[clang] [clang-tools-extra] [Clang] Add __type_list_dedup builtin to deduplicate types in template arguments (PR #106730)

[Richard Smith via cfe-commits]

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@@ -0,0 +1,57 @@
+// RUN: %clang_cc1 %s -verify
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zygoloid wrote:

I'd like to also see some testing of the case where the template arguments have different sugar but are canonically the same, and when they differ by only cv-qualifiers. Those seem like likely cases for us to get wrong. Eg:

```c++
using T = int;
using CT = const T;
static_assert(__is_same(__type_list_dedup<TypeList, T, int, const int, const T, CT, const CT>,
                        TypeList<int, const int>));
```

https://github.com/llvm/llvm-project/pull/106730