[clang] [clang][NFC] Specify Type and ExtQuals as having 16-byte alignment (PR #68377)

[Aaron Ballman via cfe-commits]

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@@ -1982,9 +1986,9 @@ class alignas(8) Type : public ExtQualsTypeCommonBase {
   Type(TypeClass tc, QualType canon, TypeDependence Dependence)
       : ExtQualsTypeCommonBase(this,
                                canon.isNull() ? QualType(this_(), 0) : canon) {
-    static_assert(sizeof(*this) <= 8 + sizeof(ExtQualsTypeCommonBase),
+    static_assert(sizeof(*this) <= 16 + sizeof(ExtQualsTypeCommonBase),
                   "changing bitfields changed sizeof(Type)!");
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AaronBallman wrote:

Would it make sense to change this to use `alignof(decltype(*this))` rather than `16` to make the connection to alignment more obvious?

https://github.com/llvm/llvm-project/pull/68377