Index: src/SynTree/Mutator.h
===================================================================
--- src/SynTree/Mutator.h	(revision 7c782aff4b836a71e18dd75c37d3b3e43582a5bc)
+++ src/SynTree/Mutator.h	(revision cfaf9beb67593b36a3927861cb7bb364983f7938)
@@ -25,104 +25,100 @@
 	virtual ~Mutator();
   public:
-	virtual DeclarationWithType * mutate( ObjectDecl * objectDecl );
-	virtual DeclarationWithType * mutate( FunctionDecl * functionDecl );
-	virtual Declaration * mutate( StructDecl * aggregateDecl );
-	virtual Declaration * mutate( UnionDecl * aggregateDecl );
-	virtual Declaration * mutate( EnumDecl * aggregateDecl );
-	virtual Declaration * mutate( TraitDecl * aggregateDecl );
-	virtual Declaration * mutate( TypeDecl * typeDecl );
-	virtual Declaration * mutate( TypedefDecl * typeDecl );
-	virtual AsmDecl * mutate( AsmDecl * asmDecl );
+	virtual DeclarationWithType * mutate( ObjectDecl * objectDecl ) = 0;
+	virtual DeclarationWithType * mutate( FunctionDecl * functionDecl ) = 0;
+	virtual Declaration * mutate( StructDecl * aggregateDecl ) = 0;
+	virtual Declaration * mutate( UnionDecl * aggregateDecl ) = 0;
+	virtual Declaration * mutate( EnumDecl * aggregateDecl ) = 0;
+	virtual Declaration * mutate( TraitDecl * aggregateDecl ) = 0;
+	virtual Declaration * mutate( TypeDecl * typeDecl ) = 0;
+	virtual Declaration * mutate( TypedefDecl * typeDecl ) = 0;
+	virtual AsmDecl * mutate( AsmDecl * asmDecl ) = 0;
 
-	virtual CompoundStmt * mutate( CompoundStmt * compoundStmt );
-	virtual Statement * mutate( ExprStmt * exprStmt );
-	virtual Statement * mutate( AsmStmt * asmStmt );
-	virtual Statement * mutate( IfStmt * ifStmt );
-	virtual Statement * mutate( WhileStmt * whileStmt );
-	virtual Statement * mutate( ForStmt * forStmt );
-	virtual Statement * mutate( SwitchStmt * switchStmt );
-	virtual Statement * mutate( CaseStmt * caseStmt );
-	virtual Statement * mutate( BranchStmt * branchStmt );
-	virtual Statement * mutate( ReturnStmt * returnStmt );
-	virtual Statement * mutate( ThrowStmt * throwStmt );
-	virtual Statement * mutate( TryStmt * tryStmt );
-	virtual Statement * mutate( CatchStmt * catchStmt );
-	virtual Statement * mutate( FinallyStmt * catchStmt );
-	virtual Statement * mutate( WaitForStmt * waitforStmt );
-	virtual Statement * mutate( WithStmt * withStmt );
-	virtual NullStmt * mutate( NullStmt * nullStmt );
-	virtual Statement * mutate( DeclStmt * declStmt );
-	virtual Statement * mutate( ImplicitCtorDtorStmt * impCtorDtorStmt );
+	virtual CompoundStmt * mutate( CompoundStmt * compoundStmt ) = 0;
+	virtual Statement * mutate( ExprStmt * exprStmt ) = 0;
+	virtual Statement * mutate( AsmStmt * asmStmt ) = 0;
+	virtual Statement * mutate( IfStmt * ifStmt ) = 0;
+	virtual Statement * mutate( WhileStmt * whileStmt ) = 0;
+	virtual Statement * mutate( ForStmt * forStmt ) = 0;
+	virtual Statement * mutate( SwitchStmt * switchStmt ) = 0;
+	virtual Statement * mutate( CaseStmt * caseStmt ) = 0;
+	virtual Statement * mutate( BranchStmt * branchStmt ) = 0;
+	virtual Statement * mutate( ReturnStmt * returnStmt ) = 0;
+	virtual Statement * mutate( ThrowStmt * throwStmt ) = 0;
+	virtual Statement * mutate( TryStmt * tryStmt ) = 0;
+	virtual Statement * mutate( CatchStmt * catchStmt ) = 0;
+	virtual Statement * mutate( FinallyStmt * catchStmt ) = 0;
+	virtual Statement * mutate( WaitForStmt * waitforStmt ) = 0;
+	virtual Statement * mutate( WithStmt * withStmt ) = 0;
+	virtual NullStmt * mutate( NullStmt * nullStmt ) = 0;
+	virtual Statement * mutate( DeclStmt * declStmt ) = 0;
+	virtual Statement * mutate( ImplicitCtorDtorStmt * impCtorDtorStmt ) = 0;
 
