Marker to identify this as a function item
OptionaltypeThe type signature of the function
The actual implementation
OptionalnameFunction name (undefined for anonymous functions)
OptionalnamespaceNamespace URI for named functions
Number of parameters
OptionalclosureCaptured closure context for inline functions
Represents a function item - a first-class function value in XPath 3.0.
Function items can be:
This interface extends XPathFunctionItem from context.ts to ensure FunctionItem values are valid XPathResult values.