[llvm][NFC] Simplify implementation of isa

[localspook]

Using a fold instead of template recursion.

[llvmbot]

@llvm/pr-subscribers-llvm-support

Author: Victor Chernyakin (localspook)

Changes

Using a fold instead of template recursion.

---

Full diff: https://github.com/llvm/llvm-project/pull/161403.diff

1 Files Affected:

• (modified) llvm/include/llvm/Support/Casting.h (+2-7)

diff --git a/llvm/include/llvm/Support/Casting.h b/llvm/include/llvm/Support/Casting.h
index 66fdcb44ea2c0..2a9a149327d83 100644
--- a/llvm/include/llvm/Support/Casting.h
+++ b/llvm/include/llvm/Support/Casting.h
@@ -544,14 +544,9 @@ struct CastInfo<To, std::optional<From>> : public OptionalValueCast<To, From> {
 ///
 ///  if (isa<Type>(myVal)) { ... }
 ///  if (isa<Type0, Type1, Type2>(myVal)) { ... }
-template <typename To, typename From>
-[[nodiscard]] inline bool isa(const From &Val) {
-  return CastInfo<To, const From>::isPossible(Val);
-}
-
-template <typename First, typename Second, typename... Rest, typename From>
+template <typename... To, typename From>
 [[nodiscard]] inline bool isa(const From &Val) {
-  return isa<First>(Val) || isa<Second, Rest...>(Val);
+  return (CastInfo<To, const From>::isPossible(Val) || ...);
 }
 
 /// cast<X> - Return the argument parameter cast to the specified type.  This

[kazutakahirata]

LGTM. Thanks!