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