[swift-users] Type inference of array element type

Toni Suter tonisuter at me.com
Fri Mar 24 05:08:35 CDT 2017


If I declare a variable and initialize it with an array literal whose elements are integer literals and nil literals,
the compiler will infer the type Array<Optional<Int>> for that variable:

let arr = [1, nil, 3]
print(type(of: arr)) 	// Array<Optional<Int>>

However, that only works with nominal types such as Int and String. If I do the same thing with an array of tuples,
I get a compile error:

let arr = [(1, false), nil, (3, true)]		// error: type of expression is ambiguous without more context
print(type(of: arr))

Why can't the compiler infer the type Array<Optional<(Int, Bool)>> in this example? Is there a reason for this or is it a bug?

Thanks and best regards,

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