[Mlir-commits] [mlir] [mlir] fix Undefined behavior in CastInfo::castFailed with From=<MLIRinterface> (PR #87145)

[River Riddle]

================
@@ -2142,6 +2143,83 @@ struct DenseMapInfo<T,
   }
   static bool isEqual(T lhs, T rhs) { return lhs == rhs; }
 };
+
+/// Add support for llvm style casts.
+/// We provide a cast between To and From if To and From is mlir::OpInterface or
+/// derives from it.
+template <typename To, typename From>
+struct CastInfo<
+    To, From,
+    std::enable_if_t<
+        std::is_base_of_v<mlir::OpInterface<To, typename To::InterfaceTraits>,
+                          To> &&
+            std::is_base_of_v<mlir::OpInterface<std::remove_const_t<From>,
+                                                typename std::remove_const_t<
+                                                    From>::InterfaceTraits>,
+                              std::remove_const_t<From>>,
+        void>> : NullableValueCastFailed<To>,
+                 DefaultDoCastIfPossible<To, From, CastInfo<To, From>> {
+
+  static inline bool isPossible(From &val) {
+    if constexpr (std::is_same_v<To, From>)
+      return true;
+    else
+      return mlir::OpInterface<To, typename To::InterfaceTraits>::
+          InterfaceBase::classof(
+              const_cast<std::remove_const_t<From> &>(val).getOperation());
----------------
River707 wrote:

Why call into classof instead of invoking `isa<To>(val.getOperation())`?

https://github.com/llvm/llvm-project/pull/87145