https://github.com/irishrover updated 
https://github.com/llvm/llvm-project/pull/172170

>From 1fee7b64e24f811b868ce4efec001fd49d51971d Mon Sep 17 00:00:00 2001
From: Zinovy Nis <[email protected]>
Date: Sat, 13 Dec 2025 13:47:01 +0300
Subject: [PATCH 1/6] [clang-tidy] Add a new check 'modernize-use-string-view'

Looks for functions returning `std::[w|u8|u16|u32]string` and suggests to
change it to `std::[...]string_view` if possible and profitable.

 Example:

```cpp
 std::string foo(int i) { // <---- can be replaced to `std::string_view 
foo(...) {`
   switch(i) {
     case 1:
       return "case1";
     case 2:
       return "case2";
     default:
       return {};
   }
 }
```
---
 .../clang-tidy/modernize/CMakeLists.txt       |   1 +
 .../modernize/ModernizeTidyModule.cpp         |   3 +
 .../modernize/UseStringViewCheck.cpp          |  84 +++++
 .../clang-tidy/modernize/UseStringViewCheck.h |  34 ++
 clang-tools-extra/docs/ReleaseNotes.rst       |  16 +-
 .../docs/clang-tidy/checks/list.rst           |   1 +
 .../checks/modernize/use-string-view.rst      |  68 ++++
 .../clang-tidy/checkers/Inputs/Headers/string |  13 +
 .../checkers/modernize/use-string-view.cpp    | 339 ++++++++++++++++++
 9 files changed, 554 insertions(+), 5 deletions(-)
 create mode 100644 
clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp
 create mode 100644 clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.h
 create mode 100644 
clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
 create mode 100644 
clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view.cpp

diff --git a/clang-tools-extra/clang-tidy/modernize/CMakeLists.txt 
b/clang-tools-extra/clang-tidy/modernize/CMakeLists.txt
index 488c359661018..858cf921f9d34 100644
--- a/clang-tools-extra/clang-tidy/modernize/CMakeLists.txt
+++ b/clang-tools-extra/clang-tidy/modernize/CMakeLists.txt
@@ -50,6 +50,7 @@ add_clang_library(clangTidyModernizeModule STATIC
   UseStdFormatCheck.cpp
   UseStdNumbersCheck.cpp
   UseStdPrintCheck.cpp
+  UseStringViewCheck.cpp
   UseTrailingReturnTypeCheck.cpp
   UseTransparentFunctorsCheck.cpp
   UseUncaughtExceptionsCheck.cpp
diff --git a/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp 
b/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
index 7224b2f32fd73..db8851159c5e8 100644
--- a/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
@@ -51,6 +51,7 @@
 #include "UseStdFormatCheck.h"
 #include "UseStdNumbersCheck.h"
 #include "UseStdPrintCheck.h"
+#include "UseStringViewCheck.h"
 #include "UseTrailingReturnTypeCheck.h"
 #include "UseTransparentFunctorsCheck.h"
 #include "UseUncaughtExceptionsCheck.h"
@@ -131,6 +132,8 @@ class ModernizeModule : public ClangTidyModule {
     CheckFactories.registerCheck<UseNoexceptCheck>("modernize-use-noexcept");
     CheckFactories.registerCheck<UseNullptrCheck>("modernize-use-nullptr");
     CheckFactories.registerCheck<UseOverrideCheck>("modernize-use-override");
+    CheckFactories.registerCheck<UseStringViewCheck>(
+        "modernize-use-string-view");
     CheckFactories.registerCheck<UseTrailingReturnTypeCheck>(
         "modernize-use-trailing-return-type");
     CheckFactories.registerCheck<UseTransparentFunctorsCheck>(
diff --git a/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp 
b/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp
new file mode 100644
index 0000000000000..1ccf21cad91d6
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp
@@ -0,0 +1,84 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "UseStringViewCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+namespace {
+AST_MATCHER(NamedDecl, isOperatorDecl) {
+  const DeclarationName::NameKind NK = Node.getDeclName().getNameKind();
+  return NK != DeclarationName::Identifier &&
+         NK != DeclarationName::CXXConstructorName &&
+         NK != DeclarationName::CXXDestructorName;
+}
+} // namespace
+
+static llvm::StringRef toStringViewTypeStr(StringRef Type) {
+  if (Type.contains("wchar_t"))
+    return "std::wstring_view";
+  if (Type.contains("char8_t"))
+    return "std::u8string_view";
+  if (Type.contains("char16_t"))
+    return "std::u16string_view";
+  if (Type.contains("char32_t"))
+    return "std::u32string_view";
+  return "std::string_view";
+}
+
+static auto getStringTypeMatcher(StringRef CharType) {
+  return hasCanonicalType(hasDeclaration(cxxRecordDecl(hasName(CharType))));
+}
+
+void UseStringViewCheck::registerMatchers(MatchFinder *Finder) {
+  const auto IsStdString = getStringTypeMatcher("::std::basic_string");
+  const auto IsStdStringView = 
getStringTypeMatcher("::std::basic_string_view");
+
+  Finder->addMatcher(
+      functionDecl(
+          isDefinition(),
+          unless(cxxMethodDecl(anyOf(isOperatorDecl(), isVirtual()))),
+          returns(IsStdString), hasDescendant(returnStmt()),
+          unless(anyOf(
+              ast_matchers::isTemplateInstantiation(),
+              isExplicitTemplateSpecialization(),
+              hasDescendant(returnStmt(hasReturnValue(unless(ignoringImplicit(
+                  anyOf(stringLiteral(), hasType(IsStdStringView),
+                        cxxConstructExpr(
+                            hasType(IsStdString),
+                            anyOf(argumentCountIs(0),
+                                  hasArgument(
+                                      0,
+                                      ignoringParenImpCasts(anyOf(
+                                          stringLiteral(),
+                                          
hasType(IsStdStringView)))))))))))))))
+          .bind("func"),
+      this);
+}
+
+void UseStringViewCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *MatchedDecl = Result.Nodes.getNodeAs<FunctionDecl>("func");
+  assert(MatchedDecl);
+  const llvm::StringRef DestReturnTypeStr = toStringViewTypeStr(
+      MatchedDecl->getReturnType().getCanonicalType().getAsString());
+
+  auto Diag = diag(MatchedDecl->getTypeSpecStartLoc(),
+                   "consider using '%0' to avoid unnecessary "
+                   "copying and allocations")
+              << DestReturnTypeStr;
+
+  for (const auto *FuncDecl : MatchedDecl->redecls())
+    Diag << FixItHint::CreateReplacement(FuncDecl->getReturnTypeSourceRange(),
+                                         DestReturnTypeStr);
+}
+
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.h 
b/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.h
new file mode 100644
index 0000000000000..056bcd823a1ac
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.h
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USESTRINGVIEWCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USESTRINGVIEWCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::modernize {
+
+/// Looks for functions returning `std::[w|u8|u16|u32]string` and suggests to
+/// change it to `std::[...]string_view` if possible and profitable.
+///
+/// For the user-facing documentation see:
+/// 
https://clang.llvm.org/extra/clang-tidy/checks/modernize/use-string-view.html
+class UseStringViewCheck : public ClangTidyCheck {
+public:
+  UseStringViewCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+    return LangOpts.CPlusPlus17;
+  }
+};
+
+} // namespace clang::tidy::modernize
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USESTRINGVIEWCHECK_H
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst 
b/clang-tools-extra/docs/ReleaseNotes.rst
index 924b2c03cfd18..da5745a235711 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -107,10 +107,10 @@ Hover
 Code completion
 ^^^^^^^^^^^^^^^
 
