C# AstExpression.GetSelfAndChildrenRecursive方法代码示例

        private static void UnboxByRefIfGeneric(XTypeReference type, AstExpression node, XTypeSystem typeSystem)
        {
            if (!type.IsGenericParameter)
                return;
            
            var resultType = node.InferredType ?? node.ExpectedType;
            if (resultType == null)
                return;

            if (!TreatAsStruct(type, resultType))
                return;

            // find the first unbox, which should be our target.
            var unbox = node.GetSelfAndChildrenRecursive<AstExpression>( n => n.Code == AstCode.Unbox).FirstOrDefault();

            if (unbox == null)
                return;

            // TODO: Of course we need to unbox generic instances as well,
            //       but at the moment the GenericInstanceConverter does
            //       not look at 'node.StoreByRefExpression' and thus
            //       does not add the required argument, resulting
            //       in unverifyable code. This should be fixed, and
            //       then these lines can be removed.
            if (resultType.IsGenericInstance)
                return;

            ConvertUnboxStruct(unbox, resultType, typeSystem);
        }

		/// <summary>
		/// Determines whether it is safe to move 'expressionBeingMoved' past 'expr'
		/// </summary>
		bool IsSafeForInlineOver(AstExpression expr, AstExpression expressionBeingMoved)
		{
			switch (expr.Code) {
				case AstCode.Ldloc:
					AstVariable loadedVar = (AstVariable)expr.Operand;
					if (numLdloca.GetOrDefault(loadedVar) != 0) {
						// abort, inlining is not possible
						return false;
					}
					foreach (AstExpression potentialStore in expressionBeingMoved.GetSelfAndChildrenRecursive<AstExpression>()) {
						if (potentialStore.Code == AstCode.Stloc && potentialStore.Operand == loadedVar)
							return false;
					}
					// the expression is loading a non-forbidden variable
					return true;
				case AstCode.Ldloca:
				case AstCode.Ldflda:
				case AstCode.Ldsflda:
				case AstCode.Ldelema:
				case AstCode.AddressOf:
				case AstCode.ValueOf:
				case AstCode.NullableOf:
					// address-loading instructions are safe if their arguments are safe
					foreach (AstExpression arg in expr.Arguments) {
						if (!IsSafeForInlineOver(arg, expressionBeingMoved))
							return false;
					}
					return true;
				default:
					// instructions with no side-effects are safe (except for Ldloc and Ldloca which are handled separately)
					return expr.HasNoSideEffects();
			}
		}