[clang] [clang] Implement CWG1719 "Layout compatibility and cv-qualification revisited" (PR #82358)

[Aaron Ballman via cfe-commits]

================
@@ -1711,13 +1711,13 @@ void is_layout_compatible(int n)
 {
   static_assert(__is_layout_compatible(void, void), "");
   static_assert(!__is_layout_compatible(void, int), "");
-  static_assert(!__is_layout_compatible(void, const void), ""); // FIXME: this is CWG1719
-  static_assert(!__is_layout_compatible(void, volatile void), ""); // FIXME: this is CWG1719
-  static_assert(!__is_layout_compatible(const int, volatile int), ""); // FIXME: this is CWG1719
+  static_assert(__is_layout_compatible(void, const void), "");
+  static_assert(__is_layout_compatible(void, volatile void), "");
+  static_assert(__is_layout_compatible(const int, volatile int), "");
   static_assert(__is_layout_compatible(int, int), "");
-  static_assert(!__is_layout_compatible(int, const int), ""); // FIXME: this is CWG1719
-  static_assert(!__is_layout_compatible(int, volatile int), ""); // FIXME: this is CWG1719
-  static_assert(!__is_layout_compatible(const int, volatile int), ""); // FIXME: this is CWG1719
+  static_assert(__is_layout_compatible(int, const int), "");
+  static_assert(__is_layout_compatible(int, volatile int), "");
+  static_assert(__is_layout_compatible(const int, volatile int), "");
----------------
AaronBallman wrote:

Another test to consider adding:
```
static_assert(__is_layout_compatible(int[], const int[]), "");
```

https://github.com/llvm/llvm-project/pull/82358