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?
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?
Offhand it seems like we should be able to properly handle this. Can you open a bug report at bugs.swift.org <Issues · apple/swift · GitHub?
Mark
···
On Mar 24, 2017, at 3:08 AM, Toni Suter via swift-users <swift-users@swift.org> wrote:
IMO this is a boundary problem.
How far do you want to go in letting the compiler deduce the actual type?
It is possible to make very elaborate constructs that would basically default to a complex tuple/array/dictionary construct with only Any?’s in them. (well, the dict would require a Hashable too)
Besides, the recent discussion on compile times illustrates another angle to this problem: if type inference is used extensively, compile times go to infinite…
So while I do not know if this is a bug or not, I would recommend not to use it anyhow.
On 24 Mar 2017, at 11:08, Toni Suter via swift-users <swift-users@swift.org> wrote:
Hi,
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?
Am 24.03.2017 um 18:51 schrieb Mark Lacey <mark.lacey@apple.com>:
On Mar 24, 2017, at 3:08 AM, Toni Suter via swift-users <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:
Hi,
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?
Offhand it seems like we should be able to properly handle this. Can you open a bug report at bugs.swift.org <Issues · apple/swift · GitHub?
On 24 Mar 2017, at 11:22, Rien via swift-users <swift-users@swift.org> wrote:
IMO this is a boundary problem.
How far do you want to go in letting the compiler deduce the actual type?
It is possible to make very elaborate constructs that would basically default to a complex tuple/array/dictionary construct with only Any?’s in them. (well, the dict would require a Hashable too)
Besides, the recent discussion on compile times illustrates another angle to this problem: if type inference is used extensively, compile times go to infinite…
So while I do not know if this is a bug or not, I would recommend not to use it anyhow.
On 24 Mar 2017, at 11:08, Toni Suter via swift-users <swift-users@swift.org> wrote:
Hi,
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?
On 24 Mar 2017, at 11:22, Rien via swift-users <swift-users@swift.org> wrote:
IMO this is a boundary problem.
How far do you want to go in letting the compiler deduce the actual type?
It is possible to make very elaborate constructs that would basically default to a complex tuple/array/dictionary construct with only Any?’s in them. (well, the dict would require a Hashable too)
Besides, the recent discussion on compile times illustrates another angle to this problem: if type inference is used extensively, compile times go to infinite…
So while I do not know if this is a bug or not, I would recommend not to use it anyhow.
On 24 Mar 2017, at 11:08, Toni Suter via swift-users <swift-users@swift.org> wrote:
Hi,
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?
On 24 Mar 2017, at 11:22, Rien via swift-users <swift-users@swift.org> wrote:
IMO this is a boundary problem.
How far do you want to go in letting the compiler deduce the actual type?
It is possible to make very elaborate constructs that would basically default to a complex tuple/array/dictionary construct with only Any?’s in them. (well, the dict would require a Hashable too)
Besides, the recent discussion on compile times illustrates another angle to this problem: if type inference is used extensively, compile times go to infinite…
So while I do not know if this is a bug or not, I would recommend not to use it anyhow.
On 24 Mar 2017, at 11:08, Toni Suter via swift-users <swift-users@swift.org> wrote:
Hi,
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?
On 24 Mar 2017, at 11:22, Rien via swift-users <swift-users@swift.org> wrote:
IMO this is a boundary problem.
How far do you want to go in letting the compiler deduce the actual type?
It is possible to make very elaborate constructs that would basically default to a complex tuple/array/dictionary construct with only Any?’s in them. (well, the dict would require a Hashable too)
Besides, the recent discussion on compile times illustrates another angle to this problem: if type inference is used extensively, compile times go to infinite…
So while I do not know if this is a bug or not, I would recommend not to use it anyhow.
On 24 Mar 2017, at 11:08, Toni Suter via swift-users <swift-users@swift.org> wrote:
Hi,
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?