// Start with the substitutions from the apply.
// Try to propagate them to find out the real substitutions required
// to invoke the method.
static ArrayRef<Substitution>
getSubstitutionsForCallee(SILModule &M, CanSILFunctionType GenCalleeType,
SILType ClassInstanceType, FullApplySite AI) {
// *NOTE*:
// Apply instruction substitutions are for the Member from a protocol or
// class B, where this member was first defined, before it got overridden by
// derived classes.
//
// The implementation F (the implementing method) which was found may have
// a different set of generic parameters, e.g. because it is implemented by a
// class D1 derived from B.
//
// ClassInstanceType may have a type different from both the type B
// the Member belongs to and from the ClassInstanceType, e.g. if
// ClassInstance is of a class D2, which is derived from D1, but does not
// override the Member.
//
// As a result, substitutions provided by AI are for Member, whereas
// substitutions in ClassInstanceType are for D2. And substitutions for D1
// are not available directly in a general case. Therefore, they have to
// be computed.
//
// What we know for sure:
// B is a superclass of D1
// D1 is a superclass of D2.
// D1 can be the same as D2. D1 can be the same as B.
//
// So, substitutions from AI are for class B.
// Substitutions for class D1 by means of bindSuperclass(), which starts
// with a bound type ClassInstanceType and checks its superclasses until it
// finds a bound superclass matching D1 and returns its substitutions.
// Class F belongs to.
CanType FSelfClass = GenCalleeType->getSelfParameter().getType();
SILType FSelfSubstType;
Module *Module = M.getSwiftModule();
ArrayRef<Substitution> ClassSubs;
if (GenCalleeType->isPolymorphic()) {
// Declaration of the class F belongs to.
if (auto *FSelfTypeDecl = FSelfClass.getNominalOrBoundGenericNominal()) {
// Get the unbound generic type F belongs to.
CanType FSelfGenericType =
FSelfTypeDecl->getDeclaredType()->getCanonicalType();
assert((isa<BoundGenericType>(ClassInstanceType.getSwiftRValueType()) ||
isa<NominalType>(ClassInstanceType.getSwiftRValueType())) &&
"Self type should be either a bound generic type"
"or a non-generic type");
assert((isa<UnboundGenericType>(FSelfGenericType) ||
isa<NominalType>(FSelfGenericType)) &&
"Method implementation self type should be generic");
if (isa<BoundGenericType>(ClassInstanceType.getSwiftRValueType())) {
auto BoundBaseType = bindSuperclass(FSelfGenericType,
ClassInstanceType);
if (auto BoundTy = BoundBaseType->getAs<BoundGenericType>()) {
ClassSubs = BoundTy->getSubstitutions(Module, nullptr);
}
}
}
} else {
// If the callee is not polymorphic, no substitutions are required.
return {};
}
if (ClassSubs.empty())
return AI.getSubstitutions();
auto AISubs = AI.getSubstitutions();
CanSILFunctionType AIGenCalleeType =
AI.getCallee().getType().castTo<SILFunctionType>();
CanType AISelfClass = AIGenCalleeType->getSelfParameter().getType();
unsigned NextMethodParamIdx = 0;
unsigned NumMethodParams = 0;
if (AIGenCalleeType->isPolymorphic()) {
NextMethodParamIdx = 0;
// Generic parameters of the method start after generic parameters
// of the instance class.
if (auto AISelfClassSig =
AISelfClass.getClassBound()->getGenericSignature()) {
NextMethodParamIdx = AISelfClassSig->getGenericParams().size();
}
NumMethodParams = AISubs.size() - NextMethodParamIdx;
}
unsigned NumSubs = ClassSubs.size() + NumMethodParams;
if (ClassSubs.size() == NumSubs)
return ClassSubs;
// Mix class subs with method specific subs from the AI substitutions.
// Assumptions: AI substitutions contain first the substitutions for
// a class of the method being invoked and then the substitutions
// for a method being invoked.
auto Subs = M.getASTContext().Allocate<Substitution>(NumSubs);
unsigned i = 0;
for (auto &S : ClassSubs) {
Subs[i++] = S;
}
for (; i < NumSubs; ++i, ++NextMethodParamIdx) {
Subs[i] = AISubs[NextMethodParamIdx];
}
return Subs;
}
