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fuchsia / third_party / swift / 32af975bc26092a6f36244ca68afa18d5abfca92 / . / lib / Sema / ConstraintSystem.cpp
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//===--- ConstraintSystem.cpp - Constraint-based Type Checking ------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This file implements the constraint-based type checker, anchored by the
// \c ConstraintSystem class, which provides type checking and type
// inference for expressions.
//
//===----------------------------------------------------------------------===//
#include "ConstraintSystem.h"
#include "ConstraintGraph.h"
#include "CSDiagnostics.h"
#include "TypeCheckType.h"
#include "swift/AST/GenericEnvironment.h"
#include "swift/AST/ParameterList.h"
#include "swift/Basic/Statistic.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Format.h"
using namespace swift;
using namespace constraints;
#define DEBUG_TYPE "ConstraintSystem"
ExpressionTimer::ExpressionTimer(Expr *E, ConstraintSystem &CS)
: E(E), WarnLimit(CS.TC.getWarnLongExpressionTypeChecking()),
Context(CS.getASTContext()),
StartTime(llvm::TimeRecord::getCurrentTime()),
PrintDebugTiming(CS.TC.getDebugTimeExpressions()), PrintWarning(true) {
if (auto *baseCS = CS.baseCS) {
// If we already have a timer in the base constraint
// system, let's seed its start time to the child.
if (baseCS->Timer) {
StartTime = baseCS->Timer->startedAt();
PrintWarning = false;
PrintDebugTiming = false;
}
}
}
ExpressionTimer::~ExpressionTimer() {
auto elapsed = getElapsedProcessTimeInFractionalSeconds();
unsigned elapsedMS = static_cast<unsigned>(elapsed * 1000);
if (PrintDebugTiming) {
// Round up to the nearest 100th of a millisecond.
llvm::errs() << llvm::format("%0.2f", ceil(elapsed * 100000) / 100)
<< "ms\t";
E->getLoc().print(llvm::errs(), Context.SourceMgr);
llvm::errs() << "\n";
}
if (!PrintWarning)
return;
if (WarnLimit != 0 && elapsedMS >= WarnLimit && E->getLoc().isValid())
Context.Diags.diagnose(E->getLoc(), diag::debug_long_expression,
elapsedMS, WarnLimit)
.highlight(E->getSourceRange());
}
ConstraintSystem::ConstraintSystem(TypeChecker &tc, DeclContext *dc,
ConstraintSystemOptions options)
: TC(tc), DC(dc), Options(options),
Arena(tc.Context, Allocator),
CG(*new ConstraintGraph(*this))
{
assert(DC && "context required");
}
ConstraintSystem::~ConstraintSystem() {
delete &CG;
}
void ConstraintSystem::incrementScopeCounter() {
CountScopes++;
// FIXME: (transitional) increment the redundant "always-on" counter.
if (TC.Context.Stats)
TC.Context.Stats->getFrontendCounters().NumConstraintScopes++;
}
void ConstraintSystem::incrementLeafScopes() {
if (TC.Context.Stats)
TC.Context.Stats->getFrontendCounters().NumLeafScopes++;
}
bool ConstraintSystem::hasFreeTypeVariables() {
// Look for any free type variables.
for (auto tv : TypeVariables) {
if (!tv->getImpl().hasRepresentativeOrFixed()) {
return true;
}
}
return false;
}
void ConstraintSystem::addTypeVariable(TypeVariableType *typeVar) {
TypeVariables.push_back(typeVar);
// Notify the constraint graph.
(void)CG[typeVar];
}
void ConstraintSystem::mergeEquivalenceClasses(TypeVariableType *typeVar1,
TypeVariableType *typeVar2,
bool updateWorkList) {
assert(typeVar1 == getRepresentative(typeVar1) &&
"typeVar1 is not the representative");
assert(typeVar2 == getRepresentative(typeVar2) &&
"typeVar2 is not the representative");
assert(typeVar1 != typeVar2 && "cannot merge type with itself");
typeVar1->getImpl().mergeEquivalenceClasses(typeVar2, getSavedBindings());
// Merge nodes in the constraint graph.
CG.mergeNodes(typeVar1, typeVar2);
if (updateWorkList) {
addTypeVariableConstraintsToWorkList(typeVar1);
}
}
/// Determine whether the given type variables occurs in the given type.
bool ConstraintSystem::typeVarOccursInType(TypeVariableType *typeVar,
Type type,
bool *involvesOtherTypeVariables) {
SmallVector<TypeVariableType *, 4> typeVars;
type->getTypeVariables(typeVars);
bool result = false;
for (auto referencedTypeVar : typeVars) {
if (referencedTypeVar == typeVar) {
result = true;
if (!involvesOtherTypeVariables || *involvesOtherTypeVariables)
break;
continue;
}
if (involvesOtherTypeVariables)
*involvesOtherTypeVariables = true;
}
return result;
}
void ConstraintSystem::assignFixedType(TypeVariableType *typeVar, Type type,
bool updateState) {
assert(!type->hasError() &&
"Should not be assigning a type involving ErrorType!");
typeVar->getImpl().assignFixedType(type, getSavedBindings());
if (!updateState)
return;
if (!type->isTypeVariableOrMember()) {
// If this type variable represents a literal, check whether we picked the
// default literal type. First, find the corresponding protocol.
ProtocolDecl *literalProtocol = nullptr;
// If we have the constraint graph, we can check all type variables in
// the equivalence class. This is the More Correct path.
// FIXME: Eliminate the less-correct path.
auto typeVarRep = getRepresentative(typeVar);
for (auto tv : CG[typeVarRep].getEquivalenceClass()) {
auto locator = tv->getImpl().getLocator();
if (!locator || !locator->getPath().empty())
continue;
auto anchor = locator->getAnchor();
if (!anchor)
continue;
literalProtocol = TC.getLiteralProtocol(anchor);
if (literalProtocol)
break;
}
// If the protocol has a default type, check it.
if (literalProtocol) {
if (auto defaultType = TC.getDefaultType(literalProtocol, DC)) {
// Check whether the nominal types match. This makes sure that we
// properly handle Array vs. Array<T>.
if (defaultType->getAnyNominal() != type->getAnyNominal())
increaseScore(SK_NonDefaultLiteral);
}
}
}
// Notify the constraint graph.
CG.bindTypeVariable(typeVar, type);
addTypeVariableConstraintsToWorkList(typeVar);
}
void ConstraintSystem::setMustBeMaterializableRecursive(Type type)
{
assert(type->isMaterializable() &&
"argument to setMustBeMaterializableRecursive may not be inherently "
"non-materializable");
type = getFixedTypeRecursive(type, /*wantRValue=*/false);
type = type->lookThroughAllOptionalTypes();
if (auto typeVar = type->getAs<TypeVariableType>()) {
typeVar->getImpl().setMustBeMaterializable(getSavedBindings());
} else if (auto *tupleTy = type->getAs<TupleType>()) {
for (auto elt : tupleTy->getElementTypes()) {
setMustBeMaterializableRecursive(elt);
}
}
}
void ConstraintSystem::addTypeVariableConstraintsToWorkList(
TypeVariableType *typeVar) {
// Gather the constraints affected by a change to this type variable.
llvm::SetVector<Constraint *> inactiveConstraints;
CG.gatherConstraints(
typeVar, inactiveConstraints, ConstraintGraph::GatheringKind::AllMentions,
[](Constraint *constraint) { return !constraint->isActive(); });
// Add any constraints that aren't already active to the worklist.
for (auto constraint : inactiveConstraints) {
ActiveConstraints.splice(ActiveConstraints.end(), InactiveConstraints,
constraint);
constraint->setActive(true);
}
}
/// Retrieve a dynamic result signature for the given declaration.
static std::tuple<char, ObjCSelector, CanType>
getDynamicResultSignature(ValueDecl *decl) {
if (auto func = dyn_cast<AbstractFunctionDecl>(decl)) {
// Handle functions.
auto type = func->getMethodInterfaceType();
return std::make_tuple(func->isStatic(), func->getObjCSelector(),
type->getCanonicalType());
}
if (auto asd = dyn_cast<AbstractStorageDecl>(decl)) {
// Handle properties and subscripts, anchored by the getter's selector.
return std::make_tuple(asd->isStatic(), asd->getObjCGetterSelector(),
asd->getInterfaceType()->getCanonicalType());
}
llvm_unreachable("Not a valid @objc member");
}
LookupResult &ConstraintSystem::lookupMember(Type base, DeclName name) {
// Check whether we've already performed this lookup.
auto &result = MemberLookups[{base, name}];
if (result) return *result;
// Lookup the member.
NameLookupOptions lookupOptions = defaultMemberLookupOptions;
if (isa<AbstractFunctionDecl>(DC))
lookupOptions |= NameLookupFlags::KnownPrivate;
result = TC.lookupMember(DC, base, name, lookupOptions);
// If we aren't performing dynamic lookup, we're done.
if (!*result || !base->isAnyObject())
return *result;
// We are performing dynamic lookup. Filter out redundant results early.
llvm::DenseMap<std::tuple<char, ObjCSelector, CanType>, ValueDecl *> known;
bool anyRemovals = false;
for (const auto &entry : *result) {
auto *decl = entry.getValueDecl();
// Remove invalid declarations so the constraint solver doesn't need to
// cope with them.
if (decl->isInvalid()) {
anyRemovals = true;
continue;
}
// If this is the first entry with the signature, record it.
auto &uniqueEntry = known[getDynamicResultSignature(decl)];
if (!uniqueEntry) {
uniqueEntry = decl;
continue;
}
// We have duplication; note that we'll need to remove something,
anyRemovals = true;
// If the entry we recorded was unavailable but this new entry is not,
// replace the recorded entry with this one.
if (uniqueEntry->getAttrs().isUnavailable(TC.Context) &&
!decl->getAttrs().isUnavailable(TC.Context)) {
uniqueEntry = decl;
}
}
// If there's anything to remove, filter it out now.
if (anyRemovals) {
result->filter([&](LookupResultEntry entry, bool isOuter) -> bool {
auto *decl = entry.getValueDecl();
// Remove invalid declarations so the constraint solver doesn't need to
// cope with them.
