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

   1 //
   2 // ExpressionTransformer.cs
   3 //
   4 // Authors:
   5 //      Roei Erez (roeie@mainsoft.com)
   6 //  Jb Evain (jbevain@novell.com)
   7 //
   8 // Copyright (C) 2007 Novell, Inc (http://www.novell.com)
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining
  11 // a copy of this software and associated documentation files (the
  12 // "Software"), to deal in the Software without restriction, including
  13 // without limitation the rights to use, copy, modify, merge, publish,
  14 // distribute, sublicense, and/or sell copies of the Software, and to
  15 // permit persons to whom the Software is furnished to do so, subject to
  16 // the following conditions:
  17 //
  18 // The above copyright notice and this permission notice shall be
  19 // included in all copies or substantial portions of the Software.
  20 //
  21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  23 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  25 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  26 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  27 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  28 //
  29
  30 using System;
  31 using System.Collections.ObjectModel;
  32 using System.Collections.Generic;
  33 using System.Linq.Expressions;
  34
  35 namespace System.Linq.Expressions {
  36
  37         abstract class ExpressionTransformer {
  38
  39                 public Expression Transform (Expression expression)
  40                 {
  41                         return Visit (expression);
  42                 }
  43
  44                 protected virtual Expression Visit (Expression exp)
  45                 {
  46                         if (exp == null) return exp;
  47
  48                         switch (exp.NodeType) {
  49                         case ExpressionType.Negate:
  50                         case ExpressionType.NegateChecked:
  51                         case ExpressionType.Not:
  52                         case ExpressionType.Convert:
  53                         case ExpressionType.ConvertChecked:
  54                         case ExpressionType.ArrayLength:
  55                         case ExpressionType.Quote:
  56                         case ExpressionType.TypeAs:
  57                         case ExpressionType.UnaryPlus:
  58                                 return this.VisitUnary ((UnaryExpression) exp);
  59                         case ExpressionType.Add:
  60                         case ExpressionType.AddChecked:
  61                         case ExpressionType.Subtract:
  62                         case ExpressionType.SubtractChecked:
  63                         case ExpressionType.Multiply:
  64                         case ExpressionType.MultiplyChecked:
  65                         case ExpressionType.Divide:
  66                         case ExpressionType.Power:
  67                         case ExpressionType.Modulo:
  68                         case ExpressionType.And:
  69                         case ExpressionType.AndAlso:
  70                         case ExpressionType.Or:
  71                         case ExpressionType.OrElse:
  72                         case ExpressionType.LessThan:
  73                         case ExpressionType.LessThanOrEqual:
  74                         case ExpressionType.GreaterThan:
  75                         case ExpressionType.GreaterThanOrEqual:
  76                         case ExpressionType.Equal:
  77                         case ExpressionType.NotEqual:
  78                         case ExpressionType.Coalesce:
  79                         case ExpressionType.ArrayIndex:
  80                         case ExpressionType.RightShift:
  81                         case ExpressionType.LeftShift:
  82                         case ExpressionType.ExclusiveOr:
  83                                 return this.VisitBinary ((BinaryExpression) exp);
  84                         case ExpressionType.TypeIs:
  85                                 return this.VisitTypeIs ((TypeBinaryExpression) exp);
  86                         case ExpressionType.Conditional:
  87                                 return this.VisitConditional ((ConditionalExpression) exp);
  88                         case ExpressionType.Constant:
  89                                 return this.VisitConstant ((ConstantExpression) exp);
  90                         case ExpressionType.Parameter:
  91                                 return this.VisitParameter ((ParameterExpression) exp);
  92                         case ExpressionType.MemberAccess:
  93                                 return this.VisitMemberAccess ((MemberExpression) exp);
  94                         case ExpressionType.Call:
  95                                 return this.VisitMethodCall ((MethodCallExpression) exp);
  96                         case ExpressionType.Lambda:
  97                                 return this.VisitLambda ((LambdaExpression) exp);
  98                         case ExpressionType.New:
  99                                 return this.VisitNew ((NewExpression) exp);
 100                         case ExpressionType.NewArrayInit:
 101                         case ExpressionType.NewArrayBounds:
 102                                 return this.VisitNewArray ((NewArrayExpression) exp);
 103                         case ExpressionType.Invoke:
 104                                 return this.VisitInvocation ((InvocationExpression) exp);
 105                         case ExpressionType.MemberInit:
 106                                 return this.VisitMemberInit ((MemberInitExpression) exp);
 107                         case ExpressionType.ListInit:
 108                                 return this.VisitListInit ((ListInitExpression) exp);
 109                         default:
 110                                 throw new Exception (string.Format ("Unhandled expression type: '{0}'", exp.NodeType));
