mcs/mcs/lambda.cs

   1 //
   2 // lambda.cs: support for lambda expressions
   3 //
   4 // Authors: Miguel de Icaza (miguel@gnu.org)
   5 //
   6 // Licensed under the terms of the GNU GPL
   7 //
   8 // (C) 2007 Novell, Inc
   9 //
  10
  11 using System;
  12 using System.Collections;
  13 using System.Reflection;
  14 using System.Reflection.Emit;
  15
  16 namespace Mono.CSharp {
  17         public class LambdaExpression : AnonymousMethodExpression {
  18                 bool explicit_parameters;
  19
  20                 //
  21                 // The parameter list can either be:
  22                 //    null: no parameters
  23                 //    arraylist of Parameter (explicitly typed parameters)
  24                 //    arraylist of strings (implicitly typed parameters)
  25                 //
  26                 public LambdaExpression (AnonymousMethodExpression parent,
  27                                          GenericMethod generic, TypeContainer host,
  28                                          Parameters parameters, Block container,
  29                                          Location loc)
  30                         : base (parent, generic, host, parameters, container, loc)
  31                 {
  32                         explicit_parameters = (parameters != null && parameters.Count > 0 && parameters [0].TypeName != null);
  33                         if (parameters == null)
  34                                 Parameters = new Parameters (new Parameter [0]);
  35                 }
  36
  37                 public bool HasImplicitParameters {
  38                         get {
  39                                 return !explicit_parameters;
  40                         }
  41                 }
  42
  43                 public bool HasExplicitParameters {
  44                         get {
  45                                 return explicit_parameters;
  46                         }
  47                 }
  48
  49                 public override Expression DoResolve (EmitContext ec)
  50                 {
  51                         eclass = ExprClass.Value;
  52                         type = TypeManager.anonymous_method_type;
  53
  54                         if (explicit_parameters){
  55                                 if (!Parameters.Resolve (ec))
  56                                         return null;
  57                         }
  58
  59                         // We will resolve parameters later, we do not
  60                         // have information at this point.
  61
  62                         return this;
  63                 }
  64
  65                 public override void Emit (EmitContext ec)
  66                 {
  67                         base.Emit (ec);
  68                 }
  69
  70                 public override bool ImplicitStandardConversionExists (Type delegate_type)
  71                 {
  72                         EmitContext ec = EmitContext.TempEc;
  73
  74                         bool result;
  75
  76                         try {
  77                                 Report.DisableErrors ();
  78                                 result = DoCompatibleTest (ec, delegate_type, true) != null;
  79                                 if (result)
  80                                         Console.WriteLine ("INFO: Lambda.Compatible Passed for {0}", delegate_type);
  81                                 else
  82                                         Console.WriteLine ("INFO: Lambda.Compatible Failed for {0}", delegate_type);
  83                         } finally {
  84                                 Report.EnableErrors ();
  85                         }
  86
  87                         // Ignore the result
  88                         anonymous = null;
  89
  90                         return result;
  91                 }
  92
  93                 //
  94                 // Returns true if this anonymous method can be implicitly
  95                 // converted to the delegate type `delegate_type'
  96                 //
  97                 public override Expression Compatible (EmitContext ec, Type delegate_type)
  98                 {
  99                         return DoCompatibleTest (ec, delegate_type, false);
 100                 }
 101
 102                 Expression DoCompatibleTest (EmitContext ec, Type delegate_type, bool clone)
 103                 {
 104                         if (anonymous != null)
 105                                 return anonymous.AnonymousDelegate;
 106
 107                         if (CompatibleChecks (ec, delegate_type) == null)
 108                                 return null;
 109
 110                         MethodGroupExpr invoke_mg = Delegate.GetInvokeMethod (
 111                                 ec.ContainerType, delegate_type, loc);
 112                         MethodInfo invoke_mb = (MethodInfo) invoke_mg.Methods [0];
 113                         ParameterData invoke_pd = TypeManager.GetParameterData (invoke_mb);
 114
 115                         //
 116                         // The lambda expression is compatible with the delegate type,
 117                         // provided that:
 118                         //
 119
 120                         //
 121                         // D and L have the same number of arguments.
 122                         if (Parameters.Count != invoke_pd.Count)
 123                                 return null;
 124
 125                         if (explicit_parameters){
 126                                 //
 127                                 // If L has an explicitly typed parameter list, each parameter
 128                                 // in D has the same type and modifiers as the corresponding
 129                                 // parameter in L.
