C# ResolveContext.Set方法代码示例

		protected override Expression DoResolve (ResolveContext ec)
		{
			eclass = ExprClass.Value;

			// FIXME: Hack
			var caller_builder = (Constructor) ec.MemberContext;

			//
			// Spec mandates that constructor initializer will not have `this' access
			//
			using (ec.Set (ResolveContext.Options.BaseInitializer)) {
				if (argument_list != null) {
					bool dynamic;
					argument_list.Resolve (ec, out dynamic);

					if (dynamic) {
						ec.Report.Error (1975, loc,
							"The constructor call cannot be dynamically dispatched within constructor initializer");

						return null;
					}
				}

				type = ec.CurrentType;
				if (this is ConstructorBaseInitializer) {
					if (ec.CurrentType.BaseType == null)
						return this;

					type = ec.CurrentType.BaseType;
					if (ec.CurrentType.IsStruct) {
						ec.Report.Error (522, loc,
							"`{0}': Struct constructors cannot call base constructors", caller_builder.GetSignatureForError ());
						return this;
					}
				}

				base_ctor = ConstructorLookup (ec, type, ref argument_list, loc);
			}
	
			if (base_ctor != null && base_ctor.MemberDefinition == caller_builder.Spec.MemberDefinition) {
				ec.Report.Error (516, loc, "Constructor `{0}' cannot call itself",
					caller_builder.GetSignatureForError ());
			}

			return this;
		}

		protected override Expression DoResolve (ResolveContext ec)
		{
			constructor_method = Delegate.GetConstructor (type);

			var invoke_method = Delegate.GetInvokeMethod (type);

			if (!ec.HasSet (ResolveContext.Options.ConditionalAccessReceiver)) {
				if (method_group.HasConditionalAccess ()) {
					conditional_access_receiver = true;
					ec.Set (ResolveContext.Options.ConditionalAccessReceiver);
				}
			}

			Arguments arguments = CreateDelegateMethodArguments (ec, invoke_method.Parameters, invoke_method.Parameters.Types, loc);
			method_group = method_group.OverloadResolve (ec, ref arguments, this, OverloadResolver.Restrictions.CovariantDelegate);

			if (conditional_access_receiver)
				ec.With (ResolveContext.Options.ConditionalAccessReceiver, false);

			if (method_group == null)
				return null;

			var delegate_method = method_group.BestCandidate;
			
			if (delegate_method.DeclaringType.IsNullableType) {
				ec.Report.Error (1728, loc, "Cannot create delegate from method `{0}' because it is a member of System.Nullable<T> type",
					delegate_method.GetSignatureForError ());
				return null;
			}		
			
			if (!AllowSpecialMethodsInvocation)
				Invocation.IsSpecialMethodInvocation (ec, delegate_method, loc);

			ExtensionMethodGroupExpr emg = method_group as ExtensionMethodGroupExpr;
			if (emg != null) {
				method_group.InstanceExpression = emg.ExtensionExpression;
				TypeSpec e_type = emg.ExtensionExpression.Type;
				if (TypeSpec.IsValueType (e_type)) {
					ec.Report.Error (1113, loc, "Extension method `{0}' of value type `{1}' cannot be used to create delegates",
						delegate_method.GetSignatureForError (), e_type.GetSignatureForError ());
				}
			}

			TypeSpec rt = method_group.BestCandidateReturnType;
			if (rt.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
				rt = ec.BuiltinTypes.Object;

			if (!Delegate.IsTypeCovariant (ec, rt, invoke_method.ReturnType)) {
				Expression ret_expr = new TypeExpression (delegate_method.ReturnType, loc);
				Error_ConversionFailed (ec, delegate_method, ret_expr);
			}

			if (method_group.IsConditionallyExcluded) {
				ec.Report.SymbolRelatedToPreviousError (delegate_method);
				MethodOrOperator m = delegate_method.MemberDefinition as MethodOrOperator;
				if (m != null && m.IsPartialDefinition) {
					ec.Report.Error (762, loc, "Cannot create delegate from partial method declaration `{0}'",
						delegate_method.GetSignatureForError ());
				} else {
					ec.Report.Error (1618, loc, "Cannot create delegate with `{0}' because it has a Conditional attribute",
						TypeManager.CSharpSignature (delegate_method));
				}
			}

