go/types: revert most recent change - we cannot rely on 1.5 features quite yet

Revert "go/types: fix Eval to use correct file set when evaluating an expression"

This reverts commit d241a1448b.

Change-Id: Ie16c57da2732d8b079108efef100fc956b71f737
Reviewed-on: https://go-review.googlesource.com/11010
Reviewed-by: David Symonds <dsymonds@golang.org>

go/types/eval.go

@@ -65,7 +65,11 @@ func Eval(fset *token.FileSet, pkg *Package, pos token.Pos, expr string) (tv Typ
 	}
 
 	// parse expressions
-	node, err := parser.ParseExprFrom(fset, "eval", expr, 0)
+	// BUG(gri) In case of type-checking errors below, the type checker
+	//          doesn't have the correct file set for expr. The correct
+	//          solution requires a ParseExpr that uses the incoming
+	//          file set fset.
+	node, err := parser.ParseExpr(expr)
 	if err != nil {
 		return TypeAndValue{}, err
 	}