Named Function Expressions

Summary

This proposes that the current function expressions, which are always anonymous (unnamed) be allowed to have names.

Motivation

This would make some code more readable, enable luau to give function expressions names other than <anonymous> in stack traces and with debug.info, enable function expressions to be recursive (call themselves), and help in miscellaneous profiling and debugging tools.

Design

The current grammar for function expressions is the following, taken from the simpleexp rule.

attributes 'function' funcbody

This proposal would change that grammar to the following.

attributes 'function' [NAME] funcbody

This adds an optional name in function expressions, which can be used like so:

foo(function factorial(n)
	return if n == 1 then 1 else n * factorial(n - 1)
end)

It is also important to note where this creates a binding to the function expression, the following example should explain:

-- 'bar' is not bound here

local foo = function bar(n)
	-- 'bar' is bound here
end

-- 'bar' is not bound here

Drawbacks

This proposal would make table function field syntax impossible without a special case. An example of this syntax:

local t = {
	function foo() end,
}

t.foo()

Alternatives

The alternative is defining a function with local function declaration syntax, which allows for recursion and gives debugging names.

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