Return the function type of the invocation based on the static type
null if the AST structure has not been resolved, or if
the invoke could not be resolved.
This will usually be a FunctionType, but it can also be
Function. In the case of interface types that have a
call method, we
store the type of that
call method here as parameterized.
DartType get staticInvokeType;
Sets the function type of the invocation based on the static type information.
set staticInvokeType(DartType value);