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AK+Everywhere: Disallow constructing Functions from incompatible types

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Previously, AK::Function would accept _any_ callable type, and try to
call it when called, first with the given set of arguments, then with
zero arguments, and if all of those failed, it would simply not call the
function and **return a value-constructed Out type**.
This lead to many, many, many hard to debug situations when someone
forgot a `const` in their lambda argument types, and many cases of
people taking zero arguments in their lambdas to ignore them.
This commit reworks the Function interface to not include any such
surprising behaviour, if your function instance is not callable with
the declared argument set of the Function, it can simply not be
assigned to that Function instance, end of story.
This commit is contained in:
Ali Mohammad Pur 2021-06-05 23:04:31 +04:30 • committed by Ali Mohammad Pur
parent 104dc93220
commit 51c2c69357
28 changed files with 99 additions and 92 deletions
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50
AK/Function.h
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@ -39,26 +39,36 @@ namespace AK {
template<typename>
class Function;
template<typename F>
inline constexpr bool IsFunctionPointer = (IsPointer<F> && IsFunction<RemovePointer<F>>);
// Not a function pointer, and not an lvalue reference.
template<typename F>
inline constexpr bool IsFunctionObject = (!IsFunctionPointer<F> && IsRvalueReference<F&&>);
template<typename Out, typename... In>
class Function<Out(In...)> {
AK_MAKE_NONCOPYABLE(Function);
public:
Function() = default;
Function(std::nullptr_t)
{
}
~Function()
{
clear(false);
}
template<typename CallableType, class = typename EnableIf<!(IsPointer<CallableType> && IsFunction<RemovePointer<CallableType>>)&&IsRvalueReference<CallableType&&>>::Type>
Function(CallableType&& callable)
template<typename CallableType>
Function(CallableType&& callable) requires((IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, In...>))
{
init_with_callable(move(callable));
init_with_callable(forward<CallableType>(callable));
}
template<typename FunctionType, class = typename EnableIf<IsPointer<FunctionType> && IsFunction<RemovePointer<FunctionType>>>::Type>
Function(FunctionType f)
template<typename FunctionType>
Function(FunctionType f) requires((IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, In...>))
{
init_with_callable(move(f));
}
@ -68,6 +78,7 @@ public:
move_from(move(other));
}
// Note: Despite this method being const, a mutable lambda _may_ modify its own captures.
Out operator()(In... in) const
{
auto* wrapper = callable_wrapper();
@ -82,16 +93,16 @@ public:
explicit operator bool() const { return !!callable_wrapper(); }
template<typename CallableType, class = typename EnableIf<!(IsPointer<CallableType> && IsFunction<RemovePointer<CallableType>>)&&IsRvalueReference<CallableType&&>>::Type>
Function& operator=(CallableType&& callable)
template<typename CallableType>
Function& operator=(CallableType&& callable) requires((IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, In...>))
{
clear();
init_with_callable(move(callable));
init_with_callable(forward<CallableType>(callable));
return *this;
}
template<typename FunctionType, class = typename EnableIf<IsPointer<FunctionType> && IsFunction<RemovePointer<FunctionType>>>::Type>
Function& operator=(FunctionType f)
template<typename FunctionType>
Function& operator=(FunctionType f) requires((IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, In...>))
{
clear();
if (f)
@ -118,7 +129,8 @@ private:
class CallableWrapperBase {
public:
virtual ~CallableWrapperBase() = default;
virtual Out call(In...) const = 0;
// Note: This is not const to allow storing mutable lambdas.
virtual Out call(In...) = 0;
virtual void destroy() = 0;
virtual void init_and_swap(u8*, size_t) = 0;
};
@ -134,17 +146,9 @@ private:
{
}
Out call(In... in) const final override
Out call(In... in) final override
{
if constexpr (requires { m_callable(forward<In>(in)...); }) {
return m_callable(forward<In>(in)...);
} else if constexpr (requires { m_callable(); }) {
return m_callable();
} else if constexpr (IsVoid<Out>) {
return;
} else {
return {};
}
return m_callable(forward<In>(in)...);
}
void destroy() final override
@ -208,10 +212,10 @@ private:
VERIFY(m_call_nesting_level == 0);
using WrapperType = CallableWrapper<Callable>;
if constexpr (sizeof(WrapperType) > inline_capacity) {
*bit_cast<CallableWrapperBase**>(&m_storage) = new WrapperType(move(callable));
*bit_cast<CallableWrapperBase**>(&m_storage) = new WrapperType(forward<Callable>(callable));
m_kind = FunctionKind::Outline;
} else {
new (m_storage) WrapperType(move(callable));
new (m_storage) WrapperType(forward<Callable>(callable));
m_kind = FunctionKind::Inline;
}
}