Regression introduced with implementation of P2036R3 (assertion error) #65067
Description
Hello,
Commit 93d7002 introduced a regression. A reproducing snippet:
template <typename T> T &declval() noexcept {}
template <typename T> struct FakeVoidToVoid {};
template <typename Func> inline auto call(Func &&func) { return func(); }
template <typename Func>
using NormalizedCallResult = FakeVoidToVoid<decltype(call(declval<Func>()))>;
template <typename T> class SemiFuture {
public:
template <typename Func> auto then(Func &&func) {
return and_then(wrapCB<T>(func));
}
template <typename Func> auto and_then(Func &&func) {
using Result = NormalizedCallResult<Func>;
}
protected:
template <typename RawArg, typename Func> auto wrapCB(Func &&func) {
return [func = func](auto... args) -> SemiFuture<decltype(func(args...))> {return {};};
}
};
auto removeDocumentsInRange(SemiFuture<void> waitForActiveQueriesToComplete) {
return waitForActiveQueriesToComplete.then([]() {});
}This has been reduced from code coming from MongoDB.
Before 93d7002, the func in decltype(func(args...) would refer to the parameter func. After the commit, it would refer to the variable func introduced by the capture. It looks like other parts of the parser (i,e, TemplateInstantiator::TransformDecl) do not expect to find a VarDecl and fail to handle them.
This regression happens for C++14 and higher, even though "Change scope of lambda trailing-return-type" was introduced with C++23.