[clang] [clang] CTAD alias: Respect explicit deduction guides defined after the first use of the alias template. (PR #125478)

[Haojian Wu via cfe-commits]

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@@ -237,8 +237,17 @@ static_assert(__is_same(decltype(s.t), int));
 // explicit deduction guide.
 Foo(int) -> Foo<X>;
 AFoo s2{i};
-// FIXME: the type should be X because of the above explicit deduction guide.
-static_assert(__is_same(decltype(s2.t), int));
+static_assert(__is_same(decltype(s2.t), X));
+
+
+template<class T>
+using BFoo = AFoo<T>;
+static_assert(__is_same(decltype(BFoo(i).t), X));
+
+
+Foo(double) -> Foo<int>;
+static_assert(__is_same(decltype(AFoo(1.0).t), int));
+static_assert(__is_same(decltype(BFoo(1.0).t), int));
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hokein wrote:

> > Does it fix this case: https://godbolt.org/z/b84rzhjjK if not we need to open a bug.
> 
> That test case doesn't look related to these changes to me, I think it's a different issue.

This is not related to this patch. Filed #125821 for tracking (thanks for spotting it!)

https://github.com/llvm/llvm-project/pull/125478