $($b:block)*) => {};
     (2. $($b:block)* $($l:lifetime)*) => {};