mcs/class/System.Core/System.Linq.Expressions/ExpressionTransformer.cs

   1 //
   2 // ExpressionTransformer.cs
   3 //
   4 // Authors:
   5 //      Roei Erez (roeie@mainsoft.com)
   6 //
   7 // Copyright (C) 2007 Novell, Inc (http://www.novell.com)
   8 //
   9 // Permission is hereby granted, free of charge, to any person obtaining
  10 // a copy of this software and associated documentation files (the
  11 // "Software"), to deal in the Software without restriction, including
  12 // without limitation the rights to use, copy, modify, merge, publish,
  13 // distribute, sublicense, and/or sell copies of the Software, and to
  14 // permit persons to whom the Software is furnished to do so, subject to
  15 // the following conditions:
  16 //
  17 // The above copyright notice and this permission notice shall be
  18 // included in all copies or substantial portions of the Software.
  19 //
  20 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  21 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  22 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  23 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  24 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  25 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  26 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  27 //
  28
  29 using System;
  30 using System.Collections.ObjectModel;
  31 using System.Collections.Generic;
  32 using System.Linq;
  33 using System.Linq.Expressions;
  34
  35 namespace System.Linq.Expressions {
  36
  37         abstract class ExpressionTransformer {
  38
  39                 public Expression Transform (Expression e)
  40                 {
  41                         return Visit (e);
  42                 }
  43
  44                 protected virtual Expression Visit (Expression expression)
  45                 {
  46                         if (expression == null)
  47                                 return null;
  48
  49                         switch (expression.NodeType) {
  50                         case ExpressionType.Negate:
  51                         case ExpressionType.NegateChecked:
  52                         case ExpressionType.Not:
  53                         case ExpressionType.Convert:
  54                         case ExpressionType.ConvertChecked:
  55                         case ExpressionType.ArrayLength:
  56                         case ExpressionType.Quote:
  57                         case ExpressionType.TypeAs:
  58                         case ExpressionType.UnaryPlus:
  59                                 return VisitUnary ((UnaryExpression) expression);
  60                         case ExpressionType.Add:
  61                         case ExpressionType.AddChecked:
  62                         case ExpressionType.Subtract:
  63                         case ExpressionType.SubtractChecked:
  64                         case ExpressionType.Multiply:
  65                         case ExpressionType.MultiplyChecked:
  66                         case ExpressionType.Divide:
  67                         case ExpressionType.Modulo:
  68                         case ExpressionType.Power:
  69                         case ExpressionType.And:
  70                         case ExpressionType.AndAlso:
  71                         case ExpressionType.Or:
  72                         case ExpressionType.OrElse:
  73                         case ExpressionType.LessThan:
  74                         case ExpressionType.LessThanOrEqual:
  75                         case ExpressionType.GreaterThan:
  76                         case ExpressionType.GreaterThanOrEqual:
  77                         case ExpressionType.Equal:
  78                         case ExpressionType.NotEqual:
  79                         case ExpressionType.Coalesce:
  80                         case ExpressionType.ArrayIndex:
  81                         case ExpressionType.RightShift:
  82                         case ExpressionType.LeftShift:
  83                         case ExpressionType.ExclusiveOr:
  84                                 return VisitBinary ((BinaryExpression) expression);
  85                         case ExpressionType.TypeIs:
  86                                 return VisitTypeIs ((TypeBinaryExpression) expression);
  87                         case ExpressionType.Conditional:
  88                                 return VisitConditional ((ConditionalExpression) expression);
  89                         case ExpressionType.Constant:
  90                                 return VisitConstant ((ConstantExpression) expression);
  91                         case ExpressionType.Parameter:
  92                                 return VisitParameter ((ParameterExpression) expression);
  93                         case ExpressionType.MemberAccess:
  94                                 return VisitMemberAccess ((MemberExpression) expression);
  95                         case ExpressionType.Call:
  96                                 return VisitMethodCall ((MethodCallExpression) expression);
  97                         case ExpressionType.Lambda:
  98                                 return VisitLambda ((LambdaExpression) expression);
  99                         case ExpressionType.New:
 100                                 return VisitNew ((NewExpression) expression);
 101                         case ExpressionType.NewArrayInit:
 102                         case ExpressionType.NewArrayBounds:
 103                                 return VisitNewArray ((NewArrayExpression) expression);
 104                         case ExpressionType.Invoke:
 105                                 return VisitInvocation ((InvocationExpression) expression);
 106                         case ExpressionType.MemberInit:
 107                                 return VisitMemberInit ((MemberInitExpression) expression);
 108                         case ExpressionType.ListInit:
 109                                 return VisitListInit ((ListInitExpression) expression);
