[SR-494] Cannot call function with variadic arguments before a required unnamed parameter

[lilyball]

Previous ID	SR-494
Radar	None
Original Reporter	@lilyball
Type	Bug

Environment

Apple Swift version 2.1.1 (swiftlang-700.1.101.15 clang-700.1.81)
Apple Swift version 2.2-dev (LLVM 3ebdbb2c7e, Clang f66c5bb67b, Swift 54dcd16)

Additional Detail from JIRA

Votes	1
Component/s	Compiler
Labels	Bug, TypeChecker
Assignee	None
Priority	Medium

md5: 9c3271fc49314ea7082f4bfb393d4cff

relates to:

• SR-2475 QoI: Warn about unlabeled parameters following a variadic parameter

Issue Description:

When declaring a function that takes variadic arguments followed by a required parameter, such as

func foo(xs: Int..., _ y: String) { print(xs, y) }

this is accepted, but there's no way to call the function. Any attempt to do so fails with an error, e.g.

foo(1, 2, "three")

fails with the error

error: missing argument for parameter #2 in call

I consider this a bug, because this call is unambiguous. There is a single required parameter after the variadic arguments, which means that the last parameter in the call must correspond with this unnamed parameter.

More generally, Swift should be able to figure out how to invoke functions that have one or more unnamed parameters after the variadic parameter list as long as the unnamed parameters do not have default values.

[belkadan]

cwillmore (JIRA User), seems like something you'd be interested in (at some point).

[AnthonyLatsis]

Fixed and covered by tests here