mcs/lambda.cs

   1 //
   2 // lambda.cs: support for lambda expressions
   3 //
   4 // Authors: Miguel de Icaza (miguel@gnu.org)
   5 //          Marek Safar (marek.safar@gmail.com)
   6 //
   7 // Dual licensed under the terms of the MIT X11 or GNU GPL
   8 //
   9 // Copyright 2007-2008 Novell, Inc
  10 //
  11
  12 using System;
  13 using System.Collections;
  14 using System.Reflection;
  15 using System.Reflection.Emit;
  16
  17 namespace Mono.CSharp {
  18         public class LambdaExpression : AnonymousMethodExpression
  19         {
  20                 //
  21                 // The parameters can either be:
  22                 //    A list of Parameters (explicitly typed parameters)
  23                 //    An ImplicitLambdaParameter
  24                 //
  25                 public LambdaExpression (Location loc)
  26                         : base (loc)
  27                 {
  28                 }
  29
  30                 protected override Expression CreateExpressionTree (ResolveContext ec, Type delegate_type)
  31                 {
  32                         if (ec.IsInProbingMode)
  33                                 return this;
  34
  35                         BlockContext bc = new BlockContext (ec.MemberContext, ec.CurrentBlock.Explicit, TypeManager.void_type) {
  36                                 CurrentAnonymousMethod = ec.CurrentAnonymousMethod
  37                         };
  38
  39                         Expression args = Parameters.CreateExpressionTree (bc, loc);
  40                         Expression expr = Block.CreateExpressionTree (ec);
  41                         if (expr == null)
  42                                 return null;
  43
  44                         Arguments arguments = new Arguments (2);
  45                         arguments.Add (new Argument (expr));
  46                         arguments.Add (new Argument (args));
  47                         return CreateExpressionFactoryCall (ec, "Lambda",
  48                                 new TypeArguments (new TypeExpression (delegate_type, loc)),
  49                                 arguments);
  50                 }
  51
  52                 public override bool HasExplicitParameters {
  53                         get {
  54                                 return Parameters.Count > 0 && !(Parameters.FixedParameters [0] is ImplicitLambdaParameter);
  55                         }
  56                 }
  57
  58                 protected override ParametersCompiled ResolveParameters (ResolveContext ec, TypeInferenceContext tic, Type delegateType)
  59                 {
  60                         if (!TypeManager.IsDelegateType (delegateType))
  61                                 return null;
  62
  63                         AParametersCollection d_params = TypeManager.GetDelegateParameters (ec, delegateType);
  64
  65                         if (HasExplicitParameters) {
  66                                 if (!VerifyExplicitParameters (ec, delegateType, d_params))
  67                                         return null;
  68
  69                                 return Parameters;
  70                         }
  71
  72                         //
  73                         // If L has an implicitly typed parameter list we make implicit parameters explicit
  74                         // Set each parameter of L is given the type of the corresponding parameter in D
  75                         //
  76                         if (!VerifyParameterCompatibility (ec, delegateType, d_params, ec.IsInProbingMode))
  77                                 return null;
  78
  79                         Type [] ptypes = new Type [Parameters.Count];
  80                         for (int i = 0; i < d_params.Count; i++) {
  81                                 // D has no ref or out parameters
  82                                 if ((d_params.FixedParameters [i].ModFlags & Parameter.Modifier.ISBYREF) != 0)
  83                                         return null;
  84
  85                                 Type d_param = d_params.Types [i];
  86
  87 #if MS_COMPATIBLE
  88                                 // Blablabla, because reflection does not work with dynamic types
  89                                 if (d_param.IsGenericParameter)
  90                                         d_param = delegateType.GetGenericArguments () [d_param.GenericParameterPosition];
  91 #endif
  92                                 //
  93                                 // When type inference context exists try to apply inferred type arguments
  94                                 //
  95                                 if (tic != null) {
  96                                         d_param = tic.InflateGenericArgument (d_param);
  97                                 }
  98
  99                                 ptypes [i] = d_param;
 100                                 ((ImplicitLambdaParameter) Parameters.FixedParameters [i]).Type = d_param;
 101                         }
 102
 103                         Parameters.Types = ptypes;
 104                         return Parameters;
