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Allow '<pattern> as T' checked patterns with subpattern bindings.

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Allow a form of 'case is T' that matches the cast result to a subpattern, 'case <pattern> as T'. This exposes an issue in switch destructuring with casting into complex class hierarchies <rdar://problem/16401831> but works for common cases.

Swift SVN r15396
This commit is contained in:
Joe Groff
2014-03-24 00:02:44 +00:00
parent cce0b2d342
commit 4fdc20f739
8 changed files with 120 additions and 37 deletions
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18
lib/SILGen/SILGenPattern.cpp
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@@ -450,20 +450,15 @@ static void destructurePattern(SILGenFunction &gen,
= specializerIsa->getCastTypeLoc().getType()->getCanonicalType();
CanType newToType = ip->getCastTypeLoc().getType()->getCanonicalType();
// If a cast pattern casts to the same type, it reduces to a wildcard.
// FIXME: 'is' patterns should have a subpattern, in which case they
// destructure to that pattern in this case.
// If a cast pattern casts to the same type, it reduces to its subpattern.
if (newFromType == newToType) {
destructured.push_back(nullptr);
destructured.push_back(ip->getSubPattern());
return;
}
// If the cast pattern casts to a superclass, it reduces to a wildcard.
// FIXME: 'is' patterns should have a subpattern, in which case they
// destructure to that pattern in this case. We'd need to arrange for the
// value to be upcast.
// If the cast pattern casts to a superclass, it reduces to its subpattern.
if (newToType->isSuperclassOf(newFromType, nullptr)) {
destructured.push_back(nullptr);
destructured.push_back(ip->getSubPattern());
return;
}
@@ -498,8 +493,9 @@ static void destructurePattern(SILGenFunction &gen,
// Create the new cast pattern.
auto *newIsa
= new (gen.F.getASTContext()) IsaPattern(p->getLoc(),
ip->getCastTypeLoc(),
newKind);
ip->getCastTypeLoc(),
const_cast<Pattern*>(ip->getSubPattern()),
newKind);
newIsa->setType(newFromType);
destructured.push_back(newIsa);