if (decl->isInvalid())
return false;
return known[getDynamicResultSignature(decl)] == decl;
});
}
return *result;
}
ArrayRef<Type> ConstraintSystem::
getAlternativeLiteralTypes(KnownProtocolKind kind) {
unsigned index;
switch (kind) {
#define PROTOCOL_WITH_NAME(Id, Name) \
case KnownProtocolKind::Id: llvm_unreachable("Not a literal protocol");
#define EXPRESSIBLE_BY_LITERAL_PROTOCOL_WITH_NAME(Id, Name)
#include "swift/AST/KnownProtocols.def"
case KnownProtocolKind::ExpressibleByArrayLiteral: index = 0; break;
case KnownProtocolKind::ExpressibleByDictionaryLiteral:index = 1; break;
case KnownProtocolKind::ExpressibleByExtendedGraphemeClusterLiteral: index = 2;
break;
case KnownProtocolKind::ExpressibleByFloatLiteral: index = 3; break;
case KnownProtocolKind::ExpressibleByIntegerLiteral: index = 4; break;
case KnownProtocolKind::ExpressibleByStringInterpolation: index = 5; break;
case KnownProtocolKind::ExpressibleByStringLiteral: index = 6; break;
case KnownProtocolKind::ExpressibleByNilLiteral: index = 7; break;
case KnownProtocolKind::ExpressibleByBooleanLiteral: index = 8; break;
case KnownProtocolKind::ExpressibleByUnicodeScalarLiteral: index = 9; break;
case KnownProtocolKind::ExpressibleByColorLiteral: index = 10; break;
case KnownProtocolKind::ExpressibleByImageLiteral: index = 11; break;
case KnownProtocolKind::ExpressibleByFileReferenceLiteral: index = 12; break;
}
static_assert(NumAlternativeLiteralTypes == 13, "Wrong # of literal types");
// If we already looked for alternative literal types, return those results.
if (AlternativeLiteralTypes[index])
return *AlternativeLiteralTypes[index];
SmallVector<Type, 4> types;
// Some literal kinds are related.
switch (kind) {
#define PROTOCOL_WITH_NAME(Id, Name) \
case KnownProtocolKind::Id: llvm_unreachable("Not a literal protocol");
#define EXPRESSIBLE_BY_LITERAL_PROTOCOL_WITH_NAME(Id, Name)
#include "swift/AST/KnownProtocols.def"
case KnownProtocolKind::ExpressibleByArrayLiteral:
case KnownProtocolKind::ExpressibleByDictionaryLiteral:
break;
case KnownProtocolKind::ExpressibleByExtendedGraphemeClusterLiteral:
case KnownProtocolKind::ExpressibleByStringInterpolation:
case KnownProtocolKind::ExpressibleByStringLiteral:
case KnownProtocolKind::ExpressibleByUnicodeScalarLiteral:
break;
case KnownProtocolKind::ExpressibleByIntegerLiteral:
// Integer literals can be treated as floating point literals.
if (auto floatProto = TC.Context.getProtocol(
KnownProtocolKind::ExpressibleByFloatLiteral)) {
if (auto defaultType = TC.getDefaultType(floatProto, DC)) {
types.push_back(defaultType);
}
}
break;
case KnownProtocolKind::ExpressibleByFloatLiteral:
break;
case KnownProtocolKind::ExpressibleByNilLiteral:
case KnownProtocolKind::ExpressibleByBooleanLiteral:
break;
case KnownProtocolKind::ExpressibleByColorLiteral:
case KnownProtocolKind::ExpressibleByImageLiteral:
case KnownProtocolKind::ExpressibleByFileReferenceLiteral:
break;
}
AlternativeLiteralTypes[index] = allocateCopy(types);
return *AlternativeLiteralTypes[index];
}
ConstraintLocator *ConstraintSystem::getConstraintLocator(
Expr *anchor,
ArrayRef<ConstraintLocator::PathElement> path,
unsigned summaryFlags) {
assert(summaryFlags == ConstraintLocator::getSummaryFlagsForPath(path));
// Check whether a locator with this anchor + path already exists.
llvm::FoldingSetNodeID id;
ConstraintLocator::Profile(id, anchor, path);
void *insertPos = nullptr;
auto locator = ConstraintLocators.FindNodeOrInsertPos(id, insertPos);
if (locator)
return locator;
// Allocate a new locator and add it to the set.
locator = ConstraintLocator::create(getAllocator(), anchor, path,
summaryFlags);
ConstraintLocators.InsertNode(locator, insertPos);
return locator;
}
ConstraintLocator *ConstraintSystem::getConstraintLocator(
const ConstraintLocatorBuilder &builder) {
// If the builder has an empty path, just extract its base locator.
if (builder.hasEmptyPath()) {
return builder.getBaseLocator();
}
// We have to build a new locator. Extract the paths from the builder.
SmallVector<LocatorPathElt, 4> path;
Expr *anchor = builder.getLocatorParts(path);
return getConstraintLocator(anchor, path, builder.getSummaryFlags());
}
Type ConstraintSystem::openUnboundGenericType(UnboundGenericType *unbound,
ConstraintLocatorBuilder locator,
OpenedTypeMap &replacements) {
auto unboundDecl = unbound->getDecl();
// If the unbound decl hasn't been validated yet, we have a circular
// dependency that isn't being diagnosed properly.
if (!unboundDecl->getGenericSignature()) {
TC.diagnose(unboundDecl, diag::circular_reference);
return Type();
}
auto parentTy = unbound->getParent();
if (parentTy) {
parentTy = openUnboundGenericType(parentTy, locator);
unbound = UnboundGenericType::get(unboundDecl, parentTy,
getASTContext());
}
// Open up the generic type.
openGeneric(unboundDecl->getInnermostDeclContext(),
unboundDecl->getDeclContext(),
unboundDecl->getGenericSignature(),
/*skipProtocolSelfConstraint=*/false,
locator,
replacements);
if (parentTy) {
auto subs = parentTy->getContextSubstitutions(
unboundDecl->getDeclContext());
for (auto pair : subs) {
auto found = replacements.find(
cast<GenericTypeParamType>(pair.first));
assert(found != replacements.end() &&
"Missing generic parameter?");
addConstraint(ConstraintKind::Equal, found->second, pair.second,
locator);
}
}
// Map the generic parameters to their corresponding type variables.
llvm::SmallVector<Type, 2> arguments;
for (auto gp : unboundDecl->getInnermostGenericParamTypes()) {
auto found = replacements.find(
cast<GenericTypeParamType>(gp->getCanonicalType()));
assert(found != replacements.end() &&
"Missing generic parameter?");
arguments.push_back(found->second);
}
// FIXME: For some reason we can end up with unbound->getDecl()
// pointing at a generic TypeAliasDecl here. If we find a way to
// handle generic TypeAliases elsewhere, this can just become a
// call to BoundGenericType::get().
return TypeChecker::applyUnboundGenericArguments(
unbound, unboundDecl,
SourceLoc(), TypeResolution::forContextual(DC), arguments);
}
static void checkNestedTypeConstraints(ConstraintSystem &cs, Type type,
ConstraintLocatorBuilder locator) {
// If this is a type defined inside of constrainted extension, let's add all
// of the generic requirements to the constraint system to make sure that it's
// something we can use.
GenericTypeDecl *decl = nullptr;
Type parentTy;
SubstitutionMap subMap;
if (auto *NAT = dyn_cast<NameAliasType>(type.getPointer())) {
decl = NAT->getDecl();
parentTy = NAT->getParent();
subMap = NAT->getSubstitutionMap();
} else if (auto *AGT = type->getAs<AnyGenericType>()) {
decl = AGT->getDecl();
parentTy = AGT->getParent();
// the context substitution map is fine here, since we can't be adding more
// info than that, unlike a typealias
}
// If this decl is generic, the constraints are handled when the generic
// parameters are applied, so we don't have to handle them here (which makes
// getting the right substitution maps easier).
if (decl && !decl->isGeneric()) {
auto extension = dyn_cast<ExtensionDecl>(decl->getDeclContext());
if (parentTy && extension && extension->isConstrainedExtension()) {
auto contextSubMap = parentTy->getContextSubstitutionMap(
extension->getParentModule(),
extension->getSelfNominalTypeDecl());
if (!subMap) {
// The substitution map wasn't set above, meaning we should grab the map
// for the extension itself.
subMap = parentTy->getContextSubstitutionMap(
extension->getParentModule(), extension);
}
if (auto *signature = decl->getGenericSignature()) {
cs.openGenericRequirements(
extension, signature, /*skipProtocolSelfConstraint*/ true, locator,
[&](Type type) {
// Why do we look in two substitution maps? We have to use the
// context substitution map to find types, because we need to
// avoid thinking about them when handling the constraints, or all
// the requirements in the signature become tautologies (if the
// extension has 'T == Int', subMap will map T -> Int, so the
// requirement becomes Int == Int no matter what the actual types
// are here). However, we need the conformances for the extension
// because the requirements might look like `T: P, T.U: Q`, where
// U is an associated type of protocol P.
return type.subst(QuerySubstitutionMap{contextSubMap},
LookUpConformanceInSubstitutionMap(subMap),
SubstFlags::UseErrorType);
});
}
}
// And now make sure sure the parent is okay, for things like X<T>.Y.Z.
if (parentTy) {
checkNestedTypeConstraints(cs, parentTy, locator);
}
}
}
Type ConstraintSystem::openUnboundGenericType(
Type type, ConstraintLocatorBuilder locator) {
assert(!type->hasTypeParameter());
checkNestedTypeConstraints(*this, type, locator);
if (!type->hasUnboundGenericType())
return type;
type = type.transform([&](Type type) -> Type {
if (auto unbound = type->getAs<UnboundGenericType>()) {
OpenedTypeMap replacements;
return openUnboundGenericType(unbound, locator, replacements);
}
return type;
});
if (!type)
return ErrorType::get(getASTContext());
return type;
}
Type ConstraintSystem::openType(Type type, OpenedTypeMap &replacements) {
assert(!type->hasUnboundGenericType());
if (!type->hasTypeParameter())
return type;
return type.transform([&](Type type) -> Type {
assert(!type->is<GenericFunctionType>());
// Replace a generic type parameter with its corresponding type variable.
