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 // Copyright 2011 Xamarin Inc
  11 //
  12
  13 #if STATIC
  14 using IKVM.Reflection.Emit;
  15 #else
  16 using System.Reflection.Emit;
  17 #endif
  18
  19 namespace Mono.CSharp {
  20         public class LambdaExpression : AnonymousMethodExpression
  21         {
  22                 //
  23                 // The parameters can either be:
  24                 //    A list of Parameters (explicitly typed parameters)
  25                 //    An ImplicitLambdaParameter
  26                 //
  27                 public LambdaExpression (Location loc)
  28                         : base (loc)
  29                 {
  30                 }
  31
  32                 protected override Expression CreateExpressionTree (ResolveContext ec, TypeSpec delegate_type)
  33                 {
  34                         if (ec.IsInProbingMode)
  35                                 return this;
  36
  37                         BlockContext bc = new BlockContext (ec.MemberContext, ec.ConstructorBlock, ec.BuiltinTypes.Void) {
  38                                 CurrentAnonymousMethod = ec.CurrentAnonymousMethod
  39                         };
  40
  41                         Expression args = Parameters.CreateExpressionTree (bc, loc);
  42                         Expression expr = Block.CreateExpressionTree (ec);
  43                         if (expr == null)
  44                                 return null;
  45
  46                         Arguments arguments = new Arguments (2);
  47                         arguments.Add (new Argument (expr));
  48                         arguments.Add (new Argument (args));
  49                         return CreateExpressionFactoryCall (ec, "Lambda",
  50                                 new TypeArguments (new TypeExpression (delegate_type, loc)),
  51                                 arguments);
  52                 }
  53
  54                 public override bool HasExplicitParameters {
  55                         get {
  56                                 return Parameters.Count > 0 && !(Parameters.FixedParameters [0] is ImplicitLambdaParameter);
  57                         }
  58                 }
  59
  60                 protected override ParametersCompiled ResolveParameters (ResolveContext ec, TypeInferenceContext tic, TypeSpec delegateType)
  61                 {
  62                         if (!delegateType.IsDelegate)
  63                                 return null;
  64
  65                         AParametersCollection d_params = Delegate.GetParameters (delegateType);
  66
  67                         if (HasExplicitParameters) {
  68                                 if (!VerifyExplicitParameters (ec, tic, delegateType, d_params))
  69                                         return null;
  70
  71                                 return Parameters;
  72                         }
  73
  74                         //
  75                         // If L has an implicitly typed parameter list we make implicit parameters explicit
  76                         // Set each parameter of L is given the type of the corresponding parameter in D
  77                         //
  78                         if (!VerifyParameterCompatibility (ec, tic, delegateType, d_params, ec.IsInProbingMode))
  79                                 return null;
  80
  81                         TypeSpec [] ptypes = new TypeSpec [Parameters.Count];
  82                         for (int i = 0; i < d_params.Count; i++) {
  83                                 // D has no ref or out parameters
  84                                 if ((d_params.FixedParameters[i].ModFlags & Parameter.Modifier.RefOutMask) != 0)
  85                                         return null;
  86
  87                                 TypeSpec d_param = d_params.Types [i];
  88
  89                                 //
  90                                 // When type inference context exists try to apply inferred type arguments
  91                                 //
  92                                 if (tic != null) {
  93                                         d_param = tic.InflateGenericArgument (ec, d_param);
  94                                 }
  95
  96                                 ptypes [i] = d_param;
  97                                 ImplicitLambdaParameter ilp = (ImplicitLambdaParameter) Parameters.FixedParameters [i];
  98                                 ilp.SetParameterType (d_param);
  99                                 ilp.Resolve (null, i);
 100                         }
 101
 102                         Parameters.Types = ptypes;
 103                         return Parameters;
 104                 }
 105
 106                 protected override AnonymousMethodBody CompatibleMethodFactory (TypeSpec returnType, TypeSpec delegateType, ParametersCompiled p, ParametersBlock b)
 107                 {
 108                         return new LambdaMethod (p, b, returnType, delegateType, loc);
 109                 }
 110
 111                 protected override bool DoResolveParameters (ResolveContext rc)
 112                 {
 113                         //
 114                         // Only explicit parameters can be resolved at this point
 115                         //
