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;
  14 using System.Reflection.Emit;
  15
  16 namespace Mono.CSharp {
  17         public class LambdaExpression : AnonymousMethodExpression
  18         {
  19                 //
  20                 // The parameters can either be:
  21                 //    A list of Parameters (explicitly typed parameters)
  22                 //    An ImplicitLambdaParameter
  23                 //
  24                 public LambdaExpression (Location loc)
  25                         : base (loc)
  26                 {
  27                 }
  28
  29                 protected override Expression CreateExpressionTree (ResolveContext ec, TypeSpec delegate_type)
  30                 {
  31                         if (ec.IsInProbingMode)
  32                                 return this;
  33
  34                         BlockContext bc = new BlockContext (ec.MemberContext, ec.ConstructorBlock, TypeManager.void_type) {
  35                                 CurrentAnonymousMethod = ec.CurrentAnonymousMethod
  36                         };
  37
  38                         Expression args = Parameters.CreateExpressionTree (bc, loc);
  39                         Expression expr = Block.CreateExpressionTree (ec);
  40                         if (expr == null)
  41                                 return null;
  42
  43                         Arguments arguments = new Arguments (2);
  44                         arguments.Add (new Argument (expr));
  45                         arguments.Add (new Argument (args));
  46                         return CreateExpressionFactoryCall (ec, "Lambda",
  47                                 new TypeArguments (new TypeExpression (delegate_type, loc)),
  48                                 arguments);
  49                 }
  50
  51                 public override bool HasExplicitParameters {
  52                         get {
  53                                 return Parameters.Count > 0 && !(Parameters.FixedParameters [0] is ImplicitLambdaParameter);
  54                         }
  55                 }
  56
  57                 protected override ParametersCompiled ResolveParameters (ResolveContext ec, TypeInferenceContext tic, TypeSpec delegateType)
  58                 {
  59                         if (!delegateType.IsDelegate)
  60                                 return null;
  61
  62                         AParametersCollection d_params = Delegate.GetParameters (ec.Compiler, delegateType);
  63
  64                         if (HasExplicitParameters) {
  65                                 if (!VerifyExplicitParameters (ec, delegateType, d_params))
  66                                         return null;
  67
  68                                 return Parameters;
  69                         }
  70
  71                         //
  72                         // If L has an implicitly typed parameter list we make implicit parameters explicit
  73                         // Set each parameter of L is given the type of the corresponding parameter in D
  74                         //
  75                         if (!VerifyParameterCompatibility (ec, delegateType, d_params, ec.IsInProbingMode))
  76                                 return null;
  77
  78                         TypeSpec [] ptypes = new TypeSpec [Parameters.Count];
  79                         for (int i = 0; i < d_params.Count; i++) {
  80                                 // D has no ref or out parameters
  81                                 if ((d_params.FixedParameters [i].ModFlags & Parameter.Modifier.ISBYREF) != 0)
  82                                         return null;
  83
  84                                 TypeSpec d_param = d_params.Types [i];
  85
  86                                 //
  87                                 // When type inference context exists try to apply inferred type arguments
  88                                 //
  89                                 if (tic != null) {
  90                                         d_param = tic.InflateGenericArgument (d_param);
  91                                 }
  92
  93                                 ptypes [i] = d_param;
  94                                 ImplicitLambdaParameter ilp = (ImplicitLambdaParameter) Parameters.FixedParameters [i];
  95                                 ilp.Type = d_param;
  96                                 ilp.Resolve (null, i);
  97                         }
  98
  99                         Parameters.Types = ptypes;
 100                         return Parameters;
 101                 }
 102
 103                 protected override AnonymousMethodBody CompatibleMethodFactory (TypeSpec returnType, TypeSpec delegateType, ParametersCompiled p, ToplevelBlock b)
 104                 {
 105                         return new LambdaMethod (p, b, returnType, delegateType, loc);
 106                 }
 107
 108                 protected override bool DoResolveParameters (ResolveContext rc)
 109                 {
 110                         //
 111                         // Only explicit parameters can be resolved at this point
 112                         //
 113                         if (HasExplicitParameters) {
 114                                 return Parameters.Resolve (rc);
 115                         }
 116
 117                         return true;
 118                 }
 119
 120                 public override string GetSignatureForError ()
 121                 {
 122                         return "lambda expression";
 123                 }
 124         }
 125
 126         class LambdaMethod : AnonymousMethodBody
 127         {
 128                 public LambdaMethod (ParametersCompiled parameters,
 129                                         ToplevelBlock block, TypeSpec return_type, TypeSpec delegate_type,
 130                                         Location loc)
 131                         : base (parameters, block, return_type, delegate_type, loc)
 132                 {
 133                 }
 134
 135                 #region Properties
 136
 137                 public override string ContainerType {
 138                         get {
 139                                 return "lambda expression";
 140                         }
 141                 }
 142
 143                 #endregion
 144
 145                 protected override void CloneTo (CloneContext clonectx, Expression target)
 146                 {
 147                         // TODO: nothing ??
 148                 }
 149
 150                 public override Expression CreateExpressionTree (ResolveContext ec)
 151                 {
 152                         BlockContext bc = new BlockContext (ec.MemberContext, Block, ReturnType);
 153                         Expression args = parameters.CreateExpressionTree (bc, loc);
 154                         Expression expr = Block.CreateExpressionTree (ec);
 155                         if (expr == null)
 156                                 return null;
 157
 158                         Arguments arguments = new Arguments (2);
 159                         arguments.Add (new Argument (expr));
 160                         arguments.Add (new Argument (args));
 161                         return CreateExpressionFactoryCall (ec, "Lambda",
 162                                 new TypeArguments (new TypeExpression (type, loc)),
 163                                 arguments);
 164                 }
 165         }
 166
 167         //
 168         // This is a return statement that is prepended lambda expression bodies that happen
 169         // to be expressions.  Depending on the return type of the delegate this will behave
 170         // as either { expr (); return (); } or { return expr (); }
 171         //
 172         public class ContextualReturn : Return
 173         {
 174                 ExpressionStatement statement;
 175
 176                 public ContextualReturn (Expression expr)
 177                         : base (expr, expr.Location)
 178                 {
 179                 }
 180
 181                 public override Expression CreateExpressionTree (ResolveContext ec)
 182                 {
 183                         return Expr.CreateExpressionTree (ec);
 184                 }
 185
 186                 public override void Emit (EmitContext ec)
 187                 {
 188                         if (statement != null) {
 189                                 statement.EmitStatement (ec);
 190                                 ec.Emit (OpCodes.Ret);
 191                                 return;
 192                         }
 193
 194                         base.Emit (ec);
 195                 }
 196
 197                 protected override bool DoResolve (BlockContext ec)
 198                 {
 199                         //
 200                         // When delegate returns void, only expression statements can be used
 201                         //
 202                         if (ec.ReturnType == TypeManager.void_type) {
 203                                 Expr = Expr.Resolve (ec);
 204                                 if (Expr == null)
 205                                         return false;
 206
 207                                 statement = Expr as ExpressionStatement;
 208                                 if (statement == null)
 209                                         Expr.Error_InvalidExpressionStatement (ec);
 210
 211                                 return true;
 212                         }
 213
 214                         return base.DoResolve (ec);
 215                 }
 216         }
 217 }