if (auto genericParam = type->getAs<GenericTypeParamType>()) {
auto known = replacements.find(
cast<GenericTypeParamType>(genericParam->getCanonicalType()));
assert(known != replacements.end());
return known->second;
}
return type;
});
}
Type ConstraintSystem::openFunctionType(
AnyFunctionType *funcType,
unsigned numArgumentLabelsToRemove,
ConstraintLocatorBuilder locator,
OpenedTypeMap &replacements,
DeclContext *innerDC,
DeclContext *outerDC,
bool skipProtocolSelfConstraint) {
Type type;
if (auto *genericFn = funcType->getAs<GenericFunctionType>()) {
// Open up the generic parameters and requirements.
openGeneric(innerDC,
outerDC,
genericFn->getGenericSignature(),
skipProtocolSelfConstraint,
locator,
replacements);
// Transform the parameters and output type.
llvm::SmallVector<AnyFunctionType::Param, 4> openedParams;
openedParams.reserve(genericFn->getNumParams());
for (const auto &param : genericFn->getParams()) {
auto type = openType(param.getPlainType(), replacements);
openedParams.push_back(AnyFunctionType::Param(type, param.getLabel(),
param.getParameterFlags()));
}
auto resultTy = openType(genericFn->getResult(), replacements);
// Build the resulting (non-generic) function type.
funcType = FunctionType::get(
openedParams, resultTy,
FunctionType::ExtInfo().withThrows(genericFn->throws()));
}
return funcType->removeArgumentLabels(numArgumentLabelsToRemove);
}
Optional<Type> ConstraintSystem::isArrayType(Type type) {
if (auto boundStruct = type->getAs<BoundGenericStructType>()) {
if (boundStruct->getDecl() == type->getASTContext().getArrayDecl())
return boundStruct->getGenericArgs()[0];
}
return None;
}
Optional<std::pair<Type, Type>> ConstraintSystem::isDictionaryType(Type type) {
if (auto boundStruct = type->getAs<BoundGenericStructType>()) {
if (boundStruct->getDecl() == type->getASTContext().getDictionaryDecl()) {
auto genericArgs = boundStruct->getGenericArgs();
return std::make_pair(genericArgs[0], genericArgs[1]);
}
}
return None;
}
Optional<Type> ConstraintSystem::isSetType(Type type) {
if (auto boundStruct = type->getAs<BoundGenericStructType>()) {
if (boundStruct->getDecl() == type->getASTContext().getSetDecl())
return boundStruct->getGenericArgs()[0];
}
return None;
}
bool ConstraintSystem::isCollectionType(Type type) {
auto &ctx = type->getASTContext();
if (auto *structType = type->getAs<BoundGenericStructType>()) {
auto *decl = structType->getDecl();
if (decl == ctx.getArrayDecl() || decl == ctx.getDictionaryDecl() ||
decl == ctx.getSetDecl())
return true;
}
return false;
}
bool ConstraintSystem::isAnyHashableType(Type type) {
if (auto tv = type->getAs<TypeVariableType>()) {
auto fixedType = getFixedType(tv);
return fixedType && isAnyHashableType(fixedType);
}
if (auto st = type->getAs<StructType>()) {
return st->getDecl() == TC.Context.getAnyHashableDecl();
}
return false;
}
Type ConstraintSystem::getFixedTypeRecursive(Type type,
TypeMatchOptions &flags,
bool wantRValue) {
if (wantRValue)
type = type->getRValueType();
if (auto depMemType = type->getAs<DependentMemberType>()) {
if (!depMemType->getBase()->isTypeVariableOrMember()) return type;
// FIXME: Perform a more limited simplification?
Type newType = simplifyType(type);
if (newType.getPointer() == type.getPointer()) return type;
// Once we've simplified a dependent member type, we need to generate a
// new constraint.
flags |= TMF_GenerateConstraints;
return getFixedTypeRecursive(newType, flags, wantRValue);
}
if (auto typeVar = type->getAs<TypeVariableType>()) {
if (auto fixed = getFixedType(typeVar))
return getFixedTypeRecursive(fixed, flags, wantRValue);
return getRepresentative(typeVar);
}
return type;
}
/// Does a var or subscript produce an l-value?
///
/// \param baseType - the type of the base on which this object
/// is being accessed; must be null if and only if this is not
/// a type member
static bool doesStorageProduceLValue(TypeChecker &TC,
AbstractStorageDecl *storage,
Type baseType, DeclContext *useDC,
const DeclRefExpr *base = nullptr) {
// Unsettable storage decls always produce rvalues.
if (!storage->isSettable(useDC, base))
return false;
if (TC.Context.LangOpts.EnableAccessControl &&
!storage->isSetterAccessibleFrom(useDC))
return false;
// If there is no base, or if the base isn't being used, it is settable.
// This is only possible for vars.
if (auto var = dyn_cast<VarDecl>(storage)) {
if (!baseType || var->isStatic())
return true;
}
// If the base is an lvalue, then a reference produces an lvalue.
if (baseType->is<LValueType>())
return true;
// Stored properties of reference types produce lvalues.
if (baseType->hasReferenceSemantics() && storage->hasStorage())
return true;
// So the base is an rvalue type. The only way an accessor can
// produce an lvalue is if we have a property where both the
// getter and setter are nonmutating.
return !storage->hasStorage() &&
!storage->isGetterMutating() &&
!storage->isSetterMutating();
}
Type ConstraintSystem::getUnopenedTypeOfReference(VarDecl *value, Type baseType,
DeclContext *UseDC,
const DeclRefExpr *base,
bool wantInterfaceType) {
return TC.getUnopenedTypeOfReference(
value, baseType, UseDC,
[&](VarDecl *var) -> Type { return getType(var, wantInterfaceType); },
base, wantInterfaceType);
}
Type TypeChecker::getUnopenedTypeOfReference(
VarDecl *value, Type baseType, DeclContext *UseDC,
llvm::function_ref<Type(VarDecl *)> getType, const DeclRefExpr *base,
bool wantInterfaceType) {
Type requestedType =
getType(value)->getWithoutSpecifierType()->getReferenceStorageReferent();
// If we're dealing with contextual types, and we referenced this type from
// a different context, map the type.
if (!wantInterfaceType && requestedType->hasArchetype()) {
auto valueDC = value->getDeclContext();
if (valueDC != UseDC) {
Type mapped = requestedType->mapTypeOutOfContext();
requestedType = UseDC->mapTypeIntoContext(mapped);
}
}
// Qualify storage declarations with an lvalue when appropriate.
// Otherwise, they yield rvalues (and the access must be a load).
if (doesStorageProduceLValue(*this, value, baseType, UseDC, base) &&
!requestedType->hasError()) {
return LValueType::get(requestedType);
}
return requestedType;
}
void ConstraintSystem::recordOpenedTypes(
ConstraintLocatorBuilder locator,
const OpenedTypeMap &replacements) {
if (replacements.empty())
return;
// If the last path element is an archetype or associated type, ignore it.
SmallVector<LocatorPathElt, 2> pathElts;
Expr *anchor = locator.getLocatorParts(pathElts);
if (!pathElts.empty() &&
pathElts.back().getKind() == ConstraintLocator::GenericParameter)
return;
// If the locator is empty, ignore it.
if (!anchor && pathElts.empty())
return;
ConstraintLocator *locatorPtr = getConstraintLocator(locator);
assert(locatorPtr && "No locator for opened types?");
assert(std::find_if(OpenedTypes.begin(), OpenedTypes.end(),
[&](const std::pair<ConstraintLocator *,
ArrayRef<OpenedType>> &entry) {
return entry.first == locatorPtr;
}) == OpenedTypes.end() &&
"already registered opened types for this locator");
OpenedType* openedTypes
= Allocator.Allocate<OpenedType>(replacements.size());
std::copy(replacements.begin(), replacements.end(), openedTypes);
OpenedTypes.push_back({ locatorPtr,
llvm::makeArrayRef(openedTypes,
replacements.size()) });
}
/// Determine how many levels of argument labels should be removed from the
/// function type when referencing the given declaration.
static unsigned getNumRemovedArgumentLabels(TypeChecker &TC, ValueDecl *decl,
bool isCurriedInstanceReference,
FunctionRefKind functionRefKind) {
unsigned numParameterLists;
// Enum elements with associated values have to be treated
// as regular function values.
//
// enum E {
// case foo(a: Int)
// }
// let bar: [Int] = []
// bar.map(E.foo)
//
// `E.foo` has to act as a regular function type passed as a value.
if (auto *EED = dyn_cast<EnumElementDecl>(decl)) {
numParameterLists = EED->hasAssociatedValues() ? 2 : 1;
// Only applicable to functions. Nothing else should have argument labels in
// the type.
} else if (auto func = dyn_cast<AbstractFunctionDecl>(decl)) {
numParameterLists = func->hasImplicitSelfDecl() ? 2 : 1;
} else {
return 0;
}
switch (functionRefKind) {
case FunctionRefKind::Unapplied:
case FunctionRefKind::Compound:
// Always remove argument labels from unapplied references and references
// that use a compound name.
return numParameterLists;
case FunctionRefKind::SingleApply:
// If we have fewer than two parameter lists, leave the labels.
if (numParameterLists < 2)
return 0;
// If this is a curried reference to an instance method, where 'self' is
// being applied, e.g., "ClassName.instanceMethod(self)", remove the
// argument labels from the resulting function type. The 'self' parameter is
// always unlabeled, so this operation is a no-op for the actual application.
return isCurriedInstanceReference ? numParameterLists : 1;
case FunctionRefKind::DoubleApply:
// Never remove argument labels from a double application.
return 0;
}
llvm_unreachable("Unhandled FunctionRefKind in switch.");
}
std::pair<Type, Type>
ConstraintSystem::getTypeOfReference(ValueDecl *value,
FunctionRefKind functionRefKind,
ConstraintLocatorBuilder locator,
DeclContext *useDC,
const DeclRefExpr *base) {
if (value->getDeclContext()->isTypeContext() && isa<FuncDecl>(value)) {
// Unqualified lookup can find operator names within nominal types.
