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.Reflection.Emit;
  13
  14 namespace Mono.CSharp {
  15         public class LambdaExpression : AnonymousMethodExpression
  16         {
  17                 //
  18                 // The parameters can either be:
  19                 //    A list of Parameters (explicitly typed parameters)
  20                 //    An ImplicitLambdaParameter
  21                 //
  22                 public LambdaExpression (Location loc)
  23                         : base (loc)
  24                 {
  25                 }
  26
  27                 protected override Expression CreateExpressionTree (ResolveContext ec, TypeSpec delegate_type)
  28                 {
  29                         if (ec.IsInProbingMode)
  30                                 return this;
  31
  32                         BlockContext bc = new BlockContext (ec.MemberContext, ec.ConstructorBlock, TypeManager.void_type) {
  33                                 CurrentAnonymousMethod = ec.CurrentAnonymousMethod
  34                         };
  35
  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, TypeSpec delegateType)
  56                 {
  57                         if (!delegateType.IsDelegate)
  58                                 return null;
  59
  60                         AParametersCollection d_params = Delegate.GetParameters (ec.Compiler, 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                         TypeSpec [] ptypes = new TypeSpec [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                                 TypeSpec d_param = d_params.Types [i];
  83
  84                                 //
  85                                 // When type inference context exists try to apply inferred type arguments
  86                                 //
  87                                 if (tic != null) {
  88                                         d_param = tic.InflateGenericArgument (d_param);
  89                                 }
  90
  91                                 ptypes [i] = d_param;
  92                                 ImplicitLambdaParameter ilp = (ImplicitLambdaParameter) Parameters.FixedParameters [i];
  93                                 ilp.SetParameterType (d_param);
  94                                 ilp.Resolve (null, i);
  95                         }
  96
  97                         Parameters.Types = ptypes;
  98                         return Parameters;
  99                 }
 100
 101                 protected override AnonymousMethodBody CompatibleMethodFactory (TypeSpec returnType, TypeSpec delegateType, ParametersCompiled p, ParametersBlock b)
 102                 {
 103                         return new LambdaMethod (p, b, returnType, delegateType, loc);
 104                 }
 105
 106                 protected override bool DoResolveParameters (ResolveContext rc)
 107                 {
 108                         //
 109                         // Only explicit parameters can be resolved at this point
 110                         //
 111                         if (HasExplicitParameters) {
 112                                 return Parameters.Resolve (rc);
 113                         }
 114
 115                         return true;
 116                 }
 117
 118                 public override string GetSignatureForError ()
 119                 {
 120                         return "lambda expression";
 121                 }
 122         }
 123
 124         class LambdaMethod : AnonymousMethodBody
 125         {
 126                 public LambdaMethod (ParametersCompiled parameters,
 127                                         ParametersBlock block, TypeSpec return_type, TypeSpec delegate_type,
 128                                         Location loc)
 129                         : base (parameters, block, return_type, delegate_type, loc)
 130                 {
 131                 }
 132
 133                 #region Properties
 134
 135                 public override string ContainerType {
 136                         get {
 137                                 return "lambda expression";
 138                         }
 139                 }
 140
 141                 #endregion
 142
 143                 protected override void CloneTo (CloneContext clonectx, Expression target)
 144                 {
 145                         // TODO: nothing ??
 146                 }
 147
 148                 public override Expression CreateExpressionTree (ResolveContext ec)
 149                 {
 150                         BlockContext bc = new BlockContext (ec.MemberContext, Block, ReturnType);
 151                         Expression args = parameters.CreateExpressionTree (bc, 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 (ec, "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                 ExpressionStatement statement;
 173
 174                 public ContextualReturn (Expression expr)
 175                         : base (expr, expr.Location)
 176                 {
 177                 }
 178
 179                 public override Expression CreateExpressionTree (ResolveContext ec)
 180                 {
 181                         return Expr.CreateExpressionTree (ec);
 182                 }
 183
 184                 public override void Emit (EmitContext ec)
 185                 {
 186                         if (statement != null) {
 187                                 statement.EmitStatement (ec);
 188                                 ec.Emit (OpCodes.Ret);
 189                                 return;
 190                         }
 191
 192                         base.Emit (ec);
 193                 }
 194
 195                 protected override bool DoResolve (BlockContext ec)
 196                 {
 197                         //
 198                         // When delegate returns void, only expression statements can be used
 199                         //
 200                         if (ec.ReturnType == TypeManager.void_type) {
 201                                 Expr = Expr.Resolve (ec);
 202                                 if (Expr == null)
 203                                         return false;
 204
 205                                 statement = Expr as ExpressionStatement;
 206                                 if (statement == null)
 207                                         Expr.Error_InvalidExpressionStatement (ec);
 208
 209                                 return true;
 210                         }
 211
 212                         return base.DoResolve (ec);
 213                 }
 214         }
 215 }