[clang] [HLSL] Add testing for space parameter on global constants (PR #106782)

[Joshua Batista via cfe-commits]

================
@@ -817,8 +821,12 @@ static void DiagnoseHLSLRegisterAttribute(Sema &S, SourceLocation &ArgLoc,
       S.Diag(TheDecl->getLocation(),
              diag::warn_hlsl_user_defined_type_missing_member)
           << regTypeNum;
-
-    return;
+    // Space argument cannot be specified for global constants
+    if (!isDeclaredWithinCOrTBuffer(TheDecl)) {
----------------
bob80905 wrote:

The diagnostic implies that space can only be specified on non-global constants. The reason that condition is needed is so that we ensure that the attribute is applied on a non-global decl. I've added 2 tests to exercise this behavior.

https://github.com/llvm/llvm-project/pull/106782