auto func = cast<FuncDecl>(value);
assert(func->isOperator() && "Lookup should only find operators");
OpenedTypeMap replacements;
auto openedType = openFunctionType(
func->getInterfaceType()->castTo<AnyFunctionType>(),
/*numArgumentLabelsToRemove=*/0,
locator, replacements,
func->getInnermostDeclContext(),
func->getDeclContext(),
/*skipProtocolSelfConstraint=*/false);
auto openedFnType = openedType->castTo<FunctionType>();
// If we opened up any type variables, record the replacements.
recordOpenedTypes(locator, replacements);
// If this is a method whose result type is dynamic Self, replace
// DynamicSelf with the actual object type.
if (!func->getDeclContext()->getSelfProtocolDecl()) {
if (func->hasDynamicSelf()) {
auto params = openedFnType->getParams();
assert(params.size() == 1);
Type selfTy = params.front().getPlainType()->getMetatypeInstanceType();
openedType = openedType->replaceCovariantResultType(selfTy, 2);
openedFnType = openedType->castTo<FunctionType>();
}
} else {
openedType = openedType->eraseDynamicSelfType();
openedFnType = openedType->castTo<FunctionType>();
}
// The reference implicitly binds 'self'.
return { openedType, openedFnType->getResult() };
}
// Unqualified reference to a local or global function.
if (auto funcDecl = dyn_cast<AbstractFunctionDecl>(value)) {
OpenedTypeMap replacements;
auto funcType = funcDecl->getInterfaceType()->castTo<AnyFunctionType>();
auto openedType =
openFunctionType(
funcType,
getNumRemovedArgumentLabels(TC, funcDecl,
/*isCurriedInstanceReference=*/false,
functionRefKind),
locator, replacements,
funcDecl->getInnermostDeclContext(),
funcDecl->getDeclContext(),
/*skipProtocolSelfConstraint=*/false);
// If we opened up any type variables, record the replacements.
recordOpenedTypes(locator, replacements);
return { openedType, openedType };
}
// Unqualified reference to a type.
if (auto typeDecl = dyn_cast<TypeDecl>(value)) {
// Resolve the reference to this type declaration in our current context.
auto type = TypeChecker::resolveTypeInContext(
typeDecl, nullptr,
TypeResolution::forContextual(useDC),
TypeResolverContext::InExpression,
/*isSpecialized=*/false);
// Open the type.
type = openUnboundGenericType(type, locator);
// Module types are not wrapped in metatypes.
if (type->is<ModuleType>())
return { type, type };
// If it's a value reference, refer to the metatype.
type = MetatypeType::get(type);
return { type, type };
}
// Only remaining case: unqualified reference to a property.
auto *varDecl = cast<VarDecl>(value);
// Determine the type of the value, opening up that type if necessary.
bool wantInterfaceType = !varDecl->getDeclContext()->isLocalContext();
Type valueType =
getUnopenedTypeOfReference(varDecl, Type(), useDC, base, wantInterfaceType);
assert(!valueType->hasUnboundGenericType() &&
!valueType->hasTypeParameter());
return { valueType, valueType };
}
/// Bind type variables for archetypes that are determined from
/// context.
///
/// For example, if we are opening a generic function type
/// nested inside another function, we must bind the outer
/// generic parameters to context archetypes, because the
/// nested function can "capture" these outer generic parameters.
///
/// Another case where this comes up is if a generic type is
/// nested inside a function. We don't support codegen for this
/// yet, but again we need to bind any outer generic parameters
/// to context archetypes, because they're not free.
///
/// A final case we have to handle, even though it is invalid, is
/// when a type is nested inside another protocol. We bind the
/// protocol type variable for the protocol Self to an unresolved
/// type, since it will conform to anything. This of course makes
/// no sense, but we can't leave the type variable dangling,
/// because then we crash later.
///
/// If we ever do want to allow nominal types to be nested inside
/// protocols, the key is to set their declared type to a
/// NominalType whose parent is the 'Self' generic parameter, and
/// not the ProtocolType. Then, within a conforming type context,
/// we can 'reparent' the NominalType to that concrete type, and
/// resolve references to associated types inside that NominalType
/// relative to this concrete 'Self' type.
///
/// Also, of course IRGen would have to know to store the 'Self'
/// metadata as an extra hidden generic parameter in the metadata
/// of such a type, etc.
static void bindArchetypesFromContext(
ConstraintSystem &cs,
DeclContext *outerDC,
ConstraintLocator *locatorPtr,
const OpenedTypeMap &replacements) {
auto bindContextArchetype = [&](Type paramTy, Type contextTy) {
auto found = replacements.find(cast<GenericTypeParamType>(
paramTy->getCanonicalType()));
// We might not have a type variable for this generic parameter
// because either we're opening up an UnboundGenericType,
// in which case we only want to infer the innermost generic
// parameters, or because this generic parameter was constrained
// away into a concrete type.
if (found != replacements.end()) {
auto typeVar = found->second;
cs.addConstraint(ConstraintKind::Bind, typeVar, contextTy,
locatorPtr);
}
};
// Find the innermost non-type context.
for (const auto *parentDC = outerDC;
!parentDC->isModuleScopeContext();
parentDC = parentDC->getParent()) {
if (parentDC->isTypeContext()) {
if (parentDC != outerDC && parentDC->getSelfProtocolDecl()) {
auto selfTy = parentDC->getSelfInterfaceType();
auto contextTy = cs.TC.Context.TheUnresolvedType;
bindContextArchetype(selfTy, contextTy);
}
continue;
}
// If it's not generic, there's nothing to do.
auto *genericSig = parentDC->getGenericSignatureOfContext();
if (!genericSig)
break;
for (auto *paramTy : genericSig->getGenericParams()) {
Type contextTy = cs.DC->mapTypeIntoContext(paramTy);
bindContextArchetype(paramTy, contextTy);
}
break;
}
}
void ConstraintSystem::openGeneric(
DeclContext *innerDC,
DeclContext *outerDC,
GenericSignature *sig,
bool skipProtocolSelfConstraint,
ConstraintLocatorBuilder locator,
OpenedTypeMap &replacements) {
if (sig == nullptr)
return;
auto locatorPtr = getConstraintLocator(locator);
// Create the type variables for the generic parameters.
for (auto gp : sig->getGenericParams()) {
locatorPtr = getConstraintLocator(
locator.withPathElement(LocatorPathElt(gp)));
auto typeVar = createTypeVariable(locatorPtr,
TVO_PrefersSubtypeBinding);
auto result = replacements.insert(
std::make_pair(cast<GenericTypeParamType>(gp->getCanonicalType()),
typeVar));
assert(result.second);
(void) result;
}
// Remember that any new constraints generated by opening this generic are
// due to the opening.
locatorPtr = getConstraintLocator(
locator.withPathElement(ConstraintLocator::OpenedGeneric));
bindArchetypesFromContext(*this, outerDC, locatorPtr, replacements);
// Add the requirements as constraints.
openGenericRequirements(
outerDC, sig, skipProtocolSelfConstraint, locator,
[&](Type type) { return openType(type, replacements); });
}
void ConstraintSystem::openGenericRequirements(
DeclContext *outerDC, GenericSignature *signature,
bool skipProtocolSelfConstraint, ConstraintLocatorBuilder locator,
llvm::function_ref<Type(Type)> substFn) {
auto requirements = signature->getRequirements();
for (unsigned pos = 0, n = requirements.size(); pos != n; ++pos) {
const auto &req = requirements[pos];
Optional<Requirement> openedReq;
auto openedFirst = substFn(req.getFirstType());
auto kind = req.getKind();
switch (kind) {
case RequirementKind::Conformance: {
auto proto = req.getSecondType()->castTo<ProtocolType>();
auto protoDecl = proto->getDecl();
// Determine whether this is the protocol 'Self' constraint we should
// skip.
if (skipProtocolSelfConstraint && protoDecl == outerDC &&
protoDecl->getSelfInterfaceType()->isEqual(req.getFirstType()))
continue;
openedReq = Requirement(kind, openedFirst, proto);
break;
}
case RequirementKind::Superclass:
case RequirementKind::SameType:
openedReq = Requirement(kind, openedFirst, substFn(req.getSecondType()));
break;
case RequirementKind::Layout:
openedReq = Requirement(kind, openedFirst, req.getLayoutConstraint());
break;
}
addConstraint(
*openedReq,
locator.withPathElement(ConstraintLocator::OpenedGeneric)
.withPathElement(
LocatorPathElt::getTypeRequirementComponent(pos, kind)));
}
}
/// Add the constraint on the type used for the 'Self' type for a member
/// reference.
///
/// \param cs The constraint system.
///
/// \param objectTy The type of the object that we're using to access the
/// member.
///
/// \param selfTy The instance type of the context in which the member is
/// declared.
static void addSelfConstraint(ConstraintSystem &cs, Type objectTy, Type selfTy,
ConstraintLocatorBuilder locator){
assert(!selfTy->is<ProtocolType>());
// Otherwise, use a subtype constraint for classes to cope with inheritance.
if (selfTy->getClassOrBoundGenericClass()) {
cs.addConstraint(ConstraintKind::Subtype, objectTy, selfTy,
cs.getConstraintLocator(locator));
return;
}
// Otherwise, the types must be equivalent.
cs.addConstraint(ConstraintKind::Equal, objectTy, selfTy,
cs.getConstraintLocator(locator));
}
/// Determine whether the given locator is for a witness or requirement.
static bool isRequirementOrWitness(const ConstraintLocatorBuilder &locator) {
if (auto last = locator.last()) {
return last->getKind() == ConstraintLocator::Requirement ||
last->getKind() == ConstraintLocator::Witness;
}
return false;
}
std::pair<Type, Type>
ConstraintSystem::getTypeOfMemberReference(
Type baseTy, ValueDecl *value, DeclContext *useDC,
bool isDynamicResult,
FunctionRefKind functionRefKind,
ConstraintLocatorBuilder locator,
const DeclRefExpr *base,
OpenedTypeMap *replacementsPtr) {
// Figure out the instance type used for the base.