			var expr = method_group.InstanceExpression;
			if (expr != null && (expr.Type.IsGenericParameter || !TypeSpec.IsReferenceType (expr.Type)))
				method_group.InstanceExpression = new BoxedCast (expr, ec.BuiltinTypes.Object);

			eclass = ExprClass.Value;
			return this;
		}

		//
		// Returns AnonymousMethod container if this anonymous method
		// expression can be implicitly converted to the delegate type `delegate_type'
		//
		public Expression Compatible (ResolveContext ec, TypeSpec type)
		{
			Expression am;
			if (compatibles.TryGetValue (type, out am))
				return am;

			TypeSpec delegate_type = CompatibleChecks (ec, type);
			if (delegate_type == null)
				return null;

			//
			// At this point its the first time we know the return type that is 
			// needed for the anonymous method.  We create the method here.
			//

			var invoke_mb = Delegate.GetInvokeMethod (delegate_type);
			TypeSpec return_type = invoke_mb.ReturnType;

			//
			// Second: the return type of the delegate must be compatible with 
			// the anonymous type.   Instead of doing a pass to examine the block
			// we satisfy the rule by setting the return type on the EmitContext
			// to be the delegate type return type.
			//

			var body = CompatibleMethodBody (ec, null, return_type, delegate_type);
			if (body == null)
				return null;

			bool etree_conversion = delegate_type != type;

			try {
				if (etree_conversion) {
					if (ec.HasSet (ResolveContext.Options.ExpressionTreeConversion)) {
						//
						// Nested expression tree lambda use same scope as parent
						// lambda, this also means no variable capturing between this
						// and parent scope
						//
						am = body.Compatible (ec, ec.CurrentAnonymousMethod);

						//
						// Quote nested expression tree
						//
						if (am != null)
							am = new Quote (am);
					} else {
						int errors = ec.Report.Errors;

						if (Block.IsAsync) {
							ec.Report.Error (1989, loc, "Async lambda expressions cannot be converted to expression trees");
						}

						using (ec.Set (ResolveContext.Options.ExpressionTreeConversion)) {
							am = body.Compatible (ec);
						}

						//
						// Rewrite expressions into expression tree when targeting Expression<T>
						//
						if (am != null && errors == ec.Report.Errors)
							am = CreateExpressionTree (ec, delegate_type);
					}
				} else {
					am = body.Compatible (ec);

					if (body.DirectMethodGroupConversion != null) {
						var errors_printer = new SessionReportPrinter ();
						var old = ec.Report.SetPrinter (errors_printer);
						var expr = new ImplicitDelegateCreation (delegate_type, body.DirectMethodGroupConversion, loc) {
							AllowSpecialMethodsInvocation = true
						}.Resolve (ec);
						ec.Report.SetPrinter (old);
						if (expr != null && errors_printer.ErrorsCount == 0)
							am = expr;
					}
				}
			} catch (CompletionResult) {
				throw;
			} catch (FatalException) {
				throw;
			} catch (Exception e) {
				throw new InternalErrorException (e, loc);
			}

			if (!ec.IsInProbingMode && !etree_conversion) {
				compatibles.Add (type, am ?? EmptyExpression.Null);
			}

			return am;
		}

		public TypeSpec InferReturnType (ResolveContext ec, TypeInferenceContext tic, TypeSpec delegate_type)
		{
			Expression expr;
			AnonymousExpression am;

			if (compatibles.TryGetValue (delegate_type, out expr)) {
				am = expr as AnonymousExpression;
				return am == null ? null : am.ReturnType;
			}

			using (ec.Set (ResolveContext.Options.ProbingMode | ResolveContext.Options.InferReturnType)) {
				ReportPrinter prev;
				if (TypeInferenceReportPrinter != null) {
					prev = ec.Report.SetPrinter (TypeInferenceReportPrinter);
				} else {
					prev = null;
				}

				var body = CompatibleMethodBody (ec, tic, null, delegate_type);
				if (body != null) {
					am = body.Compatible (ec, body);
				} else {
					am = null;
				}

				if (TypeInferenceReportPrinter != null) {
					ec.Report.SetPrinter (prev);
				}
			}

			if (am == null)
				return null;

