[clang] [SYCL] Basic diagnostics for the sycl_kernel_entry_point attribute. (PR #120327)

[Aaron Ballman via cfe-commits]

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@@ -15978,6 +15988,24 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
       CheckCoroutineWrapper(FD);
   }
 
+  // Diagnose invalid SYCL kernel entry point function declarations.
+  if (FD && !FD->isInvalidDecl() && !FD->isTemplated() &&
+      FD->hasAttr<SYCLKernelEntryPointAttr>()) {
+    if (FD->isDeleted()) {
+      Diag(FD->getAttr<SYCLKernelEntryPointAttr>()->getLocation(),
+           diag::err_sycl_entry_point_invalid)
+          << /*deleted function*/ 2;
+    } else if (FD->isDefaulted()) {
+      Diag(FD->getAttr<SYCLKernelEntryPointAttr>()->getLocation(),
+           diag::err_sycl_entry_point_invalid)
+          << /*defaulted function*/ 3;
+    } else if (FSI->isCoroutine()) {
+      Diag(FD->getAttr<SYCLKernelEntryPointAttr>()->getLocation(),
+           diag::err_sycl_entry_point_invalid)
+          << /*coroutine*/ 7;
----------------
AaronBallman wrote:

I'd prefer we don't split into separate diagnostics; that increases overhead and maintenance burden for very little gain IMO. We generally prefer using `%select` when possible (it makes it easier to reword diagnostics, fix typos, localize, etc and it avoids adding extra strings to the binary when string merging isn't possible).

https://github.com/llvm/llvm-project/pull/120327