Type baseObjTy = getFixedTypeRecursive(baseTy, /*wantRValue=*/true);
bool isInstance = true;
if (auto baseMeta = baseObjTy->getAs<AnyMetatypeType>()) {
baseObjTy = baseMeta->getInstanceType();
isInstance = false;
}
// If the base is a module type, just use the type of the decl.
if (baseObjTy->is<ModuleType>()) {
return getTypeOfReference(value, functionRefKind, locator, useDC, base);
}
FunctionType::Param baseObjParam(baseObjTy);
// Don't open existentials when accessing typealias members of
// protocols.
if (auto *alias = dyn_cast<TypeAliasDecl>(value)) {
if (baseObjTy->isExistentialType()) {
auto memberTy = alias->getInterfaceType();
// If we end up with a protocol typealias here, it's underlying
// type must be fully concrete.
assert(!memberTy->hasTypeParameter());
auto openedType = FunctionType::get({baseObjParam}, memberTy);
return { openedType, memberTy };
}
}
if (auto *typeDecl = dyn_cast<TypeDecl>(value)) {
assert(!isa<ModuleDecl>(typeDecl) && "Nested module?");
auto memberTy = TC.substMemberTypeWithBase(DC->getParentModule(),
typeDecl, baseObjTy);
// Open the type if it was a reference to a generic type.
memberTy = openUnboundGenericType(memberTy, locator);
// Wrap it in a metatype.
memberTy = MetatypeType::get(memberTy);
auto openedType = FunctionType::get({baseObjParam}, memberTy);
return { openedType, memberTy };
}
// Figure out the declaration context to use when opening this type.
DeclContext *innerDC = value->getInnermostDeclContext();
DeclContext *outerDC = value->getDeclContext();
// Open the type of the generic function or member of a generic type.
Type openedType;
OpenedTypeMap localReplacements;
auto &replacements = replacementsPtr ? *replacementsPtr : localReplacements;
bool isCurriedInstanceReference = value->isInstanceMember() && !isInstance;
unsigned numRemovedArgumentLabels =
getNumRemovedArgumentLabels(TC, value, isCurriedInstanceReference,
functionRefKind);
AnyFunctionType *funcType;
if (isa<AbstractFunctionDecl>(value) ||
isa<EnumElementDecl>(value)) {
// This is the easy case.
funcType = value->getInterfaceType()->castTo<AnyFunctionType>();
} else {
// For a property, build a type (Self) -> PropType.
// For a subscript, build a type (Self) -> (Indices...) -> ElementType.
//
// If the access is mutating, wrap the storage type in an lvalue type.
Type refType;
if (auto *subscript = dyn_cast<SubscriptDecl>(value)) {
auto elementTy = subscript->getElementInterfaceType();
if (doesStorageProduceLValue(TC, subscript, baseTy, useDC, base))
elementTy = LValueType::get(elementTy);
// See ConstraintSystem::resolveOverload() -- optional and dynamic
// subscripts are a special case, because the optionality is
// applied to the result type and not the type of the reference.
if (!isRequirementOrWitness(locator)) {
if (subscript->getAttrs().hasAttribute<OptionalAttr>() ||
isDynamicResult)
elementTy = OptionalType::get(elementTy->getRValueType());
}
auto indices = subscript->getInterfaceType()
->castTo<AnyFunctionType>()->getParams();
refType = FunctionType::get(indices, elementTy);
} else {
refType = getUnopenedTypeOfReference(cast<VarDecl>(value), baseTy, useDC,
base, /*wantInterfaceType=*/true);
}
auto selfTy = outerDC->getSelfInterfaceType();
// If self is a value type and the base type is an lvalue, wrap it in an
// inout type.
auto selfFlags = ParameterTypeFlags();
if (!outerDC->getDeclaredInterfaceType()->hasReferenceSemantics() &&
baseTy->is<LValueType>() &&
!selfTy->hasError())
selfFlags = selfFlags.withInOut(true);
// If the storage is generic, add a generic signature.
FunctionType::Param selfParam(selfTy, Identifier(), selfFlags);
if (auto *sig = innerDC->getGenericSignatureOfContext()) {
funcType = GenericFunctionType::get(sig, {selfParam}, refType);
} else {
funcType = FunctionType::get({selfParam}, refType);
}
}
openedType = openFunctionType(funcType, numRemovedArgumentLabels,
locator, replacements, innerDC, outerDC,
/*skipProtocolSelfConstraint=*/true);
if (!outerDC->getSelfProtocolDecl()) {
// Class methods returning Self as well as constructors get the
// result replaced with the base object type.
if (auto func = dyn_cast<AbstractFunctionDecl>(value)) {
if ((isa<FuncDecl>(func) && cast<FuncDecl>(func)->hasDynamicSelf()) ||
(isa<ConstructorDecl>(func) && !baseObjTy->getOptionalObjectType())) {
openedType = openedType->replaceCovariantResultType(baseObjTy, 2);
}
}
} else {
// Protocol requirements returning Self have a dynamic Self return
// type. Erase the dynamic Self since it only comes into play during
// protocol conformance checking.
openedType = openedType->eraseDynamicSelfType();
}
// If we are looking at a member of an existential, open the existential.
Type baseOpenedTy = baseObjTy;
if (baseObjTy->isExistentialType()) {
ArchetypeType *openedArchetype = ArchetypeType::getOpened(baseObjTy);
OpenedExistentialTypes.push_back({ getConstraintLocator(locator),
openedArchetype });
baseOpenedTy = openedArchetype;
}
// Constrain the 'self' object type.
auto openedFnType = openedType->castTo<FunctionType>();
auto openedParams = openedFnType->getParams();
assert(openedParams.size() == 1);
Type selfObjTy = openedParams.front().getPlainType()->getMetatypeInstanceType();
if (outerDC->getSelfProtocolDecl()) {
// For a protocol, substitute the base object directly. We don't need a
// conformance constraint because we wouldn't have found the declaration
// if it didn't conform.
addConstraint(ConstraintKind::Equal, baseOpenedTy, selfObjTy,
getConstraintLocator(locator));
} else if (!isDynamicResult) {
addSelfConstraint(*this, baseOpenedTy, selfObjTy, locator);
}
// Compute the type of the reference.
Type type;
if (!value->isInstanceMember() || isInstance) {
// For a static member referenced through a metatype or an instance
// member referenced through an instance, strip off the 'self'.
type = openedFnType->getResult();
} else {
// For an unbound instance method reference, replace the 'Self'
// parameter with the base type.
openedType = openedFnType->replaceSelfParameterType(baseObjTy);
type = openedType;
}
// When accessing protocol members with an existential base, replace
// the 'Self' type parameter with the existential type, since formally
// the access will operate on existentials and not type parameters.
if (!isDynamicResult &&
baseObjTy->isExistentialType() &&
outerDC->getSelfProtocolDecl()) {
auto selfTy = replacements[
cast<GenericTypeParamType>(outerDC->getSelfInterfaceType()
->getCanonicalType())];
type = type.transform([&](Type t) -> Type {
if (auto *selfTy = t->getAs<DynamicSelfType>())
t = selfTy->getSelfType();
if (t->is<TypeVariableType>())
if (t->isEqual(selfTy))
return baseObjTy;
if (auto *metatypeTy = t->getAs<MetatypeType>())
if (metatypeTy->getInstanceType()->isEqual(selfTy))
return ExistentialMetatypeType::get(baseObjTy);
return t;
});
}
// If we opened up any type variables, record the replacements.
recordOpenedTypes(locator, replacements);
return { openedType, type };
}
// Performance hack: if there are two generic overloads, and one is
// more specialized than the other, prefer the more-specialized one.
static void tryOptimizeGenericDisjunction(ConstraintSystem &cs,
ArrayRef<OverloadChoice> choices,
OverloadChoice *&favoredChoice) {
if (favoredChoice || choices.size() != 2)
return;
const auto &choiceA = choices[0];
const auto &choiceB = choices[1];
if (!choiceA.isDecl() || !choiceB.isDecl())
return;
auto isViable = [](ValueDecl *decl) -> bool {
assert(decl);
auto *AFD = dyn_cast<AbstractFunctionDecl>(decl);
if (!AFD || !AFD->isGeneric())
return false;
auto funcType = AFD->getInterfaceType();
auto hasAnyOrOptional = funcType.findIf([](Type type) -> bool {
if (type->getOptionalObjectType())
return true;
return type->isAny();
});
// If function declaration references `Any` or `Any?` type
// let's not attempt it, because it's unclear
// without solving which overload is going to be better.
return !hasAnyOrOptional;
};
auto *declA = choiceA.getDecl();
auto *declB = choiceB.getDecl();
if (!isViable(declA) || !isViable(declB))
return;
auto &TC = cs.TC;
auto *DC = cs.DC;
switch (TC.compareDeclarations(DC, declA, declB)) {
case Comparison::Better:
favoredChoice = const_cast<OverloadChoice *>(&choiceA);
break;
case Comparison::Worse:
favoredChoice = const_cast<OverloadChoice *>(&choiceB);
break;
case Comparison::Unordered:
break;
}
}
void ConstraintSystem::addOverloadSet(Type boundType,
ArrayRef<OverloadChoice> choices,
DeclContext *useDC,
ConstraintLocator *locator,
OverloadChoice *favoredChoice,
ArrayRef<OverloadChoice> outerAlternatives) {
assert(!choices.empty() && "Empty overload set");
// If there is a single choice, add the bind overload directly.
if (choices.size() == 1 && outerAlternatives.empty()) {
addBindOverloadConstraint(boundType, choices.front(), locator, useDC);
return;
}
tryOptimizeGenericDisjunction(*this, choices, favoredChoice);
SmallVector<Constraint *, 4> overloads;
// As we do for other favored constraints, if a favored overload has been
// specified, let it be the first term in the disjunction.
if (favoredChoice) {
auto bindOverloadConstraint =
Constraint::createBindOverload(*this,
boundType,
*favoredChoice,
useDC,
locator);
assert((!favoredChoice->isDecl() ||
!favoredChoice->getDecl()->getAttrs().isUnavailable(
getASTContext())) &&
"Cannot make unavailable decl favored!");
bindOverloadConstraint->setFavored();
overloads.push_back(bindOverloadConstraint);
}
for (auto &choice : choices) {
if (favoredChoice && (favoredChoice == &choice))
continue;
overloads.push_back(Constraint::createBindOverload(*this, boundType, choice,
useDC, locator));
}
auto innerDisjunction = Constraint::createDisjunction(*this, overloads,
locator, ForgetChoice);
if (outerAlternatives.empty()) {
if (favoredChoice)
innerDisjunction->setFavored();
addUnsolvedConstraint(innerDisjunction);
return;
}
SmallVector<Constraint *, 4> outerConstraints;
outerConstraints.push_back(innerDisjunction);
innerDisjunction->setFavored();
for (auto choice : outerAlternatives) {
outerConstraints.push_back(Constraint::createBindOverload(
*this, boundType, choice,
useDC, locator));
}
addDisjunctionConstraint(outerConstraints, locator, ForgetChoice, favoredChoice);
}
/// If we're resolving an overload set with a decl that has special type
/// checking semantics, set up the special-case type system and return true;
/// otherwise return false.
