Heuristic resolution does not find member of type referenced via alias template

[HighCommander4]

In the following code:

template <typename T>
struct Waldo {
  void find();
};

template <typename T>
using Wally = Waldo<T>;

template <typename T>
void foo(Wally<T> w) {
  w.find();
}

go-to-definition on the use of find() does not produce Waldo::find().

[HighCommander4]

This is similar to #1657, except that the fix is in HeuristicResolver rather than in CXXRecordDecl::lookupDependentName().

(With #1662 in place, the implementation of lookupDependentName() could then reuse the logic to handle alias templates that I'm going to add to HeuristicResolver in this issue.)

[HighCommander4]

I wrote a fix for this (https://reviews.llvm.org/D152500), but I'm not satisfied with it.

While my fix handles the above testcase specifically, it does not handle this modified testcase:

template <typename T>
struct Waldo {
  void find();
};

template <typename T>
struct MetaWaldo {
  using Type = Waldo<T>;
};

template <typename T>
void foo(typename MetaWaldo<T>::Type w) {
  w.find();
}

even though clangd can resolve the use of MetaWaldo<T>::Type to its declaration.

I would like to find a solution that doesn't require manual handling for every kind of type sugar.

[HighCommander4]

I have updated my patch to take a more general approach. The example in the previous comment is still not handled; I mischaracterized it as being another example of type sugar when in fact it's not -- there is a heuristic resolution step involved, because class templates can be specialized while alias templates can't. I'll file a follow-up issue for this.

[HighCommander4]

I'll file a follow-up issue for this.

The follow-up is #1671