[clang] [clang][bytecode] Improve error detection in BitCastPrim op (PR #158575)

[Timm Baeder via cfe-commits]

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@@ -572,3 +571,19 @@ namespace VectorCast {
 #endif
 }
 #endif
+
+namespace ToPrimPtrs {
+  struct S { int foo () { return 0; } };
+  auto ptr  = __builtin_bit_cast(int *, ((__INTPTR_TYPE__) 0));
+  auto nptr = __builtin_bit_cast(nullptr_t, ((__INTPTR_TYPE__)0));
+
+  constexpr auto cptr  = __builtin_bit_cast(int *, ((__INTPTR_TYPE__) 0)); // both-error {{must be initialized by a constant expression}} \
+                                                                           // both-note {{bit_cast to a pointer type is not allowed in a constant expression}}
+  constexpr auto cnptr = __builtin_bit_cast(nullptr_t, ((__INTPTR_TYPE__)0));
+
+#if !defined(_WIN32)
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tbaederr wrote:

Apparently member pointers have a different size on windows.

https://github.com/llvm/llvm-project/pull/158575