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TypeCheckDeclOverride.cpp
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//===--- TypeCheckOverride.cpp - Override Checking ------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 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 semantic analysis for declaration overrides.
//
//===----------------------------------------------------------------------===//
#include "MiscDiagnostics.h"
#include "TypeCheckAvailability.h"
#include "TypeCheckConcurrency.h"
#include "TypeCheckDecl.h"
#include "TypeCheckObjC.h"
#include "TypeChecker.h"
#include "swift/AST/ASTVisitor.h"
#include "swift/AST/Availability.h"
#include "swift/AST/Decl.h"
#include "swift/AST/GenericEnvironment.h"
#include "swift/AST/GenericSignature.h"
#include "swift/AST/NameLookupRequests.h"
#include "swift/AST/ParameterList.h"
#include "swift/AST/TypeCheckRequests.h"
using namespace swift;
static void adjustFunctionTypeForOverride(Type &type) {
// Drop 'throws'.
// FIXME: Do we want to allow overriding a function returning a value
// with one returning Never?
auto fnType = type->castTo<AnyFunctionType>();
auto extInfo = fnType->getExtInfo();
extInfo = extInfo.withThrows(false);
if (!fnType->getExtInfo().isEqualTo(extInfo, useClangTypes(fnType)))
type = fnType->withExtInfo(extInfo);
}
/// Drop the optionality of the result type of the given function type.
static Type dropResultOptionality(Type type, unsigned uncurryLevel) {
// We've hit the result type.
if (uncurryLevel == 0) {
if (auto objectTy = type->getOptionalObjectType())
return objectTy;
return type;
}
// Determine the input and result types of this function.
auto fnType = type->castTo<AnyFunctionType>();
auto parameters = fnType->getParams();
Type resultType =
dropResultOptionality(fnType->getResult(), uncurryLevel - 1);
// Produce the resulting function type.
if (auto genericFn = dyn_cast<GenericFunctionType>(fnType)) {
return GenericFunctionType::get(genericFn->getGenericSignature(),
parameters, resultType,
fnType->getExtInfo());
}
return FunctionType::get(parameters, resultType, fnType->getExtInfo());
}
Type swift::getMemberTypeForComparison(const ValueDecl *member,
const ValueDecl *derivedDecl) {
auto *method = dyn_cast<AbstractFunctionDecl>(member);
auto *ctor = dyn_cast_or_null<ConstructorDecl>(method);
auto abstractStorage = dyn_cast<AbstractStorageDecl>(member);
assert((method || abstractStorage) && "Not a method or abstractStorage?");
auto *subscript = dyn_cast_or_null<SubscriptDecl>(abstractStorage);
auto memberType = member->getInterfaceType();
if (memberType->is<ErrorType>())
return memberType;
if (derivedDecl) {
auto *dc = derivedDecl->getDeclContext();
auto owningType = dc->getDeclaredInterfaceType();
assert(owningType);
memberType = owningType->adjustSuperclassMemberDeclType(member, derivedDecl,
memberType);
}
if (method) {
// For methods, strip off the 'Self' type.
memberType = memberType->castTo<AnyFunctionType>()->getResult();
adjustFunctionTypeForOverride(memberType);
} else if (subscript) {
// For subscripts, we don't have a 'Self' type, but turn it
// into a monomorphic function type.
auto funcTy = memberType->castTo<AnyFunctionType>();
// FIXME: Verify ExtInfo state is correct, not working by accident.
FunctionType::ExtInfo info;
memberType =
FunctionType::get(funcTy->getParams(), funcTy->getResult(), info);
} else {
// For properties, strip off ownership.
memberType = memberType->getReferenceStorageReferent();
}
// Ignore the optionality of initializers when comparing types;
// we'll enforce this separately
if (ctor) {
memberType = dropResultOptionality(memberType, 1);
}
return memberType;
}
static bool
areAccessorsOverrideCompatible(const AbstractStorageDecl *storage,
const AbstractStorageDecl *parentStorage) {
// It's okay for the storage to disagree about whether to use a getter or
// a read accessor; we'll patch up any differences when setting overrides
// for the accessors. We don't want to diagnose anything involving
// `@_borrowed` because it is not yet part of the language.
