improve usability (#5753)

lib/parse.js

@@ -207,7 +207,11 @@ function JS_Parse_Error(message, filename, line, col, pos) {
     this.line = line;
     this.col = col;
     this.pos = pos;
-    configure_error_stack(this, new SyntaxError(message, filename, line, col));
+    try {
+        throw new SyntaxError(message, filename, line, col);
+    } catch (cause) {
+        configure_error_stack(this, cause);
+    }
 }
 JS_Parse_Error.prototype = Object.create(SyntaxError.prototype);
 JS_Parse_Error.prototype.constructor = JS_Parse_Error;

lib/utils.js

@@ -65,8 +65,12 @@ function configure_error_stack(ex, cause) {
                 var msg = "" + cause.message;
                 cause = null;
                 var index = stack.indexOf(msg);
-                if (index >= 0) index += msg.length;
-                index = stack.indexOf("\n", index) + 1;
+                if (index < 0) {
+                    index = 0;
+                } else {
+                    index += msg.length;
+                    index = stack.indexOf("\n", index) + 1;
+                }
                 stack = stack.slice(0, index) + stack.slice(stack.indexOf("\n", index) + 1);
             }
             return stack;
@@ -77,7 +81,11 @@ function configure_error_stack(ex, cause) {
 function DefaultsError(msg, defs) {
     this.message = msg;
     this.defs = defs;
-    configure_error_stack(this, new Error(msg));
+    try {
+        throw new Error(msg);
+    } catch (cause) {
+        configure_error_stack(this, cause);
+    }
 }
 DefaultsError.prototype = Object.create(Error.prototype);
 DefaultsError.prototype.constructor = DefaultsError;