[clang] [PAC] Add support for __ptrauth type qualifier (PR #100830)

[John McCall via cfe-commits]

================
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -triple arm64-apple-ios -fsyntax-only -verify -fptrauth-intrinsics -std=c++11 %s
+// RUN: %clang_cc1 -triple aarch64-linux-gnu -fsyntax-only -verify -fptrauth-intrinsics -std=c++11 %s
+
+template <typename T> struct G {
+  T __ptrauth(0,0,1234) test;
+  // expected-error at -1 2 {{type '__ptrauth(0,0,1234) T' is already __ptrauth-qualified}}
+};
+
+template <typename T> struct Indirect {
+  G<T> layers;
+  // expected-note at -1{{in instantiation of template class 'G<void *__ptrauth(0,0,1235)>' requested here}}
+  // expected-note at -2{{in instantiation of template class 'G<void *__ptrauth(0,0,1234)>' requested here}}
+};
+
+void f3() {
+  Indirect<void* __ptrauth(0,0,1234)> one;
+  // expected-note at -1{{in instantiation of template class 'Indirect<void *__ptrauth(0,0,1234)>' requested here}}
+  Indirect<void* __ptrauth(0,0,1235)> two;
+  // expected-note at -1{{in instantiation of template class 'Indirect<void *__ptrauth(0,0,1235)>' requested here}}
+  Indirect<void*> three;
+}
----------------
rjmccall wrote:

Yeah, that's my general intuition as well. And I agree that it would be better to land it as is and then consider whether we should loosen the rule later, as long as you're comfortable with that.

https://github.com/llvm/llvm-project/pull/100830