static bool
resolveOverloadForDeclWithSpecialTypeCheckingSemantics(ConstraintSystem &CS,
ConstraintLocator *locator,
Type boundType,
OverloadChoice choice,
Type &refType,
Type &openedFullType) {
assert(choice.getKind() == OverloadChoiceKind::Decl);
switch (CS.TC.getDeclTypeCheckingSemantics(choice.getDecl())) {
case DeclTypeCheckingSemantics::Normal:
return false;
case DeclTypeCheckingSemantics::TypeOf: {
// Proceed with a "DynamicType" operation. This produces an existential
// metatype from existentials, or a concrete metatype from non-
// existentials (as seen from the current abstraction level), which can't
// be expressed in the type system currently.
auto input = CS.createTypeVariable(
CS.getConstraintLocator(locator, ConstraintLocator::FunctionArgument));
auto output = CS.createTypeVariable(
CS.getConstraintLocator(locator, ConstraintLocator::FunctionResult));
FunctionType::Param inputArg(input,
CS.getASTContext().getIdentifier("of"));
CS.addConstraint(ConstraintKind::DynamicTypeOf, output, input,
CS.getConstraintLocator(locator, ConstraintLocator::RValueAdjustment));
refType = FunctionType::get({inputArg}, output);
openedFullType = refType;
return true;
}
case DeclTypeCheckingSemantics::WithoutActuallyEscaping: {
// Proceed with a "WithoutActuallyEscaping" operation. The body closure
// receives a copy of the argument closure that is temporarily made
// @escaping.
auto noescapeClosure = CS.createTypeVariable(
CS.getConstraintLocator(locator, ConstraintLocator::FunctionArgument));
auto escapeClosure = CS.createTypeVariable(
CS.getConstraintLocator(locator, ConstraintLocator::FunctionArgument));
CS.addConstraint(ConstraintKind::EscapableFunctionOf,
escapeClosure, noescapeClosure,
CS.getConstraintLocator(locator, ConstraintLocator::RValueAdjustment));
auto result = CS.createTypeVariable(
CS.getConstraintLocator(locator, ConstraintLocator::FunctionResult));
FunctionType::Param arg(escapeClosure);
auto bodyClosure = FunctionType::get(arg, result,
FunctionType::ExtInfo(FunctionType::Representation::Swift,
/*noescape*/ true,
/*throws*/ true));
FunctionType::Param args[] = {
FunctionType::Param(noescapeClosure),
FunctionType::Param(bodyClosure, CS.getASTContext().getIdentifier("do")),
};
refType = FunctionType::get(args, result,
FunctionType::ExtInfo(FunctionType::Representation::Swift,
/*noescape*/ false,
/*throws*/ true));
openedFullType = refType;
return true;
}
case DeclTypeCheckingSemantics::OpenExistential: {
// The body closure receives a freshly-opened archetype constrained by the
// existential type as its input.
auto openedTy = CS.createTypeVariable(
CS.getConstraintLocator(locator, ConstraintLocator::FunctionArgument));
auto existentialTy = CS.createTypeVariable(
CS.getConstraintLocator(locator, ConstraintLocator::FunctionArgument));
CS.addConstraint(ConstraintKind::OpenedExistentialOf,
openedTy, existentialTy,
CS.getConstraintLocator(locator, ConstraintLocator::RValueAdjustment));
auto result = CS.createTypeVariable(
CS.getConstraintLocator(locator, ConstraintLocator::FunctionResult));
FunctionType::Param bodyArgs[] = {FunctionType::Param(openedTy)};
auto bodyClosure = FunctionType::get(bodyArgs, result,
FunctionType::ExtInfo(FunctionType::Representation::Swift,
/*noescape*/ true,
/*throws*/ true));
FunctionType::Param args[] = {
FunctionType::Param(existentialTy),
FunctionType::Param(bodyClosure, CS.getASTContext().getIdentifier("do")),
};
refType = FunctionType::get(args, result,
FunctionType::ExtInfo(FunctionType::Representation::Swift,
/*noescape*/ false,
/*throws*/ true));
openedFullType = refType;
return true;
}
}
llvm_unreachable("Unhandled DeclTypeCheckingSemantics in switch.");
}
void ConstraintSystem::resolveOverload(ConstraintLocator *locator,
Type boundType,
OverloadChoice choice,
DeclContext *useDC) {
// Determine the type to which we'll bind the overload set's type.
Type refType;
Type openedFullType;
bool isDynamicResult = choice.getKind() == OverloadChoiceKind::DeclViaDynamic;
bool bindConstraintCreated = false;
switch (auto kind = choice.getKind()) {
case OverloadChoiceKind::Decl:
// If we refer to a top-level decl with special type-checking semantics,
// handle it now.
if (resolveOverloadForDeclWithSpecialTypeCheckingSemantics(
*this, locator, boundType, choice, refType, openedFullType))
break;
LLVM_FALLTHROUGH;
case OverloadChoiceKind::DeclViaBridge:
case OverloadChoiceKind::DeclViaDynamic:
case OverloadChoiceKind::DeclViaUnwrappedOptional:
case OverloadChoiceKind::DynamicMemberLookup: {
// Retrieve the type of a reference to the specific declaration choice.
if (auto baseTy = choice.getBaseType()) {
assert(!baseTy->hasTypeParameter());
auto getDotBase = [](const Expr *E) -> const DeclRefExpr * {
if (E == nullptr) return nullptr;
switch (E->getKind()) {
case ExprKind::MemberRef: {
auto Base = cast<MemberRefExpr>(E)->getBase();
return dyn_cast<const DeclRefExpr>(Base);
}
case ExprKind::UnresolvedDot: {
auto Base = cast<UnresolvedDotExpr>(E)->getBase();
return dyn_cast<const DeclRefExpr>(Base);
}
default:
return nullptr;
}
};
auto anchor = locator ? locator->getAnchor() : nullptr;
auto base = getDotBase(anchor);
std::tie(openedFullType, refType)
= getTypeOfMemberReference(baseTy, choice.getDecl(), useDC,
isDynamicResult,
choice.getFunctionRefKind(),
locator, base, nullptr);
} else {
std::tie(openedFullType, refType)
= getTypeOfReference(choice.getDecl(),
choice.getFunctionRefKind(), locator, useDC);
}
// For a non-subscript declaration found via dynamic lookup, strip
// off the lvalue-ness (FIXME: as a temporary hack. We eventually
// want this to work) and make a reference to that declaration be
// an implicitly unwrapped optional.
//
// Subscript declarations are handled within
// getTypeOfMemberReference(); their result types are unchecked
// optional.
if (isDynamicResult) {
if (isa<SubscriptDecl>(choice.getDecl())) {
// We always expect function type for subscripts.
auto fnTy = refType->castTo<AnyFunctionType>();
if (choice.isImplicitlyUnwrappedValueOrReturnValue()) {
auto resultTy = fnTy->getResult();
// We expect the element type to be a double-optional.
auto optTy = resultTy->getOptionalObjectType();
assert(optTy->getOptionalObjectType());
// For our original type T -> U?? we will generate:
// A disjunction V = { U?, U }
// and a disjunction boundType = { T -> V?, T -> V }
Type ty = createTypeVariable(locator);
buildDisjunctionForImplicitlyUnwrappedOptional(ty, optTy, locator);
// Create a new function type with an optional of this type
// variable as the result type.
if (auto *genFnTy = fnTy->getAs<GenericFunctionType>()) {
fnTy = GenericFunctionType::get(
genFnTy->getGenericSignature(), genFnTy->getParams(),
OptionalType::get(ty), genFnTy->getExtInfo());
} else {
fnTy = FunctionType::get(fnTy->getParams(), OptionalType::get(ty),
fnTy->getExtInfo());
}
}
buildDisjunctionForDynamicLookupResult(boundType, fnTy, locator);
} else {
Type ty = refType;
// If this is something we need to implicitly unwrap, set up a
// new type variable and disjunction that will allow us to make
// the choice of whether to do so.
if (choice.isImplicitlyUnwrappedValueOrReturnValue()) {
// Duplicate the structure of boundType, with fresh type
// variables. We'll create a binding disjunction using this,
// selecting between options for refType, which is either
// Optional or a function type returning Optional.
assert(boundType->hasTypeVariable());
ty = boundType.transform([this](Type elTy) -> Type {
if (auto *tv = dyn_cast<TypeVariableType>(elTy.getPointer())) {
return createTypeVariable(tv->getImpl().getLocator(),
tv->getImpl().getRawOptions());
}
return elTy;
});
buildDisjunctionForImplicitlyUnwrappedOptional(
ty, refType->getRValueType(), locator);
}
// Build the disjunction to attempt binding both T? and T (or
// function returning T? and function returning T).
buildDisjunctionForDynamicLookupResult(
boundType, OptionalType::get(ty->getRValueType()), locator);
// We store an Optional of the originally resolved type in the
// overload set.
refType = OptionalType::get(refType->getRValueType());
}
bindConstraintCreated = true;
} else if (!isRequirementOrWitness(locator) &&
choice.getDecl()->getAttrs().hasAttribute<OptionalAttr>() &&
!isa<SubscriptDecl>(choice.getDecl())) {
// For a non-subscript declaration that is an optional
// requirement in a protocol, strip off the lvalue-ness (FIXME:
// one cannot assign to such declarations for now) and make a
// reference to that declaration be optional.
//
// Subscript declarations are handled within
// getTypeOfMemberReference(); their result types are optional.