 111                         }
 112                 }
 113
 114                 protected virtual MemberBinding VisitBinding (MemberBinding binding)
 115                 {
 116                         switch (binding.BindingType) {
 117                         case MemberBindingType.Assignment:
 118                                 return this.VisitMemberAssignment ((MemberAssignment) binding);
 119                         case MemberBindingType.MemberBinding:
 120                                 return this.VisitMemberMemberBinding ((MemberMemberBinding) binding);
 121                         case MemberBindingType.ListBinding:
 122                                 return this.VisitMemberListBinding ((MemberListBinding) binding);
 123                         default:
 124                                 throw new Exception (string.Format ("Unhandled binding type '{0}'", binding.BindingType));
 125                         }
 126                 }
 127
 128                 protected virtual ElementInit VisitElementInitializer (ElementInit initializer)
 129                 {
 130                         ReadOnlyCollection<Expression> arguments = this.VisitExpressionList (initializer.Arguments);
 131                         if (arguments != initializer.Arguments) return Expression.ElementInit (initializer.AddMethod, arguments);
 132                         return initializer;
 133                 }
 134
 135                 protected virtual Expression VisitUnary (UnaryExpression u)
 136                 {
 137                         Expression operand = this.Visit (u.Operand);
 138                         if (operand != u.Operand) return Expression.MakeUnary (u.NodeType, operand, u.Type, u.Method);
 139                         return u;
 140                 }
 141
 142                 protected virtual Expression VisitBinary (BinaryExpression b)
 143                 {
 144                         Expression left = this.Visit (b.Left);
 145                         Expression right = this.Visit (b.Right);
 146                         Expression conversion = this.Visit (b.Conversion);
 147                         if (left != b.Left || right != b.Right || conversion != b.Conversion) {
 148                                 if (b.NodeType == ExpressionType.Coalesce && b.Conversion != null) {
 149                                         return Expression.Coalesce (left, right, conversion as LambdaExpression);
 150                                 } else {
 151                                         return Expression.MakeBinary (b.NodeType, left, right, b.IsLiftedToNull, b.Method);
 152                                 }
 153                         }
 154                         return b;
 155                 }
 156
 157                 protected virtual Expression VisitTypeIs (TypeBinaryExpression b)
 158                 {
 159                         Expression expr = this.Visit (b.Expression);
 160                         if (expr != b.Expression) {
 161                                 return Expression.TypeIs (expr, b.TypeOperand);
 162                         }
 163                         return b;
 164                 }
 165
 166                 protected virtual Expression VisitConstant (ConstantExpression c)
 167                 {
 168                         return c;
 169                 }
 170
 171                 protected virtual Expression VisitConditional (ConditionalExpression c)
 172                 {
 173                         Expression test = this.Visit (c.Test);
 174                         Expression ifTrue = this.Visit (c.IfTrue);
 175                         Expression ifFalse = this.Visit (c.IfFalse);
 176                         if (test != c.Test || ifTrue != c.IfTrue || ifFalse != c.IfFalse) {
 177                                 return Expression.Condition (test, ifTrue, ifFalse);
 178                         }
 179                         return c;
 180                 }
 181
 182                 protected virtual Expression VisitParameter (ParameterExpression p)
 183                 {
 184                         return p;
 185                 }
 186
 187                 protected virtual Expression VisitMemberAccess (MemberExpression m)
 188                 {
 189                         Expression exp = this.Visit (m.Expression);
 190                         if (exp != m.Expression) {
 191                                 return Expression.MakeMemberAccess (exp, m.Member);
 192                         }
 193                         return m;
 194                 }
 195
 196                 protected virtual Expression VisitMethodCall (MethodCallExpression m)
 197                 {
 198                         Expression obj = this.Visit (m.Object);
 199                         IEnumerable<Expression> args = this.VisitExpressionList (m.Arguments);
 200                         if (obj != m.Object || args != m.Arguments) {
 201                                 return Expression.Call (obj, m.Method, args);
 202                         }
 203                         return m;
 204                 }
 205
 206                 protected virtual ReadOnlyCollection<Expression> VisitExpressionList (ReadOnlyCollection<Expression> original)
 207                 {
 208                         var list = VisitList (original, Visit);
 209                         if (list == null) return original;
 210
 211                         return new ReadOnlyCollection<Expression> (list);
 212                 }
 213
 214                 protected virtual MemberAssignment VisitMemberAssignment (MemberAssignment assignment)
 215                 {
 216                         Expression e = this.Visit (assignment.Expression);
 217                         if (e != assignment.Expression) return Expression.Bind (assignment.Member, e);
 218                         return assignment;
 219                 }
 220
