System.Linq.Expressions.Compiler.LabelScopeInfo.ContainsTarget C# (CSharp) Method

        internal bool ContainsTarget(LabelTarget target)
        {
            if (_labels == null)
            {
                return false;
            }

            return _labels.ContainsKey(target);
        }

        // Returns true if the label was successfully defined
        // or false if the label is now ambiguous
        internal void Define(LabelScopeInfo block)
        {
            // Prevent the label from being shadowed, which enforces cleaner
            // trees. Also we depend on this for simplicity (keeping only one
            // active IL Label per LabelInfo)
            for (LabelScopeInfo j = block; j != null; j = j.Parent)
            {
                if (j.ContainsTarget(_node))
                {
                    throw Error.LabelTargetAlreadyDefined(_node.Name);
                }
            }

            _definitions.Add(block);
            block.AddLabelInfo(_node, this);

            // Once defined, validate all jumps
            if (_definitions.Count == 1)
            {
                foreach (var r in _references)
                {
                    ValidateJump(r);
                }
            }
            else
            {
                // Was just redefined, if we had any across block jumps, they're
                // now invalid
                if (_acrossBlockJump)
                {
                    throw Error.AmbiguousJump(_node.Name);
                }
                // For local jumps, we need a new IL label
                // This is okay because:
                //   1. no across block jumps have been made or will be made
                //   2. we don't allow the label to be shadowed
                _labelDefined = false;
            }
        }