[swift-evolution] Infer types of default function parameters

Kilian Koeltzsch me at kilian.io
Fri Mar 10 15:40:34 CST 2017

Hi all,

I sent the message below to swift-users@ ~a day ago, but this might be a better place to ask and gather some discussion. It is a rather minor suggestion and I'm just looking for some opinions.

Declaring a function that has default parameters currently looks like this:

func foo(bar: String = "baz") {

Now I'm wondering if there would be any problems if it were possible to omit the type annotation for default params and let Swift's type inference handle that.

func foo(bar = "baz") {

It feels to be equivalent to omitting type annotations with variable declarations. Obviously more complex types would still require annotations being specified. Off the top of my head I can't think of any negative ramifications this might bring, be it in simple function/method declarations or protocol extensions and elsewhere.
Any further input or examples for situations where this might cause issues would be much appreciated :)

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