report local ambiguity errors earlier

Author: eholk

src/libsyntax/ext/tt/earley_parser.rs

@@ -134,14 +134,16 @@ fn nameize(p_s: parse_sess, ms: ~[matcher], res: ~[@named_match])
 
 enum parse_result {
     success(hashmap<ident, @named_match>),
-    failure(codemap::span, ~str)
+    failure(codemap::span, ~str),
+    error(codemap::span, ~str)
 }
 
 fn parse_or_else(sess: parse_sess, cfg: ast::crate_cfg, rdr: reader,
                  ms: ~[matcher]) -> hashmap<ident, @named_match> {
     match parse(sess, cfg, rdr, ms) {
       success(m) => m,
-      failure(sp, str) => sess.span_diagnostic.span_fatal(sp, str)
+      failure(sp, str) => sess.span_diagnostic.span_fatal(sp, str),
+      error(sp, str) => sess.span_diagnostic.span_fatal(sp, str)
     }
 }
 
@@ -262,7 +264,7 @@ fn parse(sess: parse_sess, cfg: ast::crate_cfg, rdr: reader, ms: ~[matcher])
                     nameize(sess, ms,
                             vec::map(eof_eis[0u].matches, |dv| dv.pop())));
             } else if eof_eis.len() > 1u {
-                return failure(sp, ~"Ambiguity: multiple successful parses");
+                return error(sp, ~"Ambiguity: multiple successful parses");
             } else {
                 return failure(sp, ~"Unexpected end of macro invocation");
             }
@@ -276,7 +278,7 @@ fn parse(sess: parse_sess, cfg: ast::crate_cfg, rdr: reader, ms: ~[matcher])
                       }
                       _ => fail
                     } }), ~" or ");
-                return failure(sp, fmt!{
+                return error(sp, fmt!{
                     "Local ambiguity: multiple parsing options: \
                      built-in NTs %s or %u other options.",
                     nts, next_eis.len()});

src/libsyntax/ext/tt/macro_rules.rs

@@ -6,7 +6,7 @@ import parse::lexer::{new_tt_reader, reader};
 import parse::token::{FAT_ARROW, SEMI, LBRACE, RBRACE, nt_matchers, nt_tt};
 import parse::parser::{parser, SOURCE_FILE};
 import earley_parser::{parse, parse_or_else, success, failure, named_match,
-                       matched_seq, matched_nonterminal};
+                       matched_seq, matched_nonterminal, error};
 import std::map::hashmap;
 
 fn add_new_extension(cx: ext_ctxt, sp: span, name: ident,
@@ -80,7 +80,8 @@ fn add_new_extension(cx: ext_ctxt, sp: span, name: ident,
                   failure(sp, msg) => if sp.lo >= best_fail_spot.lo {
                     best_fail_spot = sp;
                     best_fail_msg = msg;
-                  }
+                  },
+                  error(sp, msg) => cx.span_fatal(sp, msg)
                 }
               }
               _ => cx.bug(~"non-matcher found in parsed lhses")