function property
A mirror on the function associated with this closure.
The function associated with an implicit closure of a function is that function.
The function associated with an instance of a class that has a call
method is that call method.
A Dart implementation might choose to create a class for each closure
expression, in which case function would be the same as
type.declarations[#call]. But the Dart language model does not
require this. A more typical implementation involves a single closure
class for each type signature, where the call method dispatches to a
function held in the closure rather the call method directly implementing
the closure body. So one cannot rely on closures from distinct closure
expressions having distinct classes (type), but one can rely on
them having distinct functions (function).
Required capabilities: function does not require any capabilities.
Implementation
MethodMirror get function;