// All the other checks are for non-static storage only.
if (storage->isStatic())
return true;
// The storage must agree on whether reads are mutating. For accessors,
// this is sufficient to imply that they use the same SelfAccessKind
// because we do not allow accessors to be consuming.
if (storage->isGetterMutating() != parentStorage->isGetterMutating())
return false;
// We allow covariance about whether the storage itself is mutable, so we
// can only check mutating-ness of setters if both have one.
if (storage->supportsMutation() && parentStorage->supportsMutation()) {
// The storage must agree on whether writes are mutating.
if (storage->isSetterMutating() != parentStorage->isSetterMutating())
return false;
// Those together should imply that read-write accesses have the same
// mutability.
}
return true;
}
bool swift::isOverrideBasedOnType(const ValueDecl *decl, Type declTy,
const ValueDecl *parentDecl) {
auto genericSig =
decl->getInnermostDeclContext()->getGenericSignatureOfContext();
auto canDeclTy = declTy->getReducedType(genericSig);
auto declIUOAttr = decl->isImplicitlyUnwrappedOptional();
auto parentDeclIUOAttr = parentDecl->isImplicitlyUnwrappedOptional();
if (declIUOAttr != parentDeclIUOAttr)
return false;
// If the generic signatures don't match, then return false because we don't
// want to complain if an overridden method matches multiple superclass
// methods which differ in generic signature.
//
// We can still succeed with a subtype match later in
// OverrideMatcher::match().
if (auto declCtx = decl->getAsGenericContext()) {
// The below logic now works correctly for protocol requirements which are
// themselves generic, but that would be an ABI break, since we would now
// drop the protocol requirements from witness tables. Simulate the old
// behavior by not considering generic declarations in protocols as
// overrides at all.
if (decl->getDeclContext()->getSelfProtocolDecl() &&
declCtx->isGeneric())
return false;
auto *parentCtx = parentDecl->getAsGenericContext();
if (declCtx->isGeneric() != parentCtx->isGeneric())
return false;
if (declCtx->isGeneric() &&
(declCtx->getGenericParams()->size() !=
parentCtx->getGenericParams()->size()))
return false;
auto &ctx = decl->getASTContext();
auto sig = ctx.getOverrideGenericSignature(parentDecl, decl);
if (sig &&
declCtx->getGenericSignature().getCanonicalSignature() !=
sig.getCanonicalSignature()) {
return false;
}
}
auto parentDeclTy = getMemberTypeForComparison(parentDecl, decl);
if (parentDeclTy->hasError())
return false;
auto canParentDeclTy = parentDeclTy->getReducedType(genericSig);
// If this is a constructor, let's compare only parameter types.
if (isa<ConstructorDecl>(decl)) {
// Within a protocol context, check for a failability mismatch.
if (isa<ProtocolDecl>(decl->getDeclContext())) {
if (cast<ConstructorDecl>(decl)->isFailable() !=
cast<ConstructorDecl>(parentDecl)->isFailable())
return false;
if (cast<ConstructorDecl>(decl)->isImplicitlyUnwrappedOptional() !=
cast<ConstructorDecl>(parentDecl)->isImplicitlyUnwrappedOptional())
return false;
}
auto fnType1 = declTy->castTo<AnyFunctionType>();
auto fnType2 = parentDeclTy->castTo<AnyFunctionType>();
return AnyFunctionType::equalParams(fnType1->getParams(),
fnType2->getParams());
// In a non-static protocol requirement, verify that the self access kind
// matches.
} else if (auto func = dyn_cast<FuncDecl>(decl)) {
// We only compare `isMutating()` rather than `getSelfAccessKind()`
// because we don't want to complain about `nonmutating` vs. `__consuming`
// conflicts at this time, especially since `__consuming` is not yet
// officially part of the language.
if (!func->isStatic() &&
func->isMutating() != cast<FuncDecl>(parentDecl)->isMutating())
return false;
// In abstract storage, verify that the accessor mutating-ness matches.
} else if (auto storage = dyn_cast<AbstractStorageDecl>(decl)) {
auto parentStorage = cast<AbstractStorageDecl>(parentDecl);
if (!areAccessorsOverrideCompatible(storage, parentStorage))
return false;
}
return canDeclTy == canParentDeclTy;
}
static bool isUnavailableInAllVersions(ValueDecl *decl) {
ASTContext &ctx = decl->getASTContext();
auto *attr = decl->getAttrs().getUnavailable(ctx);
if (!attr)
return false;
if (attr->isUnconditionallyUnavailable())
return true;
return attr->getVersionAvailability(ctx)
== AvailableVersionComparison::Unavailable;
}
/// Perform basic checking to determine whether a declaration can override a
/// declaration in a superclass.
