Issue 427 - Desugar arrow functions to normal or bound functions

scripts/abprewrite.js

 // This script rewrites AST to be compatible with JavaScript 1.5 and decompiles
 // the modified tree then
 
 include("../scripts/astDecompile.js");
 include("../utils/beautify.js");
 
 let headerPrinted = false;
 
 // See https://developer.mozilla.org/en-US/docs/SpiderMonkey/Parser_API for
 // AST structure.
@@ skipping 452 matching lines @@
   }
 
   // Now convert the arrow expression into a normal
   // function expression.
   ast.type = "FunctionExpression";
   ast.expression = false;
 
   // We want to avoid the .bind call if |this| isn't actually used.
   // This is not necessarily always correct, but should be good enough.
   var body = decompileAST(ast.body);
-  if (["this", "Function", "eval", "=>"].some(search => body.contains(search))) {

[Wladimir Palant, 2014/05/15 06:53:44]

I think this would be better here:

  if (/\b(this|Function|eval)\b/.test(body))

While this is still a hack, we should look for keywords rather than random
substrings.

And of course we should never generate code dynamically - already because CSP
restrictions in Chrome don't allow it. So I wonder whether creating
modifyCallExpression()/modifyNewExpression() functions that will reject new
Function(...) and eval(...) would be a better course of action here.

+  if (/((\bthis\b)|=>)/.test(body)) {
     return {
       type: "CallExpression",
       callee: Member(ast, "bind"),
       arguments: [
         {
           type: "ThisExpression"
         }
       ]
     };
   }
@@ skipping 84 matching lines @@
     let code = 'require.scopes["' + options.filename + '"] = (function() {\n' +
                'var exports = {};\n' +
                decompileAST(ast) +
                'return exports;\n' +
                '})();\n';
     _print(js_beautify(code, options));
   }
   else
     _print(js_beautify(decompileAST(ast), options));
 }