include location of error in parse error messages in EvalEnv strings

E.g. when parsing "foo = ${bar", point at the correct location of
the missing curly brace.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/eval_env.h b/src/eval_env.h
index fd0e4eb..f0108ae 100644
--- a/src/eval_env.h
+++ b/src/eval_env.h
@@ -39,7 +39,7 @@ struct BindingEnv : public Env {
 // A tokenized string that contains variable references.
 // Can be evaluated relative to an Env.
 struct EvalString {
-  bool Parse(const string& input, string* err);
+  bool Parse(const string& input, string* err, size_t* err_index=NULL);
   string Evaluate(Env* env) const;
 
   const string& unparsed() const { return unparsed_; }