static bool areOverrideCompatibleSimple(ValueDecl *decl,
ValueDecl *parentDecl) {
// If the number of argument labels does not match, these overrides cannot
// be compatible.
if (decl->getName().getArgumentNames().size() !=
parentDecl->getName().getArgumentNames().size())
return false;
// If the parent declaration is not in a class (or extension thereof) or
// a protocol, we cannot override it.
if (decl->getDeclContext()->getSelfClassDecl() &&
parentDecl->getDeclContext()->getSelfClassDecl()) {
// Okay: class override
} else if (isa<ProtocolDecl>(decl->getDeclContext()) &&
isa<ProtocolDecl>(parentDecl->getDeclContext())) {
// Okay: protocol override.
} else {
// Cannot be an override.
return false;
}
// Ignore declarations that are defined inside constrained extensions.
if (auto *ext = dyn_cast<ExtensionDecl>(parentDecl->getDeclContext()))
if (ext->isConstrainedExtension())
return false;
// The declarations must be of the same kind.
if (decl->getKind() != parentDecl->getKind())
return false;
// If the parent decl is unavailable, the subclass decl can shadow it, but it
// can't override it. To avoid complex version logic, we don't apply this to
// `obsoleted` members, only `unavailable` ones.
// FIXME: Refactor to allow that when the minimum version is always satisfied.
if (isUnavailableInAllVersions(parentDecl))
// If the subclass decl is trying to override, we'll diagnose it later.
if (!decl->getAttrs().hasAttribute<OverrideAttr>())
return false;
// Ignore invalid parent declarations.
// FIXME: Do we really need this?
if (parentDecl->isInvalid())
return false;
// If their staticness is different, they aren't compatible.
if (decl->isStatic() != parentDecl->isStatic())
return false;
// If their genericity is different, they aren't compatible.
if (auto genDecl = decl->getAsGenericContext()) {
auto genParentDecl = parentDecl->getAsGenericContext();
if (genDecl->isGeneric() != genParentDecl->isGeneric())
return false;
if (genDecl->isGeneric() &&
(genDecl->getGenericParams()->size() !=
genParentDecl->getGenericParams()->size()))
return false;
}
// Factory initializers cannot be overridden.
if (auto parentCtor = dyn_cast<ConstructorDecl>(parentDecl))
if (parentCtor->isFactoryInit())
return false;
return true;
}
static bool
diagnoseMismatchedOptionals(const ValueDecl *member,
const ParameterList *params, TypeLoc resultTL,
const ValueDecl *parentMember,
const ParameterList *parentParams, Type owningTy,
bool treatIUOResultAsError) {
auto &diags = member->getASTContext().Diags;
bool emittedError = false;
Type plainParentTy = owningTy->adjustSuperclassMemberDeclType(
parentMember, member, parentMember->getInterfaceType());
const auto *parentTy = plainParentTy->castTo<FunctionType>();
if (isa<AbstractFunctionDecl>(parentMember))
parentTy = parentTy->getResult()->castTo<FunctionType>();
// Check the parameter types.
auto checkParam = [&](const ParamDecl *decl, const ParamDecl *parentDecl) {
Type paramTy = decl->getType();
Type parentParamTy = parentDecl->getType();
auto *repr = decl->getTypeRepr();
if (!repr)
return;
bool paramIsOptional = (bool) paramTy->getOptionalObjectType();
bool parentIsOptional = (bool) parentParamTy->getOptionalObjectType();
if (paramIsOptional == parentIsOptional)
return;
if (!paramIsOptional) {
if (parentDecl->isImplicitlyUnwrappedOptional())
if (!treatIUOResultAsError)
return;
emittedError = true;
auto diag = diags.diagnose(decl->getStartLoc(),
diag::override_optional_mismatch,
member->getDescriptiveKind(),
isa<SubscriptDecl>(member),
parentParamTy, paramTy);
if (repr->isSimple()) {
diag.fixItInsertAfter(repr->getEndLoc(), "?");
} else {
diag.fixItInsert(repr->getStartLoc(), "(");
diag.fixItInsertAfter(repr->getEndLoc(), ")?");
}
return;
}
if (!decl->isImplicitlyUnwrappedOptional())
return;
// Allow silencing this warning using parens.
if (paramTy->hasParenSugar())
return;
diags
.diagnose(decl->getStartLoc(), diag::override_unnecessary_IUO,
member->getDescriptiveKind(), parentParamTy, paramTy)
.highlight(repr->getSourceRange());
if (auto iuoRepr = dyn_cast<ImplicitlyUnwrappedOptionalTypeRepr>(repr)) {
diags
.diagnose(iuoRepr->getExclamationLoc(),
diag::override_unnecessary_IUO_remove)
.fixItRemove(iuoRepr->getExclamationLoc());
}
diags.diagnose(repr->getStartLoc(), diag::override_unnecessary_IUO_silence)
.fixItInsert(repr->getStartLoc(), "(")
.fixItInsertAfter(repr->getEndLoc(), ")");
};
// FIXME: If we ever allow argument reordering, this is incorrect.
