BUG: incorrect lambda closure

Start with the Python reproducer and compare its generated JavaScript, especially the lambda's intent and method bindings inside the loop. Trace the lambda translation and scope handling; done means the generated code preserves each iteration's captured values and the reproducer calls method_one successfully.

see javascript-closure-inside-loops

1. the following code

def method_one(intent, *args):
    print(f'method_one {intent}: {args}')


def method_two(intent, *args):
    print(f'method_two {intent}: {args}')


config_list = [
    ('one', method_one),
    ('two', method_two),
]

method_dict = dict()

for intent, method in config_list:
    print(f"intent={intent} method={method}")
    method_dict[intent] = lambda *args, intent = intent, method = method : method(intent, args)

method_dict['one']()

2. produces output in python:

intent=one method=<function method_one at 0x7f7cb7111830>
intent=two method=<function method_two at 0x7f7cb7139950>
method_one one: ((),)

3. and produces error in javascript:

tester.py:28 Uncaught TypeError: method is not a function

4. due to translation:

export var method_one = function (intent) {
	var args = tuple ([].slice.apply (arguments).slice (1));
	print ('method_one {}: {}'.format (intent, args));
};
export var method_two = function (intent) {
	var args = tuple ([].slice.apply (arguments).slice (1));
	print ('method_two {}: {}'.format (intent, args));
};
export var config_list = [tuple (['one', method_one]), tuple (['two', method_two])];
export var method_dict = dict ();
for (var [intent, method] of config_list) {
	print ('intent={} method={}'.format (intent, method));
	method_dict [intent] = (function __lambda__ () {
		var intent = intent;
		var method = method;
		var args = tuple ([].slice.apply (arguments).slice (0));
		return method (intent, args);
	});
}
method_dict ['one'] ();

5. where both intent and method are undefined via incorrect lambda closure:

		var intent = intent;
		var method = method;

6 . and one way to transform is:

for (var [intent, method] of config_list) {
	const intent_ = intent // const
	const method_ = method // const
	print ('intent={} method={}'.format (intent, method));
	method_dict [intent] = (function __lambda__ () {
		var intent = intent_;
		var method = method_;
		var args = tuple ([].slice.apply (arguments).slice (0));
		return method (intent, args);
	});
}