[clang] [ASTMatchers] Migrate away from ArrayRef(std::nullopt) (NFC) (PR #145840)

[Kazu Hirata via cfe-commits]

https://github.com/kazutakahirata created https://github.com/llvm/llvm-project/pull/145840

ArrayRef has a constructor that accepts std::nullopt.  This
constructor dates back to the days when we still had llvm::Optional.

Since the use of std::nullopt outside the context of std::optional is
kind of abuse and not intuitive to new comers, I would like to move
away from the constructor and eventually remove it.

This patch migrates away from std::nullopt in favor of ArrayRef<T>().
Note that {} would be ambiguous for perfect forwarding to work here.


>From 9167309ca0d238f7d9972ae15ef69a971d175eec Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu at google.com>
Date: Wed, 25 Jun 2025 12:06:54 -0700
Subject: [PATCH] [ASTMatchers] Migrate away from ArrayRef(std::nullopt) (NFC)

ArrayRef has a constructor that accepts std::nullopt.  This
constructor dates back to the days when we still had llvm::Optional.

Since the use of std::nullopt outside the context of std::optional is
kind of abuse and not intuitive to new comers, I would like to move
away from the constructor and eventually remove it.

This patch migrates away from std::nullopt in favor of ArrayRef<T>().
Note that {} would be ambiguous for perfect forwarding to work here.
---
 clang/lib/ASTMatchers/Dynamic/Marshallers.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/lib/ASTMatchers/Dynamic/Marshallers.h b/clang/lib/ASTMatchers/Dynamic/Marshallers.h
index 0e640cbada726..d44e42a524f27 100644
--- a/clang/lib/ASTMatchers/Dynamic/Marshallers.h
+++ b/clang/lib/ASTMatchers/Dynamic/Marshallers.h
@@ -1060,7 +1060,7 @@ makeMatcherAutoMarshall(ReturnType (*Func)(), StringRef MatcherName) {
   BuildReturnTypeVector<ReturnType>::build(RetTypes);
   return std::make_unique<FixedArgCountMatcherDescriptor>(
       matcherMarshall0<ReturnType>, reinterpret_cast<void (*)()>(Func),
-      MatcherName, RetTypes, std::nullopt);
+      MatcherName, RetTypes, ArrayRef<ArgKind>());
 }
 
 /// 1-arg overload