ArrayRef<ParamDecl *> sharedParams = params->getArray();
ArrayRef<ParamDecl *> sharedParentParams = parentParams->getArray();
assert(sharedParams.size() == sharedParentParams.size());
for_each(sharedParams, sharedParentParams, checkParam);
if (!resultTL.getTypeRepr())
return emittedError;
auto checkResult = [&](TypeLoc resultTL, Type parentResultTy) {
Type resultTy = resultTL.getType();
if (!resultTy || !parentResultTy)
return;
if (!resultTy->getOptionalObjectType())
return;
TypeRepr *TR = resultTL.getTypeRepr();
bool resultIsPlainOptional = true;
if (member->isImplicitlyUnwrappedOptional())
resultIsPlainOptional = false;
if (resultIsPlainOptional || treatIUOResultAsError) {
if (parentResultTy->getOptionalObjectType())
return;
emittedError = true;
auto diag = diags.diagnose(resultTL.getSourceRange().Start,
diag::override_optional_result_mismatch,
member->getDescriptiveKind(),
isa<SubscriptDecl>(member),
parentResultTy, resultTy);
if (auto optForm = dyn_cast<OptionalTypeRepr>(TR)) {
diag.fixItRemove(optForm->getQuestionLoc());
} else if (auto iuoForm =
dyn_cast<ImplicitlyUnwrappedOptionalTypeRepr>(TR)) {
diag.fixItRemove(iuoForm->getExclamationLoc());
}
return;
}
if (!parentResultTy->getOptionalObjectType())
return;
// Allow silencing this warning using parens.
if (resultTy->hasParenSugar())
return;
diags.diagnose(resultTL.getSourceRange().Start,
diag::override_unnecessary_result_IUO,
member->getDescriptiveKind(), parentResultTy, resultTy)
.highlight(resultTL.getSourceRange());
auto sugaredForm = dyn_cast<ImplicitlyUnwrappedOptionalTypeRepr>(TR);
if (sugaredForm) {
diags.diagnose(sugaredForm->getExclamationLoc(),
diag::override_unnecessary_IUO_use_strict)
.fixItReplace(sugaredForm->getExclamationLoc(), "?");
}
diags.diagnose(resultTL.getSourceRange().Start,
diag::override_unnecessary_IUO_silence)
.fixItInsert(resultTL.getSourceRange().Start, "(")
.fixItInsertAfter(resultTL.getSourceRange().End, ")");
};
checkResult(resultTL, parentTy->getResult());
return emittedError;
}
/// Record that the \c overriding declarations overrides the
/// \c overridden declaration.
///
/// \returns true if an error occurred.
static bool checkSingleOverride(ValueDecl *override, ValueDecl *base);
/// If the difference between the types of \p decl and \p base is something
/// we feel confident about fixing (even partially), emit a note with fix-its
/// attached. Otherwise, no note will be emitted.
///
/// \returns true iff a diagnostic was emitted.
static bool noteFixableMismatchedTypes(ValueDecl *decl, const ValueDecl *base) {
auto &ctx = decl->getASTContext();
auto &diags = ctx.Diags;
Type baseTy = base->getInterfaceType();
if (baseTy->hasError())
return false;
if (auto *baseInit = dyn_cast<ConstructorDecl>(base)) {
// Special-case initializers, whose "type" isn't useful besides the
// input arguments.
