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 // Licensed under the terms of the GNU GPL
   8 //
   9 // (C) 2007 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                 readonly bool explicit_parameters;
  21
  22                 //
  23                 // The parameters can either be:
  24                 //    A list of Parameters (explicitly typed parameters)
  25                 //    An ImplicitLambdaParameter
  26                 //
  27                 public LambdaExpression (AnonymousMethodExpression parent,
  28                                          GenericMethod generic, TypeContainer host,
  29                                          Parameters parameters, Block container,
  30                                          Location loc)
  31                         : base (parent, generic, host, parameters, container, loc)
  32                 {
  33                         if (parameters.Count > 0)
  34                                 explicit_parameters = !(parameters.FixedParameters [0] is ImplicitLambdaParameter);
  35                 }
  36
  37                 protected override Expression CreateExpressionTree (EmitContext ec, Type delegate_type)
  38                 {
  39                         if (ec.IsInProbingMode)
  40                                 return this;
  41
  42                         Expression args = Parameters.CreateExpressionTree (ec, loc);
  43                         Expression expr = Block.CreateExpressionTree (ec);
  44                         if (expr == null)
  45                                 return null;
  46
  47                         ArrayList arguments = new ArrayList (2);
  48                         arguments.Add (new Argument (expr));
  49                         arguments.Add (new Argument (args));
  50                         return CreateExpressionFactoryCall ("Lambda",
  51                                 new TypeArguments (loc, new TypeExpression (delegate_type, loc)),
  52                                 arguments);
  53                 }
  54
  55                 public override bool HasExplicitParameters {
  56                         get {
  57                                 return explicit_parameters;
  58                         }
  59                 }
  60
  61                 protected override Parameters ResolveParameters (EmitContext ec, TypeInferenceContext tic, Type delegateType)
  62                 {
  63                         if (!TypeManager.IsDelegateType (delegateType))
  64                                 return null;
  65
  66                         ParameterData d_params = TypeManager.GetDelegateParameters (delegateType);
  67
  68                         if (explicit_parameters) {
  69                                 if (!VerifyExplicitParameters (delegateType, d_params, ec.IsInProbingMode))
  70                                         return null;
  71
  72                                 return Parameters;
  73                         }
  74
  75                         //
  76                         // If L has an implicitly typed parameter list we make implicit parameters explicit
  77                         // Set each parameter of L is given the type of the corresponding parameter in D
  78                         //
  79                         if (!VerifyParameterCompatibility (delegateType, d_params, ec.IsInProbingMode))
  80                                 return null;
  81
  82                         if (Parameters.Types == null)
  83                                 Parameters.Types = new Type [Parameters.Count];
  84
  85                         for (int i = 0; i < d_params.Count; i++) {
  86                                 // D has no ref or out parameters
  87                                 if ((d_params.ParameterModifier (i) & Parameter.Modifier.ISBYREF) != 0)
  88                                         return null;
  89
  90                                 Type d_param = d_params.Types [i];
  91
  92 #if MS_COMPATIBLE
  93                                 // Blablabla, because reflection does not work with dynamic types
  94                                 if (d_param.IsGenericParameter)
  95                                         d_param = delegateType.GetGenericArguments () [d_param.GenericParameterPosition];
  96 #endif
  97                                 // When inferred context exists all generics parameters have type replacements
  98                                 if (tic != null) {
  99                                         d_param = tic.InflateGenericArgument (d_param);
 100                                 }
 101
 102                                 Parameters.Types [i] = Parameters.FixedParameters[i].ParameterType = d_param;
 103                         }
 104                         return Parameters;
 105                 }
 106
 107                 public override Expression DoResolve (EmitContext ec)
 108                 {
 109                         //
 110                         // Only explicit parameters can be resolved at this point
 111                         //
 112                         if (explicit_parameters) {
 113                                 if (!Parameters.Resolve (ec))
 114                                         return null;
 115                         }
 116
 117                         eclass = ExprClass.Value;
 118                         type = TypeManager.anonymous_method_type;
 119                         return this;
 120                 }
 121
 122                 protected override AnonymousMethod CompatibleMethodFactory (Type returnType, Type delegateType, Parameters p, ToplevelBlock b)
 123                 {
 124                         return new LambdaMethod (RootScope, Host,
 125                                 GenericMethod, p, Container, b, returnType,
 126                                 delegateType, loc);
 127                 }
 128
 129                 public override string GetSignatureForError ()
 130                 {
 131                         return "lambda expression";
 132                 }
 133         }
 134
 135         public class LambdaMethod : AnonymousMethod
 136         {
 137                 public LambdaMethod (RootScopeInfo root_scope,
 138                                         DeclSpace host, GenericMethod generic,
 139                                         Parameters parameters, Block container,
 140                                         ToplevelBlock block, Type return_type, Type delegate_type,
 141                                         Location loc)
 142                         : base (root_scope, host, generic, parameters, container, block,
 143                                 return_type, delegate_type, loc)
 144                 {
 145                 }
 146
 147                 public override string ContainerType {
 148                         get {
 149                                 return "lambda expression";
 150                         }
 151                 }
 152         }
 153
 154         //
 155         // This is a return statement that is prepended lambda expression bodies that happen
 156         // to be expressions.  Depending on the return type of the delegate this will behave
 157         // as either { expr (); return (); } or { return expr (); }
 158         //
 159         public class ContextualReturn : Return
 160         {
 161                 public ContextualReturn (Expression expr)
 162                         : base (expr, expr.Location)
 163                 {
 164                 }
 165
 166                 public override Expression CreateExpressionTree (EmitContext ec)
 167                 {
 168                         return Expr.CreateExpressionTree (ec);
 169                 }
 170
 171                 public override void Emit (EmitContext ec)
 172                 {
 173                         if (ec.ReturnType == TypeManager.void_type)
 174                                 ((ExpressionStatement) Expr).EmitStatement (ec);
 175                         else
 176                                 base.Emit (ec);
 177                 }
 178
 179                 public override bool Resolve (EmitContext ec)
 180                 {
 181                         //
 182                         // When delegate returns void, only expression statements can be used
 183                         //
 184                         if (ec.ReturnType == TypeManager.void_type) {
 185                                 Expr = Expr.Resolve (ec);
 186                                 if (Expr == null)
 187                                         return false;
 188
 189                                 if (Expr is ExpressionStatement) {
 190                                         if (Expr is Invocation)
 191                                                 return TypeManager.IsEqual (Expr.Type, TypeManager.void_type);
 192                                         return true;
 193                                 }
 194
 195                                 Expr.Error_InvalidExpressionStatement ();
 196                                 return false;
 197                         }
 198
 199                         return base.Resolve (ec);
 200                 }
 201         }
 202 }