/// Emit a collection downcast expression.
///
/// \param conditional Whether to emit a conditional downcast; if
/// false, this will emit a forced downcast.
static RValue emitCollectionDowncastExpr(SILGenFunction &SGF,
ManagedValue source,
Type sourceType,
SILLocation loc,
Type destType,
SGFContext C,
bool conditional) {
// Compute substitutions for the intrinsic call.
auto fromCollection = cast<BoundGenericStructType>(
sourceType->getCanonicalType());
auto toCollection = cast<BoundGenericStructType>(
destType->getCanonicalType());
// Get the intrinsic function.
auto &ctx = SGF.getASTContext();
FuncDecl *fn = nullptr;
if (fromCollection->getDecl() == ctx.getArrayDecl()) {
fn = conditional ? SGF.SGM.getArrayConditionalCast(loc)
: SGF.SGM.getArrayForceCast(loc);
} else if (fromCollection->getDecl() == ctx.getDictionaryDecl()) {
fn = (conditional
? SGF.SGM.getDictionaryDownCastConditional(loc)
: SGF.SGM.getDictionaryDownCast(loc));
} else if (fromCollection->getDecl() == ctx.getSetDecl()) {
fn = (conditional
? SGF.SGM.getSetDownCastConditional(loc)
: SGF.SGM.getSetDownCast(loc));
} else {
llvm_unreachable("unsupported collection upcast kind");
}
// This will have been diagnosed by the accessors above.
if (!fn) return SGF.emitUndefRValue(loc, destType);
auto fnGenericParams = fn->getGenericSignature()->getGenericParams();
auto fromSubsts = fromCollection->gatherAllSubstitutions(
SGF.SGM.SwiftModule, nullptr);
auto toSubsts = toCollection->gatherAllSubstitutions(
SGF.SGM.SwiftModule, nullptr);
assert(fnGenericParams.size() == fromSubsts.size() + toSubsts.size() &&
"wrong number of generic collection parameters");
(void) fnGenericParams;
// Form type parameter substitutions.
SmallVector<Substitution, 4> subs;
subs.append(fromSubsts.begin(), fromSubsts.end());
subs.append(toSubsts.begin(), toSubsts.end());
return SGF.emitApplyOfLibraryIntrinsic(loc, fn, subs, {source}, C);
}
