TypePtr deduceReturnType(const FunctionTypePtr& funType, const TypeList& argumentTypes, bool unitOnFail) {
try {
// try deducing the return type ...
return tryDeduceReturnType(funType, argumentTypes);
} catch (const ReturnTypeDeductionException&) {
// didn't work => print a warning
LOG(DEBUG) << "Unable to deduce return type for call to function of type "
<< toString(*funType) << " using arguments " << join(", ", argumentTypes, print<deref<TypePtr>>());
}
// return null ptr
return unitOnFail ? funType->getNodeManager().getLangBasic().getUnit() : TypePtr();
}
TypePtr tryDeduceReturnType(const FunctionTypePtr& funType, const TypeList& argumentTypes) {
NodeManager& manager = funType->getNodeManager();
// try deducing variable instantiations the argument types
auto varInstantiation = types::getTypeVariableInstantiation(manager, funType->getParameterTypes()->getTypes(), argumentTypes);
// check whether derivation was successful
if(!varInstantiation) {
std::stringstream msg;
msg << "Cannot match arguments (" << join(", ", argumentTypes, print<deref<TypePtr>>()) << ") \n"
" to parameters ("
<< join(", ", funType->getParameterTypes(), print<deref<TypePtr>>()) << ")";
throw ReturnTypeDeductionException(msg.str());
}
// extract return type
const TypePtr& resType = funType->getReturnType();
// compute and return the expected return type
return varInstantiation->applyTo(manager, resType);
}
/**
* Computes a join or meet type for the given pair of types. The join flag allows to determine
* whether the join or meet type is computed.
*/
TypePtr getJoinMeetType(const TypePtr& typeA, const TypePtr& typeB, bool join) {
static const TypePtr fail = 0;
// add a structure based algorithm for computing the Join-Type
// shortcut for equal types
if (*typeA == *typeB) {
return typeA;
}
// the rest depends on the node types
NodeType nodeTypeA = typeA->getNodeType();
NodeType nodeTypeB = typeB->getNodeType();
// handle generic types
if (nodeTypeA == NT_GenericType && nodeTypeB == NT_GenericType) {
// let the join computation handle the case
const GenericTypePtr& genTypeA = static_pointer_cast<const GenericType>(typeA);
const GenericTypePtr& genTypeB = static_pointer_cast<const GenericType>(typeB);
return (join) ? getJoinType(genTypeA, genTypeB) : getMeetType(genTypeA, genTypeB);
}
// handle vector types (only if array super type of A is a super type of B)
// make sure typeA is the vector
if (nodeTypeA != NT_VectorType && nodeTypeB == NT_VectorType) {
// switch sides
return getJoinMeetType(typeB, typeA, join);
}
// handle vector-array conversion (only works for joins)
if (join && nodeTypeA == NT_VectorType) {
VectorTypePtr vector = static_pointer_cast<const VectorType>(typeA);
// the only potential super type is an array of the same element type
IRBuilder builder(vector->getNodeManager());
ArrayTypePtr array = builder.arrayType(vector->getElementType());
if (isSubTypeOf(typeB, array)) {
return array;
}
// no common super type!
return fail;
}
// the rest can only work if it is of the same kind
if (nodeTypeA != nodeTypeB) {
// => no common super type
return fail;
}
// check for functions
if (nodeTypeA == NT_FunctionType) {
FunctionTypePtr funTypeA = static_pointer_cast<const FunctionType>(typeA);
FunctionTypePtr funTypeB = static_pointer_cast<const FunctionType>(typeB);
// check number of arguments
auto paramsA = funTypeA->getParameterTypes();
auto paramsB = funTypeB->getParameterTypes();
if (paramsA.size() != paramsB.size()) {
// not matching
return fail;
}
// check function kind
FunctionKind resKind = funTypeA->getKind();
if (funTypeA->getKind() != funTypeB->getKind()) {
// differences are only allowed when going from plain to closure type
if ((funTypeA->isPlain() && funTypeB->isClosure()) || (funTypeA->isClosure() && funTypeB->isPlain())) {
resKind = FK_CLOSURE;
} else {
return fail;
}
}
// compute join type
// JOIN/MEET result and argument types - if possible
TypePtr cur = getJoinMeetType(funTypeA->getReturnType(), funTypeB->getReturnType(), join);
TypePtr resType = cur;
// continue with parameters
TypeList params;
for (std::size_t i=0; i<paramsA.size(); i++) {
// ATTENTION: this goes in the reverse direction
cur = getJoinMeetType(paramsA[i], paramsB[i], !join);
// if a pair can not be matched => fail
if (!cur) return fail;
params.push_back(cur);
}
// construct resulting type
IRBuilder builder(funTypeA->getNodeManager());
return builder.functionType(params, resType, resKind);
}
// everything else does not have a common join/meet type
return fail;
}