//			compatibles.Add (delegate_type, am);
			return am.ReturnType;
		}

		//
		// Returns true if the body of lambda expression can be implicitly
		// converted to the delegate of type `delegate_type'
		//
		public bool ImplicitStandardConversionExists (ResolveContext ec, TypeSpec delegate_type)
		{
			using (ec.With (ResolveContext.Options.InferReturnType, false)) {
				using (ec.Set (ResolveContext.Options.ProbingMode)) {
					var prev = ec.Report.SetPrinter (TypeInferenceReportPrinter ?? new NullReportPrinter ());

					var res = Compatible (ec, delegate_type) != null;

					ec.Report.SetPrinter (prev);

					return res;
				}
			}
		}

		protected override Expression DoResolve (ResolveContext ec)
		{
			right = right.Resolve (ec);
			if (right == null)
				return null;

			MemberAccess ma = target as MemberAccess;
			using (ec.Set (ResolveContext.Options.CompoundAssignmentScope)) {
				target = target.Resolve (ec);
			}
			
			if (target == null)
				return null;

			if (target is MethodGroupExpr){
				ec.Report.Error (1656, loc,
					"Cannot assign to `{0}' because it is a `{1}'",
					((MethodGroupExpr)target).Name, target.ExprClassName);
				return null;
			}

			var event_expr = target as EventExpr;
			if (event_expr != null) {
				source = Convert.ImplicitConversionRequired (ec, right, target.Type, loc);
				if (source == null)
					return null;

				Expression rside;
				if (op == Binary.Operator.Addition)
					rside = EmptyExpression.EventAddition;
				else if (op == Binary.Operator.Subtraction)
					rside = EmptyExpression.EventSubtraction;
				else
					rside = null;

				target = target.ResolveLValue (ec, rside);
				if (target == null)
					return null;

				eclass = ExprClass.Value;
				type = event_expr.Operator.ReturnType;
				return this;
			}

			//
			// Only now we can decouple the original source/target
			// into a tree, to guarantee that we do not have side
			// effects.
			//
			if (left == null)
				left = new TargetExpression (target);

			source = new Binary (op, left, right, true);

			if (target is DynamicMemberAssignable) {
				Arguments targs = ((DynamicMemberAssignable) target).Arguments;
				source = source.Resolve (ec);

				Arguments args = new Arguments (targs.Count + 1);
				args.AddRange (targs);
				args.Add (new Argument (source));

				var binder_flags = CSharpBinderFlags.ValueFromCompoundAssignment;

				//
				// Compound assignment does target conversion using additional method
				// call, set checked context as the binary operation can overflow
				//
				if (ec.HasSet (ResolveContext.Options.CheckedScope))
					binder_flags |= CSharpBinderFlags.CheckedContext;

				if (target is DynamicMemberBinder) {
					source = new DynamicMemberBinder (ma.Name, binder_flags, args, loc).Resolve (ec);

					// Handles possible event addition/subtraction
					if (op == Binary.Operator.Addition || op == Binary.Operator.Subtraction) {
						args = new Arguments (targs.Count + 1);
						args.AddRange (targs);
						args.Add (new Argument (right));
						string method_prefix = op == Binary.Operator.Addition ?
							Event.AEventAccessor.AddPrefix : Event.AEventAccessor.RemovePrefix;

						var invoke = DynamicInvocation.CreateSpecialNameInvoke (
							new MemberAccess (right, method_prefix + ma.Name, loc), args, loc).Resolve (ec);

						args = new Arguments (targs.Count);
						args.AddRange (targs);
						source = new DynamicEventCompoundAssign (ma.Name, args,
							(ExpressionStatement) source, (ExpressionStatement) invoke, loc).Resolve (ec);
					}
				} else {
					source = new DynamicIndexBinder (binder_flags, args, loc).Resolve (ec);
				}

				return source;
			}

			return base.DoResolve (ec);
		}