[SR-3734] Mangling variadicity of function parameters

[ematejska]

Previous ID	SR-3734
Radar	rdar://problem/31411197
Original Reporter	@ematejska
Type	Task
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	1
Component/s
Labels	Task, AffectsABI
Assignee	None
Priority	Medium

md5: aa7ae25b44fc094a36a956e624b0a24e

relates to:

• SR-4058 Compiler crashes if overloaded method signature contains varargs followed by a second parameter

Issue Description:

Ahead of ABI stability, consider if we need to more carefully mangle variadicity of function parameters.

[swift-ci]

Comment by Pawel Szot (JIRA)

There is a bug related to this: SR-4058

Variadicity marker is only applied if the last parameter is variadic. So these functions have the same mangled name:

func xxx(f1: [Int], bar: Int) { }
func xxx(f1: Int..., bar: Int) { }

Additionaly, after a bit of investigation I have found that variadicity is marked for whole tuple, therefore these two functions would also have the same name if I tried to fix current mangling logic:

func xxx(f1: [Int],  f2: Int..., bar: Int) { }
func xxx(f1: Int...,  f2: [Int], bar: Int) { }

Perhaps variadicity should be reduced to syntatic sugar, so that func foo(a : Int...) is always of type ([Int]) -> (), and users can call it with array.

[bob-wilson]

@swift-ci create

[bob-wilson]

This was fixed in the new mangling scheme in Swift 4.