also try to parse the module as script

this should allow with() in a weird module

Author: sokra

lib/Parser.js

@@ -956,13 +956,38 @@ Parser.prototype.parseCalculatedString = function parseCalculatedString(expressi
 	};
 });
 
+var POSSIBLE_AST_OPTIONS = [{
+	ranges: true,
+	locations: true,
+	ecmaVersion: 6,
+	sourceType: "module"
+}, {
+	ranges: true,
+	locations: true,
+	ecmaVersion: 6,
+	sourceType: "script"
+}]
+
 Parser.prototype.parse = function parse(source, initialState) {
-	var ast = acorn.parse(source, {
-		ranges: true,
-		locations: true,
-		ecmaVersion: 6,
-		sourceType: "module"
-	});
+	var ast;
+	for(var i = 0; i < POSSIBLE_AST_OPTIONS.length; i++) {
+		if(!ast) {
+			try {
+				ast = acorn.parse(source, POSSIBLE_AST_OPTIONS[i]);
+			} catch(e) {
+				// ignore the error
+			}
+		}
+	}
+	if(!ast) {
+		// for the error
+		ast = acorn.parse(source, {
+			ranges: true,
+			locations: true,
+			ecmaVersion: 6,
+			sourceType: "module"
+		});
+	}
 	if(!ast || typeof ast !== "object")
 		throw new Error("Source couldn't be parsed");
 	var oldScope = this.scope;