-- Added a new ``MacroFilter`` configuration option to ``Completion`` to 
-  allow fuzzy-matching with the ``FuzzyMatch`` option when suggesting 
-  macros. ``ExactPrefix`` is the default, which retains previous 
-  behavior of suggesting macros which match the prefix exactly.  
+- Added a new ``MacroFilter`` configuration option to ``Completion`` to
+  allow fuzzy-matching with the ``FuzzyMatch`` option when suggesting
+  macros. ``ExactPrefix`` is the default, which retains previous
+  behavior of suggesting macros which match the prefix exactly.
 
 Code actions
 ^^^^^^^^^^^^
@@ -201,7 +201,7 @@ Improvements to clang-tidy
 
 - Improved :program:`clang-tidy` by adding the `--removed-arg` option to remove
   arguments sent to the compiler when invoking Clang-Tidy. This option was also
-  added to :program:`run-clang-tidy.py` and :program:`clang-tidy-diff.py` and 
+  added to :program:`run-clang-tidy.py` and :program:`clang-tidy-diff.py` and
   can be configured in the config file through the `RemovedArgs` option.
 
 - Deprecated the :program:`clang-tidy` ``zircon`` module. All checks have been
@@ -261,6 +261,12 @@ New checks
   Finds virtual function overrides with different visibility than the function
   in the base class.
 
