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swift-mirror/lib/AST/GenericSignatureBuilder.h
Slava Pestov d993e02c52 GSB: Disable conditional requirement inference in protocols 
If you have a pair of requirements T : P and T == G<U>, the conformance
G : P might be conditional, imposing arbitrary requirements on U.

In particular, these conditional requirements can mention arbitrary
protocols on the right hand side.

Introducing these conformance requirements during property map construction
is totally fine when building a top-level generic signature, but when
building a protocol requirement signature, things get a bit tricky.

Because of the design of the requirement machine, it is better if the set
of protocols appearing on the right hand side of conformance requirements
in another protocol (the "protocol dependencies") are known *before* we
start building the requirement signature, because we build the requirement
signatures of all protocols in a connected component of this graph
simultaneously.

Introducing conformance requirements to hithero-unseen protocols after
the graph of connected components had already been built would require
mutating it in a tricky way, and possibly merging connected components.

I didn't find any examples of protocols that rely on conditional
requirement inference in our test suite, or in the source compatibility
suite.

So for now, I'm going to try to disable this feature inside protocols.

Another argument in favor of not doing conditional requirement
inference in protocols is that we don't do the ordinary kind of requirement
inference there either. That is, the following is an error:

    protocol P {
      associatedtype T == Set<U>
      associatedtype U
    }

Unlike with an ordinary top-level generic signature, we don't infer
'U : Hashable' here. So arguably the current behavior of protocols inferring
these requirements in the case of a conditional conformance only is also
rather odd.
2021-12-08 16:34:27 -05:00

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//===--- GenericSignatureBuilder.h - Generic signature builder --*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Support for collecting a set of generic requirements, whether they are
// explicitly stated, inferred from a type signature, or implied by other
// requirements, and computing the canonicalized, minimized generic signature
// from those requirements.
//
//===----------------------------------------------------------------------===//
#ifndef SWIFT_GENERICSIGNATUREBUILDER_H
#define SWIFT_GENERICSIGNATUREBUILDER_H
#include "swift/AST/Decl.h"
#include "swift/AST/DiagnosticEngine.h"
#include "swift/AST/GenericParamList.h"
#include "swift/AST/GenericSignature.h"
#include "swift/AST/Identifier.h"
#include "swift/AST/ProtocolConformanceRef.h"
#include "swift/AST/Types.h"
#include "swift/AST/TypeLoc.h"
#include "swift/AST/TypeRepr.h"
#include "swift/Basic/Debug.h"
#include "swift/Basic/LLVM.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/ilist.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/TrailingObjects.h"
#include <functional>
#include <memory>
namespace swift {
class DeclContext;
class DependentMemberType;
class GenericParamList;
class GenericSignatureBuilder;
class GenericTypeParamType;
class ModuleDecl;
class Pattern;
class ProtocolConformance;
class Requirement;
class RequirementRepr;
class SILModule;
class SourceLoc;
class SubstitutionMap;
class Type;
class TypeRepr;
class ASTContext;
class DiagnosticEngine;
/// Determines how to resolve a dependent type to a potential archetype.
enum class ArchetypeResolutionKind {
/// Only create a potential archetype when it is well-formed (e.g., a nested
/// type should exist) and make sure we have complete information about
/// that potential archetype.
CompleteWellFormed,
/// Only create a new potential archetype to describe this dependent type
/// if it is already known.
AlreadyKnown,
/// Only create a potential archetype when it is well-formed (i.e., we know
/// that there is a nested type with that name), but (unlike \c AlreadyKnown)
/// allow the creation of a new potential archetype.
WellFormed,
};
/// Collects a set of requirements of generic parameters, both explicitly
/// stated and inferred, and determines the set of archetypes for each of
/// the generic parameters.
class GenericSignatureBuilder {
public:
/// Describes a potential archetype, which stands in for a generic parameter
/// type or some type derived from it.
class PotentialArchetype;
using UnresolvedType = llvm::PointerUnion<PotentialArchetype *, Type>;
class ResolvedType;
using UnresolvedRequirementRHS =
llvm::PointerUnion<Type, PotentialArchetype *, LayoutConstraint>;
using RequirementRHS =
llvm::PointerUnion<Type, ProtocolDecl *, LayoutConstraint>;
class RequirementSource;
class FloatingRequirementSource;
class DelayedRequirement;
template<typename T> struct Constraint;
/// Describes a concrete constraint on a potential archetype where, where the
/// other parameter is a concrete type.
typedef Constraint<Type> ConcreteConstraint;
/// Describes an equivalence class of potential archetypes.
struct EquivalenceClass : llvm::ilist_node<EquivalenceClass> {
/// The list of protocols to which this equivalence class conforms.
///
/// The keys form the (semantic) list of protocols to which this type
/// conforms. The values are the conformance constraints as written on
/// this equivalence class.
llvm::MapVector<ProtocolDecl *, std::vector<Constraint<ProtocolDecl *>>>
conformsTo;
/// Same-type constraints within this equivalence class.
std::vector<Constraint<Type>> sameTypeConstraints;
/// Concrete type to which this equivalence class is equal.
///
/// This is the semantic concrete type; the constraints as written
/// (or implied) are stored in \c concreteTypeConstraints;
Type concreteType;
/// The same-type-to-concrete constraints written within this
/// equivalence class.
std::vector<ConcreteConstraint> concreteTypeConstraints;
/// Superclass constraint, which requires that the type fulfilling the
/// requirements of this equivalence class to be the same as or a subtype
/// of this superclass.
Type superclass;
/// Superclass constraints written within this equivalence class.
std::vector<ConcreteConstraint> superclassConstraints;
/// \The layout constraint for this equivalence class.
LayoutConstraint layout;
/// Layout constraints written within this equivalence class.
std::vector<Constraint<LayoutConstraint>> layoutConstraints;
/// The members of the equivalence class.
///
/// This list of members is slightly ordered, in that the first
/// element always has a depth no greater than the depth of any other
/// member.
TinyPtrVector<PotentialArchetype *> members;
/// Describes a component within the graph of same-type constraints within
/// the equivalence class that is held together by derived constraints.
struct DerivedSameTypeComponent {
/// The type that acts as the anchor for this component.
Type type;
/// The (best) requirement source within the component that makes the
/// potential archetypes in this component equivalent to the concrete
/// type.
const RequirementSource *concreteTypeSource;
};
/// The set of connected components within this equivalence class, using
/// only the derived same-type constraints in the graph.
std::vector<DerivedSameTypeComponent> derivedSameTypeComponents;
/// Delayed requirements that could be resolved by a change to this
/// equivalence class.
std::vector<DelayedRequirement> delayedRequirements;
/// Whether we have detected recursion during the substitution of
/// the concrete type.
unsigned recursiveConcreteType : 1;
/// Whether we have an invalid concrete type.
unsigned invalidConcreteType : 1;
/// Whether we have detected recursion during the substitution of
/// the superclass type.
unsigned recursiveSuperclassType : 1;
/// Construct a new equivalence class containing only the given
/// potential archetype (which represents itself).
EquivalenceClass(PotentialArchetype *representative);
/// Note that this equivalence class has been modified.
void modified(GenericSignatureBuilder &builder);
EquivalenceClass(const EquivalenceClass &) = delete;
EquivalenceClass(EquivalenceClass &&) = delete;
EquivalenceClass &operator=(const EquivalenceClass &) = delete;
EquivalenceClass &operator=(EquivalenceClass &&) = delete;
/// Add a new member to this equivalence class.
void addMember(PotentialArchetype *pa);
/// Record the conformance of this equivalence class to the given
/// protocol as found via the given requirement source.
///
/// \returns true if this conformance is new to the equivalence class,
/// and false otherwise.
bool recordConformanceConstraint(GenericSignatureBuilder &builder,
ResolvedType type,
ProtocolDecl *proto,
const RequirementSource *source);
/// Find a source of the same-type constraint that maps a potential
/// archetype in this equivalence class to a concrete type along with
/// that concrete type as written.
Optional<ConcreteConstraint>
findAnyConcreteConstraintAsWritten(Type preferredType = Type()) const;
/// Find a source of the superclass constraint in this equivalence class
/// that has a type equivalence to \c superclass, along with that
/// superclass type as written.
Optional<ConcreteConstraint>
findAnySuperclassConstraintAsWritten(Type preferredType = Type()) const;
/// Determine whether conformance to the given protocol is satisfied by
/// a superclass requirement.
bool isConformanceSatisfiedBySuperclass(ProtocolDecl *proto) const;
/// Lookup a nested type with the given name within this equivalence
/// class.
TypeDecl *lookupNestedType(
GenericSignatureBuilder &builder,
Identifier name);
/// Retrieve the "anchor" type that canonically describes this equivalence
/// class, for use in the canonical type.
Type getAnchor(GenericSignatureBuilder &builder,
TypeArrayView<GenericTypeParamType> genericParams);
/// Dump a debugging representation of this equivalence class,
void dump(llvm::raw_ostream &out,
GenericSignatureBuilder *builder = nullptr) const;
SWIFT_DEBUG_DUMPER(dump(GenericSignatureBuilder *builder = nullptr));
/// Caches.
/// The cached archetype anchor.
struct {
/// The cached anchor itself.
Type anchor;
/// The generation at which the anchor was last computed.
unsigned lastGeneration;
} archetypeAnchorCache;
/// Describes a cached nested type.
struct CachedNestedType {
unsigned numConformancesPresent;
CanType superclassPresent;
CanType concreteTypePresent;
TypeDecl *type = nullptr;
};
/// Cached nested-type information, which contains the best declaration
/// for a given name.
llvm::SmallDenseMap<Identifier, CachedNestedType> nestedTypeNameCache;
};
friend class RequirementSource;
/// The result of introducing a new constraint.
enum class ConstraintResult {
/// The constraint was resolved and the relative potential archetypes
/// have been updated.
Resolved,
/// The constraint was written directly on a concrete type.
Concrete,
/// The constraint conflicted with existing constraints in some way;
/// the generic signature is ill-formed.
Conflicting,
/// The constraint could not be resolved immediately.
Unresolved,
};
/// Enum used to indicate how we should handle a constraint that cannot be
/// processed immediately for some reason.
enum class UnresolvedHandlingKind : char {
/// Generate a new, unresolved constraint and consider the constraint
/// "resolved" at this point.
GenerateConstraints = 0,
/// Generate an unresolved constraint but still return
/// \c ConstraintResult::Unresolved so the caller knows what happened.
GenerateUnresolved = 1,
};
/// The set of constraints that are invalid because the constraint
/// type isn't constrained to a protocol or a class
std::vector<Constraint<Type>> invalidIsaConstraints;
private:
class InferRequirementsWalker;
friend class InferRequirementsWalker;
friend class GenericSignature;
ASTContext &Context;
DiagnosticEngine &Diags;
struct Implementation;
std::unique_ptr<Implementation> Impl;
GenericSignatureBuilder(const GenericSignatureBuilder &) = delete;
GenericSignatureBuilder &operator=(const GenericSignatureBuilder &) = delete;
/// When a particular requirement cannot be resolved due to, e.g., a
/// currently-unresolvable or nested type, this routine should be
/// called to cope with the unresolved requirement.
///
/// \returns \c ConstraintResult::Resolved or ConstraintResult::Delayed,
/// as appropriate based on \c unresolvedHandling.
ConstraintResult handleUnresolvedRequirement(RequirementKind kind,
UnresolvedType lhs,
UnresolvedRequirementRHS rhs,
FloatingRequirementSource source,
EquivalenceClass *unresolvedEquivClass,
UnresolvedHandlingKind unresolvedHandling);
/// Add any conditional requirements from the given conformance.
void addConditionalRequirements(ProtocolConformanceRef conformance,
ModuleDecl *inferForModule);
/// Resolve the conformance of the given type to the given protocol when the
/// potential archetype is known to be equivalent to a concrete type.
///
/// \returns the requirement source for the resolved conformance, or nullptr
/// if the conformance could not be resolved.
const RequirementSource *resolveConcreteConformance(ResolvedType type,
ProtocolDecl *proto,
bool explicitConformance);
/// Retrieve the constraint source conformance for the superclass constraint
/// of the given potential archetype (if present) to the given protocol.
///
/// \param type The type whose superclass constraint is being queried.
///
/// \param proto The protocol to which we are establishing conformance.
const RequirementSource *resolveSuperConformance(ResolvedType type,
ProtocolDecl *proto,
bool explicitConformance);
public:
/// Add a new conformance requirement specifying that the given
/// type conforms to the given protocol.
ConstraintResult addConformanceRequirement(ResolvedType type,
ProtocolDecl *proto,
FloatingRequirementSource source);
/// "Expand" the conformance of the given \c pa to the protocol \c proto,
/// adding the requirements from its requirement signature, rooted at
/// the given requirement \c source.
ConstraintResult expandConformanceRequirement(
ResolvedType selfType,
ProtocolDecl *proto,
const RequirementSource *source,
bool onlySameTypeConstraints);
/// Add a new same-type requirement between two fully resolved types
/// (output of \c GenericSignatureBuilder::resolve).
///
/// If the types refer to two concrete types that are fundamentally
/// incompatible (e.g. \c Foo<Bar<T>> and \c Foo<Baz>), \c diagnoseMismatch is
/// called with the two types that don't match (\c Bar<T> and \c Baz for the
/// previous example).
ConstraintResult
addSameTypeRequirementDirect(
ResolvedType paOrT1, ResolvedType paOrT2,
FloatingRequirementSource Source,
llvm::function_ref<void(Type, Type)> diagnoseMismatch);
/// Add a new same-type requirement between two unresolved types.
///
/// The types are resolved with \c GenericSignatureBuilder::resolve, and must
/// not be incompatible concrete types.
ConstraintResult addSameTypeRequirement(
UnresolvedType paOrT1,
UnresolvedType paOrT2,
FloatingRequirementSource Source,
UnresolvedHandlingKind unresolvedHandling);
/// Add a new same-type requirement between two unresolved types.
///
/// The types are resolved with \c GenericSignatureBuilder::resolve. \c
/// diagnoseMismatch is called if the two types refer to incompatible concrete
/// types.
ConstraintResult
addSameTypeRequirement(UnresolvedType paOrT1, UnresolvedType paOrT2,
FloatingRequirementSource Source,
UnresolvedHandlingKind unresolvedHandling,
llvm::function_ref<void(Type, Type)> diagnoseMismatch);
/// Update the superclass for the equivalence class of \c T.
///
/// This assumes that the constraint has already been recorded.
///
/// \returns true if anything in the equivalence class changed, false
/// otherwise.
bool updateSuperclass(ResolvedType type,
Type superclass,
FloatingRequirementSource source);
/// Update the layout constraint for the equivalence class of \c T.
///
/// This assumes that the constraint has already been recorded.
///
/// \returns true if anything in the equivalence class changed, false
/// otherwise.
bool updateLayout(ResolvedType type,
LayoutConstraint layout);
private:
/// Add a new superclass requirement specifying that the given
/// potential archetype has the given type as an ancestor.
ConstraintResult addSuperclassRequirementDirect(
ResolvedType type,
Type superclass,
FloatingRequirementSource source);
/// Add a new type requirement specifying that the given
/// type conforms-to or is a superclass of the second type.
///
/// \param inferForModule Infer additional requirements from the types
/// relative to the given module.
ConstraintResult addTypeRequirement(UnresolvedType subject,
UnresolvedType constraint,
FloatingRequirementSource source,
UnresolvedHandlingKind unresolvedHandling,
ModuleDecl *inferForModule);
/// Note that we have added the nested type nestedPA
void addedNestedType(PotentialArchetype *nestedPA);
/// Add a rewrite rule from that makes the two types equivalent.
///
/// \returns true if a new rewrite rule was added, and false otherwise.
bool addSameTypeRewriteRule(CanType type1, CanType type2);
/// Add a same-type requirement between two types that are known to
/// refer to type parameters.
ConstraintResult addSameTypeRequirementBetweenTypeParameters(
ResolvedType type1, ResolvedType type2,
const RequirementSource *source);
/// Add a new conformance requirement specifying that the given
/// potential archetype is bound to a concrete type.
ConstraintResult addSameTypeRequirementToConcrete(ResolvedType type,
Type concrete,
const RequirementSource *Source);
/// Add a new same-type requirement specifying that the given two
/// types should be the same.
///
/// \param diagnoseMismatch Callback invoked when the types in the same-type
/// requirement mismatch.
ConstraintResult addSameTypeRequirementBetweenConcrete(
Type T1, Type T2, FloatingRequirementSource Source,
llvm::function_ref<void(Type, Type)> diagnoseMismatch);
/// Add a new layout requirement directly on the potential archetype.
///
/// \returns true if this requirement makes the set of requirements
/// inconsistent, in which case a diagnostic will have been issued.
ConstraintResult addLayoutRequirementDirect(ResolvedType type,
LayoutConstraint layout,
FloatingRequirementSource source);
/// Add a new layout requirement to the subject.
ConstraintResult addLayoutRequirement(
UnresolvedType subject,
LayoutConstraint layout,
FloatingRequirementSource source,
UnresolvedHandlingKind unresolvedHandling);
/// Add the requirements placed on the given type parameter
/// to the given potential archetype.
///
/// \param inferForModule Infer additional requirements from the types
/// relative to the given module.
ConstraintResult addInheritedRequirements(
TypeDecl *decl,
UnresolvedType type,
const RequirementSource *parentSource,
ModuleDecl *inferForModule);
public:
/// Construct a new generic signature builder.
explicit GenericSignatureBuilder(ASTContext &ctx,
bool requirementSignature=false);
GenericSignatureBuilder(GenericSignatureBuilder &&);
~GenericSignatureBuilder();
/// Retrieve the AST context.
ASTContext &getASTContext() const { return Context; }
/// Functor class suitable for use as a \c LookupConformanceFn to look up a
/// conformance in a generic signature builder.
class LookUpConformanceInBuilder {
GenericSignatureBuilder *builder;
public:
explicit LookUpConformanceInBuilder(GenericSignatureBuilder *builder)
: builder(builder) {}
ProtocolConformanceRef operator()(CanType dependentType,
Type conformingReplacementType,
ProtocolDecl *conformedProtocol) const;
};
/// Retrieve a function that can perform conformance lookup for this
/// builder.
LookUpConformanceInBuilder getLookupConformanceFn();
/// Lookup a protocol conformance in a module-agnostic manner.
ProtocolConformanceRef lookupConformance(Type conformingReplacementType,
ProtocolDecl *conformedProtocol);
/// Enumerate the requirements that describe the signature of this
/// generic signature builder.
void enumerateRequirements(
TypeArrayView<GenericTypeParamType> genericParams,
SmallVectorImpl<Requirement> &requirements);
/// Retrieve the generic parameters used to describe the generic
/// signature being built.
TypeArrayView<GenericTypeParamType> getGenericParams() const;
/// Add a new generic parameter for which there may be requirements.
void addGenericParameter(GenericTypeParamDecl *GenericParam);
/// Add the requirements placed on the given abstract type parameter
/// to the given potential archetype.
///
/// \returns true if an error occurred, false otherwise.
bool addGenericParameterRequirements(GenericTypeParamDecl *GenericParam);
/// Add a new generic parameter for which there may be requirements.
void addGenericParameter(GenericTypeParamType *GenericParam);
/// Add a new requirement.
///
/// \param inferForModule Infer additional requirements from the types
/// relative to the given module.
///
/// \returns true if this requirement makes the set of requirements
/// inconsistent, in which case a diagnostic will have been issued.
ConstraintResult addRequirement(const Requirement &req,
FloatingRequirementSource source,
ModuleDecl *inferForModule);
/// Add an already-checked requirement.
///
/// Adding an already-checked requirement cannot fail. This is used to
/// re-inject requirements from outer contexts.
///
/// \param inferForModule Infer additional requirements from the types
/// relative to the given module.
///
/// \returns true if this requirement makes the set of requirements
/// inconsistent, in which case a diagnostic will have been issued.
ConstraintResult addRequirement(const Requirement &req,
const RequirementRepr *reqRepr,
FloatingRequirementSource source,
const SubstitutionMap *subMap,
ModuleDecl *inferForModule);
/// Add all of a generic signature's parameters and requirements.
void addGenericSignature(GenericSignature sig);
/// Infer requirements from the given type, recursively.
///
/// This routine infers requirements from a type that occurs within the
/// signature of a generic function. For example, given:
///
/// \code
/// func f<K, V>(dict : Dictionary<K, V>) { ... }
/// \endcode
///
/// where \c Dictionary requires that its key type be \c Hashable,
/// the requirement \c K : Hashable is inferred from the parameter type,
/// because the type \c Dictionary<K,V> cannot be formed without it.
void inferRequirements(ModuleDecl &module,
Type type,
FloatingRequirementSource source);
/// Infer requirements from the given pattern, recursively.
///
/// This routine infers requirements from a type that occurs within the
/// signature of a generic function. For example, given:
///
/// \code
/// func f<K, V>(dict : Dictionary<K, V>) { ... }
/// \endcode
///
/// where \c Dictionary requires that its key type be \c Hashable,
/// the requirement \c K : Hashable is inferred from the parameter type,
/// because the type \c Dictionary<K,V> cannot be formed without it.
void inferRequirements(ModuleDecl &module, ParameterList *params);
GenericSignature rebuildSignatureWithoutRedundantRequirements(
bool allowConcreteGenericParams,
const ProtocolDecl *requirementSignatureSelfProto) &&;
bool hadAnyError() const;
/// Finalize the set of requirements and compute the generic
/// signature.
///
/// After this point, one cannot introduce new requirements, and the
/// generic signature builder no longer has valid state.
GenericSignature computeGenericSignature(
bool allowConcreteGenericParams = false,
const ProtocolDecl *requirementSignatureSelfProto = nullptr) &&;
private:
/// Finalize the set of requirements, performing any remaining checking
/// required before generating archetypes.
///
/// \param allowConcreteGenericParams If true, allow generic parameters to
/// be made concrete.
void finalize(TypeArrayView<GenericTypeParamType> genericParams,
bool allowConcreteGenericParams,
const ProtocolDecl *requirementSignatureSelfProto);
public:
/// Process any delayed requirements that can be handled now.
void processDelayedRequirements();
class ExplicitRequirement;
bool isRedundantExplicitRequirement(const ExplicitRequirement &req) const;
private:
using GetKindAndRHS = llvm::function_ref<std::pair<RequirementKind, RequirementRHS>()>;
void getBaseRequirements(
GetKindAndRHS getKindAndRHS,
const RequirementSource *source,
const ProtocolDecl *requirementSignatureSelfProto,
SmallVectorImpl<ExplicitRequirement> &result);
/// Determine if an explicit requirement can be derived from the
/// requirement given by \p otherSource and \p otherRHS, using the
/// knowledge of any existing redundant requirements discovered so far.
Optional<ExplicitRequirement>
isValidRequirementDerivationPath(
llvm::SmallDenseSet<ExplicitRequirement, 4> &visited,
RequirementKind otherKind,
const RequirementSource *otherSource,
RequirementRHS otherRHS,
const ProtocolDecl *requirementSignatureSelfProto);
/// Determine if the explicit requirement \p req can be derived from any
/// of the constraints in \p constraints, using the knowledge of any
/// existing redundant requirements discovered so far.
///
/// Use \p filter to screen out less-specific and conflicting constraints
/// if the requirement is a superclass, concrete type or layout requirement.
template<typename T, typename Filter>
void checkIfRequirementCanBeDerived(
const ExplicitRequirement &req,
const std::vector<Constraint<T>> &constraints,
const ProtocolDecl *requirementSignatureSelfProto,
Filter filter);
void computeRedundantRequirements(
const ProtocolDecl *requirementSignatureSelfProto);
void diagnoseProtocolRefinement(
const ProtocolDecl *requirementSignatureSelfProto);
void diagnoseRedundantRequirements(
bool onlyDiagnoseExplicitConformancesImpliedByConcrete=false) const;
void diagnoseConflictingConcreteTypeRequirements(
const ProtocolDecl *requirementSignatureSelfProto);
/// Describes the relationship between a given constraint and
/// the canonical constraint of the equivalence class.
enum class ConstraintRelation {
/// The constraint is unrelated.
///
/// This is a conservative result that can be used when, for example,
/// we have incomplete information to make a determination.
Unrelated,
/// The constraint is redundant and can be removed without affecting the
/// semantics.
Redundant,
/// The constraint conflicts, meaning that the signature is erroneous.
Conflicting,
};
/// Check a list of constraints, removing self-derived constraints
/// and diagnosing redundant constraints.
///
/// \param isSuitableRepresentative Determines whether the given constraint
/// is a suitable representative.
///
/// \param checkConstraint Checks the given constraint against the
/// canonical constraint to determine which diagnostics (if any) should be
/// emitted.
///
/// \returns the representative constraint.
template<typename T>
Constraint<T> checkConstraintList(
TypeArrayView<GenericTypeParamType> genericParams,
std::vector<Constraint<T>> &constraints,
RequirementKind kind,
llvm::function_ref<bool(const Constraint<T> &)>
isSuitableRepresentative,
llvm::function_ref<
ConstraintRelation(const Constraint<T>&)>
checkConstraint,
Optional<Diag<unsigned, Type, T, T>>
conflictingDiag,
Diag<Type, T> redundancyDiag,
Diag<unsigned, Type, T> otherNoteDiag);
/// Check the concrete type constraints within the equivalence
/// class of the given potential archetype.
void checkConcreteTypeConstraints(
TypeArrayView<GenericTypeParamType> genericParams,
EquivalenceClass *equivClass);
/// Check same-type constraints within the equivalence class of the
/// given potential archetype.
void checkSameTypeConstraints(
TypeArrayView<GenericTypeParamType> genericParams,
EquivalenceClass *equivClass);
public:
/// Try to resolve the equivalence class of the given type.
///
/// \param type The type to resolve.
///
/// \param resolutionKind How to perform the resolution.
///
/// \param wantExactPotentialArchetype Whether to return the precise
/// potential archetype described by the type (vs. just the equivalence
/// class and resolved type).
ResolvedType maybeResolveEquivalenceClass(
Type type,
ArchetypeResolutionKind resolutionKind,
bool wantExactPotentialArchetype);
/// Resolve the equivalence class for the given type parameter,
/// which provides information about that type.
///
/// The \c resolutionKind parameter describes how resolution should be
/// performed. If the potential archetype named by the given dependent type
/// already exists, it will be always returned. If it doesn't exist yet,
/// the \c resolutionKind dictates whether the potential archetype will
/// be created or whether null will be returned.
///
/// For any type that cannot refer to an equivalence class, this routine
/// returns null.
EquivalenceClass *resolveEquivalenceClass(
Type type,
ArchetypeResolutionKind resolutionKind);
/// Resolve the given type as far as this Builder knows how.
///
/// If successful, this returns either a non-typealias potential archetype
/// or a Type, if \c type is concrete.
/// If the type cannot be resolved, e.g., because it is "too" recursive
/// given the source, returns an unresolved result containing the equivalence
/// class that would need to change to resolve this type.
ResolvedType resolve(UnresolvedType type, FloatingRequirementSource source);
/// Determine whether the two given types are in the same equivalence class.
bool areInSameEquivalenceClass(Type type1, Type type2);
/// Simplify the given dependent type down to its canonical representation.
Type getCanonicalTypeParameter(Type type);
/// Replace any non-canonical dependent types in the given type with their
/// canonical representation. This is not a canonical type in the AST sense;
/// type sugar is preserved. The GenericSignature::getCanonicalTypeInContext()
/// method combines this with a subsequent getCanonicalType() call.
Type getCanonicalTypeInContext(Type type,
TypeArrayView<GenericTypeParamType> genericParams);
/// Retrieve the conformance access path used to extract the conformance of
/// interface \c type to the given \c protocol.
///
/// \param type The interface type whose conformance access path is to be
/// queried.
/// \param protocol A protocol to which \c type conforms.
///
/// \returns the conformance access path that starts at a requirement of
/// this generic signature and ends at the conformance that makes \c type
/// conform to \c protocol.
///
/// \seealso ConformanceAccessPath
ConformanceAccessPath getConformanceAccessPath(Type type,
ProtocolDecl *protocol,
GenericSignature sig);
/// Dump all of the requirements, both specified and inferred. It cannot be
/// statically proven that this doesn't modify the GSB.
SWIFT_DEBUG_HELPER(void dump());
/// Dump all of the requirements to the given output stream. It cannot be
/// statically proven that this doesn't modify the GSB.
void dump(llvm::raw_ostream &out);
};
/// Describes how a generic signature determines a requirement, from its origin
/// in some requirement written in the source, inferred through a path of
/// other implications (e.g., introduced by a particular protocol).
///
/// Requirement sources are uniqued within a generic signature builder.
class GenericSignatureBuilder::RequirementSource final
: public llvm::FoldingSetNode,
private llvm::TrailingObjects<RequirementSource, ProtocolDecl *,
SourceLoc> {
friend class FloatingRequirementSource;
friend class GenericSignature;
public:
enum Kind : uint8_t {
/// A requirement stated explicitly, e.g., in a where clause or type
/// parameter declaration.
///
/// Explicitly-stated requirement can be tied to a specific requirement
/// in a 'where' clause (which stores a \c RequirementRepr), a type in an
/// 'inheritance' clause (which stores a \c TypeRepr), or can be 'abstract',
/// , e.g., due to canonicalization, deserialization, or other
/// source-independent formulation.
///
/// This is a root requirement source.
Explicit,
/// A requirement inferred from part of the signature of a declaration,
/// e.g., the type of a generic function. For example:
///
/// func f<T>(_: Set<T>) { } // infers T: Hashable
///
/// This is a root requirement source, which can be described by a
/// \c TypeRepr.
Inferred,
/// A requirement for the creation of the requirement signature of a
/// protocol.
///
/// This is a root requirement source, which is described by the protocol
/// whose requirement signature is being computed.
RequirementSignatureSelf,
/// The requirement came from two nested types of the equivalent types whose
/// names match.
///
/// This is a root requirement source.
NestedTypeNameMatch,
/// The requirement is a protocol requirement.
///
/// This stores the protocol that introduced the requirement as well as the
/// dependent type (relative to that protocol) to which the conformance
/// appertains.
ProtocolRequirement,
/// The requirement is a protocol requirement that is inferred from
/// some part of the protocol definition.
///
/// This stores the protocol that introduced the requirement as well as the
/// dependent type (relative to that protocol) to which the conformance
/// appertains.
InferredProtocolRequirement,
/// A requirement that was resolved via a superclass requirement.
///
/// This stores the \c ProtocolConformanceRef used to resolve the
/// requirement.
Superclass,
/// A requirement that was resolved for a nested type via its parent
/// type.
Parent,
/// A requirement that was resolved for a nested type via a same-type-to-
/// concrete constraint.
///
/// This stores the \c ProtocolConformance* used to resolve the
/// requirement.
Concrete,
/// A requirement that was resolved based on a layout requirement
/// imposed by a superclass constraint.
///
/// This stores the \c LayoutConstraint used to resolve the
/// requirement.
Layout,
/// A requirement that was provided for another type in the
/// same equivalence class, but which we want to "re-root" on a new
/// type.
EquivalentType,
};
/// The kind of requirement source.
const Kind kind;
private:
/// The kind of storage we have.
enum class StorageKind : uint8_t {
None,
StoredType,
ProtocolConformance,
AssociatedTypeDecl,
};
/// The kind of storage we have.
const StorageKind storageKind;
/// Whether there is a trailing written requirement location.
const bool hasTrailingSourceLoc;
private:
/// The actual storage, described by \c storageKind.
union {
/// The type to which a requirement applies.
TypeBase *type;
/// A protocol conformance used to satisfy the requirement.
void *conformance;
/// An associated type to which a requirement is being applied.
AssociatedTypeDecl *assocType;
} storage;
friend TrailingObjects;
/// The trailing protocol declaration, if there is one.
size_t numTrailingObjects(OverloadToken<ProtocolDecl *>) const {
switch (kind) {
case RequirementSignatureSelf:
case ProtocolRequirement:
case InferredProtocolRequirement:
return 1;
case Explicit:
case Inferred:
case NestedTypeNameMatch:
case Superclass:
case Parent:
case Concrete:
case Layout:
case EquivalentType:
return 0;
}
llvm_unreachable("Unhandled RequirementSourceKind in switch.");
}
/// The trailing written requirement location, if there is one.
size_t numTrailingObjects(OverloadToken<SourceLoc>) const {
return hasTrailingSourceLoc ? 1 : 0;
}
#ifndef NDEBUG
/// Determines whether we have been provided with an acceptable storage kind
/// for the given requirement source kind.
static bool isAcceptableStorageKind(Kind kind, StorageKind storageKind);
#endif
/// Retrieve the opaque storage as a single pointer, for use in uniquing.
const void *getOpaqueStorage1() const;
/// Retrieve the second opaque storage as a single pointer, for use in
/// uniquing.
const void *getOpaqueStorage2() const;
/// Retrieve the third opaque storage as a single pointer, for use in
/// uniquing.
const void *getOpaqueStorage3() const;
/// Whether this kind of requirement source is a root.
static bool isRootKind(Kind kind) {
switch (kind) {
case Explicit:
case Inferred:
case RequirementSignatureSelf:
case NestedTypeNameMatch:
return true;
case ProtocolRequirement:
case InferredProtocolRequirement:
case Superclass:
case Parent:
case Concrete:
case Layout:
case EquivalentType:
return false;
}
llvm_unreachable("Unhandled RequirementSourceKind in switch.");
}
public:
/// The "parent" of this requirement source.
///
/// The chain of parent requirement sources will eventually terminate in a
/// requirement source with one of the "root" kinds.
const RequirementSource * const parent;
RequirementSource(Kind kind, Type rootType,
ProtocolDecl *protocol,
SourceLoc writtenReqLoc)
: kind(kind), storageKind(StorageKind::StoredType),
hasTrailingSourceLoc(writtenReqLoc.isValid()),
parent(nullptr) {
assert(isAcceptableStorageKind(kind, storageKind) &&
"RequirementSource kind/storageKind mismatch");
storage.type = rootType.getPointer();
if (kind == RequirementSignatureSelf)
getTrailingObjects<ProtocolDecl *>()[0] = protocol;
if (hasTrailingSourceLoc)
getTrailingObjects<SourceLoc>()[0] = writtenReqLoc;
}
RequirementSource(Kind kind, const RequirementSource *parent,
Type type, ProtocolDecl *protocol,
SourceLoc writtenReqLoc)
: kind(kind), storageKind(StorageKind::StoredType),
hasTrailingSourceLoc(writtenReqLoc.isValid()),
parent(parent) {
assert((static_cast<bool>(parent) != isRootKind(kind)) &&
"Root RequirementSource should not have parent (or vice versa)");
assert(isAcceptableStorageKind(kind, storageKind) &&
"RequirementSource kind/storageKind mismatch");
storage.type = type.getPointer();
if (isProtocolRequirement())
getTrailingObjects<ProtocolDecl *>()[0] = protocol;
if (hasTrailingSourceLoc)
getTrailingObjects<SourceLoc>()[0] = writtenReqLoc;
}
RequirementSource(Kind kind, const RequirementSource *parent,
ProtocolConformanceRef conformance)
: kind(kind), storageKind(StorageKind::ProtocolConformance),
hasTrailingSourceLoc(false), parent(parent) {
assert((static_cast<bool>(parent) != isRootKind(kind)) &&
"Root RequirementSource should not have parent (or vice versa)");
assert(isAcceptableStorageKind(kind, storageKind) &&
"RequirementSource kind/storageKind mismatch");
storage.conformance = conformance.getOpaqueValue();
}
RequirementSource(Kind kind, const RequirementSource *parent,
AssociatedTypeDecl *assocType)
: kind(kind), storageKind(StorageKind::AssociatedTypeDecl),
hasTrailingSourceLoc(false), parent(parent) {
assert((static_cast<bool>(parent) != isRootKind(kind)) &&
"Root RequirementSource should not have parent (or vice versa)");
assert(isAcceptableStorageKind(kind, storageKind) &&
"RequirementSource kind/storageKind mismatch");
storage.assocType = assocType;
}
RequirementSource(Kind kind, const RequirementSource *parent)
: kind(kind), storageKind(StorageKind::None),
hasTrailingSourceLoc(false), parent(parent) {
assert((static_cast<bool>(parent) != isRootKind(kind)) &&
"Root RequirementSource should not have parent (or vice versa)");
assert(isAcceptableStorageKind(kind, storageKind) &&
"RequirementSource kind/storageKind mismatch");
}
RequirementSource(Kind kind, const RequirementSource *parent,
Type newType)
: kind(kind), storageKind(StorageKind::StoredType),
hasTrailingSourceLoc(false), parent(parent) {
assert((static_cast<bool>(parent) != isRootKind(kind)) &&
"Root RequirementSource should not have parent (or vice versa)");
assert(isAcceptableStorageKind(kind, storageKind) &&
"RequirementSource kind/storageKind mismatch");
storage.type = newType.getPointer();
}
public:
/// Retrieve an abstract requirement source.
static const RequirementSource *forAbstract(GenericSignatureBuilder &builder,
Type rootType);
/// Retrieve a requirement source representing an explicit requirement
/// stated in an 'inheritance' or 'where' clause.
static const RequirementSource *forExplicit(GenericSignatureBuilder &builder,
Type rootType,
SourceLoc writtenLoc);
/// Retrieve a requirement source representing a requirement that is
/// inferred from some part of a generic declaration's signature, e.g., the
/// parameter or result type of a generic function.
static const RequirementSource *forInferred(GenericSignatureBuilder &builder,
Type rootType,
SourceLoc writtenLoc);
/// Retrieve a requirement source representing the requirement signature
/// computation for a protocol.
static const RequirementSource *forRequirementSignature(
GenericSignatureBuilder &builder,
Type rootType,
ProtocolDecl *protocol);
/// Retrieve a requirement source for nested type name matches.
static const RequirementSource *forNestedTypeNameMatch(
GenericSignatureBuilder &builder,
Type rootType);
private:
/// A requirement source that describes that a requirement comes from a
/// requirement of the given protocol described by the parent.
const RequirementSource *viaProtocolRequirement(
GenericSignatureBuilder &builder,
Type dependentType,
ProtocolDecl *protocol,
bool inferred,
SourceLoc writtenLoc =
SourceLoc()) const;
public:
/// A requirement source that describes a conformance requirement resolved
/// via a superclass requirement.
const RequirementSource *viaSuperclass(
GenericSignatureBuilder &builder,
ProtocolConformanceRef conformance) const;
/// A requirement source that describes a conformance requirement resolved
/// via a concrete type requirement with a conforming nominal type.
const RequirementSource *viaConcrete(
GenericSignatureBuilder &builder,
ProtocolConformanceRef conformance) const;
/// A requirement source that describes that a requirement that is resolved
/// via a concrete type requirement with an existential self-conforming type.
const RequirementSource *viaConcrete(
GenericSignatureBuilder &builder,
Type existentialType) const;
/// A constraint source that describes a layout constraint that was implied
/// by a superclass requirement.
const RequirementSource *viaLayout(GenericSignatureBuilder &builder,
Type superclass) const;
/// A constraint source that describes that a constraint that is resolved
/// for a nested type via a constraint on its parent.
///
/// \param assocType the associated type that
const RequirementSource *viaParent(GenericSignatureBuilder &builder,
AssociatedTypeDecl *assocType) const;
/// A constraint source that describes a constraint that is structurally
/// derived from another constraint but does not require further information.
const RequirementSource *viaEquivalentType(GenericSignatureBuilder &builder,
Type newType) const;
/// Form a new requirement source without the subpath [start, end).
///
/// Removes a redundant sub-path \c [start, end) from the requirement source,
/// creating a new requirement source comprised on \c start followed by
/// everything that follows \c end.
/// It is the caller's responsibility to ensure that the path up to \c start
/// and the path through \c start to \c end produce the same thing.
const RequirementSource *withoutRedundantSubpath(
GenericSignatureBuilder &builder,
const RequirementSource *start,
const RequirementSource *end) const;
/// Retrieve the root requirement source.
const RequirementSource *getRoot() const;
/// Retrieve the type at the root.
Type getRootType() const;
/// Retrieve the type to which this source refers.
Type getAffectedType() const;
/// Visit each of the types along the path, from the root type
/// each type named via (e.g.) a protocol requirement or parent source.
///
/// \param visitor Called with each type along the path along
/// with the requirement source that is being applied on top of that
/// type. Can return \c true to halt the search.
///
/// \returns a null type if any call to \c visitor returned true. Otherwise,
/// returns the type to which the entire source refers.
Type visitPotentialArchetypesAlongPath(
llvm::function_ref<bool(Type,
const RequirementSource *)> visitor) const;
/// Whether this source is a requirement in a protocol.
bool isProtocolRequirement() const {
return kind == ProtocolRequirement || kind == InferredProtocolRequirement;
}
/// Whether the requirement is inferred or derived from an inferred
/// requirement.
bool isInferredRequirement() const;
/// Classify the kind of this source for diagnostic purposes.
unsigned classifyDiagKind() const;
/// Whether the requirement can be derived from something in its path.
///
/// Derived requirements will not be recorded in a minimized generic
/// signature, because the information can be re-derived by following the
/// path.
bool isDerivedRequirement() const;
/// Same as above, but we consider RequirementSignatureSelf to not be
/// derived.
bool isDerivedNonRootRequirement() const;
/// Whether we should diagnose a redundant constraint based on this
/// requirement source.
///
/// \param primary Whether this is the "primary" requirement source, on which
/// a "redundant constraint" warning would be emitted vs. the requirement
/// source that would be used for the accompanying note.
bool shouldDiagnoseRedundancy(bool primary) const;
/// Determine whether the given derived requirement \c source, when rooted at
/// the potential archetype \c pa, is actually derived from the same
/// requirement. Such "self-derived" requirements do not make the original
/// requirement redundant, because without said original requirement, the
/// derived requirement ceases to hold.
bool isSelfDerivedSource(GenericSignatureBuilder &builder,
Type type) const;
/// For a requirement source that describes the requirement \c type:proto,
/// retrieve the minimal subpath of this requirement source that will
/// compute that requirement.
///
/// When the result is different from (i.e., a subpath of) \c this or is
/// nullptr (indicating an embedded, distinct self-derived subpath), the
/// conformance requirement is considered to be "self-derived".
const RequirementSource *getMinimalConformanceSource(
GenericSignatureBuilder &builder,
Type type,
ProtocolDecl *proto) const;
/// Retrieve a source location that corresponds to the requirement.
SourceLoc getLoc() const;
/// Compare two requirement sources to determine which has the more
/// optimal path.
///
/// \returns -1 if the \c this is better, 1 if the \c other is better, and 0
/// if they are equivalent in length.
int compare(const RequirementSource *other) const;
/// Retrieve the written requirement location, if there is one.
SourceLoc getSourceLoc() const {
if (!hasTrailingSourceLoc) return SourceLoc();
return getTrailingObjects<SourceLoc>()[0];
}
/// Retrieve the type stored in this requirement.
Type getStoredType() const;
/// Retrieve the protocol for this requirement, if there is one.
ProtocolDecl *getProtocolDecl() const;
/// Retrieve the protocol conformance for this requirement, if there is one.
ProtocolConformanceRef getProtocolConformance() const {
assert(storageKind == StorageKind::ProtocolConformance);
return ProtocolConformanceRef::getFromOpaqueValue(storage.conformance);
}
/// Retrieve the associated type declaration for this requirement, if there
/// is one.
AssociatedTypeDecl *getAssociatedType() const {
if (storageKind != StorageKind::AssociatedTypeDecl) return nullptr;
return storage.assocType;
}
/// Profiling support for \c FoldingSet.
void Profile(llvm::FoldingSetNodeID &ID) {
Profile(ID, kind, parent, getOpaqueStorage1(), getOpaqueStorage2(),
getOpaqueStorage3());
}
/// Profiling support for \c FoldingSet.
static void Profile(llvm::FoldingSetNodeID &ID, Kind kind,
const RequirementSource *parent, const void *storage1,
const void *storage2, const void *storage3) {
ID.AddInteger(kind);
ID.AddPointer(parent);
ID.AddPointer(storage1);
ID.AddPointer(storage2);
ID.AddPointer(storage3);
}
SWIFT_DEBUG_DUMP;
SWIFT_DEBUG_DUMPER(print());
/// Dump the requirement source.
void dump(llvm::raw_ostream &out, SourceManager *SrcMgr,
unsigned indent) const;
/// Print the requirement source (shorter form)
void print(llvm::raw_ostream &out, SourceManager *SrcMgr) const;
};
/// A requirement source that potentially lacks a root \c PotentialArchetype.
/// The root will be supplied as soon as the appropriate dependent type is
/// resolved.
class GenericSignatureBuilder::FloatingRequirementSource {
enum Kind : uint8_t {
/// A fully-resolved requirement source, which does not need a root.
Resolved,
/// An explicit requirement in a generic signature.
Explicit,
/// A requirement inferred from a concrete type application in a
/// generic signature.
Inferred,
/// An explicit requirement written inside a protocol.
ProtocolRequirement,
/// A requirement inferred from a concrete type application inside a
/// protocol.
InferredProtocolRequirement,
/// A requirement source for a nested-type-name match introduced by
/// the given source.
NestedTypeNameMatch,
} kind;
const RequirementSource *source;
SourceLoc loc;
// Additional storage for an abstract protocol requirement.
union {
ProtocolDecl *protocol = nullptr;
Identifier nestedName;
};
FloatingRequirementSource(Kind kind, const RequirementSource *source)
: kind(kind), source(source) { }
public:
/// Implicit conversion from a resolved requirement source.
FloatingRequirementSource(const RequirementSource *source)
: FloatingRequirementSource(Resolved, source) { }
static FloatingRequirementSource forAbstract() {
return { Explicit, nullptr };
}
static FloatingRequirementSource forExplicit(SourceLoc loc) {
FloatingRequirementSource result{ Explicit, nullptr };
result.loc = loc;
return result;
}
static FloatingRequirementSource forInferred(SourceLoc loc) {
FloatingRequirementSource result{ Inferred, nullptr };
result.loc = loc;
return result;
}
static FloatingRequirementSource viaProtocolRequirement(
const RequirementSource *base,
ProtocolDecl *inProtocol,
bool inferred) {
auto kind = (inferred ? InferredProtocolRequirement : ProtocolRequirement);
FloatingRequirementSource result{ kind, base };
result.protocol = inProtocol;
return result;
}
static FloatingRequirementSource viaProtocolRequirement(
const RequirementSource *base,
ProtocolDecl *inProtocol,
SourceLoc written,
bool inferred) {
auto kind = (inferred ? InferredProtocolRequirement : ProtocolRequirement);
FloatingRequirementSource result{ kind, base };
result.protocol = inProtocol;
result.loc = written;
return result;
}
static FloatingRequirementSource forNestedTypeNameMatch(
Identifier nestedName) {
FloatingRequirementSource result{ NestedTypeNameMatch, nullptr };
result.nestedName = nestedName;
return result;
};
/// Retrieve the complete requirement source rooted at the given type.
const RequirementSource *getSource(GenericSignatureBuilder &builder,
ResolvedType type) const;
/// Retrieve the source location for this requirement.
SourceLoc getLoc() const;
/// Whether this is an explicitly-stated requirement.
bool isExplicit() const;
/// Whether this is a derived requirement.
bool isDerived() const;
/// Whether this is a top-level requirement written in source.
/// FIXME: This is a hack because expandConformanceRequirement()
/// is too eager; we should remove this once we fix it properly.
bool isTopLevel() const { return kind == Explicit; }
/// Return the "inferred" version of this source, if it isn't already
/// inferred.
FloatingRequirementSource asInferred(const TypeRepr *typeRepr) const;
/// Whether this requirement source is recursive.
bool isRecursive(GenericSignatureBuilder &builder) const;
};
/// Describes a specific constraint on a particular type.
template<typename T>
struct GenericSignatureBuilder::Constraint {
/// The specific subject of the constraint.
///
/// This may either be a (resolved) dependent type or the potential
/// archetype that it resolves to.
mutable UnresolvedType subject;
/// A value used to describe the constraint.
T value;
/// The requirement source used to derive this constraint.
const RequirementSource *source;
/// Retrieve the dependent type describing the subject of the constraint.
Type getSubjectDependentType(
TypeArrayView<GenericTypeParamType> genericParams) const;
/// Determine whether the subject is equivalence to the given type.
bool isSubjectEqualTo(Type type) const;
/// Determine whether the subject is equivalence to the given type.
bool isSubjectEqualTo(const PotentialArchetype *pa) const;
/// Determine whether this constraint has the same subject as the
/// given constraint.
bool hasSameSubjectAs(const Constraint<T> &other) const;
};
class GenericSignatureBuilder::PotentialArchetype {
/// The parent of this potential archetype, for a nested type.
PotentialArchetype* parent;
/// The representative of the equivalence class of potential archetypes
/// to which this potential archetype belongs, or (for the representative)
/// the equivalence class itself.
mutable llvm::PointerUnion<PotentialArchetype *, EquivalenceClass *>
representativeOrEquivClass;
mutable CanType depType;
/// A stored nested type.
struct StoredNestedType {
/// The potential archetypes describing this nested type, all of which
/// are equivalent.
llvm::TinyPtrVector<PotentialArchetype *> archetypes;
typedef llvm::TinyPtrVector<PotentialArchetype *>::iterator iterator;
iterator begin() { return archetypes.begin(); }
iterator end() { return archetypes.end(); }
typedef llvm::TinyPtrVector<PotentialArchetype *>::const_iterator
const_iterator;
const_iterator begin() const { return archetypes.begin(); }
const_iterator end() const { return archetypes.end(); }
PotentialArchetype *front() const { return archetypes.front(); }
PotentialArchetype *back() const { return archetypes.back(); }
unsigned size() const { return archetypes.size(); }
bool empty() const { return archetypes.empty(); }
void push_back(PotentialArchetype *pa) {
archetypes.push_back(pa);
}
};
/// The set of nested types of this archetype.
///
/// For a given nested type name, there may be multiple potential archetypes
/// corresponding to different associated types (from different protocols)
/// that share a name.
llvm::MapVector<Identifier, StoredNestedType> NestedTypes;
/// Construct a new potential archetype for a concrete declaration.
PotentialArchetype(PotentialArchetype *parent, AssociatedTypeDecl *assocType);
/// Construct a new potential archetype for a generic parameter.
explicit PotentialArchetype(GenericTypeParamType *genericParam);
public:
/// Retrieve the representative for this archetype, performing
/// path compression on the way.
PotentialArchetype *getRepresentative() const;
friend class GenericSignatureBuilder;
friend class GenericSignature;
public:
~PotentialArchetype();
/// Retrieve the debug name of this potential archetype.
std::string getDebugName() const;
/// Retrieve the parent of this potential archetype, which will be non-null
/// when this potential archetype is an associated type.
PotentialArchetype *getParent() const {
return parent;
}
/// Retrieve the type declaration to which this nested type was resolved.
AssociatedTypeDecl *getResolvedType() const {
return cast<DependentMemberType>(depType)->getAssocType();
}
/// Determine whether this is a generic parameter.
bool isGenericParam() const {
return parent == nullptr;
}
/// Retrieve the set of nested types.
const llvm::MapVector<Identifier, StoredNestedType> &getNestedTypes() const {
return NestedTypes;
}
/// Determine the nesting depth of this potential archetype, e.g.,
/// the number of associated type references.
unsigned getNestingDepth() const;
/// Determine whether two potential archetypes are in the same equivalence
/// class.
bool isInSameEquivalenceClassAs(const PotentialArchetype *other) const {
return getRepresentative() == other->getRepresentative();
}
/// Retrieve the equivalence class, if it's already present.
///
/// Otherwise, return null.
EquivalenceClass *getEquivalenceClassIfPresent() const {
return getRepresentative()->representativeOrEquivClass
.dyn_cast<EquivalenceClass *>();
}
/// Retrieve or create the equivalence class.
EquivalenceClass *getOrCreateEquivalenceClass(
GenericSignatureBuilder &builder) const;
/// Retrieve the equivalence class containing this potential archetype.
TinyPtrVector<PotentialArchetype *> getEquivalenceClassMembers() const {
if (auto equivClass = getEquivalenceClassIfPresent())
return equivClass->members;
return TinyPtrVector<PotentialArchetype *>(
const_cast<PotentialArchetype *>(this));
}
/// Update the named nested type when we know this type conforms to the given
/// protocol.
///
/// \returns the potential archetype associated with the associated
/// type of the given protocol, unless the \c kind implies that
/// a potential archetype should not be created if it's missing.
PotentialArchetype *
getOrCreateNestedType(GenericSignatureBuilder &builder,
AssociatedTypeDecl *assocType,
ArchetypeResolutionKind kind);
/// Retrieve the dependent type that describes this potential
/// archetype.
CanType getDependentType() const {
return depType;
}
/// Retrieve the dependent type that describes this potential
/// archetype.
///
/// \param genericParams The set of generic parameters to use in the resulting
/// dependent type.
Type getDependentType(TypeArrayView<GenericTypeParamType> genericParams) const;
/// True if the potential archetype has been bound by a concrete type
/// constraint.
bool isConcreteType() const {
if (auto equivClass = getEquivalenceClassIfPresent())
return static_cast<bool>(equivClass->concreteType);
return false;
}
SWIFT_DEBUG_DUMP;
void dump(llvm::raw_ostream &Out, SourceManager *SrcMgr,
unsigned Indent) const;
friend class GenericSignatureBuilder;
};
template <typename C>
bool GenericSignatureBuilder::Constraint<C>::isSubjectEqualTo(Type T) const {
return getSubjectDependentType({ })->isEqual(T);
}
template <typename T>
bool GenericSignatureBuilder::Constraint<T>::isSubjectEqualTo(const GenericSignatureBuilder::PotentialArchetype *PA) const {
return getSubjectDependentType({ })->isEqual(PA->getDependentType({ }));
}
template <typename T>
bool GenericSignatureBuilder::Constraint<T>::hasSameSubjectAs(const GenericSignatureBuilder::Constraint<T> &C) const {
return getSubjectDependentType({ })->isEqual(C.getSubjectDependentType({ }));
}
/// Describes a requirement whose processing has been delayed for some reason.
class GenericSignatureBuilder::DelayedRequirement {
public:
enum Kind {
/// A type requirement, which may be a conformance or a superclass
/// requirement.
Type,
/// A layout requirement.
Layout,
/// A same-type requirement.
SameType,
};
Kind kind;
UnresolvedType lhs;
UnresolvedRequirementRHS rhs;
FloatingRequirementSource source;
/// Dump a debugging representation of this delayed requirement class.
void dump(llvm::raw_ostream &out) const;
SWIFT_DEBUG_DUMP;
};
/// Whether the given constraint result signals an error.
inline bool isErrorResult(GenericSignatureBuilder::ConstraintResult result) {
switch (result) {
case GenericSignatureBuilder::ConstraintResult::Concrete:
case GenericSignatureBuilder::ConstraintResult::Conflicting:
return true;
case GenericSignatureBuilder::ConstraintResult::Resolved:
case GenericSignatureBuilder::ConstraintResult::Unresolved:
return false;
}
llvm_unreachable("unhandled result");
}
template<typename T>
Type GenericSignatureBuilder::Constraint<T>::getSubjectDependentType(
TypeArrayView<GenericTypeParamType> genericParams) const {
if (auto type = subject.dyn_cast<Type>())
return type;
return subject.get<PotentialArchetype *>()->getDependentType(genericParams);
}
} // end namespace swift
#endif
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