[IDE] Inspect all equivalent type variables to replace a type variable by an archetype #63849
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…e by an archetype Sometimes the type variable itself doesn't have have an originator that can be replaced by an archetype but one of its equivalent type variable does. Search thorough all equivalent type variables, looking for one that can be replaced by a generic parameter.
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| for (auto binding : bindings) { | ||
| if (auto placeholder = binding.second->getAs<PlaceholderType>()) { | ||
| if (placeholder->getOriginator().dyn_cast<TypeVariableType *>() == | ||
| typeVar) { |
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I don't quite understand what is going on here... Could you please elaborate on what you are trying to archive?
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The motivation is what we are already doing above: If we have a placeholder whose originator is a type variable that represents a generic parameter, we want to replace that placeholder by the generic parameter before printing code completion results because for example in the test case I modified MyStruct<T> looks more useful than MyStruct<_>.
But, again in the test case below, we are receiving the following solution
--- Solution ---
Fixed score: <default 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0>
Type variables:
$T0 as <<placeholder for $T8>> @ locator@0x138048218 [Type@/Users/alex/swift-src/swift/test/IDE/complete_subscript.swift:40:11 -> generic parameter 'T']
$T1 as Int @ locator@0x1380482f0 [CodeCompletion@/Users/alex/swift-src/swift/test/IDE/complete_subscript.swift:40:20]
$T2 as MyStruct<<<placeholder for $T8>>> @ locator@0x1380483a8 [Subscript@/Users/alex/swift-src/swift/test/IDE/complete_subscript.swift:40:19 -> function result]
$T3 as (Int, <<placeholder for $T8>>) -> MyStruct<<<placeholder for $T8>>> @ locator@0x138048380 [Subscript@/Users/alex/swift-src/swift/test/IDE/complete_subscript.swift:40:19 -> subscript member]
$T7 as <<placeholder for $T8>> @ locator@0x138048ab8 [Subscript@/Users/alex/swift-src/swift/test/IDE/complete_subscript.swift:40:19 -> subscript member -> generic parameter 'T']
$T8 as <<placeholder for $T8>> @ locator@0x138048d78 [Subscript@/Users/alex/swift-src/swift/test/IDE/complete_subscript.swift:40:19 -> apply argument -> comparing call argument #1 to parameter #1 -> synthesized argument #1]
And the argument we want to look up has type T8. Now T8 doesn’t represent a generic parameter and thus we were outputting _ for the placeholder in the results. But actually looking at the solution, you can see that T8 has the same type as T0 (because T0 is bound to T8) and T0 represents a generic parameter. Thus, for printing purposes we can replace the placeholder for T8 by the generic parameter that T0 represents, which is T.
Does this make sense?
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Maybe this transformation should happen in ConstraintSystem::finalize while we are forming a complete solution in code completion mode instead?
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As discussed offline, I’ll do this in a follow up PR and filed rdar://106082607 so we don’t forget about it.
Sometimes the type variable itself doesn't have have an originator that can be replaced by an archetype but one of its equivalent type variable does. Search thorough all equivalent type variables, looking for one that can be replaced by a generic parameter.