[swift-evolution] Mutability inference

[David Smith]

One tricky thing with languages like this (javascript, for example) is that it becomes easy to accidentally introduce a new variable rather than refer to an existing one.

	David

> On Feb 23, 2016, at 11:06 PM, Darko Damjanovic via swift-evolution <swift-evolution at swift.org> wrote:
> 
> In the current Swift version the compiler is warning me if a variable is never written to and therefore should be a "let" constant. So now the compiler knows best if "let" or "var" should be applied. During writing code I experience repetitive hints about using "let" or "var" so why do I have to declare it all the time by myself if the compiler anyway knows best?
> 
> My proposal would be to make the declaration of "let" and "var" optional.
> 
> Example:
> x = 0 // <- implicitly declared as "var x" because later was written to, no need to declare it manually
> x = 5  
> 
> Example:
> y = 0 // <- implicitly declared as "let y" because later was not written to
> print(y) 
> 
> Example Optional Binding:
> if index = myArray.indexOf("A") {
> 	print(index) // here it's clear that index can be "let index"
> }
> 
> etc...
> 
> This would _not_ mean to disallow or remove the "var and "let" mutability declarations - just to make them optional. If I still want to write it to make it clear just by reading thru the code then this is ok. But I can omit "var and "let" if I want -  why bother about it at all if I can go sure that the compiler is already doing the best?
> 
> Another option (if this is "too much" change) would be to just make "let" optional and "var" still should be explicitly written. So "let" would be the default and if I want mutability I have explicitly declare it as "var". This is already the rule for function parameters.
> 
> Kind regards,
> Darko Damjanovic-Lichtfuss
> 
> 
> 
> 
> 
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