auto *fnType = baseTy->getAs<AnyFunctionType>();
baseTy = fnType->getResult();
Type argTy = FunctionType::composeTuple(
ctx, baseTy->getAs<AnyFunctionType>()->getParams(),
ParameterFlagHandling::IgnoreNonEmpty);
auto diagKind = diag::override_type_mismatch_with_fixits_init;
unsigned numArgs = baseInit->getParameters()->size();
return computeFixitsForOverriddenDeclaration(
decl, base, [&](bool HasNotes) -> Optional<InFlightDiagnostic> {
if (!HasNotes)
return None;
return diags.diagnose(decl, diagKind,
/*plural*/ std::min(numArgs, 2U), argTy);
});
} else {
if (isa<AbstractFunctionDecl>(base))
baseTy = baseTy->getAs<AnyFunctionType>()->getResult();
return computeFixitsForOverriddenDeclaration(
decl, base, [&](bool HasNotes) -> Optional<InFlightDiagnostic> {
if (!HasNotes)
return None;
return diags.diagnose(decl, diag::override_type_mismatch_with_fixits,
base->getDescriptiveKind(), baseTy);
});
}
return false;
}
namespace {
enum class OverrideCheckingAttempt {
PerfectMatch,
MismatchedSendability,
MismatchedOptional,
MismatchedTypes,
BaseName,
BaseNameWithMismatchedOptional,
Final
};
OverrideCheckingAttempt &operator++(OverrideCheckingAttempt &attempt) {
assert(attempt != OverrideCheckingAttempt::Final);
attempt = static_cast<OverrideCheckingAttempt>(1+static_cast<int>(attempt));
return attempt;
}
struct OverrideMatch {
ValueDecl *Decl;
bool IsExact;
};
}
static void diagnoseGeneralOverrideFailure(ValueDecl *decl,
ArrayRef<OverrideMatch> matches,
OverrideCheckingAttempt attempt) {
auto &diags = decl->getASTContext().Diags;
switch (attempt) {
case OverrideCheckingAttempt::PerfectMatch:
diags.diagnose(decl, diag::override_multiple_decls_base,
decl->getName());
break;
case OverrideCheckingAttempt::MismatchedSendability: {
SendableCheckContext fromContext(decl->getDeclContext(),
SendableCheck::Explicit);
auto baseDeclClass =
decl->getOverriddenDecl()->getDeclContext()->getSelfClassDecl();
diagnoseSendabilityErrorBasedOn(baseDeclClass, fromContext,
[&](DiagnosticBehavior limit) {
diags.diagnose(decl, diag::override_sendability_mismatch, decl->getName())
.limitBehavior(limit);
return false;
});
break;
}
case OverrideCheckingAttempt::BaseName:
diags.diagnose(decl, diag::override_multiple_decls_arg_mismatch,
decl->getName());
break;
case OverrideCheckingAttempt::MismatchedOptional:
case OverrideCheckingAttempt::MismatchedTypes:
case OverrideCheckingAttempt::BaseNameWithMismatchedOptional: {
auto isClassContext = decl->getDeclContext()->getSelfClassDecl() != nullptr;
auto diag = diag::method_does_not_override;
if (isa<ConstructorDecl>(decl))
diag = diag::initializer_does_not_override;
else if (isa<SubscriptDecl>(decl))
diag = diag::subscript_does_not_override;
else if (isa<VarDecl>(decl))
diag = diag::property_does_not_override;
diags.diagnose(decl, diag, isClassContext);
break;
}
case OverrideCheckingAttempt::Final:
llvm_unreachable("should have exited already");
}
for (auto match : matches) {
auto matchDecl = match.Decl;
if (attempt == OverrideCheckingAttempt::PerfectMatch) {
diags.diagnose(matchDecl, diag::overridden_here);
continue;
}
auto diag = diags.diagnose(matchDecl, diag::overridden_near_match_here,
matchDecl->getDescriptiveKind(),
matchDecl->getName());
if (attempt == OverrideCheckingAttempt::BaseName) {
fixDeclarationName(diag, decl, matchDecl->getName());
}
}
}
static bool parameterTypesMatch(const ValueDecl *derivedDecl,
const ValueDecl *baseDecl,
TypeMatchOptions matchMode) {
const ParameterList *derivedParams = nullptr;
const ParameterList *baseParams = nullptr;
if ((isa<AbstractFunctionDecl>(derivedDecl) &&
isa<AbstractFunctionDecl>(baseDecl)) ||
isa<SubscriptDecl>(baseDecl)) {
derivedParams = getParameterList(const_cast<ValueDecl *>(derivedDecl));
baseParams = getParameterList(const_cast<ValueDecl *>(baseDecl));
}
if (!derivedParams && !baseParams) {
return false;
}
if (baseParams->size() != derivedParams->size())
return false;
auto subs = SubstitutionMap::getOverrideSubstitutions(baseDecl, derivedDecl);
for (auto i : indices(baseParams->getArray())) {
auto *baseParam = baseParams->get(i);
auto *derivedParam = derivedParams->get(i);
// Make sure inout-ness and varargs match.