 116                         if (HasExplicitParameters) {
 117                                 return Parameters.Resolve (rc);
 118                         }
 119
 120                         return true;
 121                 }
 122
 123                 public override string GetSignatureForError ()
 124                 {
 125                         return "lambda expression";
 126                 }
 127
 128                 public override object Accept (StructuralVisitor visitor)
 129                 {
 130                         return visitor.Visit (this);
 131                 }
 132         }
 133
 134         class LambdaMethod : AnonymousMethodBody
 135         {
 136                 public LambdaMethod (ParametersCompiled parameters,
 137                                         ParametersBlock block, TypeSpec return_type, TypeSpec delegate_type,
 138                                         Location loc)
 139                         : base (parameters, block, return_type, delegate_type, loc)
 140                 {
 141                 }
 142
 143                 #region Properties
 144
 145                 public override string ContainerType {
 146                         get {
 147                                 return "lambda expression";
 148                         }
 149                 }
 150
 151                 #endregion
 152
 153                 protected override void CloneTo (CloneContext clonectx, Expression target)
 154                 {
 155                         // TODO: nothing ??
 156                 }
 157
 158                 public override Expression CreateExpressionTree (ResolveContext ec)
 159                 {
 160                         BlockContext bc = new BlockContext (ec.MemberContext, Block, ReturnType);
 161                         Expression args = parameters.CreateExpressionTree (bc, loc);
 162                         Expression expr = Block.CreateExpressionTree (ec);
 163                         if (expr == null)
 164                                 return null;
 165
 166                         Arguments arguments = new Arguments (2);
 167                         arguments.Add (new Argument (expr));
 168                         arguments.Add (new Argument (args));
 169                         return CreateExpressionFactoryCall (ec, "Lambda",
 170                                 new TypeArguments (new TypeExpression (type, loc)),
 171                                 arguments);
 172                 }
 173         }
 174
 175         //
 176         // This is a return statement that is prepended lambda expression bodies that happen
 177         // to be expressions.  Depending on the return type of the delegate this will behave
 178         // as either { expr (); return (); } or { return expr (); }
 179         //
 180         public class ContextualReturn : Return
 181         {
 182                 ExpressionStatement statement;
 183
 184                 public ContextualReturn (Expression expr)
 185                         : base (expr, expr.StartLocation)
 186                 {
 187                 }
 188
 189                 public override Expression CreateExpressionTree (ResolveContext ec)
 190                 {
 191                         return Expr.CreateExpressionTree (ec);
 192                 }
 193
 194                 protected override void DoEmit (EmitContext ec)
 195                 {
 196                         if (statement != null) {
 197                                 statement.EmitStatement (ec);
 198                                 if (unwind_protect)
 199                                         ec.Emit (OpCodes.Leave, ec.CreateReturnLabel ());
 200                                 else {
 201                                         ec.Emit (OpCodes.Ret);
 202                                 }
 203                                 return;
 204                         }
 205
 206                         base.DoEmit (ec);
 207                 }
 208
 209                 protected override bool DoResolve (BlockContext ec)
 210                 {
 211                         //
 212                         // When delegate returns void, only expression statements can be used
 213                         //
 214                         if (ec.ReturnType.Kind == MemberKind.Void) {
 215                                 Expr = Expr.Resolve (ec);
 216                                 if (Expr == null)
 217                                         return false;
 218
 219                                 statement = Expr as ExpressionStatement;
 220                                 if (statement == null) {
 221                                         var reduced = Expr as IReducedExpressionStatement;
 222                                         if (reduced != null) {
 223                                                 statement = EmptyExpressionStatement.Instance;
 224                                         } else {
 225                                                 Expr.Error_InvalidExpressionStatement (ec);
 226                                         }
 227                                 }
 228
 229                                 return true;
 230                         }
 231
 232                         return base.DoResolve (ec);
 233                 }
 234         }
 235 }