[CodeCompletion] Unresolved member completion at type parameter position

[rintaro]

Enable unresolved member completion at generic parameter type context. e.g.

protocol HasStatic {
  static var instance: Self { get }
}

func foo<T: HasStatic>() -> T {
  return .#^HERE^#
}

We need to map GenericTypeParamType to ArchetypeType to lookup its members.

rdar://problem/46657585

[rintaro]

@swift-ci Please smoke test

[benlangmuir]

I don't understand what effect this change has. getTypeOfMember in code-completion seems to do a bunch of things that the one on TypeBase doesn't, including eraseArchetypes, and they also use different substitution flags. We currently are trying hard to avoid having archetypes leak into results where they show up badly when printed, per the comment on eraseArchetypes.

[benlangmuir]

Are the changes below to mapTypeIntoContext supposed to rectify this? If so, how does that compare to eraseArchetypes?

[rintaro]

We want to keep ArchetypeType here because T might be an ArchetypeType and we want to check if result of declTy is convertible to T.

Let's say T is archetype U which conforms to HasStatic protocol and VD is static var instance: Self { get }, getTypeOfMember(VD, T) returns HasStatic protocol, but that is not convertible to archetype U. But T->getTypeOfMember(CurrModule, VD) correctly returns U.

This is just a filtering logic that checks VD can be referenced by "implicit member expression" syntax in T type context. The result of declTy isn't used anywhere else. The type name for completion result is re-constructed by result builder.

[benlangmuir]

Okay, thanks for explaining!

[benlangmuir]

Is this legal to do with any target DeclContext, or is this relying on DC being related to the context we originally got this type from?

[rintaro]

To be honest, I'm not sure about this. But I guess the DeclContext should be the context where the parameter is declared. I updated the PR so that it extract decl context from the GenericTypeParamType itself. @slavapestov am I doing the right thing?

[slavapestov]

You want to use the DeclContext of the function itself.

[slavapestov]

I think you can replace this whole block with DC->mapTypeIntoContext(ty). Please don't use GenericTypeParamType::getDecl().

[rintaro]

Thanks! Updated the PR.

[rintaro]

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[rintaro]

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[rintaro]

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[rintaro]

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