Improve location of error messages around identifiers.

Lexer::ReadIdent() now sets last_token_ before returning, like
Lexer::ReadEvalString() does. So all "expected identifiers" and things
that call ReadIdent (pool parser, rule parser, let parser, code parsing
the rule name after a : in a build line) now point the "^ near here" at
what was there instead of the previous last_token

According to manifest_parser_perftest, this is perf-neutral.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/lexer.in.cc b/src/lexer.in.cc
index f861239..20ed442 100644
--- a/src/lexer.in.cc
+++ b/src/lexer.in.cc
@@ -182,16 +182,21 @@ void Lexer::EatWhitespace() {
 
 bool Lexer::ReadIdent(string* out) {
   const char* p = ofs_;
+  const char* start;
   for (;;) {
-    const char* start = p;
+    start = p;
     /*!re2c
     varname {
       out->assign(start, p - start);
       break;
     }
-    [^] { return false; }
+    [^] {
+      last_token_ = start;
+      return false;
+    }
     */
   }
+  last_token_ = start;
   ofs_ = p;
   EatWhitespace();
   return true;