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