 110                         default:
 111                                 throw new ArgumentException (string.Format ("Unhandled expression type: '{0}'", expression.NodeType));
 112                         }
 113                 }
 114
 115                 protected virtual MemberBinding VisitBinding (MemberBinding binding)
 116                 {
 117                         switch (binding.BindingType) {
 118                         case MemberBindingType.Assignment:
 119                                 return VisitMemberAssignment ((MemberAssignment) binding);
 120                         case MemberBindingType.MemberBinding:
 121                                 return VisitMemberMemberBinding ((MemberMemberBinding) binding);
 122                         case MemberBindingType.ListBinding:
 123                                 return VisitMemberListBinding ((MemberListBinding) binding);
 124                         default:
 125                                 throw new ArgumentException (string.Format ("Unhandled binding type '{0}'", binding.BindingType));
 126                         }
 127                 }
 128
 129                 protected virtual ElementInit VisitElementInitializer (ElementInit initializer)
 130                 {
 131                         ReadOnlyCollection<Expression> transformed = VisitExpressionList (initializer.Arguments);
 132                         if (transformed != initializer.Arguments)
 133                                 return Expression.ElementInit (initializer.AddMethod, transformed);
 134                         return initializer;
 135                 }
 136
 137                 protected virtual UnaryExpression VisitUnary (UnaryExpression unary)
 138                 {
 139                         Expression transformedOperand = Visit (unary.Operand);
 140                         if (transformedOperand != unary.Operand)
 141                                 return Expression.MakeUnary (unary.NodeType, transformedOperand, unary.Type, unary.Method);
 142                         return unary;
 143                 }
 144
 145                 protected virtual BinaryExpression VisitBinary (BinaryExpression binary)
 146                 {
 147                         Expression left = Visit (binary.Left);
 148                         Expression right = Visit (binary.Right);
 149                         LambdaExpression conversion = VisitLambda (binary.Conversion);
 150                         if (left != binary.Left || right != binary.Right || conversion != binary.Conversion)
 151                                 return Expression.MakeBinary (binary.NodeType, left, right, binary.IsLiftedToNull, binary.Method, conversion);
 152                         return binary;
 153                 }
 154
 155                 protected virtual TypeBinaryExpression VisitTypeIs (TypeBinaryExpression type)
 156                 {
 157                         Expression inner = Visit (type.Expression);
 158                         if (inner != type.Expression)
 159                                 return Expression.TypeIs (inner, type.TypeOperand);
 160                         return type;
 161                 }
 162
 163                 protected virtual ConstantExpression VisitConstant (ConstantExpression constant)
 164                 {
 165                         return constant;
 166                 }
 167
 168                 protected virtual ConditionalExpression VisitConditional (ConditionalExpression conditional)
 169                 {
 170                         Expression test = Visit (conditional.Test);
 171                         Expression ifTrue = Visit (conditional.IfTrue);
 172                         Expression ifFalse = Visit (conditional.IfFalse);
 173                         if (test != conditional.Test || ifTrue != conditional.IfTrue || ifFalse != conditional.IfFalse)
 174                                 return Expression.Condition (test, ifTrue, ifFalse);
 175                         return conditional;
 176                 }
 177
 178                 protected virtual ParameterExpression VisitParameter (ParameterExpression parameter)
 179                 {
 180                         return parameter;
 181                 }
 182
 183                 protected virtual MemberExpression VisitMemberAccess (MemberExpression member)
 184                 {
 185                         Expression memberExp = Visit (member.Expression);
 186                         if (memberExp != member.Expression)
 187                                 return Expression.MakeMemberAccess (memberExp, member.Member);
 188                         return member;
 189                 }
 190
 191                 protected virtual MethodCallExpression VisitMethodCall (MethodCallExpression methodCall)
 192                 {
 193                         Expression instance = Visit (methodCall.Object);
 194                         ReadOnlyCollection<Expression> args = VisitExpressionList (methodCall.Arguments);
 195                         if (instance != methodCall.Object || args != methodCall.Arguments)
 196                                 return Expression.Call (instance, methodCall.Method, args);
 197                         return methodCall;
 198                 }
 199
 200                 protected virtual ReadOnlyCollection<Expression> VisitExpressionList (ReadOnlyCollection<Expression> list)
 201                 {
 202                         return VisitList<Expression> (list, Visit);
 203                 }
 204
 205                 private ReadOnlyCollection<T> VisitList<T> (ReadOnlyCollection<T> list, Func<T,T> selector) where T :class
 206                 {
 207                         int index = 0;
 208                         T [] arr = null;
 209                         foreach (T e in list) {
 210                                 T visited = selector (e);
 211                                 if (visited != e || arr != null) {
 212                                         if (arr == null)
