[SYCL] Improve error diagnostic for invalid SYCL kernel name

[smanna12]

According to SYCL 2020 spec:
The kernel name must be forward declarable at namespace scope (including global namespace scope) and may not be forward declared other than at namespace scope.

The use of nested struct-case (where the name IS globally visible but just not forward-declarable) in a SYCL kernel name currently generates invalid error message:

error: '{{.*}}' should be globally visible

This patch modifies the error diagnostic message when the kernel name is declared at non-namespace scope (i.e. Inside a function or class/struct).

Signed-off-by: Soumi Manna soumi.manna@intel.com

[smanna12]

I do not think we can separate nested struct case used as kernel name and add a separate diagnostic for this.
I have updated current error message instead of using globally visible to make it generic for all cases and also match with current spec wording.

// Check if the kernel name is a Tag declaration
 // local to a non-namespace scope (i.e. Inside a function or within
 // another Tag etc).
if (!DeclCtx->isTranslationUnit() && !isa<NamespaceDecl>(DeclCtx)) {
        if (const auto *Tag = dyn_cast<TagDecl>(DeclNamed)) {
          // Check if the declaration is completely defined within a
          // function or class/struct.
          if (Tag->isCompleteDefinition()) {
            S.Diag(KernelInvocationFuncLoc,
                   diag::err_sycl_kernel_incorrectly_named)
                << /* non-forward-declarable type is invalid */ 0
                << KernelNameType;
            IsInvalid = true;
          } else {
            S.Diag(KernelInvocationFuncLoc, diag::warn_sycl_implicit_decl);
            S.Diag(DeclNamed->getLocation(), diag::note_previous_decl)
                << DeclNamed->getName();
          }
        }
      }
    

Please let me know if i missed something. Any suggestion if the updated diagnostic message is not clear or too long?

[elizabethandrews]

LGTM. Thanks!

[smanna12]

Thanks for the reviews everyone.