if (baseParam->isInOut() != derivedParam->isInOut() ||
baseParam->isVariadic() != derivedParam->isVariadic()) {
return false;
}
auto baseParamTy = baseParam->getInterfaceType();
baseParamTy = baseParamTy.subst(subs);
auto derivedParamTy = derivedParam->getInterfaceType();
if (baseParam->isInOut() || baseParam->isVariadic()) {
// Inout and vararg parameters must match exactly.
if (baseParamTy->isEqual(derivedParamTy))
continue;
} else {
// Attempt contravariant match.
if (baseParamTy->matchesParameter(derivedParamTy, matchMode))
continue;
// Try once more for a match, using the underlying type of an
// IUO if we're allowing that.
if (baseParam->isImplicitlyUnwrappedOptional() &&
matchMode.contains(TypeMatchFlags::AllowNonOptionalForIUOParam)) {
baseParamTy = baseParamTy->getOptionalObjectType();
if (baseParamTy->matches(derivedParamTy, matchMode))
continue;
}
}
// If there is no match, then we're done.
return false;
}
return true;
}
/// Returns true if `derivedDecl` has a `@differentiable` attribute that
/// overrides one from `baseDecl`.
static bool hasOverridingDifferentiableAttribute(ValueDecl *derivedDecl,
ValueDecl *baseDecl) {
ASTContext &ctx = derivedDecl->getASTContext();
auto &diags = ctx.Diags;
auto *derivedAFD = dyn_cast<AbstractFunctionDecl>(derivedDecl);
auto *baseAFD = dyn_cast<AbstractFunctionDecl>(baseDecl);
if (!derivedAFD || !baseAFD)
return false;
auto derivedDAs =
derivedAFD->getAttrs()
.getAttributes<DifferentiableAttr, /*AllowInvalid*/ true>();
auto baseDAs = baseAFD->getAttrs().getAttributes<DifferentiableAttr>();
// Make sure all the `@differentiable` attributes on `baseDecl` are
// also declared on `derivedDecl`.
bool diagnosed = false;
for (auto *baseDA : baseDAs) {
auto baseParameters = baseDA->getParameterIndices();
auto defined = false;
for (auto derivedDA : derivedDAs) {
auto derivedParameters = derivedDA->getParameterIndices();
// If base and derived parameter indices are both defined, check whether
// base parameter indices are a subset of derived parameter indices.
if (derivedParameters && baseParameters &&
baseParameters->isSubsetOf(derivedParameters)) {
defined = true;
break;
}
// Parameter indices may not be resolved because override matching happens
// before attribute checking for declaration type-checking.
// If parameter indices have not been resolved, avoid emitting diagnostic.
// Assume that attributes are valid.
if (!derivedParameters || !baseParameters) {
defined = true;
break;
}
}
if (defined)
continue;
diagnosed = true;
// Emit an error and fix-it showing the missing base declaration's
// `@differentiable` attribute.
// Omit printing `wrt:` clause if attribute's differentiability parameters
// match inferred differentiability parameters.
auto *inferredParameters =
TypeChecker::inferDifferentiabilityParameters(derivedAFD, nullptr);
bool omitWrtClause =
!baseParameters ||
baseParameters->getNumIndices() == inferredParameters->getNumIndices();
// Get `@differentiable` attribute description.
std::string baseDiffAttrString;
llvm::raw_string_ostream os(baseDiffAttrString);
baseDA->print(os, derivedDecl, omitWrtClause);
os.flush();
diags
.diagnose(derivedDecl,
diag::overriding_decl_missing_differentiable_attr,
baseDiffAttrString)
.fixItInsert(derivedDecl->getStartLoc(), baseDiffAttrString + ' ');
diags.diagnose(baseDecl, diag::overridden_here);
}
// If a diagnostic was produced, return false.
if (diagnosed)
return false;
// If there is no `@differentiable` attribute in `derivedDecl`, then
// overriding is not allowed.
auto *derivedDC = derivedDecl->getDeclContext();
auto *baseDC = baseDecl->getDeclContext();
if (derivedDC->getSelfClassDecl() && baseDC->getSelfClassDecl())
return false;
// Finally, go through all `@differentiable` attributes in `derivedDecl` and
// check if they subsume any of the `@differentiable` attributes in
// `baseDecl`.