 221                 protected virtual MemberMemberBinding VisitMemberMemberBinding (MemberMemberBinding binding)
 222                 {
 223                         IEnumerable<MemberBinding> bindings = this.VisitBindingList (binding.Bindings);
 224                         if (bindings != binding.Bindings) return Expression.MemberBind (binding.Member, bindings);
 225                         return binding;
 226                 }
 227
 228                 protected virtual MemberListBinding VisitMemberListBinding (MemberListBinding binding)
 229                 {
 230                         IEnumerable<ElementInit> initializers = this.VisitElementInitializerList (binding.Initializers);
 231                         if (initializers != binding.Initializers) return Expression.ListBind (binding.Member, initializers);
 232                         return binding;
 233                 }
 234
 235                 protected virtual IEnumerable<MemberBinding> VisitBindingList (ReadOnlyCollection<MemberBinding> original)
 236                 {
 237                         return VisitList (original, VisitBinding);
 238                 }
 239
 240                 protected virtual IEnumerable<ElementInit> VisitElementInitializerList (ReadOnlyCollection<ElementInit> original)
 241                 {
 242                         return VisitList (original, VisitElementInitializer);
 243                 }
 244
 245                 private IList<TElement> VisitList<TElement> (ReadOnlyCollection<TElement> original, Func<TElement, TElement> visit)
 246                 {
 247                         List<TElement> list = null;
 248                         for (int i = 0, n = original.Count; i < n; i++) {
 249                                 TElement element = visit (original [i]);
 250                                 if (list != null) {
 251                                         list.Add (element);
 252                                 } else if (!EqualityComparer<TElement>.Default.Equals (element, original [i])) {
 253                                         list = new List<TElement> (n);
 254                                         for (int j = 0; j < i; j++) {
 255                                                 list.Add (original [j]);
 256                                         }
 257                                         list.Add (element);
 258                                 }
 259                         }
 260                         if (list != null)
 261                                 return list;
 262
 263                         return original;
 264                 }
 265
 266                 protected virtual Expression VisitLambda (LambdaExpression lambda)
 267                 {
 268                         Expression body = this.Visit (lambda.Body);
 269                         if (body != lambda.Body) return Expression.Lambda (lambda.Type, body, lambda.Parameters);
 270                         return lambda;
 271                 }
 272
 273                 protected virtual NewExpression VisitNew (NewExpression nex)
 274                 {
 275                         IEnumerable<Expression> args = this.VisitExpressionList (nex.Arguments);
 276                         if (args != nex.Arguments) {
 277                                 if (nex.Members != null)
 278                                         return Expression.New (nex.Constructor, args, nex.Members);
 279                                 else
 280                                         return Expression.New (nex.Constructor, args);
 281                         }
 282                         return nex;
 283                 }
 284
 285                 protected virtual Expression VisitMemberInit (MemberInitExpression init)
 286                 {
 287                         NewExpression n = this.VisitNew (init.NewExpression);
 288                         IEnumerable<MemberBinding> bindings = this.VisitBindingList (init.Bindings);
 289                         if (n != init.NewExpression || bindings != init.Bindings) return Expression.MemberInit (n, bindings);
 290                         return init;
 291                 }
 292
 293                 protected virtual Expression VisitListInit (ListInitExpression init)
 294                 {
 295                         NewExpression n = this.VisitNew (init.NewExpression);
 296                         IEnumerable<ElementInit> initializers = this.VisitElementInitializerList (init.Initializers);
 297                         if (n != init.NewExpression || initializers != init.Initializers) return Expression.ListInit (n, initializers);
 298                         return init;
 299                 }
 300
 301                 protected virtual Expression VisitNewArray (NewArrayExpression na)
 302                 {
 303                         IEnumerable<Expression> exprs = this.VisitExpressionList (na.Expressions);
 304                         if (exprs != na.Expressions) {
 305                                 if (na.NodeType == ExpressionType.NewArrayInit) {
 306                                         return Expression.NewArrayInit (na.Type.GetElementType (), exprs);
 307                                 } else {
 308                                         return Expression.NewArrayBounds (na.Type.GetElementType (), exprs);
 309                                 }
 310                         }
 311                         return na;
 312                 }
 313
 314                 protected virtual Expression VisitInvocation (InvocationExpression iv)
 315                 {
 316                         IEnumerable<Expression> args = this.VisitExpressionList (iv.Arguments);
 317                         Expression expr = this.Visit (iv.Expression);
 318                         if (args != iv.Arguments || expr != iv.Expression) return Expression.Invoke (expr, args);
 319                         return iv;
 320                 }
 321         }
 322 }