 130                                 //
 131                                 if (!VerifyExplicitParameterCompatibility (delegate_type, invoke_pd))
 132                                         return null;
 133                         } else {
 134                                 //
 135                                 // If L has an implicitly typed parameter list, D has no ref or
 136                                 // out parameters
 137                                 //
 138                                 // Note: We currently do nothing, because the preview does not
 139                                 // follow the above rule.
 140
 141                                 //
 142                                 // each parameter of L is given the type of the corresponding parameter in D
 143                                 //
 144
 145                                 for (int i = 0; i < invoke_pd.Count; i++)
 146                                         Parameters [i].TypeName = new TypeExpression (
 147                                                 invoke_pd.ParameterType (i),
 148                                                 Parameters [i].Location);
 149                         }
 150
 151                         //
 152                         // The return type of the delegate must be compatible with
 153                         // the anonymous type.   Instead of doing a pass to examine the block
 154                         // we satisfy the rule by setting the return type on the EmitContext
 155                         // to be the delegate type return type.
 156                         //
 157
 158                         ToplevelBlock b = clone ? (ToplevelBlock) Block.PerformClone () : Block;
 159
 160                         anonymous = new AnonymousMethod (
 161                                 Parent != null ? Parent.AnonymousMethod : null, RootScope, Host,
 162                                 GenericMethod, Parameters, Container, b, invoke_mb.ReturnType,
 163                                 delegate_type, loc);
 164
 165                         if (!anonymous.Resolve (ec))
 166                                 return null;
 167
 168                         return anonymous.AnonymousDelegate;
 169                 }
 170         }
 171
 172         //
 173         // This is a return statement that is prepended lambda expression bodies that happen
 174         // to be expressions.  Depending on the return type of the delegate this will behave
 175         // as either { expr (); return (); } or { return expr (); }
 176         //
 177         public class ContextualReturn : Statement {
 178                 public Expression Expr;
 179
 180                 public ContextualReturn (Expression e)
 181                 {
 182                         Expr = e;
 183                         loc = Expr.Location;
 184                 }
 185
 186                 bool unwind_protect;
 187
 188                 public override bool Resolve (EmitContext ec)
 189                 {
 190                         AnonymousContainer am = ec.CurrentAnonymousMethod;
 191                         if ((am != null) && am.IsIterator && ec.InIterator) {
 192                                 Report.Error (1622, loc, "Cannot return a value from iterators. Use the yield return " +
 193                                               "statement to return a value, or yield break to end the iteration");
 194                                 return false;
 195                         }
 196
 197                         Expr = Expr.Resolve (ec);
 198                         if (Expr == null)
 199                                 return false;
 200
 201                         if (ec.ReturnType == null){
 202                                 if (!(Expr is ExpressionStatement)){
 203                                         Expression.Error_InvalidExpressionStatement (Expr.Location);
 204                                         return false;
 205                                 }
 206                         } else {
 207                                 if (Expr.Type != ec.ReturnType) {
 208                                         Expr = Convert.ImplicitConversionRequired (
 209                                                 ec, Expr, ec.ReturnType, loc);
 210                                         if (Expr == null)
 211                                                 return false;
 212                                 }
 213                         }
 214
 215                         int errors = Report.Errors;
 216                         unwind_protect = ec.CurrentBranching.AddReturnOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
 217                         if (unwind_protect)
 218                                 ec.NeedReturnLabel ();
 219                         ec.CurrentBranching.CurrentUsageVector.Return ();
 220                         return errors == Report.Errors;
 221                 }
 222
 223                 protected override void DoEmit (EmitContext ec)
 224                 {
 225                         Expr.Emit (ec);
 226
 227                         if (unwind_protect){
 228                                 ec.ig.Emit (OpCodes.Stloc, ec.TemporaryReturn ());
 229                                 ec.ig.Emit (OpCodes.Leave, ec.ReturnLabel);
 230                         }
 231                         ec.ig.Emit (OpCodes.Ret);
 232                 }
 233
 234                 protected override void CloneTo (CloneContext clonectx, Statement t)
 235                 {
 236                         ContextualReturn cr = (ContextualReturn) t;
 237
 238                         cr.Expr = Expr.Clone (clonectx);
 239                 }
 240         }
 241 }