mcs/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.Reflection.Emit;
  14
  15 namespace Mono.CSharp {
  16         public class LambdaExpression : AnonymousMethodExpression
  17         {
  18                 //
  19                 // The parameters can either be:
  20                 //    A list of Parameters (explicitly typed parameters)
  21                 //    An ImplicitLambdaParameter
  22                 //
  23                 public LambdaExpression (Location loc)
  24                         : base (loc)
  25                 {
  26                 }
  27
  28                 protected override Expression CreateExpressionTree (ResolveContext ec, TypeSpec delegate_type)
  29                 {
  30                         if (ec.IsInProbingMode)
  31                                 return this;
  32
  33                         BlockContext bc = new BlockContext (ec.MemberContext, ec.ConstructorBlock, TypeManager.void_type) {
  34                                 CurrentAnonymousMethod = ec.CurrentAnonymousMethod
  35                         };
  36
  37                         Expression args = Parameters.CreateExpressionTree (bc, loc);
  38                         Expression expr = Block.CreateExpressionTree (ec);
  39                         if (expr == null)
  40                                 return null;
  41
  42                         Arguments arguments = new Arguments (2);
  43                         arguments.Add (new Argument (expr));
  44                         arguments.Add (new Argument (args));
  45                         return CreateExpressionFactoryCall (ec, "Lambda",
  46                                 new TypeArguments (new TypeExpression (delegate_type, loc)),
  47                                 arguments);
  48                 }
  49
  50                 public override bool HasExplicitParameters {
  51                         get {
  52                                 return Parameters.Count > 0 && !(Parameters.FixedParameters [0] is ImplicitLambdaParameter);
  53                         }
  54                 }
  55
  56                 protected override ParametersCompiled ResolveParameters (ResolveContext ec, TypeInferenceContext tic, TypeSpec delegateType)
  57                 {
  58                         if (!delegateType.IsDelegate)
  59                                 return null;
  60
  61                         AParametersCollection d_params = Delegate.GetParameters (ec.Compiler, delegateType);
  62
  63                         if (HasExplicitParameters) {
  64                                 if (!VerifyExplicitParameters (ec, delegateType, d_params))
  65                                         return null;
  66
  67                                 return Parameters;
  68                         }
  69
  70                         //
  71                         // If L has an implicitly typed parameter list we make implicit parameters explicit
  72                         // Set each parameter of L is given the type of the corresponding parameter in D
  73                         //
  74                         if (!VerifyParameterCompatibility (ec, delegateType, d_params, ec.IsInProbingMode))
  75                                 return null;
  76
  77                         TypeSpec [] ptypes = new TypeSpec [Parameters.Count];
  78                         for (int i = 0; i < d_params.Count; i++) {
  79                                 // D has no ref or out parameters
  80                                 if ((d_params.FixedParameters [i].ModFlags & Parameter.Modifier.ISBYREF) != 0)
  81                                         return null;
  82
  83                                 TypeSpec d_param = d_params.Types [i];
  84
  85                                 //
  86                                 // When type inference context exists try to apply inferred type arguments
  87                                 //
  88                                 if (tic != null) {
  89                                         d_param = tic.InflateGenericArgument (d_param);
  90                                 }
  91
  92                                 ptypes [i] = d_param;
  93                                 ImplicitLambdaParameter ilp = (ImplicitLambdaParameter) Parameters.FixedParameters [i];
  94                                 ilp.SetParameterType (d_param);
  95                                 ilp.Resolve (null, i);
  96                         }
  97
  98                         Parameters.Types = ptypes;
  99                         return Parameters;
 100                 }
 101
 102                 protected override AnonymousMethodBody CompatibleMethodFactory (TypeSpec returnType, TypeSpec delegateType, ParametersCompiled p, ParametersBlock b)
 103                 {
 104                         return new LambdaMethod (p, b, returnType, delegateType, loc);
 105                 }
 106
 107                 protected override bool DoResolveParameters (ResolveContext rc)
 108                 {
 109                         //
 110                         // Only explicit parameters can be resolved at this point
 111                         //
 112                         if (HasExplicitParameters) {
 113                                 return Parameters.Resolve (rc);
 114                         }
 115
 116                         return true;
 117                 }
 118
 119                 public override string GetSignatureForError ()
 120                 {
 121                         return "lambda expression";
 122                 }
 123         }
 124
 125         class LambdaMethod : AnonymousMethodBody
 126         {
 127                 public LambdaMethod (ParametersCompiled parameters,
 128                                         ParametersBlock block, TypeSpec return_type, TypeSpec delegate_type,
 129                                         Location loc)
 130                         : base (parameters, block, return_type, delegate_type, loc)
 131                 {
 132                 }
 133
 134                 #region Properties
 135
 136                 public override string ContainerType {
 137                         get {
 138                                 return "lambda expression";
 139                         }
 140                 }
 141
 142                 #endregion
 143
 144                 protected override void CloneTo (CloneContext clonectx, Expression target)
 145                 {
 146                         // TODO: nothing ??
 147                 }
 148
 149                 public override Expression CreateExpressionTree (ResolveContext ec)
 150                 {
 151                         BlockContext bc = new BlockContext (ec.MemberContext, Block, ReturnType);
 152                         Expression args = parameters.CreateExpressionTree (bc, loc);
 153                         Expression expr = Block.CreateExpressionTree (ec);
 154                         if (expr == null)
 155                                 return null;
 156
 157                         Arguments arguments = new Arguments (2);
 158                         arguments.Add (new Argument (expr));
 159                         arguments.Add (new Argument (args));
 160                         return CreateExpressionFactoryCall (ec, "Lambda",
 161                                 new TypeArguments (new TypeExpression (type, loc)),
 162                                 arguments);
 163                 }
 164         }
 165
 166         //
 167         // This is a return statement that is prepended lambda expression bodies that happen
 168         // to be expressions.  Depending on the return type of the delegate this will behave
 169         // as either { expr (); return (); } or { return expr (); }
 170         //
 171         public class ContextualReturn : Return
 172         {
 173                 ExpressionStatement statement;
 174
 175                 public ContextualReturn (Expression expr)
 176                         : base (expr, expr.Location)
 177                 {
 178                 }
 179
 180                 public override Expression CreateExpressionTree (ResolveContext ec)
 181                 {
 182                         return Expr.CreateExpressionTree (ec);
 183                 }
 184
 185                 public override void Emit (EmitContext ec)
 186                 {
 187                         if (statement != null) {
 188                                 statement.EmitStatement (ec);
 189                                 ec.Emit (OpCodes.Ret);
 190                                 return;
 191                         }
 192
 193                         base.Emit (ec);
 194                 }
 195
 196                 protected override bool DoResolve (BlockContext ec)
 197                 {
 198                         //
 199                         // When delegate returns void, only expression statements can be used
 200                         //
 201                         if (ec.ReturnType == TypeManager.void_type) {
 202                                 Expr = Expr.Resolve (ec);
 203                                 if (Expr == null)
 204                                         return false;
 205
 206                                 statement = Expr as ExpressionStatement;
 207                                 if (statement == null)
 208                                         Expr.Error_InvalidExpressionStatement (ec);
 209
 210                                 return true;
 211                         }
 212
 213                         return base.DoResolve (ec);
 214                 }
 215         }
 216 }