Protocol typealias fixes #2992
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Protocol typealias fixes #2992
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This wasn't doing the right thing for TypeAliasDecls. NFC for now, but exposed by some other changes I am working on.
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@swift-ci Please test |
This is a big refactoring of resolveTypeInContext() which makes
the function clearer to understand by merging various special
cases and generalizing the logic for walking parent and superclass
contexts to cover more cases.
This improves typealiases in protocols a bit:
1) Previously a typealias in a protocol either had to be concrete,
or consist of a single path of member types from Self, eg
Self.A.B. Lift this restriction, so we can now write things like
protocol Fireworks {
associatedtype Exploding
typealias Exploder = Exploding -> [Exploding]
}
2) Protocol typealiases can now be accessed via qualified lookup
on concrete types. Getting this working for unqualified lookup
requires further refactorings which will be in a subsequent
patch.
Avoid calling lookupMemberType() with an existential base altogether. With the previous resolveTypeInContext() patch, a compiler_crasher regressed and hit this, because the behavior of lookupMemberType() changed to return nullptr in fewer cases.
…n-types earlier
With the previous resolveTypeInContext() patch, a few compiler
crashers regressed with this problem, presumably because we were now
performing lookups in more contexts than before.
This is a class of problems where we would attempt a recursive
validation:
1) Generic signature validation begins for type T
2) Name lookup in type context finds a non-type declaration D nested in T
3) Generic signature validation begins for D
4) The outer generic context of D is T, but T doesn't have a generic
signature yet
The right way to break such cycles is to implement the iterative
decl checker design. However when the recursion is via name lookup,
we can try to avoid the problem in the first place by not validating
non-type declarations if the client requested a type-only lookup.
Note that there is a small semantic change here, where programs that
were previously rejected as invalid because of name clashes are
now valid. It is arguable if we want to allow stuff like this or not:
class A {
func A(a: A) {}
}
or
class Case {}
enum Foo {
case Case(Case)
}
However at the very least, the new behavior is better because it
gives us an opportunity to add a diagnostic in the right place
later. The old diagnostics were not very good, for example the
second example just yields "use of undeclared type 'Case'".
In other examples, the undeclared type diagnostic would come up
multiple times, or we would generate a cryptic "type 'A' used within
its own definition".
As far as I understand, this should not change behavior of any existing
valid code.
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@swift-ci Please test |
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@swift-ci Please test and merge |
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milseman
reviewed
Oct 22, 2016
| fromType = resolver->resolveGenericTypeParamType(selfType); | ||
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| if (assocType) { | ||
| // Odd special case, ask Doug to explain it over pizza one day |
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Finally this fixes my earlier patch that got reverted:
14d0be2