Optional args

[mbroughani81]

No description provided.

[LPTK]

It seems that the branch you merged earlier was still a wildly outdated version. That's why it would help you to use a git GUI, which would allow you to better visualize what you're doing.

[mbroughani81]

It seems that the branch you merged earlier was still a wildly outdated version. That's why it would help you to use a git GUI, which would allow you to better visualize what you're doing.

I will give it a try!
BTW, I resolved the conflict. Almost all was because of the FldFlags new fields.

[LPTK]

You messed up the merge a bit. File QML_exist_Classes_CT.mls was deleted from the main branch and you mistakenly reinstated it.

[LPTK]

Test cases to add

As discussed on Discord, here are expected usages of optional parameters:

fun foo0(x: Int?) = if x is undefined then 0 else x + 1

fun foo1(x?) = if x is undefined then 0 else x + 1

The following should not type check

:e
fun foo0(x: Int?) = x + 1

:e
fun foo1(x?) = x + 1

To do this, you have to adapt the typing of tuples when in pattern positions.

And some interesting cases to add, which contain signature checks:

fun foo: (x: Int?) -> Int
fun foo(x?) = if x is undefined then 0 else x + 1

// Ok: function with optional parameter can be widened to function with mandatory parameter
fun foo: (x: Int) -> Int
fun foo(x?) = if x is undefined then 0 else x + 1

:e // The definition's parameter spec is too strong
fun foo: (x: Int?) -> Int
fun foo(x) = x + 1

And some subtype tests:

fun f(x) = (x : [Int, Int?]) : ['a, 'b]

I expect we could accept the case above by constraining Int | undefined <: 'b