[SR-7799] Matching optional enums against non-optional values #50338
Comments
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@swift-ci create |
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@slavapestov @jckarter I have made a change in the type checker to look through optionals when checking an `EnumElementPattern`, however it seems like I need to handle it in SIL as well. For example, at the moment, SILVerification throws an error: SIL verification failed: switch_enum dispatches on enum element that is not part of its type: elt->getDeclContext() == uDeclfor enum Foo { case bar}
let foo: Foo? = .bar
switch foo { case .bar: print("bar") default: print("default") }This makes sense, because we're switching over Foo? rather than Foo, so the emitted SIL looks like: alloc_global @$s12testmetatype3fooAA3FooOSgvp // id: %2
%3 = global_addr @$s12testmetatype3fooAA3FooOSgvp : $*Optional<Foo> // users: %8, %7
%4 = metatype $@thin Foo.Type
%5 = enum $Foo, #Foo.bar!enumelt // user: %6
%6 = enum $Optional<Foo>, #Optional.some!enumelt.1, %5 : $Foo // user: %7
store %6 to [trivial] %3 : $*Optional<Foo> // id: %7
%8 = load [trivial] %3 : $*Optional<Foo> // user: %9
switch_enum %8 : $Optional<Foo>, case #Foo.bar!enumelt: bb1 // id: %9What would be the best approach here? Do we switch over Foo instead, or do we wrap the case in `.some()`? |
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Or should we re-write the element in the type checker to wrap it in `.some()` so we don't have to make changes to SIL? |
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PR: #22486 |
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Fixed on master, this will be available in the next Swift release! |
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@martinr448, Could you verify if the problem is fixed and if so move the JIRA to "Closed"? Thanks! |
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This compiles now, and `case .a:` matches the `Optional(MyEnum.a)`: enum MyEnum { case a, b }
let e = Optional(MyEnum.a)
switch e {
case .a: print("a")
default: print("default")
}Tested with Xcode 11.0 beta 5 (11M382q). |
Additional Detail from JIRA
md5: 866262f404c0af00426fbd898e2b0060
Issue Description:
We can match an optional
Intagainst a non-optional value:But the same does not compile with an optional
enum:Tested with Xcode 9.3.1, with both the default toolchain and the Swift 4.2 snapshot from May 20, 2018.
Related discussion in the Swift forum: Matching optionals in a switch statement, where Joe Groff said:
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