macros: Do not match on "complex" nonterminals requiring AST comparisons

1 files changed, 17 insertions, 1 deletions

diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index 8da79f92768..35a745ccdee 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -565,7 +565,7 @@ impl Token {
     }
 }
 
-#[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash)]
+#[derive(Clone, RustcEncodable, RustcDecodable, Eq, Hash)]
 /// For interpolation during macro expansion.
 pub enum Nonterminal {
     NtItem(P<ast::Item>),
@@ -591,6 +591,22 @@ pub enum Nonterminal {
     NtArg(ast::Arg),
 }
 
+impl PartialEq for Nonterminal {
+    fn eq(&self, rhs: &Self) -> bool {
+        match (self, rhs) {
+            (NtIdent(ident_lhs, is_raw_lhs), NtIdent(ident_rhs, is_raw_rhs)) =>
+                ident_lhs == ident_rhs && is_raw_lhs == is_raw_rhs,
+            (NtLifetime(ident_lhs), NtLifetime(ident_rhs)) => ident_lhs == ident_rhs,
+            (NtTT(tt_lhs), NtTT(tt_rhs)) => tt_lhs == tt_rhs,
+            // FIXME: Assume that all "complex" nonterminal are not equal, we can't compare them
+            // correctly based on data from AST. This will prevent them from matching each other
+            // in macros. The comparison will become possible only when each nonterminal has an
+            // attached token stream from which it was parsed.
+            _ => false,
+        }
+    }
+}
+
 impl fmt::Debug for Nonterminal {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {