include/swift/AST/TypeMatcher.h - third_party/swift - Git at Google

 //===--- TypeMatcher.h - Recursive Type Matcher -----------------*- 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
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines TypeMatcher, which performs a structural match between
 // two types, calling out differences for subclasses to process specifically.
 //
 //===----------------------------------------------------------------------===//

 #ifndef SWIFT_AST_TYPE_MATCHER_H
 #define SWIFT_AST_TYPE_MATCHER_H

 #include "swift/AST/CanTypeVisitor.h"

 namespace swift {

 /// Recursively match the structure of two types, calling out those places
 /// where the types are not structurally identical and allowing the
 /// implementing subclass to take specific actions in response to such
 /// mismatches.
 ///
 /// Subclasses must implement the 'mismatch' method, which will be called when
 /// a mismatch between the two given types is detected. The most general form
 /// of 'mismatch', which all subclasses will likely implement as a catch-all,
 /// takes two \c TypeBase pointers:
 ///
 /// \code
 /// bool mismatch(TypeBase *firstType, TypeBase *secondType,
 ///               Type sugaredFirstType);
 /// /\endcode
 ///
 /// \c mismatch will be called with the most specific types. Thus, a client that
 /// wants to (say) bind type variables in the first type to types in the second
 /// type could isolate that case with a 'mismatch' overload:
 ///
 /// \code
 /// bool mismatch(TypeVariableType *firstTypeVar, TypeBase *secondType,
 ///               Type sugaredFirstType);
 /// \endcode
 ///
 /// While having other mismatches fall to the original case. The 'mismatch'
 /// function should return true to indicate that matching should continue,
 /// or false to indicate that matching should exit early.
 template<typename ImplClass>
 class TypeMatcher {
   class MatchVisitor : public CanTypeVisitor<MatchVisitor, bool, Type, Type> {
     TypeMatcher &Matcher;

     /// Dispatch to the derived class when we've destructured the second type.
     template<typename FirstType, typename SecondType>
     bool mismatch(FirstType *firstType, SecondType *secondType,
                   Type sugaredFirstType) {
       return Matcher.asDerived().mismatch(firstType, secondType,
                                           sugaredFirstType);
     }

     /// Dispatch to the most-derived class when we have not yet destructured the
     /// second type.
     template<typename FirstType>
     bool mismatch(FirstType *firstType, Type secondType,
                   Type sugaredFirstType) {
       switch (secondType->getKind()) {
 #define TYPE(CLASS, PARENT)                                         \
       case TypeKind::CLASS:                                         \
         return mismatch(firstType,                                  \
                         cast<CLASS##Type>(secondType.getPointer()), \
                         sugaredFirstType);
 #include "swift/AST/TypeNodes.def"
       }

       llvm_unreachable("Unhandled TypeKind in switch.");
     }

     /// Honeypot to catch cases where we should redispatch the second type, but
     /// we have a stray ".getPointer()" in the dispatch call.
     template<typename FirstType>
     bool mismatch(FirstType *firstType, TypeBase *secondType,
                   Type sugaredFirstType) = delete;

   public:
     MatchVisitor(TypeMatcher &matcher) : Matcher(matcher) { }

 #define TRIVIAL_CASE(TheType)                                              \
       bool visit##TheType(Can##TheType firstType, Type secondType,         \
                           Type sugaredFirstType) {                         \
         /* If the types match, continue. */                                \
         if (firstType->isEqual(secondType))                                \
           return true;                                                     \
                                                                            \
         /* Otherwise, let the derived class deal with the mismatch. */     \
         return mismatch(firstType.getPointer(), secondType,                \
                         sugaredFirstType);                                 \
       }

     TRIVIAL_CASE(ErrorType)
     TRIVIAL_CASE(BuiltinIntegerType)
     TRIVIAL_CASE(BuiltinIntegerLiteralType)
     TRIVIAL_CASE(BuiltinFloatType)
     TRIVIAL_CASE(BuiltinRawPointerType)
     TRIVIAL_CASE(BuiltinNativeObjectType)
     TRIVIAL_CASE(BuiltinBridgeObjectType)
     TRIVIAL_CASE(BuiltinUnknownObjectType)
     TRIVIAL_CASE(BuiltinUnsafeValueBufferType)
     TRIVIAL_CASE(BuiltinVectorType)
     TRIVIAL_CASE(SILTokenType)

     bool visitTupleType(CanTupleType firstTuple, Type secondType,
                         Type sugaredFirstType) {
       if (auto secondTuple = secondType->getAs<TupleType>()) {
         auto sugaredFirstTuple = sugaredFirstType->getAs<TupleType>();
         if (firstTuple->getNumElements() != secondTuple->getNumElements())
           return mismatch(firstTuple.getPointer(), secondTuple,
                           sugaredFirstType);

         for (unsigned i = 0, n = firstTuple->getNumElements(); i != n; ++i) {
           const auto &firstElt = firstTuple->getElements()[i];
           const auto &secondElt = secondTuple->getElements()[i];

           if (firstElt.getName() != secondElt.getName() ||
               firstElt.isVararg() != secondElt.isVararg())
             return mismatch(firstTuple.getPointer(), secondTuple,
                             sugaredFirstType);

           // Recurse on the tuple elements.
           if (!this->visit(firstTuple.getElementType(i), secondElt.getType(),
                            sugaredFirstTuple->getElementType(i)))
             return false;
         }

         return true;
       }

       // Tuple/non-tuple mismatch.
       return mismatch(firstTuple.getPointer(), secondType, sugaredFirstType);
     }

     bool visitReferenceStorageType(CanReferenceStorageType firstStorage,
                                    Type secondType, Type sugaredFirstType) {
       auto _secondStorage = secondType->getCanonicalType();
       if (firstStorage->getKind() == _secondStorage->getKind()) {
         auto secondStorage = cast<ReferenceStorageType>(_secondStorage);
         return this->visit(firstStorage.getReferentType(),
                            secondStorage->getReferentType(),
                            sugaredFirstType->castTo<ReferenceStorageType>()
                              ->getReferentType());
       }

       return mismatch(firstStorage.getPointer(), secondType, sugaredFirstType);
     }

     bool visitNominalType(CanNominalType firstNominal,
                           Type secondType, Type sugaredFirstType) {
       auto _secondNominal = secondType->getCanonicalType();
       if (firstNominal->getKind() == _secondNominal->getKind()) {
         auto secondNominal = cast<NominalType>(_secondNominal);
         if (firstNominal->getDecl() != secondNominal->getDecl())
           return mismatch(firstNominal.getPointer(), secondNominal,
                           sugaredFirstType);

         if (firstNominal.getParent())
           return this->visit(firstNominal.getParent(),
                              secondNominal->getParent(),
                              sugaredFirstType->castTo<NominalType>()
                                ->getParent());

         return true;
       }

       return mismatch(firstNominal.getPointer(), secondType, sugaredFirstType);
     }

     bool visitAnyMetatypeType(CanAnyMetatypeType firstMeta,
                               Type secondType, Type sugaredFirstType) {
       auto _secondMeta = secondType->getCanonicalType();
       if (firstMeta->getKind() == _secondMeta->getKind()) {
         auto secondMeta = cast<AnyMetatypeType>(_secondMeta);
         return this->visit(firstMeta.getInstanceType(),
                            secondMeta->getInstanceType(),
                            sugaredFirstType->castTo<AnyMetatypeType>()
                              ->getInstanceType());
       }

       return mismatch(firstMeta.getPointer(), secondType, sugaredFirstType);
     }

     TRIVIAL_CASE(ModuleType)
     TRIVIAL_CASE(DynamicSelfType)
     TRIVIAL_CASE(ArchetypeType)
     TRIVIAL_CASE(GenericTypeParamType)
     TRIVIAL_CASE(DependentMemberType)

     /// FIXME: Split this out into cases?
     bool visitAnyFunctionType(CanAnyFunctionType firstFunc, Type secondType,
                               Type sugaredFirstType) {
       if (auto secondFunc = secondType->getAs<AnyFunctionType>()) {
         // FIXME: Compare throws()? Both existing subclasses would prefer
         // to mismatch on (!firstFunc->throws() && secondFunc->throws()), but
         // embedding that non-commutativity in this general matcher is icky.
         if (firstFunc->isNoEscape() != secondFunc->isNoEscape())
           return mismatch(firstFunc.getPointer(), secondFunc, sugaredFirstType);

         auto sugaredFirstFunc = sugaredFirstType->castTo<AnyFunctionType>();
         if (firstFunc->getParams().size() != secondFunc->getParams().size())
           return mismatch(firstFunc.getPointer(), secondFunc, sugaredFirstFunc);

         for (unsigned i = 0, n = firstFunc->getParams().size(); i != n; ++i) {
           const auto &firstElt = firstFunc->getParams()[i];
           const auto &secondElt = secondFunc->getParams()[i];

           if (firstElt.getLabel() != secondElt.getLabel() ||
               firstElt.isVariadic() != secondElt.isVariadic() ||
               firstElt.isInOut() != secondElt.isInOut())
             return mismatch(firstElt.getOldType().getPointer(),
                             secondElt.getOldType(),
                             sugaredFirstFunc->getParams()[i].getOldType());

           // Recurse on parameter components.
           if (!this->visit(firstElt.getOldType()->getCanonicalType(),
                            secondElt.getOldType(),
                            sugaredFirstFunc->getParams()[i].getOldType()))
             return false;
         }

         return this->visit(firstFunc.getResult(), secondFunc->getResult(),
                            sugaredFirstFunc->getResult());
       }

       return mismatch(firstFunc.getPointer(), secondType, sugaredFirstType);
     }

     TRIVIAL_CASE(SILFunctionType)
     TRIVIAL_CASE(SILBlockStorageType)
     TRIVIAL_CASE(SILBoxType)
     TRIVIAL_CASE(ProtocolCompositionType)

     bool visitLValueType(CanLValueType firstLValue, Type secondType,
                          Type sugaredFirstType) {
       if (auto secondLValue = secondType->getAs<LValueType>()) {
         return this->visit(firstLValue.getObjectType(),
                            secondLValue->getObjectType(),
                            sugaredFirstType->castTo<LValueType>()
                             ->getObjectType());
       }

       return mismatch(firstLValue.getPointer(), secondType, sugaredFirstType);
     }

     bool visitInOutType(CanInOutType firstInOut, Type secondType,
                         Type sugaredFirstType) {
       if (auto secondInOut = secondType->getAs<InOutType>()) {
         return this->visit(firstInOut.getObjectType(),
                            secondInOut->getObjectType(),
                            sugaredFirstType->castTo<InOutType>()
                              ->getObjectType());
       }

       return mismatch(firstInOut.getPointer(), secondType, sugaredFirstType);
     }

     bool visitUnboundBoundGenericType(CanUnboundGenericType firstUBGT,
                                       Type secondType, Type sugaredFirstType) {
       if (auto secondUBGT = secondType->getAs<UnboundGenericType>()) {
         if (firstUBGT->getDecl() != secondUBGT->getDecl())
           return mismatch(firstUBGT.getPointer(), secondUBGT, sugaredFirstType);

         if (firstUBGT.getParent())
           return this->visit(firstUBGT.getParent(), secondUBGT->getParent(),
                              sugaredFirstType->castTo<UnboundGenericType>()
                                ->getParent());

         return true;
       }

       return mismatch(firstUBGT.getPointer(), secondType, sugaredFirstType);
     }

     bool visitBoundGenericType(CanBoundGenericType firstBGT,
                                Type secondType, Type sugaredFirstType) {
       auto _secondBGT = secondType->getCanonicalType();
       if (firstBGT->getKind() == _secondBGT->getKind()) {
         auto secondBGT = cast<BoundGenericType>(_secondBGT);
         if (firstBGT->getDecl() != secondBGT->getDecl())
           return mismatch(firstBGT.getPointer(), secondBGT, sugaredFirstType);

         auto sugaredFirstBGT = sugaredFirstType->castTo<BoundGenericType>();
         if (firstBGT->getParent() &&
             !this->visit(firstBGT.getParent(), secondBGT->getParent(),
                          sugaredFirstBGT->getParent()))
           return false;

         for (unsigned i = 0, n = firstBGT->getGenericArgs().size();
              i != n; ++i) {
           if (!this->visit(firstBGT.getGenericArgs()[i],
                            secondBGT->getGenericArgs()[i],
                            sugaredFirstBGT->getGenericArgs()[i]))
             return false;
         }

         return true;
       }

       return mismatch(firstBGT.getPointer(), secondType, sugaredFirstType);
     }

     TRIVIAL_CASE(TypeVariableType)

 #undef TRIVIAL_CASE
   };

   ImplClass &asDerived() { return static_cast<ImplClass &>(*this); }

   const ImplClass &asDerived() const {
     return static_cast<const ImplClass &>(*this);
   }

 public:
   bool match(Type first, Type second) {
     return MatchVisitor(*this).visit(first->getCanonicalType(), second,
                                      first);
   }
 };

 } // end namespace swift

 #endif // SWIFT_AST_TYPE_MATCHER_H
	//===--- TypeMatcher.h - Recursive Type Matcher ------------------ 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
	//
	//===----------------------------------------------------------------------===//
	//
	// This file defines TypeMatcher, which performs a structural match between
	// two types, calling out differences for subclasses to process specifically.
	//
	//===----------------------------------------------------------------------===//

	#ifndef SWIFT_AST_TYPE_MATCHER_H
	#define SWIFT_AST_TYPE_MATCHER_H

	#include "swift/AST/CanTypeVisitor.h"

	namespace swift {

	/// Recursively match the structure of two types, calling out those places
	/// where the types are not structurally identical and allowing the
	/// implementing subclass to take specific actions in response to such
	/// mismatches.
	///
	/// Subclasses must implement the 'mismatch' method, which will be called when
	/// a mismatch between the two given types is detected. The most general form
	/// of 'mismatch', which all subclasses will likely implement as a catch-all,
	/// takes two \c TypeBase pointers:
	///
	/// \code
	/// bool mismatch(TypeBase firstType, TypeBase secondType,
	/// Type sugaredFirstType);
	/// /\endcode
	///
	/// \c mismatch will be called with the most specific types. Thus, a client that
	/// wants to (say) bind type variables in the first type to types in the second
	/// type could isolate that case with a 'mismatch' overload:
	///
	/// \code
	/// bool mismatch(TypeVariableType firstTypeVar, TypeBase secondType,
	/// Type sugaredFirstType);
	/// \endcode
	///
	/// While having other mismatches fall to the original case. The 'mismatch'
	/// function should return true to indicate that matching should continue,
	/// or false to indicate that matching should exit early.
	template<typename ImplClass>
	class TypeMatcher {
	class MatchVisitor : public CanTypeVisitor<MatchVisitor, bool, Type, Type> {
	TypeMatcher &Matcher;

	/// Dispatch to the derived class when we've destructured the second type.
	template<typename FirstType, typename SecondType>
	bool mismatch(FirstType firstType, SecondType secondType,
	Type sugaredFirstType) {
	return Matcher.asDerived().mismatch(firstType, secondType,
	sugaredFirstType);
	}

	/// Dispatch to the most-derived class when we have not yet destructured the
	/// second type.
	template<typename FirstType>
	bool mismatch(FirstType *firstType, Type secondType,
	Type sugaredFirstType) {
	switch (secondType->getKind()) {
	#define TYPE(CLASS, PARENT) \
	case TypeKind::CLASS: \
	return mismatch(firstType, \
	cast<CLASS##Type>(secondType.getPointer()), \
	sugaredFirstType);
	#include "swift/AST/TypeNodes.def"
	}

	llvm_unreachable("Unhandled TypeKind in switch.");
	}

	/// Honeypot to catch cases where we should redispatch the second type, but
	/// we have a stray ".getPointer()" in the dispatch call.
	template<typename FirstType>
	bool mismatch(FirstType firstType, TypeBase secondType,
	Type sugaredFirstType) = delete;

	public:
	MatchVisitor(TypeMatcher &matcher) : Matcher(matcher) { }

	#define TRIVIAL_CASE(TheType) \
	bool visit##TheType(Can##TheType firstType, Type secondType, \
	Type sugaredFirstType) { \
	/* If the types match, continue. */ \
	if (firstType->isEqual(secondType)) \
	return true; \
	\
	/* Otherwise, let the derived class deal with the mismatch. */ \
	return mismatch(firstType.getPointer(), secondType, \
	sugaredFirstType); \
	}

	TRIVIAL_CASE(ErrorType)
	TRIVIAL_CASE(BuiltinIntegerType)
	TRIVIAL_CASE(BuiltinIntegerLiteralType)
	TRIVIAL_CASE(BuiltinFloatType)
	TRIVIAL_CASE(BuiltinRawPointerType)
	TRIVIAL_CASE(BuiltinNativeObjectType)
	TRIVIAL_CASE(BuiltinBridgeObjectType)
	TRIVIAL_CASE(BuiltinUnknownObjectType)
	TRIVIAL_CASE(BuiltinUnsafeValueBufferType)
	TRIVIAL_CASE(BuiltinVectorType)
	TRIVIAL_CASE(SILTokenType)

	bool visitTupleType(CanTupleType firstTuple, Type secondType,
	Type sugaredFirstType) {
	if (auto secondTuple = secondType->getAs<TupleType>()) {
	auto sugaredFirstTuple = sugaredFirstType->getAs<TupleType>();
	if (firstTuple->getNumElements() != secondTuple->getNumElements())
	return mismatch(firstTuple.getPointer(), secondTuple,
	sugaredFirstType);

	for (unsigned i = 0, n = firstTuple->getNumElements(); i != n; ++i) {
	const auto &firstElt = firstTuple->getElements()[i];
	const auto &secondElt = secondTuple->getElements()[i];

	if (firstElt.getName() != secondElt.getName() \|\|
	firstElt.isVararg() != secondElt.isVararg())
	return mismatch(firstTuple.getPointer(), secondTuple,
	sugaredFirstType);

	// Recurse on the tuple elements.
	if (!this->visit(firstTuple.getElementType(i), secondElt.getType(),
	sugaredFirstTuple->getElementType(i)))
	return false;
	}

	return true;
	}

	// Tuple/non-tuple mismatch.
	return mismatch(firstTuple.getPointer(), secondType, sugaredFirstType);
	}

	bool visitReferenceStorageType(CanReferenceStorageType firstStorage,
	Type secondType, Type sugaredFirstType) {
	auto _secondStorage = secondType->getCanonicalType();
	if (firstStorage->getKind() == _secondStorage->getKind()) {
	auto secondStorage = cast<ReferenceStorageType>(_secondStorage);
	return this->visit(firstStorage.getReferentType(),
	secondStorage->getReferentType(),
	sugaredFirstType->castTo<ReferenceStorageType>()
	->getReferentType());
	}

	return mismatch(firstStorage.getPointer(), secondType, sugaredFirstType);
	}

	bool visitNominalType(CanNominalType firstNominal,
	Type secondType, Type sugaredFirstType) {
	auto _secondNominal = secondType->getCanonicalType();
	if (firstNominal->getKind() == _secondNominal->getKind()) {
	auto secondNominal = cast<NominalType>(_secondNominal);
	if (firstNominal->getDecl() != secondNominal->getDecl())
	return mismatch(firstNominal.getPointer(), secondNominal,
	sugaredFirstType);

	if (firstNominal.getParent())
	return this->visit(firstNominal.getParent(),
	secondNominal->getParent(),
	sugaredFirstType->castTo<NominalType>()
	->getParent());

	return true;
	}

	return mismatch(firstNominal.getPointer(), secondType, sugaredFirstType);
	}

	bool visitAnyMetatypeType(CanAnyMetatypeType firstMeta,
	Type secondType, Type sugaredFirstType) {
	auto _secondMeta = secondType->getCanonicalType();
	if (firstMeta->getKind() == _secondMeta->getKind()) {
	auto secondMeta = cast<AnyMetatypeType>(_secondMeta);
	return this->visit(firstMeta.getInstanceType(),
	secondMeta->getInstanceType(),
	sugaredFirstType->castTo<AnyMetatypeType>()
	->getInstanceType());
	}

	return mismatch(firstMeta.getPointer(), secondType, sugaredFirstType);
	}

	TRIVIAL_CASE(ModuleType)
	TRIVIAL_CASE(DynamicSelfType)
	TRIVIAL_CASE(ArchetypeType)
	TRIVIAL_CASE(GenericTypeParamType)
	TRIVIAL_CASE(DependentMemberType)

	/// FIXME: Split this out into cases?
	bool visitAnyFunctionType(CanAnyFunctionType firstFunc, Type secondType,
	Type sugaredFirstType) {
	if (auto secondFunc = secondType->getAs<AnyFunctionType>()) {
	// FIXME: Compare throws()? Both existing subclasses would prefer
	// to mismatch on (!firstFunc->throws() && secondFunc->throws()), but
	// embedding that non-commutativity in this general matcher is icky.
	if (firstFunc->isNoEscape() != secondFunc->isNoEscape())
	return mismatch(firstFunc.getPointer(), secondFunc, sugaredFirstType);

	auto sugaredFirstFunc = sugaredFirstType->castTo<AnyFunctionType>();
	if (firstFunc->getParams().size() != secondFunc->getParams().size())
	return mismatch(firstFunc.getPointer(), secondFunc, sugaredFirstFunc);

	for (unsigned i = 0, n = firstFunc->getParams().size(); i != n; ++i) {
	const auto &firstElt = firstFunc->getParams()[i];
	const auto &secondElt = secondFunc->getParams()[i];

	if (firstElt.getLabel() != secondElt.getLabel() \|\|
	firstElt.isVariadic() != secondElt.isVariadic() \|\|
	firstElt.isInOut() != secondElt.isInOut())
	return mismatch(firstElt.getOldType().getPointer(),
	secondElt.getOldType(),
	sugaredFirstFunc->getParams()[i].getOldType());