for (auto derivedDA : derivedDAs) {
auto derivedParameters = derivedDA->getParameterIndices();
auto overrides = true;
for (auto baseDA : baseDAs) {
auto baseParameters = baseDA->getParameterIndices();
// If the parameter indices of `derivedDA` are a subset of those of
// `baseDA`, then `baseDA` subsumes `derivedDA` and the function is
// marked as overridden.
if (derivedParameters && baseParameters &&
derivedParameters->isSubsetOf(baseParameters)) {
overrides = false;
break;
}
}
if (overrides)
return true;
}
return false;
}
/// Returns true if the given declaration is for the `NSObject.hashValue`
/// property.
static bool isNSObjectHashValue(ValueDecl *baseDecl) {
ASTContext &ctx = baseDecl->getASTContext();
if (auto baseVar = dyn_cast<VarDecl>(baseDecl)) {
if (auto classDecl = baseVar->getDeclContext()->getSelfClassDecl()) {
return baseVar->getName() == ctx.Id_hashValue &&
classDecl->isNSObject();
}
}
return false;
}
/// Returns true if the given declaration is for the `NSObject.hash(into:)`
/// function.
static bool isNSObjectHashMethod(ValueDecl *baseDecl) {
auto baseFunc = dyn_cast<FuncDecl>(baseDecl);
if (!baseFunc)
return false;
if (auto classDecl = baseFunc->getDeclContext()->getSelfClassDecl()) {
ASTContext &ctx = baseDecl->getASTContext();
return baseFunc->getBaseName() == ctx.Id_hash && classDecl->isNSObject();
}
return false;
}
namespace {
/// Class that handles the checking of a particular declaration against
/// superclass entities that it could override.
class OverrideMatcher {
ASTContext &ctx;
ValueDecl *decl;
/// The set of declarations in which we'll look for overridden
/// methods.
SmallVector<NominalTypeDecl *, 2> superContexts;
/// Cached member lookup results.
SmallVector<ValueDecl *, 4> members;
/// The lookup name used to find \c members.
DeclName membersName;
/// The type of the declaration, cached here once it has been computed.
Type cachedDeclType;
public:
OverrideMatcher(ValueDecl *decl);
/// Returns true when it's possible to perform any override matching.
explicit operator bool() const {
return !superContexts.empty();
}
/// Whether this is an override of a class member.
bool isClassOverride() const {
return decl->getDeclContext()->getSelfClassDecl() != nullptr;
}
/// Whether this is an override of a protocol member.
bool isProtocolOverride() const {
return decl->getDeclContext()->getSelfProtocolDecl() != nullptr;
}
/// Match this declaration against potential members in the superclass,
/// using the heuristics appropriate for the given \c attempt.
SmallVector<OverrideMatch, 2> match(OverrideCheckingAttempt attempt);
/// Check each of the given matches, returning only those that
/// succeeded.
TinyPtrVector<ValueDecl *> checkPotentialOverrides(
SmallVectorImpl<OverrideMatch> &matches,
OverrideCheckingAttempt attempt);
private:
/// We have determined that we have an override of the given \c baseDecl.
///
/// Check that the override itself is valid.
bool checkOverride(ValueDecl *baseDecl,
OverrideCheckingAttempt attempt);
/// Retrieve the type of the declaration, to be used in comparisons.
Type getDeclComparisonType() {
if (!cachedDeclType) {
cachedDeclType = getMemberTypeForComparison(decl);
}
return cachedDeclType;
}
/// Adjust the interface of the given declaration, which is found in
/// a supertype of the given type.
Type getSuperMemberDeclType(ValueDecl *baseDecl) const {
auto selfType = decl->getDeclContext()->getSelfInterfaceType();
if (selfType->getClassOrBoundGenericClass()) {
selfType = selfType->getSuperclass();
assert(selfType && "No superclass type?");
}
return selfType->adjustSuperclassMemberDeclType(
baseDecl, decl, baseDecl->getInterfaceType());
}
};
}
OverrideMatcher::OverrideMatcher(ValueDecl *decl)
: ctx(decl->getASTContext()), decl(decl) {
// The final step for this constructor is to set up the superclass type,
// without which we will not perform an matching. Early exits therefore imply
// that there is no way we can match this declaration.
