[Type system] Infer 'Any' for array elements and dictionary values an… #4027
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@swift-ci please test |
DougGregor
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@swift-ci please test |
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@rudkx can you review? |
| var hetero1: DictionaryLiteral = ["a": 1 as NSNumber, "b": "Foo" as NSString] | ||
| expectType(DictionaryLiteral<String, NSObject>.self, &hetero1) | ||
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| var hetero2: DictionaryLiteral = ["a": 1 as NSNumber, "b": "Foo" as NSString] | ||
| expectType(DictionaryLiteral<String, NSObject>.self, &hetero2) | ||
| #endif |
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Did you mean to leave this #if/#endif in?
[nevermind, I see the note below...]
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Yeah, I'm working on a fix independently, which should be an small optimization (prior to this PR) that brings back the functionality above.
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@DougGregor LGTM! |
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@swift-ci please test Linux |
…d 'AnyHashable' for dictionary keys.
The id-as-Any work regressed cases where Swift code could specify
heterogeneous collection literals, e.g.,
var states: [String: Any] = [
"California": [
"population": 37_000_000,
"cities": ["Los Angeles", "San Diego", "San Jose"],
],
"Oregon": [
"population": 4_000_000,
"cities": ["Portland", "Salem", "Eugene"],
]
]
Prior to this, the code worked (when Foundation was imported) because
we'd end up with literals of type [NSObject : AnyObject].
The new defaulting rule says that the element type of an array literal
and the key/value types of a dictionary literal can be defaulted if no
stronger type can be inferred. The default type is:
Any, for the element type of an array literal or the value type of a
dictionary literal, or
AnyHashable, for the key type of a dictionary literal.
The latter is intended to compose with implicit conversions to
AnyHashable, so the most-general inferred dictionary type is
[AnyHashable : Any] and will work for any plausible dictionary
literal.
To prevent this inference from diluting types too greatly, we don't
allow this inference in "top-level" expressions, e.g.,
let d = ["a" : 1, "b" : "two"]
will produce an error because it's a heterogeneous dictionary literal
at the top level. One should annotate this with, e.g.,
let d = ["a" : 1, "b" : "two"] as [String : Any]
However, we do permit heterogeneous collections in nested positions,
to support cases like the original motivating example.
Fixes rdar://problem/27661580.
DougGregor
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@swift-ci please smoke test and merge |
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Now that I've committed the basic 'meet' operation, this no longer regressions anywhere I've seen. |
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Grrrr. That Linux failure is the same LLDB issue that's been failing for 7 hours. |
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What's in this pull request?
This pull request implements a defaulting rule for the elements of array and dictionary literals.
The id-as-Any work regressed cases where Swift code could specify heterogeneous collection literals, e.g.,
Prior to this, the code worked (when Foundation was imported) because we'd end up with literals of type
[NSObject : AnyObject].The new defaulting rule says that the element type of an array literal and the key/value types of a dictionary literal can be defaulted if no stronger type can be inferred. The default type is:
Any, for the element type of an array literal or the value type of a dictionary literal, orAnyHashable, for the key type of a dictionary literal.The latter is intended to compose with implicit conversions to
AnyHashable, so the most-general inferred dictionary type is[AnyHashable : Any]and will work for any plausible dictionary literal.To prevent this inference from diluting types too greatly, we don't allow this inference in "top-level" expressions, e.g.,
will produce an error because it's a heterogeneous dictionary literal at the top level. One should annotate this with, e.g.,
However, we do permit heterogeneous collections in nested positions, to support cases like the original motivating example.
Resolved bug number: (rdar://problem/27661580)
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…d 'AnyHashable' for dictionary keys.
The id-as-Any work regressed cases where Swift code could specify
heterogeneous collection literals, e.g.,
Prior to this, the code worked (when Foundation was imported) because
we'd end up with literals of type [NSObject : AnyObject].
The new defaulting rule says that the element type of an array literal
and the key/value types of a dictionary literal can be defaulted if no
stronger type can be inferred. The default type is:
Any, for the element type of an array literal or the value type of a
dictionary literal, or
AnyHashable, for the key type of a dictionary literal.
The latter is intended to compose with implicit conversions to
AnyHashable, so the most-general inferred dictionary type is
[AnyHashable : Any] and will work for any plausible dictionary
literal.
To prevent this inference from diluting types too greatly, we don't
allow this inference in "top-level" expressions, e.g.,
let d = ["a" : 1, "b" : "two"]
will produce an error because it's a heterogeneous dictionary literal
at the top level. One should annotate this with, e.g.,
let d = ["a" : 1, "b" : "two"] as [String : Any]
However, we do permit heterogeneous collections in nested positions,
to support cases like the original motivating example.
Fixes rdar://problem/27661580.