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;
  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, TypeSpec 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, TypeSpec delegateType)
  58                 {
  59                         if (!delegateType.IsDelegate)
  60                                 return null;
  61
  62                         AParametersCollection d_params = Delegate.GetParameters (ec.Compiler, 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                         TypeSpec [] ptypes = new TypeSpec [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                                 TypeSpec d_param = d_params.Types [i];
  85
  86                                 //
  87                                 // When type inference context exists try to apply inferred type arguments
  88                                 //
  89                                 if (tic != null) {
  90                                         d_param = tic.InflateGenericArgument (d_param);
  91                                 }
  92
  93                                 ptypes [i] = d_param;
  94                                 ImplicitLambdaParameter ilp = (ImplicitLambdaParameter) Parameters.FixedParameters [i];
  95                                 ilp.Type = d_param;
  96                                 ilp.Resolve (null, i);
  97                         }
  98
  99                         Parameters.Types = ptypes;
 100                         return Parameters;
 101                 }
 102
 103                 protected override Expression DoResolve (ResolveContext 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 (TypeSpec returnType, TypeSpec 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, TypeSpec return_type, TypeSpec 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 (ResolveContext ec)
 150                 {
 151                         BlockContext bc = new BlockContext (ec.MemberContext, Block, ReturnType);
 152                         Expression args = parameters.CreateExpressionTree (bc, loc);
 153                         Expression expr = Block.CreateExpressionTree (ec);
 154                         if (expr == null)
 155                                 return null;
 156
 157                         Arguments arguments = new Arguments (2);
 158                         arguments.Add (new Argument (expr));
 159                         arguments.Add (new Argument (args));
 160                         return CreateExpressionFactoryCall (ec, "Lambda",
 161                                 new TypeArguments (new TypeExpression (type, loc)),
 162                                 arguments);
 163                 }
 164         }
 165
 166         //
 167         // This is a return statement that is prepended lambda expression bodies that happen
 168         // to be expressions.  Depending on the return type of the delegate this will behave
 169         // as either { expr (); return (); } or { return expr (); }
 170         //
 171         public class ContextualReturn : Return
 172         {
 173                 ExpressionStatement statement;
 174
 175                 public ContextualReturn (Expression expr)
 176                         : base (expr, expr.Location)
 177                 {
 178                 }
 179
 180                 public override Expression CreateExpressionTree (ResolveContext ec)
 181                 {
 182                         return Expr.CreateExpressionTree (ec);
 183                 }
 184
 185                 public override void Emit (EmitContext ec)
 186                 {
 187                         if (statement != null) {
 188                                 statement.EmitStatement (ec);
 189                                 ec.Emit (OpCodes.Ret);
 190                                 return;
 191                         }
 192
 193                         base.Emit (ec);
 194                 }
 195
 196                 protected override bool DoResolve (BlockContext ec)
 197                 {
 198                         //
 199                         // When delegate returns void, only expression statements can be used
 200                         //
 201                         if (ec.ReturnType == TypeManager.void_type) {
 202                                 Expr = Expr.Resolve (ec);
 203                                 if (Expr == null)
 204                                         return false;
 205
 206                                 statement = Expr as ExpressionStatement;
 207                                 if (statement == null)
 208                                         Expr.Error_InvalidExpressionStatement (ec);
 209
 210                                 return true;
 211                         }
 212
 213                         return base.DoResolve (ec);
 214                 }
 215         }
 216 }