+- New :doc:`modernize-use-string-view
+  <clang-tidy/checks/modernize/use-string-view>` check.
+
+  Looks for functions returning ``std::[w|u8|u16|u32]string`` and suggests to
+  change it to ``std::[...]string_view`` for performance reasons if possible.
+
 - New :doc:`readability-redundant-parentheses
   <clang-tidy/checks/readability/redundant-parentheses>` check.
 
diff --git a/clang-tools-extra/docs/clang-tidy/checks/list.rst 
b/clang-tools-extra/docs/clang-tidy/checks/list.rst
index e5e77b5cc418b..d61316f022a8c 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/list.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/list.rst
@@ -330,6 +330,7 @@ Clang-Tidy Checks
    :doc:`modernize-use-std-format <modernize/use-std-format>`, "Yes"
    :doc:`modernize-use-std-numbers <modernize/use-std-numbers>`, "Yes"
    :doc:`modernize-use-std-print <modernize/use-std-print>`, "Yes"
+   :doc:`modernize-use-string-view <modernize/use-string-view>`, "Yes"
    :doc:`modernize-use-trailing-return-type 
<modernize/use-trailing-return-type>`, "Yes"
    :doc:`modernize-use-transparent-functors 
<modernize/use-transparent-functors>`, "Yes"
    :doc:`modernize-use-uncaught-exceptions 
<modernize/use-uncaught-exceptions>`, "Yes"
diff --git 
a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst 
b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
new file mode 100644
index 0000000000000..1b3bdc58db5ab
--- /dev/null
+++ b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
@@ -0,0 +1,68 @@
+.. title:: clang-tidy - modernize-use-string-view
+
+modernize-use-string-view
+====================================
+
+Looks for functions returning ``std::[w|u8|u16|u32]string`` and suggests to
+change it to ``std::[...]string_view`` for performance reasons if possible.
+
+Rationale:
+
+Each time a new ``std::string`` is created from a literal, a copy of that
+literal is allocated either in ``std::string``'s internal buffer
+(for short literals) or in a heap.
+
+For the cases where ``std::string`` is returned from a function,
+such allocations can sometimes be eliminated by using ``std::string_view``
+as a return type.
+
+This check looks for such functions returning ``std::string`` baked from the
+literals and suggests replacing their return type to ``std::string_view``.
+
+It handles ``std::string``, ``std::wstring``, ``std::u8string``,
+``std::u16string`` and ``std::u32string`` along with their aliases and selects
+the proper kind of ``std::string_view`` to return.
+
+Example:
+
+Consider the following code:
+
+.. code-block:: c++
+
+    std::string foo(int i) {
+      switch(i)
+      {
+        case 1:
+          return "case 1";
+        case 2:
+          return "case 2";
+        case 3:
+          return "case 3";
+        default:
+          return "default";
+      }
+    }
+
+In the code above a new ``std::string`` object is created on each function
+invocation, making a copy of a string literal and possibly allocating a memory
+in a heap.
+
+The check gets this code transformed into:
+
+.. code-block:: c++
+
+    std::string_view foo(int i) {
+      switch(i)
+      {
+        case 1:
+          return "case 1";
+        case 2:
+          return "case 2";
+        case 3:
+          return "case 3";
+        default:
+          return "default";
+      }
+    }
+
+New version re-uses statically allocated literals without additional overhead.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/Inputs/Headers/string 
b/clang-tools-extra/test/clang-tidy/checkers/Inputs/Headers/string
index 6cedda4202f14..c792b6e43836a 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/Inputs/Headers/string
+++ b/clang-tools-extra/test/clang-tidy/checkers/Inputs/Headers/string
@@ -22,6 +22,7 @@ struct basic_string {
   typedef size_t size_type;
   typedef basic_string<C, T, A> _Type;
   basic_string();
+  basic_string(basic_string_view<C, T>);
   basic_string(const C *p, const A &a = A());
   basic_string(const C *p, size_type count);
   basic_string(const C *b, const C *e);
@@ -90,8 +91,14 @@ struct basic_string {
 
 typedef basic_string<char> string;
 typedef basic_string<wchar_t> wstring;
+#if __cplusplus >= 202002L
+typedef basic_string<char8_t> u8string;
+typedef basic_string<char16_t> u16string;
+typedef basic_string<char32_t> u32string;
+#else
 typedef basic_string<char16> u16string;
 typedef basic_string<char32> u32string;
+#endif
 
 template <typename C, typename T>
 struct basic_string_view {
@@ -136,8 +143,14 @@ struct basic_string_view {
 
 typedef basic_string_view<char> string_view;
 typedef basic_string_view<wchar_t> wstring_view;
+#if __cplusplus >= 202002L
+typedef basic_string_view<char8_t> u8string_view;
+typedef basic_string_view<char16_t> u16string_view;
+typedef basic_string_view<char32_t> u32string_view;
+#else
 typedef basic_string_view<char16> u16string_view;
 typedef basic_string_view<char32> u32string_view;
+#endif
 
