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                         } finally {
  80                                 Report.EnableErrors ();
  81                         }
  82
  83                         // Ignore the result
  84                         anonymous = null;
  85
  86                         return result;
  87                 }
  88
  89                 //
  90                 // Returns true if this anonymous method can be implicitly
  91                 // converted to the delegate type `delegate_type'
  92                 //
  93                 public override Expression Compatible (EmitContext ec, Type delegate_type)
  94                 {
  95                         return DoCompatibleTest (ec, delegate_type, false);
  96                 }
  97
  98                 Expression DoCompatibleTest (EmitContext ec, Type delegate_type, bool clone)
  99                 {
 100                         if (anonymous != null)
 101                                 return anonymous.AnonymousDelegate;
 102
 103                         if (CompatibleChecks (ec, delegate_type) == null)
 104                                 return null;
 105
 106                         MethodGroupExpr invoke_mg = Delegate.GetInvokeMethod (
 107                                 ec.ContainerType, delegate_type, loc);
 108                         MethodInfo invoke_mb = (MethodInfo) invoke_mg.Methods [0];
 109                         ParameterData invoke_pd = TypeManager.GetParameterData (invoke_mb);
 110
 111                         //
 112                         // The lambda expression is compatible with the delegate type,
 113                         // provided that:
 114                         //
 115
 116                         //
 117                         // D and L have the same number of arguments.
 118                         if (Parameters.Count != invoke_pd.Count)
 119                                 return null;
 120
 121                         if (explicit_parameters){
 122                                 //
 123                                 // If L has an explicitly typed parameter list, each parameter
 124                                 // in D has the same type and modifiers as the corresponding
 125                                 // parameter in L.
 126                                 //
 127                                 if (!VerifyExplicitParameterCompatibility (delegate_type, invoke_pd))
 128                                         return null;
 129                         } else {
 130                                 //
 131                                 // If L has an implicitly typed parameter list, D has no ref or
 132                                 // out parameters
 133                                 //
 134                                 // Note: We currently do nothing, because the preview does not
 135                                 // follow the above rule.
 136
 137                                 //
 138                                 // each parameter of L is given the type of the corresponding parameter in D
 139                                 //
 140
 141                                 for (int i = 0; i < invoke_pd.Count; i++)
 142                                         Parameters [i].TypeName = new TypeExpression (
 143                                                 invoke_pd.ParameterType (i),
 144                                                 Parameters [i].Location);
 145                         }
 146
 147                         //
 148                         // The return type of the delegate must be compatible with
 149                         // the anonymous type.   Instead of doing a pass to examine the block
 150                         // we satisfy the rule by setting the return type on the EmitContext
 151                         // to be the delegate type return type.
 152                         //
 153
 154                         ToplevelBlock b = clone ? (ToplevelBlock) Block.PerformClone () : Block;
 155
 156                         anonymous = new AnonymousMethod (
 157                                 Parent != null ? Parent.AnonymousMethod : null, RootScope, Host,
 158                                 GenericMethod, Parameters, Container, b, invoke_mb.ReturnType,
 159                                 delegate_type, loc);
 160
 161                         if (!anonymous.Resolve (ec))
 162                                 return null;
 163
 164                         return anonymous.AnonymousDelegate;
 165                 }
 166         }
 167
 168         //
 169         // This is a return statement that is prepended lambda expression bodies that happen
 170         // to be expressions.  Depending on the return type of the delegate this will behave
 171         // as either { expr (); return (); } or { return expr (); }
 172         //
 173         public class ContextualReturn : Statement {
 174                 public Expression Expr;
 175
 176                 public ContextualReturn (Expression e)
 177                 {
 178                         Expr = e;
 179                         loc = Expr.Location;
 180                 }
 181
 182                 bool unwind_protect;
 183
 184                 public override bool Resolve (EmitContext ec)
 185                 {
 186                         AnonymousContainer am = ec.CurrentAnonymousMethod;
 187                         if ((am != null) && am.IsIterator && ec.InIterator) {
 188                                 Report.Error (1622, loc, "Cannot return a value from iterators. Use the yield return " +
 189                                               "statement to return a value, or yield break to end the iteration");
 190                                 return false;
 191                         }
 192
 193                         Expr = Expr.Resolve (ec);
 194                         if (Expr == null)
 195                                 return false;
 196
 197                         if (ec.ReturnType == null){
 198                                 if (!(Expr is ExpressionStatement)){
 199                                         Expression.Error_InvalidExpressionStatement (Expr.Location);
 200                                         return false;
 201                                 }
 202                         } else {
 203                                 if (Expr.Type != ec.ReturnType) {
 204                                         Expr = Convert.ImplicitConversionRequired (
 205                                                 ec, Expr, ec.ReturnType, loc);
 206                                         if (Expr == null)
 207                                                 return false;
 208                                 }
 209                         }
 210
 211                         int errors = Report.Errors;
 212                         unwind_protect = ec.CurrentBranching.AddReturnOrigin (ec.CurrentBranching.CurrentUsageVector, loc);
 213                         if (unwind_protect)
 214                                 ec.NeedReturnLabel ();
 215                         ec.CurrentBranching.CurrentUsageVector.Goto ();
 216                         return errors == Report.Errors;
 217                 }
 218
 219                 protected override void DoEmit (EmitContext ec)
 220                 {
 221                         Expr.Emit (ec);
 222
 223                         if (unwind_protect){
 224                                 ec.ig.Emit (OpCodes.Stloc, ec.TemporaryReturn ());
 225                                 ec.ig.Emit (OpCodes.Leave, ec.ReturnLabel);
 226                         }
 227                         ec.ig.Emit (OpCodes.Ret);
 228                 }
 229
 230                 protected override void CloneTo (CloneContext clonectx, Statement t)
 231                 {
 232                         ContextualReturn cr = (ContextualReturn) t;
 233
 234                         cr.Expr = Expr.Clone (clonectx);
 235                 }
 236         }
 237 }