fix identifier lexemes

src/scanner.zig

@@ -110,6 +110,10 @@ pub const Scanner = struct {
         return self.source[self.current - 1];
     }
 
+    fn rollback(self: *Scanner) void {
+        self.current -= 1;
+    }
+
     pub fn currentLexeme(self: *Scanner) []const u8 {
         return self.source[self.start..self.current];
     }
@@ -257,6 +261,9 @@ pub const Scanner = struct {
             toktype = TokenType.Identifier;
         }
 
+        // ugly hack.
+        self.rollback();
+
         return self.makeToken(toktype);
     }