 std::string operator+(const std::string&, const std::string&);
 std::string operator+(const std::string&, const char*);
diff --git 
a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view.cpp 
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view.cpp
new file mode 100644
index 0000000000000..b90f36eec26cc
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view.cpp
@@ -0,0 +1,339 @@
+// RUN: %check_clang_tidy -std=c++20-or-later %s modernize-use-string-view %t 
-- -- -isystem %clang_tidy_headers
+
+#include <string>
+
+namespace std {
+namespace literals {
+namespace string_literals {
+  string operator""s(const char *, size_t);
+}
+namespace string_view_literals {
+  string_view operator""sv(const char *, size_t);
+}
+}
+template <class T, class U> struct is_same { static constexpr bool value = 
false; };
+template <class T> struct is_same<T, T> { static constexpr bool value = true; 
};
+template <class T, class U> constexpr bool is_same_v = is_same<T, U>::value;
+} // namespace std
+
+
+// ==========================================================
+// Positive tests
+// ==========================================================
+
+std::string simpleLiteral() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view simpleLiteral() {
+  return "simpleLiteral";
+}
+
+std::wstring simpleLiteralW() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::wstring_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::wstring_view simpleLiteralW() {
+  return L"wide literal";
+}
+
+std::u8string simpleLiteral8() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::u8string_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::u8string_view simpleLiteral8() {
+  return u8"simpleLiteral";
+}
+
+std::u16string simpleLiteral16() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::u16string_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::u16string_view simpleLiteral16() {
+  return u"simpleLiteral";
+}
+
+std::u32string simpleLiteral32() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::u32string_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::u32string_view simpleLiteral32() {
+  return U"simpleLiteral";
+}
+
+std::string simpleRLiteral() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view simpleRLiteral() {
+  return R"(simpleLiteral)";
+}
+
+[[nodiscard]] std::string Attributed() {
+// CHECK-MESSAGES:[[@LINE-1]]:15: warning: consider using 'std::string_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: {{\[\[nodiscard\]\]}} std::string_view Attributed() {
+  return "attributed";
+}
+
+const std::string Const() {
+// CHECK-MESSAGES:[[@LINE-1]]:7: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: const std::string_view Const() {
+  return "Const";
+}
+
+auto Trailing() -> std::string {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// TODO: support fixes for deduced types
+  return "Trailing";
+}
+
+std::string emptyReturn() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view emptyReturn() {
+  return {};
+}
+
+std::string ctorReturn() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view ctorReturn() {
+  return std::string();
+}
+
+std::string initList() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view initList() {
+  return {"list"};
+}
+
+std::string switchCaseTest(int i) {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view switchCaseTest(int i) {
+  switch (i) {
+  case 1:
+    return "case1";
+  case 2:
+    return "case2";
+  case 3:
+    return {};
+  default:
+    return "default";
+  }
+}
+
+std::string ifElseTest(bool flag) {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view ifElseTest(bool flag) {
+  if (flag)
+    return "true";
+  return "false";
+}
+
+class A {
+  std::string classMethodInt() { return "internal"; }
+// CHECK-MESSAGES:[[@LINE-1]]:3: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view classMethodInt() { return "internal"; }
+
+  std::string classMethodExt();
+// CHECK-FIXES: std::string_view classMethodExt();
+};
+
+std::string A::classMethodExt() { return "external"; }
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view A::classMethodExt() { return "external"; }
+
+#define MACRO "MACRO LITERAL"
+std::string macro() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view macro() {
+  return MACRO;
+}
+
+#define my_string std::string
+my_string macro_type() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view macro_type() {
+  return "MACTO LITERAL";
+}
+
+// ==========================================================
+// Negative tests
+// ==========================================================
+
+std::string localVariable() {
+  std::string s = "local variable";
+  // TODO: extract and return literal
+  return s;
+}
+
+std::string dynamicCalculation() {
+  std::string s1 = "hello ";
+  return s1 + "world";
+}
+
+std::string mixedReturns(bool flag) {
+  if (flag) {
+    return "safe static literal";
+  }
+  std::string s = "unsafe dynamic";
+  return s;
+}
+
+std::string ternary(bool flag) {
+  return flag ? "true" : "false";
+}
+
+std::string_view alreadyGood() {
+  return "alreadyGood";
+}
+
+std::wstring_view alreadyGoodW() {
+  return L"alreadyGood";
+}
+
+std::u8string_view alreadyGoodU8() {
+  return u8"alreadyGood";
+}
+
+std::u16string_view alreadyGoodU16() {
+  return u"alreadyGood";
+}
+
+std::u32string_view alreadyGoodU32() {
+  return U"alreadyGood";
+}
+
+std::string simpleLiteralS() {
+  // TODO: replace ""s to literal and return string_view
+  using namespace std::literals::string_literals;
+  return "simpleLiteral"s;
+}
+
+std::string_view alreadyGoodSV() {
+  using namespace std::literals::string_view_literals;
+  return "alreadyGood"sv;
+}
+
+std::string returnArgCopy(std::string s) {
+  // Must not be converted to string_view because of use-after-free on stack
+  return s;
+}
+
+std::string returnIndirection(const char* ptr) {
+  // Can be unsafe or intentional, like converting string_view into string
+  return ptr;
+}
+
+std::string localBuffer() {
+  char buf[] = "local buffer";
+  // Must not be converted to string_view because of use-after-free on stack
+  return buf;
+}
+
+std::string returnConstVar() {
+  // TODO: seems safe
+  constexpr auto kVar = "const string";
+  return kVar;
+}
+
+std::string passStringView(std::string_view sv) {
+  // Can be unsafe or intentional, like converting string_view into string
+  return std::string(sv);
+}
+
+std::string explicitConstruction() {
+  // Cannot be std::string_view: returning address of local temporary object
+  // TODO: extract and return literal
+  return std::string("explicitConstruction");
+}
+
+struct B {
+  virtual ~B() = default;
+  virtual std::string virtMethod1() { return "B::virtual1"; }
+  virtual std::string virtMethod2();
+};
+
+ std::string B::virtMethod2() { return "B::virtual2"; }
+
+struct C: public B {
+  std::string virtMethod1() override { return "C::virtual"; }
+  std::string virtMethod2() override;
+};
+
+std::string C::virtMethod2() { return "C::virtual"; }
+
+std::string lambda() {
+  // TODO: extract and return literal from lambda
+  return []() {
+     return "lambda";
+  }();
+}
+
+struct TemplateString {
+  static constexpr char* val = "TEMPLATE";
+  template<typename T>
+  // TODO: extract and return literal
+  std::string templateFunc() { return T::val; }
+  std::string templateFuncCall() {
+    return templateFunc<TemplateString>();
+  }
+};
+
+template <class T>
+std::basic_string<T> templateStringConditional() {
+  if constexpr(std::is_same_v<T, wchar_t>) {
+    return L"TEMPLATE";
+  } else {
+    return "TEMPLATE";
+  }
+}
+
+template <class T>
+std::basic_string<T> templateStringMixedConditional() {
+  if constexpr(std::is_same_v<T, wchar_t>) {
+    return L"TEMPLATE";
+  } else {
+    std::string s = "haha";
+    return s;
+  }
+}
+
+void UseTemplateStringConditional() {
+  templateStringConditional<char>();
+  templateStringConditional<wchar_t>();
+
+  templateStringMixedConditional<char>();
+  templateStringMixedConditional<wchar_t>();
+}
+
+std::string& Ref() {
+  static std::string s = "Ref";
+  return s;
+}
+
+const std::string& ConstRef() {
+  static std::string s = "ConstRef";
+  return s;
+}
+
+auto autoReturn() {
+  // Deduced to const char*
+  return "autoReturn";
+}
+
+template <class T>
+std::basic_string<T> templateString() {
+// Intentionally skip templates
+  return L"TEMPLATE";
+}
+std::wstring returnTemplateString() {
+  return templateString<wchar_t>();
+}
+
+template <typename R> R f() {
+// Intentionally skip templates
+  return "str";
+}
+template std::string f();
+
+struct stringOperator {
+  operator std::string() const {
+    return "conversion";
+  }
+};
+
+std::string safeFunctionWithLambda() {
+  auto lambda = []() -> std::string {
+    std::string local = "unsafe";
+    return local;
+  };
+  // TODO: fix hasDescendant(returnStmt(hasReturnValue... which is too strict
+  return "safe literal";
+}
\ No newline at end of file

