Try to clarify comments with an example

Author: Fznamznon

clang/lib/Sema/SemaSYCL.cpp

@@ -6485,17 +6485,31 @@ void SYCLIntegrationHeader::emit(raw_ostream &O) {
     Policy.FullyQualifiedName = true;
     Policy.EnforceScopeForElaboratedTypes = true;
 
+    // Now we need to print the declaration of the kernel itself.
+    // Example:
+    // template <typename T, typename = int> struct Arg {
+    //   T val;
+    // };
+    // For the following free function kernel:
+    // template <typename = T>
+    // SYCL_EXT_ONEAPI_FUNCTION_PROPERTY(
+    //     (ext::oneapi::experimental::nd_range_kernel<1>))
+    // void foo(Arg<int> arg) {}
+    // Integration header must contain the following declaration:
+    // template <typename>
+    // void foo(Arg<int, int> arg);
     // SuppressDefaultTemplateArguments is a downstream addition that suppresses
-    // default template arguments in function declarations. It should be set to
-    // true to emit function declaration that won't cause any compilation errors
-    // when present in the integration header.
-    // SuppressDefaultTemplateArgs is a flag from community code which adds
-    // suppression of template arguments that match default template arguments
-    // in template-ids printing.
+    // default template arguments in the function declaration. It should be set
+    // to true to emit function declaration that won't cause any compilation
+    // errors when present in the integration header.
+    // To print Arg<int, int> in the function declaration and shim functions we
+    // need to disable default arguments printing suppression via community flag
+    // SuppressDefaultTemplateArgs, otherwise they will be suppressed even for
+    // canonical types or if even written in the original source code.
     Policy.SuppressDefaultTemplateArguments = true;
     // EnforceDefaultTemplateArgs is a downstream addition that forces printing
     // template arguments that match default template arguments while printing
-    // template-ids, even if the source code doesn't referece them.
+    // template-ids, even if the source code doesn't reference them.
     Policy.EnforceDefaultTemplateArgs = true;
     if (FTD) {
       FTD->print(O, Policy);