Added optional support for hashbang directives.

Fixes #180.

acorn.js

@@ -74,6 +74,9 @@
     // When enabled, import/export statements are not constrained to
     // appearing at the top of the program.
     allowImportExportEverywhere: false,
+    // When enabled, hashbang directive in the beginning of file
+    // is allowed and treated as a line comment.
+    allowHashBang: false,
     // When `locations` is on, `loc` properties holding objects with
     // `start` and `end` properties in `{line, column}` form (with
     // line being 1-based and column 0-based) will be attached to the
@@ -615,6 +618,9 @@
     tokRegexpAllowed = true;
     metParenL = 0;
     templates = [];
+    if (tokPos === 0 && options.allowHashBang && input.slice(0, 2) === '#!') {
+      skipLineComment(2);
+    }
   }
 
   // Called at the end of every token. Sets `tokEnd`, `tokVal`, and

acorn_loose.js

@@ -45,7 +45,6 @@
   exports.parse_dammit = function(inpt, opts) {
     if (!opts) opts = {};
     input = String(inpt);
-    if (/^#!.*/.test(input)) input = "//" + input.slice(2);
     fetchToken = acorn.tokenize(input, opts);
     options = fetchToken.options;
     sourceFile = options.sourceFile || null;

test/tests.js

@@ -28834,3 +28834,14 @@ test('var x = (1 + 2)', {}, {
 });
 
 test("function f(f) { 'use strict'; }", {});
+
+// https://github.com/marijnh/acorn/issues/180
+test("#!/usr/bin/node\n;", {}, {
+  allowHashBang: true,
+  onComment: [{
+    type: "Line",
+    value: "/usr/bin/node",
+    start: 0,
+    end: 15
+  }]
+});