// FIXME: Break the cycle here.
if (decl->hasInterfaceType() && decl->isInvalid())
return;
auto *dc = decl->getDeclContext();
if (auto classDecl = dc->getSelfClassDecl()) {
if (auto superclassDecl = classDecl->getSuperclassDecl())
superContexts.push_back(superclassDecl);
} else if (auto protocol = dyn_cast<ProtocolDecl>(dc)) {
auto inheritedProtocols = protocol->getInheritedProtocols();
superContexts.insert(superContexts.end(), inheritedProtocols.begin(),
inheritedProtocols.end());
}
}
SmallVector<OverrideMatch, 2> OverrideMatcher::match(
OverrideCheckingAttempt attempt) {
// If there's no matching we can do, fail.
if (!*this) return { };
auto dc = decl->getDeclContext();
// Determine what name we should look for.
DeclName name;
switch (attempt) {
case OverrideCheckingAttempt::PerfectMatch:
case OverrideCheckingAttempt::MismatchedSendability:
case OverrideCheckingAttempt::MismatchedOptional:
case OverrideCheckingAttempt::MismatchedTypes:
name = decl->getName();
break;
case OverrideCheckingAttempt::BaseName:
case OverrideCheckingAttempt::BaseNameWithMismatchedOptional:
name = decl->getBaseName();
break;
case OverrideCheckingAttempt::Final:
// Give up.
return { };
}
// If we don't have members available yet, or we looked them up based on a
// different name, look them up now.
if (members.empty() || name != membersName) {
membersName = name;
members.clear();
// FIXME: This suggests we need to use TypeChecker's high-level lookup
// entrypoints. But first we need one that supports additive qualified
// lookup.
for (auto *ctx : superContexts) {
ctx->synthesizeSemanticMembersIfNeeded(membersName);
}
dc->lookupQualified(superContexts, DeclNameRef(membersName),
NL_QualifiedDefault, members);
}
// Check each member we found.
SmallVector<OverrideMatch, 2> matches;
for (auto parentDecl : members) {
// Check whether there are any obvious reasons why the two given
// declarations do not have an overriding relationship.
if (!areOverrideCompatibleSimple(decl, parentDecl))
continue;
// Check whether the derived declaration has a `@differentiable` attribute
// that overrides one from the parent declaration.
if (hasOverridingDifferentiableAttribute(decl, parentDecl))
continue;
auto parentMethod = dyn_cast<AbstractFunctionDecl>(parentDecl);
auto parentStorage = dyn_cast<AbstractStorageDecl>(parentDecl);
assert(parentMethod || parentStorage);
(void)parentMethod;
(void)parentStorage;
// If the generic requirements don't match, don't try anything else below,
// because it will compute an invalid interface type by applying malformed
// substitutions.
if (isClassOverride()) {
using Direction = ASTContext::OverrideGenericSignatureReqCheck;
if (decl->getAsGenericContext()) {
if (!ctx.overrideGenericSignatureReqsSatisfied(
parentDecl, decl, Direction::DerivedReqSatisfiedByBase)) {
continue;
}
}
}
// Check whether the types are identical.
Type declTy = getDeclComparisonType();
if (isOverrideBasedOnType(decl, declTy, parentDecl)) {
matches.push_back({parentDecl, true});
continue;
}
// If this is a property, we accept the match and then reject it below
// if the types don't line up, since you can't overload properties based
// on types.
if ((isa<VarDecl>(parentDecl) && isClassOverride()) ||
attempt == OverrideCheckingAttempt::MismatchedTypes) {
matches.push_back({parentDecl, false});
continue;
}
// For a protocol override, we require an exact match.
if (isProtocolOverride()) {
continue;
}
// Failing that, check for subtyping.
TypeMatchOptions matchMode = TypeMatchFlags::AllowOverride;
if (attempt == OverrideCheckingAttempt::MismatchedOptional ||
attempt == OverrideCheckingAttempt::BaseNameWithMismatchedOptional){
matchMode |= TypeMatchFlags::AllowTopLevelOptionalMismatch;
} else if (parentDecl->isObjC()) {
matchMode |= TypeMatchFlags::AllowNonOptionalForIUOParam;
matchMode |= TypeMatchFlags::IgnoreNonEscapingForOptionalFunctionParam;
}
if (attempt == OverrideCheckingAttempt::MismatchedSendability)
matchMode |= TypeMatchFlags::IgnoreFunctionSendability;
auto declFnTy = getDeclComparisonType()->getAs<AnyFunctionType>();
auto parentDeclTy = getMemberTypeForComparison(parentDecl, decl);