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[CodeCompletion] Report type relations when completing inside result builders

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This requires navigating the constraint system solution to retrieve the argument type of the `buildBlock` call. The comments in the code should describe what I’m doing well enough.

rdar://83846531
This commit is contained in:
Alex Hoppen
2022-04-08 11:24:31 +02:00
parent 1abd15ba23
commit 0b9644a0d4
2 changed files with 107 additions and 16 deletions
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75
lib/Sema/ConstraintSystem.cpp
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@@ -3558,18 +3558,79 @@ Type Solution::simplifyTypeForCodeCompletion(Type Ty) const {
// Replace all type variables (which must come from placeholders) by their
// generic parameters. Because we call into simplifyTypeImpl
Ty = CS.simplifyTypeImpl(Ty, [](TypeVariableType *typeVar) -> Type {
if (auto *GP = typeVar->getImpl().getGenericParameter()) {
// Code completion depends on generic parameter type being
// represented in terms of `ArchetypeType` since it's easy
// to extract protocol requirements from it.
if (auto *GPD = GP->getDecl()) {
return GPD->getInnermostDeclContext()->mapTypeIntoContext(GP);
Ty = CS.simplifyTypeImpl(Ty, [&CS](TypeVariableType *typeVar) -> Type {
// Code completion depends on generic parameter type being represented in
// terms of `ArchetypeType` since it's easy to extract protocol requirements
// from it.
auto getTypeVarAsArchetype = [](TypeVariableType *typeVar) -> Type {
if (auto *GP = typeVar->getImpl().getGenericParameter()) {
if (auto *GPD = GP->getDecl()) {
return GPD->getInnermostDeclContext()->mapTypeIntoContext(GP);
}
}
return Type();
};
if (auto archetype = getTypeVarAsArchetype(typeVar)) {
return archetype;
}
// When applying the logic below to get contextual types inside result
// builders, the code completion type variable is connected by a one-way
// constraint to a type variable in the buildBlock call, but that is not the
// type variable that represents the argument type. We need to find the type
// variable representing the argument to retrieve protocol requirements from
// it. Look for a ArgumentConversion constraint that allows us to retrieve
// the argument type var.
for (auto argConstraint :
CS.getConstraintGraph()[typeVar].getConstraints()) {
if (argConstraint->getKind() == ConstraintKind::ArgumentConversion &&
argConstraint->getFirstType()->getRValueType()->isEqual(typeVar)) {
if (auto argTV =
argConstraint->getSecondType()->getAs<TypeVariableType>()) {
if (auto archetype = getTypeVarAsArchetype(argTV)) {
return archetype;
}
}
}
}
return typeVar;
});
// Logic to determine the contextual type inside buildBlock result builders:
//
// When completing inside a result builder, the result builder
// @ViewBuilder var body: some View {
// Text("Foo")
// #^COMPLETE^#
// }
// gets rewritten to
// @ViewBuilder var body: some View {
// let $__builder2: Text
// let $__builder0 = Text("Foo")
// let $__builder1 = #^COMPLETE^#
// $__builder2 = ViewBuilder.buildBlock($__builder0, $__builder1)
// return $__builder2
// }
// Inside the constraint system
// let $__builder1 = #^COMPLETE^#
// gets type checked without context, so we can't know the contexutal type for
// the code completion token. But we know that $__builder1 (and thus the type
// of #^COMPLETE^#) is used as the second argument to ViewBuilder.buildBlock,
// so we can extract the contextual type from that call. To do this, figure
// out the type variable that is used for $__builder1 in the buildBlock call.
// This type variable is connected to the type variable of $__builder1's
// definition by a one-way constraint.
if (auto TV = Ty->getAs<TypeVariableType>()) {
for (auto constraint : CS.getConstraintGraph()[TV].getConstraints()) {
if (constraint->getKind() == ConstraintKind::OneWayEqual &&
constraint->getSecondType()->isEqual(TV)) {
return simplifyTypeForCodeCompletion(constraint->getFirstType());
}
}
}
// Remove any remaining type variables and placeholders
Ty = simplifyType(Ty);