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, Type delegate_type)
  30                 {
  31                         if (ec.IsInProbingMode)
  32                                 return this;
  33
  34                         BlockContext bc = new BlockContext (ec.MemberContext, ec.CurrentBlock.Explicit, 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, Type delegateType)
  58                 {
  59                         if (!TypeManager.IsDelegateType (delegateType))
  60                                 return null;
  61
  62                         AParametersCollection d_params = TypeManager.GetDelegateParameters (ec, 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                         Type [] ptypes = new Type [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                                 Type d_param = d_params.Types [i];
  85
  86 #if MS_COMPATIBLE
  87                                 // Blablabla, because reflection does not work with dynamic types
  88                                 if (d_param.IsGenericParameter)
  89                                         d_param = delegateType.GetGenericArguments () [d_param.GenericParameterPosition];
  90 #endif
  91                                 //
  92                                 // When type inference context exists try to apply inferred type arguments
  93                                 //
  94                                 if (tic != null) {
  95                                         d_param = tic.InflateGenericArgument (d_param);
  96                                 }
  97
  98                                 ptypes [i] = d_param;
  99                                 ((ImplicitLambdaParameter) Parameters.FixedParameters [i]).Type = d_param;
 100                         }
 101
 102                         Parameters.Types = ptypes;
 103                         return Parameters;
 104                 }
 105
 106                 protected override Expression DoResolve (ResolveContext ec)
 107                 {
 108                         //
 109                         // Only explicit parameters can be resolved at this point
 110                         //
 111                         if (HasExplicitParameters) {
 112                                 if (!Parameters.Resolve (ec))
 113                                         return null;
 114                         }
 115
 116                         eclass = ExprClass.Value;
 117                         type = InternalType.AnonymousMethod;
 118                         return this;
 119                 }
 120
 121                 protected override AnonymousMethodBody CompatibleMethodFactory (Type returnType, Type delegateType, ParametersCompiled p, ToplevelBlock b)
 122                 {
 123                         return new LambdaMethod (p, b, returnType, delegateType, loc);
 124                 }
 125
 126                 public override string GetSignatureForError ()
 127                 {
 128                         return "lambda expression";
 129                 }
 130         }
 131
 132         public class LambdaMethod : AnonymousMethodBody
 133         {
 134                 public LambdaMethod (ParametersCompiled parameters,
 135                                         ToplevelBlock block, Type return_type, Type delegate_type,
 136                                         Location loc)
 137                         : base (parameters, block, return_type, delegate_type, loc)
 138                 {
 139                 }
 140
 141                 protected override void CloneTo (CloneContext clonectx, Expression target)
 142                 {
 143                         // TODO: nothing ??
 144                 }
 145
 146                 public override string ContainerType {
 147                         get {
 148                                 return "lambda expression";
 149                         }
 150                 }
 151
 152                 public override Expression CreateExpressionTree (ResolveContext ec)
 153                 {
 154                         BlockContext bc = new BlockContext (ec.MemberContext, Block, ReturnType);
 155                         Expression args = parameters.CreateExpressionTree (bc, loc);
 156                         Expression expr = Block.CreateExpressionTree (ec);
 157                         if (expr == null)
 158                                 return null;
 159
 160                         Arguments arguments = new Arguments (2);
 161                         arguments.Add (new Argument (expr));
 162                         arguments.Add (new Argument (args));
 163                         return CreateExpressionFactoryCall (ec, "Lambda",
 164                                 new TypeArguments (new TypeExpression (type, loc)),
 165                                 arguments);
 166                 }
 167         }
 168
 169         //
 170         // This is a return statement that is prepended lambda expression bodies that happen
 171         // to be expressions.  Depending on the return type of the delegate this will behave
 172         // as either { expr (); return (); } or { return expr (); }
 173         //
 174         public class ContextualReturn : Return
 175         {
 176                 ExpressionStatement statement;
 177
 178                 public ContextualReturn (Expression expr)
 179                         : base (expr, expr.Location)
 180                 {
 181                 }
 182
 183                 public override Expression CreateExpressionTree (ResolveContext ec)
 184                 {
 185                         return Expr.CreateExpressionTree (ec);
 186                 }
 187
 188                 public override void Emit (EmitContext ec)
 189                 {
 190                         if (statement != null) {
 191                                 statement.EmitStatement (ec);
 192                                 ec.ig.Emit (OpCodes.Ret);
 193                                 return;
 194                         }
 195
 196                         base.Emit (ec);
 197                 }
 198
 199                 protected override bool DoResolve (BlockContext ec)
 200                 {
 201                         //
 202                         // When delegate returns void, only expression statements can be used
 203                         //
 204                         if (ec.ReturnType == TypeManager.void_type) {
 205                                 Expr = Expr.Resolve (ec);
 206                                 if (Expr == null)
 207                                         return false;
 208
 209                                 statement = Expr as ExpressionStatement;
 210                                 if (statement == null)
 211                                         Expr.Error_InvalidExpressionStatement (ec);
 212
 213                                 return true;
 214                         }
 215
 216                         return base.DoResolve (ec);
 217                 }
 218         }
 219 }