// Deal with values declared as implicitly unwrapped, or
// functions with return types that are implicitly unwrapped.
if (choice.isImplicitlyUnwrappedValueOrReturnValue()) {
// Build the disjunction to attempt binding both T? and T (or
// function returning T? and function returning T).
Type ty = createTypeVariable(locator, TVO_CanBindToLValue);
buildDisjunctionForImplicitlyUnwrappedOptional(ty, refType, locator);
addConstraint(ConstraintKind::Bind, boundType,
OptionalType::get(ty->getRValueType()), locator);
bindConstraintCreated = true;
}
refType = OptionalType::get(refType->getRValueType());
}
// If the declaration is unavailable, note that in the score.
if (choice.getDecl()->getAttrs().isUnavailable(getASTContext())) {
increaseScore(SK_Unavailable);
}
if (kind == OverloadChoiceKind::DynamicMemberLookup) {
// DynamicMemberLookup results are always a (dynamicMember:T1)->T2
// subscript.
auto refFnType = refType->castTo<FunctionType>();
// If this is a dynamic member lookup, then the decl we have is for the
// subscript(dynamicMember:) member, but the type we need to return is the
// result of the subscript. Dig through it.
refType = refFnType->getResult();
// Before we drop the argument type on the floor, we need to constrain it
// to having a literal conformance to ExpressibleByStringLiteral. This
// makes the index default to String if otherwise unconstrained.
assert(refFnType->getParams().size() == 1 &&
"subscript always has one arg");
auto argType = refFnType->getParams()[0].getPlainType();
auto protoKind = KnownProtocolKind::ExpressibleByStringLiteral;
auto protocol = getTypeChecker().getProtocol(choice.getDecl()->getLoc(),
protoKind);
if (!protocol)
break;
addConstraint(ConstraintKind::LiteralConformsTo, argType,
protocol->getDeclaredType(),
locator);
}
break;
}
case OverloadChoiceKind::BaseType:
refType = choice.getBaseType();
break;
case OverloadChoiceKind::TupleIndex:
if (auto lvalueTy = choice.getBaseType()->getAs<LValueType>()) {
// When the base of a tuple lvalue, the member is always an lvalue.
auto tuple = lvalueTy->getObjectType()->castTo<TupleType>();
refType = tuple->getElementType(choice.getTupleIndex())->getRValueType();
refType = LValueType::get(refType);
} else {
// When the base is a tuple rvalue, the member is always an rvalue.
auto tuple = choice.getBaseType()->castTo<TupleType>();
refType = tuple->getElementType(choice.getTupleIndex())->getRValueType();
}
break;
case OverloadChoiceKind::KeyPathApplication: {
// Key path application looks like a subscript(keyPath: KeyPath<Base, T>).
// The element type is T or @lvalue T based on the key path subtype and
// the mutability of the base.
auto keyPathIndexTy = createTypeVariable(
getConstraintLocator(locator, ConstraintLocator::FunctionArgument));
auto elementTy = createTypeVariable(
getConstraintLocator(locator, ConstraintLocator::FunctionArgument),
TVO_CanBindToLValue);
auto elementObjTy = createTypeVariable(
getConstraintLocator(locator, ConstraintLocator::FunctionArgument));
addConstraint(ConstraintKind::Equal, elementTy, elementObjTy, locator);
// The element result is an lvalue or rvalue based on the key path class.
addKeyPathApplicationConstraint(
keyPathIndexTy, choice.getBaseType(), elementTy, locator);
FunctionType::Param indices[] = {
FunctionType::Param(keyPathIndexTy, getASTContext().Id_keyPath),
};
auto subscriptTy = FunctionType::get(indices, elementTy);
FunctionType::Param baseParam(choice.getBaseType());
auto fullTy = FunctionType::get({baseParam}, subscriptTy);
openedFullType = fullTy;
refType = subscriptTy;
// Increase the score so that actual subscripts get preference.
increaseScore(SK_KeyPathSubscript);
break;
}
}
assert(!refType->hasTypeParameter() && "Cannot have a dependent type here");
// If we're binding to an init member, the 'throws' need to line up between
// the bound and reference types.
if (choice.isDecl()) {
auto decl = choice.getDecl();
if (auto CD = dyn_cast<ConstructorDecl>(decl)) {
auto boundFunctionType = boundType->getAs<AnyFunctionType>();
if (boundFunctionType &&
CD->hasThrows() != boundFunctionType->throws()) {
boundType = boundFunctionType->withExtInfo(
boundFunctionType->getExtInfo().withThrows());
}
}
}
// Note that we have resolved this overload.
resolvedOverloadSets
= new (*this) ResolvedOverloadSetListItem{resolvedOverloadSets,
boundType,
choice,
locator,
openedFullType,
refType};
// In some cases we already created the appropriate bind constraints.
if (!bindConstraintCreated) {
if (choice.isImplicitlyUnwrappedValueOrReturnValue()) {
// Build the disjunction to attempt binding both T? and T (or
// function returning T? and function returning T).
buildDisjunctionForImplicitlyUnwrappedOptional(boundType, refType,
locator);
} else {
// Add the type binding constraint.
addConstraint(ConstraintKind::Bind, boundType, refType, locator);
}
}
if (TC.getLangOpts().DebugConstraintSolver) {
auto &log = getASTContext().TypeCheckerDebug->getStream();
log.indent(solverState ? solverState->depth * 2 : 2)
<< "(overload set choice binding "
<< boundType->getString() << " := "
<< refType->getString() << ")\n";
}
}
template <typename Fn>
Type simplifyTypeImpl(ConstraintSystem &cs, Type type, Fn getFixedTypeFn) {
return type.transform([&](Type type) -> Type {
if (auto tvt = dyn_cast<TypeVariableType>(type.getPointer()))
return getFixedTypeFn(tvt);
// If this is a dependent member type for which we end up simplifying
// the base to a non-type-variable, perform lookup.
if (auto depMemTy = dyn_cast<DependentMemberType>(type.getPointer())) {
// Simplify the base.
Type newBase = simplifyTypeImpl(cs, depMemTy->getBase(), getFixedTypeFn);
// If nothing changed, we're done.
if (newBase.getPointer() == depMemTy->getBase().getPointer())
return type;
// Dependent member types should only be created for associated types.
auto assocType = depMemTy->getAssocType();
assert(depMemTy->getAssocType() && "Expected associated type!");
// FIXME: It's kind of weird in general that we have to look
// through lvalue, inout and IUO types here
Type lookupBaseType = newBase->getWithoutSpecifierType();
if (lookupBaseType->mayHaveMembers()) {
auto *proto = assocType->getProtocol();
auto conformance = cs.DC->getParentModule()->lookupConformance(
lookupBaseType, proto);
if (!conformance)
return DependentMemberType::get(lookupBaseType, assocType);
auto subs = SubstitutionMap::getProtocolSubstitutions(
proto, lookupBaseType, *conformance);
auto result = assocType->getDeclaredInterfaceType().subst(subs);
if (result && !result->hasError())
return result;
}
return DependentMemberType::get(lookupBaseType, assocType);
}
return type;
});
}
Type ConstraintSystem::simplifyType(Type type) {
if (!type->hasTypeVariable())
return type;
// Map type variables down to the fixed types of their representatives.
return simplifyTypeImpl(
*this, type,
[&](TypeVariableType *tvt) -> Type {
if (auto fixed = getFixedType(tvt))
return simplifyType(fixed);
return getRepresentative(tvt);
});
}
Type Solution::simplifyType(Type type) const {
if (!type->hasTypeVariable())
return type;
// Map type variables to fixed types from bindings.
return simplifyTypeImpl(
getConstraintSystem(), type,
[&](TypeVariableType *tvt) -> Type {
auto known = typeBindings.find(tvt);
assert(known != typeBindings.end());
return known->second;
});
}
size_t Solution::getTotalMemory() const {
return sizeof(*this) + typeBindings.getMemorySize() +
overloadChoices.getMemorySize() +
ConstraintRestrictions.getMemorySize() +
llvm::capacity_in_bytes(Fixes) + DisjunctionChoices.getMemorySize() +
OpenedTypes.getMemorySize() + OpenedExistentialTypes.getMemorySize() +
(DefaultedConstraints.size() * sizeof(void *)) +
llvm::capacity_in_bytes(Conformances);
}
DeclName OverloadChoice::getName() const {
switch (getKind()) {
case OverloadChoiceKind::Decl:
case OverloadChoiceKind::DeclViaDynamic:
case OverloadChoiceKind::DeclViaBridge:
case OverloadChoiceKind::DeclViaUnwrappedOptional:
return getDecl()->getFullName();
case OverloadChoiceKind::KeyPathApplication:
// TODO: This should probably produce subscript(keyPath:), but we
// don't currently pre-filter subscript overload sets by argument
// keywords, so "subscript" is still the name that keypath subscripts
// are looked up by.
return DeclBaseName::createSubscript();
case OverloadChoiceKind::DynamicMemberLookup:
return DeclName(DynamicNameAndFRK.getPointer());
case OverloadChoiceKind::BaseType:
case OverloadChoiceKind::TupleIndex:
llvm_unreachable("no name!");
}
llvm_unreachable("Unhandled OverloadChoiceKind in switch.");
}
bool OverloadChoice::isImplicitlyUnwrappedValueOrReturnValue() const {
if (!isDecl())
return false;
auto *decl = getDecl();
if (!decl->getAttrs().hasAttribute<ImplicitlyUnwrappedOptionalAttr>())
return false;
auto itfType = decl->getInterfaceType();
if (!itfType->getAs<AnyFunctionType>())
return true;
switch (getFunctionRefKind()) {
case FunctionRefKind::Unapplied:
case FunctionRefKind::Compound:
return false;
case FunctionRefKind::SingleApply:
case FunctionRefKind::DoubleApply:
return true;
}
llvm_unreachable("unhandled kind");
}
bool ConstraintSystem::salvage(SmallVectorImpl<Solution> &viable, Expr *expr) {
if (TC.getLangOpts().DebugConstraintSolver) {
auto &log = TC.Context.TypeCheckerDebug->getStream();
log << "---Attempting to salvage and emit diagnostics---\n";
}
// Attempt to solve again, capturing all states that come from our attempts to
// select overloads or bind type variables.