-	virtual Expression * mutate( ApplicationExpr * applicationExpr );
-	virtual Expression * mutate( UntypedExpr * untypedExpr );
-	virtual Expression * mutate( NameExpr * nameExpr );
-	virtual Expression * mutate( AddressExpr * castExpr );
-	virtual Expression * mutate( LabelAddressExpr * labAddressExpr );
-	virtual Expression * mutate( CastExpr * castExpr );
-	virtual Expression * mutate( VirtualCastExpr * castExpr );
-	virtual Expression * mutate( UntypedMemberExpr * memberExpr );
-	virtual Expression * mutate( MemberExpr * memberExpr );
-	virtual Expression * mutate( VariableExpr * variableExpr );
-	virtual Expression * mutate( ConstantExpr * constantExpr );
-	virtual Expression * mutate( SizeofExpr * sizeofExpr );
-	virtual Expression * mutate( AlignofExpr * alignofExpr );
-	virtual Expression * mutate( UntypedOffsetofExpr * offsetofExpr );
-	virtual Expression * mutate( OffsetofExpr * offsetofExpr );
-	virtual Expression * mutate( OffsetPackExpr * offsetPackExpr );
-	virtual Expression * mutate( AttrExpr * attrExpr );
-	virtual Expression * mutate( LogicalExpr * logicalExpr );
-	virtual Expression * mutate( ConditionalExpr * conditionalExpr );
-	virtual Expression * mutate( CommaExpr * commaExpr );
-	virtual Expression * mutate( TypeExpr * typeExpr );
-	virtual Expression * mutate( AsmExpr * asmExpr );
-	virtual Expression * mutate( ImplicitCopyCtorExpr * impCpCtorExpr );
-	virtual Expression * mutate( ConstructorExpr * ctorExpr );
-	virtual Expression * mutate( CompoundLiteralExpr * compLitExpr );
-	virtual Expression * mutate( RangeExpr * rangeExpr );
-	virtual Expression * mutate( UntypedTupleExpr * tupleExpr );
-	virtual Expression * mutate( TupleExpr * tupleExpr );
-	virtual Expression * mutate( TupleIndexExpr * tupleExpr );
-	virtual Expression * mutate( TupleAssignExpr * assignExpr );
-	virtual Expression * mutate( StmtExpr  * stmtExpr );
-	virtual Expression * mutate( UniqueExpr  * uniqueExpr );
-	virtual Expression * mutate( UntypedInitExpr  * initExpr );
-	virtual Expression * mutate( InitExpr  * initExpr );
+	virtual Expression * mutate( ApplicationExpr * applicationExpr ) = 0;
+	virtual Expression * mutate( UntypedExpr * untypedExpr ) = 0;
+	virtual Expression * mutate( NameExpr * nameExpr ) = 0;
+	virtual Expression * mutate( AddressExpr * castExpr ) = 0;
+	virtual Expression * mutate( LabelAddressExpr * labAddressExpr ) = 0;
+	virtual Expression * mutate( CastExpr * castExpr ) = 0;
+	virtual Expression * mutate( VirtualCastExpr * castExpr ) = 0;
+	virtual Expression * mutate( UntypedMemberExpr * memberExpr ) = 0;
+	virtual Expression * mutate( MemberExpr * memberExpr ) = 0;
+	virtual Expression * mutate( VariableExpr * variableExpr ) = 0;
+	virtual Expression * mutate( ConstantExpr * constantExpr ) = 0;
+	virtual Expression * mutate( SizeofExpr * sizeofExpr ) = 0;
+	virtual Expression * mutate( AlignofExpr * alignofExpr ) = 0;
+	virtual Expression * mutate( UntypedOffsetofExpr * offsetofExpr ) = 0;
+	virtual Expression * mutate( OffsetofExpr * offsetofExpr ) = 0;
+	virtual Expression * mutate( OffsetPackExpr * offsetPackExpr ) = 0;
+	virtual Expression * mutate( AttrExpr * attrExpr ) = 0;
+	virtual Expression * mutate( LogicalExpr * logicalExpr ) = 0;
+	virtual Expression * mutate( ConditionalExpr * conditionalExpr ) = 0;
+	virtual Expression * mutate( CommaExpr * commaExpr ) = 0;
+	virtual Expression * mutate( TypeExpr * typeExpr ) = 0;
+	virtual Expression * mutate( AsmExpr * asmExpr ) = 0;
+	virtual Expression * mutate( ImplicitCopyCtorExpr * impCpCtorExpr ) = 0;
+	virtual Expression * mutate( ConstructorExpr * ctorExpr ) = 0;
+	virtual Expression * mutate( CompoundLiteralExpr * compLitExpr ) = 0;
+	virtual Expression * mutate( RangeExpr * rangeExpr ) = 0;
+	virtual Expression * mutate( UntypedTupleExpr * tupleExpr ) = 0;
+	virtual Expression * mutate( TupleExpr * tupleExpr ) = 0;
+	virtual Expression * mutate( TupleIndexExpr * tupleExpr ) = 0;
+	virtual Expression * mutate( TupleAssignExpr * assignExpr ) = 0;
+	virtual Expression * mutate( StmtExpr  * stmtExpr ) = 0;
+	virtual Expression * mutate( UniqueExpr  * uniqueExpr ) = 0;
+	virtual Expression * mutate( UntypedInitExpr  * initExpr ) = 0;
+	virtual Expression * mutate( InitExpr  * initExpr ) = 0;
 	virtual Expression * mutate( DeletedExpr * delExpr ) = 0;
 
