[MLIR] Fix warnings in AttrTypeSubElements.h

[bondhugula]

Summary

Fix warnings in AttrTypeSubElements.h (below) with GCC 9.4.0.

mlir/lib/IR/ExtensibleDialect.cpp:443:62:   required from here
mlir/include/mlir/IR/AttrTypeSubElements.h:412:37: warning: parameter ‘derived’ set but not used [-Wunused-but-set-parameter]
  412 | void walkImmediateSubElementsImpl(T derived,
      |                                   ~~^~~

[bondhugula]

Drop extra braces + else nearly.

[mehdi_amini]

mlir/include/mlir/IR/AttrTypeSubElements.h

418

Can you mention the warning in the description, I really don't know why gcc could want this for function arg but I'm curious.

[bondhugula]

Update commit summary.

[bondhugula]

mlir/include/mlir/IR/AttrTypeSubElements.h

418

Sure - I see warnings like these:

/home/uday/llvm-project-upstream/mlir/lib/IR/ExtensibleDialect.cpp:443:62:   required from here
/home/uday/llvm-project-upstream/mlir/include/mlir/IR/AttrTypeSubElements.h:412:37: warning: parameter ‘derived’ set but not used [-Wunused-but-set-parameter]
  412 | void walkImmediateSubElementsImpl(T derived,
      |                                   ~~^~~~~~~
/home/uday/llvm-project-upstream/mlir/include/mlir/IR/AttrTypeSubElements.h:413:65: warning: parameter ‘walkAttrsFn’ set but not used [-Wunused-but-set-parameter]
  413 |                                   function_ref<void(Attribute)> walkAttrsFn,
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
/home/uday/llvm-project-upstream/mlir/include/mlir/IR/AttrTypeSubElements.h:414:60: warning: parameter ‘walkTypesFn’ set but not used [-Wunused-but-set-parameter]
  414 |                                   function_ref<void(Type)> walkTypesFn) {
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~

mlir/include/mlir/IR/AttrTypeSubElements.h

 /// This function provides the underlying implementation for the
 /// SubElementInterface walk method, using the key type of the derived
 /// attribute/type to interact with the individual parameters.
 template <typename T>
 void walkImmediateSubElementsImpl(T derived,
                                   function_ref<void(Attribute)> walkAttrsFn,
                                   function_ref<void(Type)> walkTypesFn) {
   using ImplT = typename T::ImplType;
+  (void)derived;
+  (void)walkAttrsFn;
+  (void)walkTypesFn;
   if constexpr (llvm::is_detected<has_get_as_key, ImplT>::value) {
     auto key = static_cast<ImplT *>(derived.getImpl())->getAsKey();
 
     // If we don't have any sub-elements, there is nothing to do.
-    if constexpr (!has_sub_attr_or_type_v<decltype(key)>) {
+    if constexpr (!has_sub_attr_or_type_v<decltype(key)>)
       return;
-    } else {
-      AttrTypeImmediateSubElementWalker walker(walkAttrsFn, walkTypesFn);
-      AttrTypeSubElementHandler<decltype(key)>::walk(key, walker);
-    }
-  }
-}
 
 /// This function invokes the proper `get` method for  a type `T` with the given
 /// values.
 template <typename T, typename... Ts>
 auto constructSubElementReplacement(MLIRContext *ctx, Ts &&...params) {
   // Prefer a direct `get` method if one exists.
   if constexpr (llvm::is_detected<has_get_method, T, Ts...>::value) {
     (void)ctx;