>From 754547f8c6bf480c82fae1b24358d6cd3bda34f2 Mon Sep 17 00:00:00 2001
From: Zinovy Nis <[email protected]>
Date: Sun, 21 Dec 2025 10:24:51 +0300
Subject: [PATCH 2/6] Auto-fix remarks

Co-authored-by: Baranov Victor <[email protected]>
---
 .../clang-tidy/modernize/UseStringViewCheck.cpp      |  4 ++--
 .../clang-tidy/checks/modernize/use-string-view.rst  | 12 ++----------
 2 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp 
b/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp
index 1ccf21cad91d6..0bfc56d2fbd0c 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp
@@ -23,7 +23,7 @@ AST_MATCHER(NamedDecl, isOperatorDecl) {
 }
 } // namespace
 
-static llvm::StringRef toStringViewTypeStr(StringRef Type) {
+static StringRef toStringViewTypeStr(StringRef Type) {
   if (Type.contains("wchar_t"))
     return "std::wstring_view";
   if (Type.contains("char8_t"))
@@ -68,7 +68,7 @@ void UseStringViewCheck::registerMatchers(MatchFinder 
*Finder) {
 void UseStringViewCheck::check(const MatchFinder::MatchResult &Result) {
   const auto *MatchedDecl = Result.Nodes.getNodeAs<FunctionDecl>("func");
   assert(MatchedDecl);
-  const llvm::StringRef DestReturnTypeStr = toStringViewTypeStr(
+  const StringRef DestReturnTypeStr = toStringViewTypeStr(
       MatchedDecl->getReturnType().getCanonicalType().getAsString());
 
   auto Diag = diag(MatchedDecl->getTypeSpecStartLoc(),
diff --git 
a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst 
b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
index 1b3bdc58db5ab..70dd2726e5f0a 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
@@ -1,13 +1,11 @@
 .. title:: clang-tidy - modernize-use-string-view
 
 modernize-use-string-view
-====================================
+=========================
 
 Looks for functions returning ``std::[w|u8|u16|u32]string`` and suggests to
 change it to ``std::[...]string_view`` for performance reasons if possible.
 