//
// FIXME: can this be removed? We need to arrange for recordFixes to be
// eliminated.
viable.clear();
{
// Set up solver state.
SolverState state(expr, *this, FreeTypeVariableBinding::Disallow);
state.recordFixes = true;
// Solve the system.
solve(viable);
// Check whether we have a best solution; this can happen if we found
// a series of fixes that worked.
if (auto best = findBestSolution(viable, state.ExprWeights,
/*minimize=*/true)) {
if (*best != 0)
viable[0] = std::move(viable[*best]);
viable.erase(viable.begin() + 1, viable.end());
return false;
}
// FIXME: If we were able to actually fix things along the way,
// we may have to hunt for the best solution. For now, we don't care.
// Before removing any "fixed" solutions, let's check
// if ambiguity is caused by fixes and diagnose if possible.
if (diagnoseAmbiguityWithFixes(expr, viable))
return true;
// Remove solutions that require fixes; the fixes in those systems should
// be diagnosed rather than any ambiguity.
auto hasFixes = [](const Solution &sol) { return !sol.Fixes.empty(); };
auto newEnd = std::remove_if(viable.begin(), viable.end(), hasFixes);
viable.erase(newEnd, viable.end());
// If there are multiple solutions, try to diagnose an ambiguity.
if (viable.size() > 1) {
if (getASTContext().LangOpts.DebugConstraintSolver) {
auto &log = getASTContext().TypeCheckerDebug->getStream();
log << "---Ambiguity error: " << viable.size()
<< " solutions found---\n";
int i = 0;
for (auto &solution : viable) {
log << "---Ambiguous solution #" << i++ << "---\n";
solution.dump(log);
log << "\n";
}
}
if (diagnoseAmbiguity(expr, viable)) {
return true;
}
}
// Fall through to produce diagnostics.
}
if (getExpressionTooComplex(viable)) {
TC.diagnose(expr->getLoc(), diag::expression_too_complex)
.highlight(expr->getSourceRange());
return true;
}
// If all else fails, diagnose the failure by looking through the system's
// constraints.
diagnoseFailureForExpr(expr);
return true;
}
bool ConstraintSystem::diagnoseAmbiguityWithFixes(
Expr *expr, ArrayRef<Solution> solutions) {
if (solutions.empty())
return false;
auto getOverloadDecl = [&](SelectedOverload &overload) -> ValueDecl * {
auto &choice = overload.choice;
return choice.isDecl() ? choice.getDecl() : nullptr;
};
// Problems related to fixes forming ambiguous solution set
// could only be diagnosed (at the moment), if all of the fixes
// are attached to the same anchor, which means they fix
// different overloads of the same declaration.
Expr *commonAnchor = nullptr;
SmallPtrSet<ValueDecl *, 4> distinctChoices;
SmallVector<std::pair<const Solution *, const ConstraintFix *>, 4>
viableSolutions;
bool diagnosable = llvm::all_of(solutions, [&](const Solution &solution) {
ArrayRef<ConstraintFix *> fixes = solution.Fixes;
// Currently only support a single fix in a solution,
// but ultimately should be able to deal with multiple.
if (fixes.size() != 1)
return false;
const auto *fix = fixes.front();
if (commonAnchor && commonAnchor != fix->getAnchor())
return false;
commonAnchor = fix->getAnchor();
SmallVector<SelectedOverload, 2> overloads;
solution.getOverloadChoices(commonAnchor, overloads);
// There is unfortunately no way, at the moment, to figure out
// what declaration the fix is attached to, so we have to make
// sure that there is only one declaration associated with common
// anchor to be sure that the right problem is being diagnosed.
if (overloads.size() != 1)
return false;
auto *decl = getOverloadDecl(overloads.front());
if (!decl)
return false;
// If this declaration is distinct, let's record this solution
// as viable, otherwise we'd produce the same diagnostic multiple
// times, which means that actual problem is elsewhere.
if (distinctChoices.insert(decl).second)
viableSolutions.push_back({&solution, fix});
return true;
});
if (!diagnosable || viableSolutions.size() < 2)
return false;
auto *decl = *distinctChoices.begin();
assert(solverState);
bool diagnosed = true;
{
DiagnosticTransaction transaction(TC.Diags);
TC.diagnose(commonAnchor->getLoc(), diag::ambiguous_reference_to_decl,
decl->getDescriptiveKind(), decl->getFullName());
for (const auto &viable : viableSolutions) {
// Create scope so each applied solution is rolled back.
ConstraintSystem::SolverScope scope(*this);
applySolution(*viable.first);
// All of the solutions supposed to produce a "candidate" note.
diagnosed &= viable.second->diagnose(expr, /*asNote*/ true);
}
// If not all of the fixes produced a note, we can't diagnose this.
if (!diagnosed)
transaction.abort();
}
return diagnosed;
}
/// \brief Determine the number of distinct overload choices in the
/// provided set.
static unsigned countDistinctOverloads(ArrayRef<OverloadChoice> choices) {
llvm::SmallPtrSet<void *, 4> uniqueChoices;
unsigned result = 0;
for (auto choice : choices) {
if (uniqueChoices.insert(choice.getOpaqueChoiceSimple()).second)
++result;
}
return result;
}
/// \brief Determine the name of the overload in a set of overload choices.
static DeclName getOverloadChoiceName(ArrayRef<OverloadChoice> choices) {
DeclName name;
for (auto choice : choices) {
if (!choice.isDecl())
continue;
DeclName nextName = choice.getDecl()->getFullName();
if (!name) {
name = nextName;
continue;
}
if (name != nextName) {
// Assume all choices have the same base name and only differ in
// argument labels. This may not be a great assumption, but we don't
// really have a way to recover for diagnostics otherwise.
return name.getBaseName();
}
}
return name;
}
bool ConstraintSystem::diagnoseAmbiguity(Expr *expr,
ArrayRef<Solution> solutions) {
// Produce a diff of the solutions.
SolutionDiff diff(solutions);
// Find the locators which have the largest numbers of distinct overloads.
Optional<unsigned> bestOverload;
// Overloads are scored by lexicographical comparison of (# of distinct
// overloads, depth, *reverse* of the index). N.B. - cannot be used for the
// reversing: the score version of index == 0 should be > than that of 1, but
// -0 == 0 < UINT_MAX == -1, whereas ~0 == UINT_MAX > UINT_MAX - 1 == ~1.
auto score = [](unsigned distinctOverloads, unsigned depth, unsigned index) {
return std::make_tuple(distinctOverloads, depth, ~index);
};
auto bestScore = score(0, 0, std::numeric_limits<unsigned>::max());
// Get a map of expressions to their depths and post-order traversal indices.
// Heuristically, all other things being equal, we should complain about the
// ambiguous expression that (1) has the most overloads, (2) is deepest, or
// (3) comes earliest in the expression.
auto depthMap = expr->getDepthMap();
auto indexMap = expr->getPreorderIndexMap();
for (unsigned i = 0, n = diff.overloads.size(); i != n; ++i) {
auto &overload = diff.overloads[i];
// If we can't resolve the locator to an anchor expression with no path,
// we can't diagnose this well.
auto *anchor = simplifyLocatorToAnchor(*this, overload.locator);
if (!anchor)
continue;
auto it = indexMap.find(anchor);
if (it == indexMap.end())
continue;
unsigned index = it->second;
it = depthMap.find(anchor);
if (it == depthMap.end())
continue;
unsigned depth = it->second;
// If we don't have a name to hang on to, it'll be hard to diagnose this
// overload.
if (!getOverloadChoiceName(overload.choices))
continue;
unsigned distinctOverloads = countDistinctOverloads(overload.choices);
// We need at least two overloads to make this interesting.
if (distinctOverloads < 2)
continue;
// If we have more distinct overload choices for this locator than for
// prior locators, just keep this locator.
auto thisScore = score(distinctOverloads, depth, index);
if (thisScore > bestScore) {
bestScore = thisScore;
bestOverload = i;
continue;
}
// We have better results. Ignore this one.
}
// FIXME: Should be able to pick the best locator, e.g., based on some
// depth-first numbering of expressions.
if (bestOverload) {
auto &overload = diff.overloads[*bestOverload];
auto name = getOverloadChoiceName(overload.choices);
auto anchor = simplifyLocatorToAnchor(*this, overload.locator);
// Emit the ambiguity diagnostic.
auto &tc = getTypeChecker();
tc.diagnose(anchor->getLoc(),
name.isOperator() ? diag::ambiguous_operator_ref
: diag::ambiguous_decl_ref,
name);
TrailingClosureAmbiguityFailure failure(expr, *this, anchor,
overload.choices);
if (failure.diagnoseAsNote())
return true;
// Emit candidates. Use a SmallPtrSet to make sure only emit a particular
// candidate once. FIXME: Why is one candidate getting into the overload
// set multiple times? (See also tryDiagnoseTrailingClosureAmbiguity.)
SmallPtrSet<Decl *, 8> EmittedDecls;
for (auto choice : overload.choices) {
switch (choice.getKind()) {
case OverloadChoiceKind::Decl:
case OverloadChoiceKind::DeclViaDynamic:
case OverloadChoiceKind::DeclViaBridge:
case OverloadChoiceKind::DeclViaUnwrappedOptional:
// FIXME: show deduced types, etc, etc.
if (EmittedDecls.insert(choice.getDecl()).second)
tc.diagnose(choice.getDecl(), diag::found_candidate);
break;
case OverloadChoiceKind::KeyPathApplication:
case OverloadChoiceKind::DynamicMemberLookup:
// Skip key path applications and dynamic member lookups, since we don't
// want them to noise up unrelated subscript diagnostics.
break;
case OverloadChoiceKind::BaseType:
case OverloadChoiceKind::TupleIndex:
// FIXME: Actually diagnose something here.
break;
}
}
return true;
}
// FIXME: If we inferred different types for literals (for example),
// could diagnose ambiguity that way as well.
return false;
}
Expr *constraints::simplifyLocatorToAnchor(ConstraintSystem &cs,
ConstraintLocator *locator) {
if (!locator || !locator->getAnchor())
return nullptr;
SourceRange range;
locator = simplifyLocator(cs, locator, range);
if (!locator->getAnchor() || !locator->getPath().empty())
return nullptr;
return locator->getAnchor();
}