	// Recurse on parameter components.
	if (!this->visit(firstElt.getOldType()->getCanonicalType(),
	secondElt.getOldType(),
	sugaredFirstFunc->getParams()[i].getOldType()))
	return false;
	}

	return this->visit(firstFunc.getResult(), secondFunc->getResult(),
	sugaredFirstFunc->getResult());
	}

	return mismatch(firstFunc.getPointer(), secondType, sugaredFirstType);
	}

	TRIVIAL_CASE(SILFunctionType)
	TRIVIAL_CASE(SILBlockStorageType)
	TRIVIAL_CASE(SILBoxType)
	TRIVIAL_CASE(ProtocolCompositionType)

	bool visitLValueType(CanLValueType firstLValue, Type secondType,
	Type sugaredFirstType) {
	if (auto secondLValue = secondType->getAs<LValueType>()) {
	return this->visit(firstLValue.getObjectType(),
	secondLValue->getObjectType(),
	sugaredFirstType->castTo<LValueType>()
	->getObjectType());
	}

	return mismatch(firstLValue.getPointer(), secondType, sugaredFirstType);
	}

	bool visitInOutType(CanInOutType firstInOut, Type secondType,
	Type sugaredFirstType) {
	if (auto secondInOut = secondType->getAs<InOutType>()) {
	return this->visit(firstInOut.getObjectType(),
	secondInOut->getObjectType(),
	sugaredFirstType->castTo<InOutType>()
	->getObjectType());
	}

	return mismatch(firstInOut.getPointer(), secondType, sugaredFirstType);
	}

	bool visitUnboundBoundGenericType(CanUnboundGenericType firstUBGT,
	Type secondType, Type sugaredFirstType) {
	if (auto secondUBGT = secondType->getAs<UnboundGenericType>()) {
	if (firstUBGT->getDecl() != secondUBGT->getDecl())
	return mismatch(firstUBGT.getPointer(), secondUBGT, sugaredFirstType);

	if (firstUBGT.getParent())
	return this->visit(firstUBGT.getParent(), secondUBGT->getParent(),
	sugaredFirstType->castTo<UnboundGenericType>()
	->getParent());

	return true;
	}

	return mismatch(firstUBGT.getPointer(), secondType, sugaredFirstType);
	}

	bool visitBoundGenericType(CanBoundGenericType firstBGT,
	Type secondType, Type sugaredFirstType) {
	auto _secondBGT = secondType->getCanonicalType();
	if (firstBGT->getKind() == _secondBGT->getKind()) {
	auto secondBGT = cast<BoundGenericType>(_secondBGT);
	if (firstBGT->getDecl() != secondBGT->getDecl())
	return mismatch(firstBGT.getPointer(), secondBGT, sugaredFirstType);

	auto sugaredFirstBGT = sugaredFirstType->castTo<BoundGenericType>();
	if (firstBGT->getParent() &&
	!this->visit(firstBGT.getParent(), secondBGT->getParent(),
	sugaredFirstBGT->getParent()))
	return false;

	for (unsigned i = 0, n = firstBGT->getGenericArgs().size();
	i != n; ++i) {
	if (!this->visit(firstBGT.getGenericArgs()[i],
	secondBGT->getGenericArgs()[i],
	sugaredFirstBGT->getGenericArgs()[i]))
	return false;
	}

	return true;
	}

	return mismatch(firstBGT.getPointer(), secondType, sugaredFirstType);
	}

	TRIVIAL_CASE(TypeVariableType)

	#undef TRIVIAL_CASE
	};

	ImplClass &asDerived() { return static_cast<ImplClass &>(*this); }

	const ImplClass &asDerived() const {
	return static_cast<const ImplClass &>(*this);
	}

	public:
	bool match(Type first, Type second) {
	return MatchVisitor(*this).visit(first->getCanonicalType(), second,
	first);
	}
	};

	} // end namespace swift

	#endif // SWIFT_AST_TYPE_MATCHER_H