-Rationale:
-
 Each time a new ``std::string`` is created from a literal, a copy of that
 literal is allocated either in ``std::string``'s internal buffer
 (for short literals) or in a heap.
@@ -23,9 +21,7 @@ It handles ``std::string``, ``std::wstring``, 
``std::u8string``,
 ``std::u16string`` and ``std::u32string`` along with their aliases and selects
 the proper kind of ``std::string_view`` to return.
 
-Example:
-
-Consider the following code:
+Consider the following example:
 
 .. code-block:: c++
 
@@ -34,10 +30,6 @@ Consider the following code:
       {
         case 1:
           return "case 1";
-        case 2:
-          return "case 2";
-        case 3:
-          return "case 3";
         default:
           return "default";
       }

>From bc03ac7407ebcff8062bdc55fed31f5e0b46c4da Mon Sep 17 00:00:00 2001
From: Zinovy Nis <[email protected]>
Date: Sun, 21 Dec 2025 11:07:21 +0300
Subject: [PATCH 3/6] Fix remarks

---
 .../modernize/UseStringViewCheck.cpp          |  51 ++++----
 .../clang-tidy/modernize/UseStringViewCheck.h |  15 ++-
 .../checks/modernize/use-string-view.rst      |  25 ++--
 .../modernize/use-string-view-cxx20.cpp       |  42 +++++++
 .../modernize/use-string-view-ignored.cpp     |  56 +++++++++
 .../checkers/modernize/use-string-view.cpp    | 116 +++++++++++-------
 6 files changed, 227 insertions(+), 78 deletions(-)
 create mode 100644 
clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view-cxx20.cpp
 create mode 100644 
clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view-ignored.cpp

diff --git a/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp 
b/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp
index 0bfc56d2fbd0c..d1b6223f971e0 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.cpp
@@ -7,6 +7,7 @@
 
//===----------------------------------------------------------------------===//
 
 #include "UseStringViewCheck.h"
+#include "../utils/Matchers.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
 
@@ -14,15 +15,6 @@ using namespace clang::ast_matchers;
 
 namespace clang::tidy::modernize {
 
-namespace {
-AST_MATCHER(NamedDecl, isOperatorDecl) {
-  const DeclarationName::NameKind NK = Node.getDeclName().getNameKind();
-  return NK != DeclarationName::Identifier &&
-         NK != DeclarationName::CXXConstructorName &&
-         NK != DeclarationName::CXXDestructorName;
-}
-} // namespace
-
 static StringRef toStringViewTypeStr(StringRef Type) {
   if (Type.contains("wchar_t"))
     return "std::wstring_view";
@@ -42,25 +34,26 @@ static auto getStringTypeMatcher(StringRef CharType) {
 void UseStringViewCheck::registerMatchers(MatchFinder *Finder) {
   const auto IsStdString = getStringTypeMatcher("::std::basic_string");
   const auto IsStdStringView = 
getStringTypeMatcher("::std::basic_string_view");
-
+  const auto IgnoredFunctionsMatcher =
+      matchers::matchesAnyListedName(IgnoredFunctions);
+  const auto TernaryOperator = conditionalOperator(
+      hasTrueExpression(ignoringParenImpCasts(stringLiteral())),
+      hasFalseExpression(ignoringParenImpCasts(stringLiteral())));
+  const auto VirtualOrOperator =
+      cxxMethodDecl(anyOf(cxxConversionDecl(), isVirtual()));
   Finder->addMatcher(
       functionDecl(
-          isDefinition(),
-          unless(cxxMethodDecl(anyOf(isOperatorDecl(), isVirtual()))),
-          returns(IsStdString), hasDescendant(returnStmt()),
-          unless(anyOf(
-              ast_matchers::isTemplateInstantiation(),
-              isExplicitTemplateSpecialization(),
-              hasDescendant(returnStmt(hasReturnValue(unless(ignoringImplicit(
-                  anyOf(stringLiteral(), hasType(IsStdStringView),
-                        cxxConstructExpr(
-                            hasType(IsStdString),
-                            anyOf(argumentCountIs(0),
-                                  hasArgument(
-                                      0,
-                                      ignoringParenImpCasts(anyOf(
-                                          stringLiteral(),
-                                          
hasType(IsStdStringView)))))))))))))))
+          isDefinition(), unless(VirtualOrOperator),
+          unless(IgnoredFunctionsMatcher), returns(IsStdString),
+          hasDescendant(returnStmt()),
+          unless(hasDescendant(returnStmt(hasReturnValue(unless(
+              anyOf(stringLiteral(), hasType(IsStdStringView), TernaryOperator,
+                    cxxConstructExpr(anyOf(
+                        allOf(hasType(IsStdString), argumentCountIs(0)),
+                        allOf(isListInitialization(),
+                              unless(cxxTemporaryObjectExpr()),
+                              hasArgument(0, ignoringParenImpCasts(
+                                                 stringLiteral()))))))))))))
           .bind("func"),
       this);
 }
@@ -77,8 +70,10 @@ void UseStringViewCheck::check(const 
MatchFinder::MatchResult &Result) {
               << DestReturnTypeStr;
 
