[clang-tools-extra] [NFC][clang-tidy]refactor isAssignmentToMemberOf in PreferMemberInitializerCheck (PR #71006)

[Congcong Cai via cfe-commits]

https://github.com/HerrCai0907 created https://github.com/llvm/llvm-project/pull/71006

isAssignmentToMemberOf will return `std::make_pair(nullptr, nullptr)` when failed.
Using `std::optional` can describe failed case clearly.

>From 69b7688f56f7fe96031201eef1c3804f391c5abe Mon Sep 17 00:00:00 2001
From: Congcong Cai <congcongcai0907 at 163.com>
Date: Thu, 2 Nov 2023 08:49:22 +0800
Subject: [PATCH] [NFC][clang-tidy]refactor isAssignmentToMemberOf in
 PreferMemberInitializerCheck

---
 .../PreferMemberInitializerCheck.cpp          | 29 ++++++++++---------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp
index b6daf8b936bde0f..f0070265e6a734a 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp
@@ -118,45 +118,45 @@ static void updateAssignmentLevel(
   }
 }
 
-static std::pair<const FieldDecl *, const Expr *>
+static std::optional<std::pair<const FieldDecl *, const Expr *>>
 isAssignmentToMemberOf(const CXXRecordDecl *Rec, const Stmt *S,
                        const CXXConstructorDecl *Ctor) {
   if (const auto *BO = dyn_cast<BinaryOperator>(S)) {
     if (BO->getOpcode() != BO_Assign)
-      return std::make_pair(nullptr, nullptr);
+      return {};
 
     const auto *ME = dyn_cast<MemberExpr>(BO->getLHS()->IgnoreParenImpCasts());
     if (!ME)
-      return std::make_pair(nullptr, nullptr);
+      return {};
 
     const auto *Field = dyn_cast<FieldDecl>(ME->getMemberDecl());
     if (!Field)
-      return std::make_pair(nullptr, nullptr);
+      return {};
 
     if (!isa<CXXThisExpr>(ME->getBase()))
-      return std::make_pair(nullptr, nullptr);
+      return {};
     const Expr *Init = BO->getRHS()->IgnoreParenImpCasts();
     return std::make_pair(Field, Init);
   }
   if (const auto *COCE = dyn_cast<CXXOperatorCallExpr>(S)) {
     if (COCE->getOperator() != OO_Equal)
-      return std::make_pair(nullptr, nullptr);
+      return {};
 
     const auto *ME =
         dyn_cast<MemberExpr>(COCE->getArg(0)->IgnoreParenImpCasts());
     if (!ME)
-      return std::make_pair(nullptr, nullptr);
+      return {};
 
     const auto *Field = dyn_cast<FieldDecl>(ME->getMemberDecl());
     if (!Field)
-      return std::make_pair(nullptr, nullptr);
+      return {};
 
     if (!isa<CXXThisExpr>(ME->getBase()))
-      return std::make_pair(nullptr, nullptr);
+      return {};
     const Expr *Init = COCE->getArg(1)->IgnoreParenImpCasts();
     return std::make_pair(Field, Init);
   }
-  return std::make_pair(nullptr, nullptr);
+  return {};
 }
 
 PreferMemberInitializerCheck::PreferMemberInitializerCheck(
@@ -216,11 +216,12 @@ void PreferMemberInitializerCheck::check(
         return;
     }
 
-    const FieldDecl *Field = nullptr;
-    const Expr *InitValue = nullptr;
-    std::tie(Field, InitValue) = isAssignmentToMemberOf(Class, S, Ctor);
-    if (!Field)
+    std::optional<std::pair<const FieldDecl *, const Expr *>>
+        AssignmentToMember = isAssignmentToMemberOf(Class, S, Ctor);
+    if (!AssignmentToMember)
       continue;
+    const FieldDecl *Field = AssignmentToMember.value().first;
+    const Expr *InitValue = AssignmentToMember.value().second;
     updateAssignmentLevel(Field, InitValue, Ctor, AssignedFields);
     if (!canAdvanceAssignment(AssignedFields[Field]))
       continue;