 213                                                 arr = new T [list.Count];
 214                                         arr [index] = visited;
 215                                 }
 216                                 index++;
 217                         }
 218                         if (arr != null)
 219                                 return arr.ToReadOnlyCollection ();
 220                         return list;
 221                 }
 222
 223                 protected virtual MemberAssignment VisitMemberAssignment (MemberAssignment assignment)
 224                 {
 225                         Expression inner = Visit (assignment.Expression);
 226                         if (inner != assignment.Expression)
 227                                 return Expression.Bind (assignment.Member, inner);
 228                         return assignment;
 229                 }
 230
 231                 protected virtual MemberMemberBinding VisitMemberMemberBinding (MemberMemberBinding binding)
 232                 {
 233                         ReadOnlyCollection<MemberBinding> bindingExp = VisitBindingList (binding.Bindings);
 234                         if (bindingExp != binding.Bindings)
 235                                 return Expression.MemberBind (binding.Member, bindingExp);
 236                         return binding;
 237                 }
 238
 239                 protected virtual MemberListBinding VisitMemberListBinding (MemberListBinding binding)
 240                 {
 241                         ReadOnlyCollection<ElementInit> initializers =
 242                                 VisitElementInitializerList (binding.Initializers);
 243                         if (initializers != binding.Initializers)
 244                                 return Expression.ListBind (binding.Member, initializers);
 245                         return binding;
 246                 }
 247
 248                 protected virtual ReadOnlyCollection<MemberBinding> VisitBindingList (ReadOnlyCollection<MemberBinding> list)
 249                 {
 250                         return VisitList<MemberBinding> (list, VisitBinding);
 251                 }
 252
 253                 protected virtual ReadOnlyCollection<ElementInit> VisitElementInitializerList (ReadOnlyCollection<ElementInit> list)
 254                 {
 255                         return VisitList<ElementInit> (list, VisitElementInitializer);
 256                 }
 257
 258                 protected virtual LambdaExpression VisitLambda (LambdaExpression lambda)
 259                 {
 260                         Expression body = Visit (lambda.Body);
 261                         ReadOnlyCollection<ParameterExpression> parameters =
 262                                 VisitList<ParameterExpression> (lambda.Parameters, VisitParameter);
 263                         if (body != lambda.Body || parameters != lambda.Parameters)
 264                                 return Expression.Lambda (body, parameters.ToArray());
 265                         return lambda;
 266                 }
 267
 268                 protected virtual NewExpression VisitNew (NewExpression nex)
 269                 {
 270                         ReadOnlyCollection<Expression> args = VisitList (nex.Arguments, Visit);
 271                         if (args != nex.Arguments)
 272                                 return Expression.New (nex.Constructor, args);
 273                         return nex;
 274                 }
 275
 276                 protected virtual MemberInitExpression VisitMemberInit (MemberInitExpression init)
 277                 {
 278                         NewExpression  newExp = VisitNew (init.NewExpression);
 279                         ReadOnlyCollection<MemberBinding> bindings = VisitBindingList (init.Bindings);
 280                         if (newExp != init.NewExpression || bindings != init.Bindings)
 281                                 return Expression.MemberInit (newExp, bindings);
 282                         return init;
 283                 }
 284
 285                 protected virtual ListInitExpression VisitListInit (ListInitExpression init)
 286                 {
 287                         NewExpression newExp = VisitNew (init.NewExpression);
 288                         ReadOnlyCollection<ElementInit> initializers = VisitElementInitializerList (init.Initializers);
 289                         if (newExp != init.NewExpression || initializers != init.Initializers)
 290                                 return Expression.ListInit (newExp, initializers.ToArray());
 291                         return init;
 292                 }
 293
 294                 protected virtual NewArrayExpression VisitNewArray (NewArrayExpression newArray)
 295                 {
 296                         ReadOnlyCollection<Expression> expressions = VisitExpressionList (newArray.Expressions);
 297                         if (expressions != newArray.Expressions) {
 298                                 if (newArray.NodeType == ExpressionType.NewArrayBounds)
 299                                         return Expression.NewArrayBounds (newArray.Type, expressions);
 300                                 else
 301                                         return Expression.NewArrayInit (newArray.Type, expressions);
 302                         }
 303                         return newArray;
 304                 }
 305
 306                 protected virtual InvocationExpression VisitInvocation (InvocationExpression invocation)
 307                 {
 308                         ReadOnlyCollection<Expression> args = VisitExpressionList (invocation.Arguments);
 309                         Expression invocationExp = Visit (invocation.Expression);
 310                         if (args != invocation.Arguments || invocationExp != invocation.Expression)
 311                                 return Expression.Invoke (invocationExp, args);
 312                         return invocation;
 313                 }
 314         }
 315 }