   for (const auto *FuncDecl : MatchedDecl->redecls())
-    Diag << FixItHint::CreateReplacement(FuncDecl->getReturnTypeSourceRange(),
-                                         DestReturnTypeStr);
+    if (const SourceRange ReturnTypeRange =
+            FuncDecl->getReturnTypeSourceRange();
+        ReturnTypeRange.isValid())
+      Diag << FixItHint::CreateReplacement(ReturnTypeRange, DestReturnTypeStr);
 }
 
 } // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.h 
b/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.h
index 056bcd823a1ac..0658ba081c7bf 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseStringViewCheck.h
@@ -10,6 +10,7 @@
 #define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USESTRINGVIEWCHECK_H
 
 #include "../ClangTidyCheck.h"
+#include "../utils/OptionsUtils.h"
 
 namespace clang::tidy::modernize {
 
@@ -21,12 +22,24 @@ namespace clang::tidy::modernize {
 class UseStringViewCheck : public ClangTidyCheck {
 public:
   UseStringViewCheck(StringRef Name, ClangTidyContext *Context)
-      : ClangTidyCheck(Name, Context) {}
+      : ClangTidyCheck(Name, Context),
+        IgnoredFunctions(utils::options::parseStringList(Options.get(
+            "IgnoredFunctions", "toString$;ToString$;to_string$;to_s$"))) {}
   void registerMatchers(ast_matchers::MatchFinder *Finder) override;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
   bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
     return LangOpts.CPlusPlus17;
   }
+  std::optional<TraversalKind> getCheckTraversalKind() const override {
+    return TK_IgnoreUnlessSpelledInSource;
+  }
+  void storeOptions(ClangTidyOptions::OptionMap &Opts) override {
+    Options.store(Opts, "IgnoredFunctions",
+                  utils::options::serializeStringList(IgnoredFunctions));
+  }
+
+private:
+  const std::vector<StringRef> IgnoredFunctions;
 };
 
 } // namespace clang::tidy::modernize
diff --git 
a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst 
b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
index 70dd2726e5f0a..1eac38be8af2a 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
@@ -26,10 +26,10 @@ Consider the following example:
 .. code-block:: c++
 
     std::string foo(int i) {
-      switch(i)
-      {
+      switch(i) {
         case 1:
           return "case 1";
+        ...
         default:
           return "default";
       }
@@ -44,17 +44,26 @@ The check gets this code transformed into:
 .. code-block:: c++
 
     std::string_view foo(int i) {
-      switch(i)
-      {
+      switch(i) {
         case 1:
           return "case 1";
-        case 2:
-          return "case 2";
-        case 3:
-          return "case 3";
+        ...
         default:
           return "default";
       }
     }
 
 New version re-uses statically allocated literals without additional overhead.
+
+Options
+-------
+
+.. option:: IgnoredFunctions
+
+   A semicolon-separated list of the names of functions or methods to be
+   ignored. Regular expressions are accepted, e.g. ``[Rr]ef(erence)?$`` matches
+   every type with suffix ``Ref``, ``ref``, ``Reference`` and ``reference``.
+   The default is {``toString$;ToString$;to_string$;to_s$``}. If a
+   name in the list contains the sequence `::` it is matched against the
+   qualified type name (i.e. ``namespace::Type``), otherwise it is matched
+   against only the type name (i.e. ``Type``).
diff --git 
a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view-cxx20.cpp
 
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view-cxx20.cpp
new file mode 100644
index 0000000000000..65f94c5354f38
--- /dev/null
+++ 
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view-cxx20.cpp
@@ -0,0 +1,42 @@
+// RUN: %check_clang_tidy -std=c++20-or-later %s modernize-use-string-view %t 
-- -- -isystem %clang_tidy_headers
+
+#include <string>
+
+// ==========================================================
+// Positive tests
+// ==========================================================
+
+std::string simpleLiteral() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view simpleLiteral() {
+  return "simpleLiteral";
+}
+
+std::wstring simpleLiteralW() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::wstring_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::wstring_view simpleLiteralW() {
+  return L"wide literal";
+}
+
+std::u8string simpleLiteral8() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::u8string_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::u8string_view simpleLiteral8() {
+  return u8"simpleLiteral";
+}
+
+std::u16string simpleLiteral16() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::u16string_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::u16string_view simpleLiteral16() {
+  return u"simpleLiteral";
+}
+
+std::u32string simpleLiteral32() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::u32string_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::u32string_view simpleLiteral32() {
+  return U"simpleLiteral";
+}
+
+// ==========================================================
+// Negative tests
+// ==========================================================
+
diff --git 
a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view-ignored.cpp
 
