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Utilize argument type information to favor overload binding constraints on initializers. Doing so addresses a number of cases where the type checker was going exponential on seemingly simple user code.

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Also, these changes fix the performance regressions that were introduced as a result of September's convertible/init requirement modifications, and allow us to roll back the associated workarounds that were added to the Adventure sample (rdar://problem/18942100).

Swift SVN r24520
This commit is contained in:
Joe Pamer
2015-01-19 20:59:14 +00:00
parent f56949846f
commit 35184ff7b5
4 changed files with 127 additions and 24 deletions
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42
lib/Sema/CSSimplify.cpp
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@@ -2758,6 +2758,15 @@ ConstraintSystem::simplifyMemberConstraint(const Constraint &constraint) {
return SolutionKind::Error;
}
TypeBase *favoredType = nullptr;
if (auto anchor = constraint.getLocator()->getAnchor()) {
if (auto applyExpr = dyn_cast<ApplyExpr>(anchor)) {
favoredType = this->getFavoredType(applyExpr->getArg());
}
}
OverloadChoice favoredChoice;
// Introduce a new overload set.
retry_ctors_after_fail:
@@ -2788,6 +2797,34 @@ ConstraintSystem::simplifyMemberConstraint(const Constraint &constraint) {
SourceLoc anchorLoc = constraint.getLocator()->getAnchor()->getLoc();
auto unavailReason = TC.checkDeclarationAvailability(constructor,
anchorLoc, DC);
// If the invocation's argument expression has a favored constraint,
// use that information to determine whether a specific overload for
// the initializer should be favored.
if (favoredType && !favoredChoice.getDecl()) {
// Only try and favor monomorphic initializers.
if (auto fnTypeWithSelf =
constructor->getType()->getAs<FunctionType>()) {
if (auto fnType =
fnTypeWithSelf->getResult()->getAs<FunctionType>()) {
auto argType = fnType->getInput();
if (auto parenType =
dyn_cast<ParenType>(argType.getPointer())) {
argType = parenType->getUnderlyingType();
}
if (argType->isEqual(favoredType)) {
favoredChoice = OverloadChoice(baseTy, constructor,
/*isSpecialized=*/false, *this,
unavailReason);
}
}
}
}
choices.push_back(OverloadChoice(baseTy, constructor,
/*isSpecialized=*/false, *this,
unavailReason));
@@ -2810,7 +2847,10 @@ ConstraintSystem::simplifyMemberConstraint(const Constraint &constraint) {
return SolutionKind::Error;
}
addOverloadSet(memberTy, choices, constraint.getLocator());
addOverloadSet(memberTy,
choices,
constraint.getLocator(),
favoredChoice.getDecl() ? &favoredChoice : nullptr);
return SolutionKind::Solved;
}