Nim: Support default arguments in sugar.`=>` and sugar.`->`

[hlaaftana]

Summary

The macros sugar.=> and sugar.-> do not have support for default arguments.

Description

The syntax would be like (a = 5) => echo a/(a = 5) -> void without a type annotation, and ((a: int) = 5) => echo a/((a: int) = 5) -> void with one, the reason being that (a: int = 5) does not parse as an expression.

Alternatives

Idk

Additional Information

• I overlooked this in #14200 and I would have implemented it if I knew, but someone else doing it now would be greatly appreciated

[dom96]

Meh, I think at that point you can just write out proc... the lambda syntax sugar shouldn't support every single thing, especially when it requires those extra parens.

[awr1]

As of right now the sugar macros seem fine as-is, the only thing that I find slightly annoying about them is the lack of semicolon support for syntactic consistency's sake but this is a minor nitpick.

Default arguments seem kind of heavyweight for concise lambda syntax where the point is being able to write small, typically one-line functions. Having default argument support seems kinda weird when almost all of the time lambdas are used in a higher-order context - do procedures with default arguments even work correctly in higher-order functions?

Is the point of this more for concise function declaration (i.e. let foo = x => ... as opposed to proc foo(x :int) :auto = ...) as opposed to higher-orders? If so I would just say if you need default arguments, maybe just write a proc.

[hlaaftana]

Ok, if someone really cares they can make a PR, closing. Implementing semicolons is another topic that might be a little difficult, for it to parse correctly, all colons would have to be replaced with a semicolon (StmtListExpr).