Auto merge of #46895 - ricochet1k:macro-lifetimes, r=jseyfried

Allow lifetimes in macros

This is a resurrection of PR #41927 which was a resurrection of #33135, which is intended to fix #34303.

In short, this allows macros_rules! to use :lifetime as a matcher to match 'lifetimes.

Still to do:
- [x]  Feature gate

2 files changed, 33 insertions, 13 deletions

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 1a2146509e3..812e3c4967a 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -1295,6 +1295,10 @@ impl<'a> Parser<'a> {
     fn get_label(&mut self) -> ast::Ident {
         match self.token {
             token::Lifetime(ref ident) => *ident,
+            token::Interpolated(ref nt) => match nt.0 {
+                token::NtLifetime(lifetime) => lifetime.ident,
+                _ => self.bug("not a lifetime"),
+            },
             _ => self.bug("not a lifetime"),
         }
     }
@@ -2031,14 +2035,12 @@ impl<'a> Parser<'a> {
     }
 
     /// Parse single lifetime 'a or panic.
-    fn expect_lifetime(&mut self) -> Lifetime {
-        match self.token {
-            token::Lifetime(ident) => {
-                let ident_span = self.span;
-                self.bump();
-                Lifetime { ident: ident, span: ident_span, id: ast::DUMMY_NODE_ID }
-            }
-            _ => self.span_bug(self.span, "not a lifetime")
+    pub fn expect_lifetime(&mut self) -> Lifetime {
+        if let Some(lifetime) = self.token.lifetime(self.span) {
+            self.bump();
+            lifetime
+        } else {
+            self.span_bug(self.span, "not a lifetime")
         }
     }
 
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index 05368c52d2c..bd4f7f9853d 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -251,7 +251,7 @@ impl Token {
             Lt | BinOp(Shl)             | // associated path
             ModSep                      => true, // global path
             Interpolated(ref nt) => match nt.0 {
-                NtIdent(..) | NtTy(..) | NtPath(..) => true,
+                NtIdent(..) | NtTy(..) | NtPath(..) | NtLifetime(..) => true,
                 _ => false,
             },
             _ => false,
@@ -314,14 +314,26 @@ impl Token {
         false
     }
 
-    /// Returns `true` if the token is a lifetime.
-    pub fn is_lifetime(&self) -> bool {
+    /// Returns a lifetime with the span and a dummy id if it is a lifetime,
+    /// or the original lifetime if it is an interpolated lifetime, ignoring
+    /// the span.
+    pub fn lifetime(&self, span: Span) -> Option<ast::Lifetime> {
         match *self {
-            Lifetime(..) => true,
-            _            => false,
+            Lifetime(ident) =>
+                Some(ast::Lifetime { ident: ident, span: span, id: ast::DUMMY_NODE_ID }),
+            Interpolated(ref nt) => match nt.0 {
+                NtLifetime(lifetime) => Some(lifetime),
+                _ => None,
+            },
+            _ => None,
         }
     }
 
+    /// Returns `true` if the token is a lifetime.
+    pub fn is_lifetime(&self) -> bool {
+        self.lifetime(syntax_pos::DUMMY_SP).is_some()
+    }
+
     /// Returns `true` if the token is either the `mut` or `const` keyword.
     pub fn is_mutability(&self) -> bool {
         self.is_keyword(keywords::Mut) ||
@@ -486,6 +498,10 @@ impl Token {
                 let token = Token::Ident(ident.node);
                 tokens = Some(TokenTree::Token(ident.span, token).into());
             }
+            Nonterminal::NtLifetime(lifetime) => {
+                let token = Token::Lifetime(lifetime.ident);
+                tokens = Some(TokenTree::Token(lifetime.span, token).into());
+            }
             Nonterminal::NtTT(ref tt) => {
                 tokens = Some(tt.clone().into());
             }
@@ -524,6 +540,7 @@ pub enum Nonterminal {
     NtGenerics(ast::Generics),
     NtWhereClause(ast::WhereClause),
     NtArg(ast::Arg),
+    NtLifetime(ast::Lifetime),
 }
 
 impl fmt::Debug for Nonterminal {
@@ -546,6 +563,7 @@ impl fmt::Debug for Nonterminal {
             NtWhereClause(..) => f.pad("NtWhereClause(..)"),
             NtArg(..) => f.pad("NtArg(..)"),
             NtVis(..) => f.pad("NtVis(..)"),
+            NtLifetime(..) => f.pad("NtLifetime(..)"),
         }
     }
 }