-	virtual Type * mutate( VoidType * basicType );
-	virtual Type * mutate( BasicType * basicType );
-	virtual Type * mutate( PointerType * pointerType );
-	virtual Type * mutate( ArrayType * arrayType );
-	virtual Type * mutate( ReferenceType * refType );
-	virtual Type * mutate( FunctionType * functionType );
-	virtual Type * mutate( StructInstType * aggregateUseType );
-	virtual Type * mutate( UnionInstType * aggregateUseType );
-	virtual Type * mutate( EnumInstType * aggregateUseType );
-	virtual Type * mutate( TraitInstType * aggregateUseType );
-	virtual Type * mutate( TypeInstType * aggregateUseType );
-	virtual Type * mutate( TupleType * tupleType );
-	virtual Type * mutate( TypeofType * typeofType );
-	virtual Type * mutate( AttrType * attrType );
-	virtual Type * mutate( VarArgsType * varArgsType );
-	virtual Type * mutate( ZeroType * zeroType );
-	virtual Type * mutate( OneType * oneType );
+	virtual Type * mutate( VoidType * basicType ) = 0;
+	virtual Type * mutate( BasicType * basicType ) = 0;
+	virtual Type * mutate( PointerType * pointerType ) = 0;
+	virtual Type * mutate( ArrayType * arrayType ) = 0;
+	virtual Type * mutate( ReferenceType * refType ) = 0;
+	virtual Type * mutate( FunctionType * functionType ) = 0;
+	virtual Type * mutate( StructInstType * aggregateUseType ) = 0;
+	virtual Type * mutate( UnionInstType * aggregateUseType ) = 0;
+	virtual Type * mutate( EnumInstType * aggregateUseType ) = 0;
+	virtual Type * mutate( TraitInstType * aggregateUseType ) = 0;
+	virtual Type * mutate( TypeInstType * aggregateUseType ) = 0;
+	virtual Type * mutate( TupleType * tupleType ) = 0;
+	virtual Type * mutate( TypeofType * typeofType ) = 0;
+	virtual Type * mutate( AttrType * attrType ) = 0;
+	virtual Type * mutate( VarArgsType * varArgsType ) = 0;
+	virtual Type * mutate( ZeroType * zeroType ) = 0;
+	virtual Type * mutate( OneType * oneType ) = 0;
 
-	virtual Designation * mutate( Designation * designation );
-	virtual Initializer * mutate( SingleInit * singleInit );
-	virtual Initializer * mutate( ListInit * listInit );
-	virtual Initializer * mutate( ConstructorInit * ctorInit );
+	virtual Designation * mutate( Designation * designation ) = 0 ;
+	virtual Initializer * mutate( SingleInit * singleInit ) = 0 ;
+	virtual Initializer * mutate( ListInit * listInit ) = 0 ;
+	virtual Initializer * mutate( ConstructorInit * ctorInit ) = 0 ;
 
-	virtual Subrange * mutate( Subrange * subrange );
+	virtual Subrange * mutate( Subrange * subrange ) = 0;
 
-	virtual Constant * mutate( Constant * constant );
+	virtual Constant * mutate( Constant * constant ) = 0;
 
-	virtual Attribute * mutate( Attribute * attribute );
+	virtual Attribute * mutate( Attribute * attribute ) = 0;
 
-	virtual TypeSubstitution * mutate( TypeSubstitution * sub );
-  private:
-	virtual Declaration * handleAggregateDecl(AggregateDecl * aggregateDecl );
-	virtual Declaration * handleNamedTypeDecl(NamedTypeDecl * typeDecl );
-	virtual Type * handleReferenceToType(ReferenceToType * aggregateUseType );
+	virtual TypeSubstitution * mutate( TypeSubstitution * sub ) = 0;
 };
 
