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                         Expression args = Parameters.CreateExpressionTree (bc, loc);
  37                         Expression expr = Block.CreateExpressionTree (ec);
  38                         if (expr == null)
  39                                 return null;
  40
  41                         Arguments arguments = new Arguments (2);
  42                         arguments.Add (new Argument (expr));
  43                         arguments.Add (new Argument (args));
  44                         return CreateExpressionFactoryCall (ec, "Lambda",
  45                                 new TypeArguments (new TypeExpression (delegate_type, loc)),
  46                                 arguments);
  47                 }
  48
  49                 public override bool HasExplicitParameters {
  50                         get {
  51                                 return Parameters.Count > 0 && !(Parameters.FixedParameters [0] is ImplicitLambdaParameter);
  52                         }
  53                 }
  54
  55                 protected override ParametersCompiled ResolveParameters (ResolveContext ec, TypeInferenceContext tic, Type delegateType)
  56                 {
  57                         if (!TypeManager.IsDelegateType (delegateType))
  58                                 return null;
  59
  60                         AParametersCollection d_params = TypeManager.GetDelegateParameters (ec, delegateType);
  61
  62                         if (HasExplicitParameters) {
  63                                 if (!VerifyExplicitParameters (ec, delegateType, d_params))
  64                                         return null;
  65
  66                                 return Parameters;
  67                         }
  68
  69                         //
  70                         // If L has an implicitly typed parameter list we make implicit parameters explicit
  71                         // Set each parameter of L is given the type of the corresponding parameter in D
  72                         //
  73                         if (!VerifyParameterCompatibility (ec, delegateType, d_params, ec.IsInProbingMode))
  74                                 return null;
  75
  76                         Type [] ptypes = new Type [Parameters.Count];
  77                         for (int i = 0; i < d_params.Count; i++) {
  78                                 // D has no ref or out parameters
  79                                 if ((d_params.FixedParameters [i].ModFlags & Parameter.Modifier.ISBYREF) != 0)
  80                                         return null;
  81
  82                                 Type d_param = d_params.Types [i];
  83
  84 #if MS_COMPATIBLE
  85                                 // Blablabla, because reflection does not work with dynamic types
  86                                 if (d_param.IsGenericParameter)
  87                                         d_param = delegateType.GetGenericArguments () [d_param.GenericParameterPosition];
  88 #endif
  89                                 //
  90                                 // When type inference context exists try to apply inferred type arguments
  91                                 //
  92                                 if (tic != null) {
  93                                         d_param = tic.InflateGenericArgument (d_param);
  94                                 }
  95
  96                                 ptypes [i] = d_param;
  97                                 ((ImplicitLambdaParameter) Parameters.FixedParameters [i]).Type = d_param;
  98                         }
  99
 100                         Parameters.Types = ptypes;
 101                         return Parameters;
 102                 }
 103
 104                 public override Expression DoResolve (ResolveContext ec)
 105                 {
 106                         //
 107                         // Only explicit parameters can be resolved at this point
 108                         //
 109                         if (HasExplicitParameters) {
 110                                 if (!Parameters.Resolve (ec))
 111                                         return null;
 112                         }
 113
 114                         eclass = ExprClass.Value;
 115                         type = InternalType.AnonymousMethod;
 116                         return this;
 117                 }
 118
 119                 protected override AnonymousMethodBody CompatibleMethodFactory (Type returnType, Type delegateType, ParametersCompiled p, ToplevelBlock b)
 120                 {
 121                         return new LambdaMethod (p, b, returnType, delegateType, loc);
 122                 }
 123
 124                 public override string GetSignatureForError ()
 125                 {
 126                         return "lambda expression";
 127                 }
 128         }
 129
 130         public class LambdaMethod : AnonymousMethodBody
 131         {
 132                 public LambdaMethod (ParametersCompiled parameters,
 133                                         ToplevelBlock block, Type return_type, Type delegate_type,
 134                                         Location loc)
 135                         : base (parameters, block, return_type, delegate_type, loc)
 136                 {
 137                 }
 138
 139                 protected override void CloneTo (CloneContext clonectx, Expression target)
 140                 {
 141                         // TODO: nothing ??
 142                 }
 143
 144                 public override string ContainerType {
 145                         get {
 146                                 return "lambda expression";
 147                         }
 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.ig.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 }