function property Null safety

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).