 105                 }
 106
 107                 protected override Expression DoResolve (ResolveContext ec)
 108                 {
 109                         //
 110                         // Only explicit parameters can be resolved at this point
 111                         //
 112                         if (HasExplicitParameters) {
 113                                 if (!Parameters.Resolve (ec))
 114                                         return null;
 115                         }
 116
 117                         eclass = ExprClass.Value;
 118                         type = InternalType.AnonymousMethod;
 119                         return this;
 120                 }
 121
 122                 protected override AnonymousMethodBody CompatibleMethodFactory (Type returnType, Type delegateType, ParametersCompiled p, ToplevelBlock b)
 123                 {
 124                         return new LambdaMethod (p, b, returnType, delegateType, loc);
 125                 }
 126
 127                 public override string GetSignatureForError ()
 128                 {
 129                         return "lambda expression";
 130                 }
 131         }
 132
 133         public class LambdaMethod : AnonymousMethodBody
 134         {
 135                 public LambdaMethod (ParametersCompiled parameters,
 136                                         ToplevelBlock block, Type return_type, Type delegate_type,
 137                                         Location loc)
 138                         : base (parameters, block, return_type, delegate_type, loc)
 139                 {
 140                 }
 141
 142                 protected override void CloneTo (CloneContext clonectx, Expression target)
 143                 {
 144                         // TODO: nothing ??
 145                 }
 146
 147                 public override string ContainerType {
 148                         get {
 149                                 return "lambda expression";
 150                         }
 151                 }
 152
 153                 public override Expression CreateExpressionTree (ResolveContext ec)
 154                 {
 155                         BlockContext bc = new BlockContext (ec.MemberContext, Block, ReturnType);
 156                         Expression args = parameters.CreateExpressionTree (bc, loc);
 157                         Expression expr = Block.CreateExpressionTree (ec);
 158                         if (expr == null)
 159                                 return null;
 160
 161                         Arguments arguments = new Arguments (2);
 162                         arguments.Add (new Argument (expr));
 163                         arguments.Add (new Argument (args));
 164                         return CreateExpressionFactoryCall (ec, "Lambda",
 165                                 new TypeArguments (new TypeExpression (type, loc)),
 166                                 arguments);
 167                 }
 168         }
 169
 170         //
 171         // This is a return statement that is prepended lambda expression bodies that happen
 172         // to be expressions.  Depending on the return type of the delegate this will behave
 173         // as either { expr (); return (); } or { return expr (); }
 174         //
 175         public class ContextualReturn : Return
 176         {
 177                 ExpressionStatement statement;
 178
 179                 public ContextualReturn (Expression expr)
 180                         : base (expr, expr.Location)
 181                 {
 182                 }
 183
 184                 public override Expression CreateExpressionTree (ResolveContext ec)
 185                 {
 186                         return Expr.CreateExpressionTree (ec);
 187                 }
 188
 189                 public override void Emit (EmitContext ec)
 190                 {
 191                         if (statement != null) {
 192                                 statement.EmitStatement (ec);
 193                                 ec.ig.Emit (OpCodes.Ret);
 194                                 return;
 195                         }
 196
 197                         base.Emit (ec);
 198                 }
 199
 200                 protected override bool DoResolve (BlockContext ec)
 201                 {
 202                         //
 203                         // When delegate returns void, only expression statements can be used
 204                         //
 205                         if (ec.ReturnType == TypeManager.void_type) {
 206                                 Expr = Expr.Resolve (ec);
 207                                 if (Expr == null)
 208                                         return false;
 209
 210                                 statement = Expr as ExpressionStatement;
 211                                 if (statement == null)
 212                                         Expr.Error_InvalidExpressionStatement (ec);
 213
 214                                 return true;
 215                         }
 216
 217                         return base.DoResolve (ec);
 218                 }
 219         }
 220 }