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view-ignored.cpp
new file mode 100644
index 0000000000000..642d804a745a1
--- /dev/null
+++ 
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view-ignored.cpp
@@ -0,0 +1,56 @@
+// RUN: %check_clang_tidy \
+// RUN: -std=c++17-or-later %s modernize-use-string-view %t -- \
+// RUN: --config="{CheckOptions: {modernize-use-string-view.IgnoredFunctions: 
'GoodButIgnored;GoodTooButAlsoIgnored'}}" \
+// RUN: -- -isystem %clang_tidy_headers
+
+#include <string>
+
+namespace std {
+namespace literals {
+namespace string_literals {
+  string operator""s(const char *, size_t);
+}
+namespace string_view_literals {
+  string_view operator""sv(const char *, size_t);
+}
+}
+template <class T, class U> struct is_same { static constexpr bool value = 
false; };
+template <class T> struct is_same<T, T> { static constexpr bool value = true; 
};
+template <class T, class U> constexpr bool is_same_v = is_same<T, U>::value;
+} // namespace std
+
+
+// ==========================================================
+// Positive tests
+// ==========================================================
+
+std::string toString() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view toString() {
+  return "not ignored by custom options";
+}
+
+std::string ToString() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view ToString() {
+  return "not ignored by custom options";
+}
+
+std::string to_string() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view to_string() {
+  return "not ignored by custom options";
+}
+
+// ==========================================================
+// Negative tests
+// ==========================================================
+
+std::string GoodButIgnored() {
+  return "ignored by explicit options";
+}
+
+std::string GoodTooButAlsoIgnored() {
+  return "also ignored by explicit options";
+}
+
diff --git 
a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view.cpp 
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view.cpp
index b90f36eec26cc..3e66ecfdaf614 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-string-view.cpp
@@ -1,4 +1,6 @@
-// RUN: %check_clang_tidy -std=c++20-or-later %s modernize-use-string-view %t 
-- -- -isystem %clang_tidy_headers
+// RUN: %check_clang_tidy \
+// RUN: -std=c++17-or-later %s modernize-use-string-view %t -- \
+// RUN: -- -isystem %clang_tidy_headers
 
 #include <string>
 
@@ -33,24 +35,6 @@ std::wstring simpleLiteralW() {
   return L"wide literal";
 }
 
-std::u8string simpleLiteral8() {
-// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::u8string_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
-// CHECK-FIXES: std::u8string_view simpleLiteral8() {
-  return u8"simpleLiteral";
-}
-
-std::u16string simpleLiteral16() {
-// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::u16string_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
-// CHECK-FIXES: std::u16string_view simpleLiteral16() {
-  return u"simpleLiteral";
-}
-
-std::u32string simpleLiteral32() {
-// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::u32string_view' 
to avoid unnecessary copying and allocations [modernize-use-string-view]
-// CHECK-FIXES: std::u32string_view simpleLiteral32() {
-  return U"simpleLiteral";
-}
-
 std::string simpleRLiteral() {
 // CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
 // CHECK-FIXES: std::string_view simpleRLiteral() {
@@ -75,10 +59,10 @@ auto Trailing() -> std::string {
   return "Trailing";
 }
 
-std::string emptyReturn() {
+std::string initList() {
 // CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
-// CHECK-FIXES: std::string_view emptyReturn() {
-  return {};
+// CHECK-FIXES: std::string_view initList() {
+  return {"list"};
 }
 
 std::string ctorReturn() {
@@ -87,10 +71,16 @@ std::string ctorReturn() {
   return std::string();
 }
 
-std::string initList() {
+std::string ctorWithInitListReturn() {
 // CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
-// CHECK-FIXES: std::string_view initList() {
-  return {"list"};
+// CHECK-FIXES: std::string_view ctorWithInitListReturn() {
+  return std::string{};
+}
+
+std::string emptyReturn() {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view emptyReturn() {
+  return {};
 }
 
 std::string switchCaseTest(int i) {
@@ -116,6 +106,12 @@ std::string ifElseTest(bool flag) {
   return "false";
 }
 
+std::string ternary(bool flag) {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+// CHECK-FIXES: std::string_view ternary(bool flag) {
+  return flag ? "true" : "false";
+}
+
 class A {
   std::string classMethodInt() { return "internal"; }
 // CHECK-MESSAGES:[[@LINE-1]]:3: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
@@ -143,10 +139,28 @@ my_string macro_type() {
   return "MACTO LITERAL";
 }
 
+#define my_definition std::string function_inside_macro()
+my_definition {
+// CHECK-MESSAGES:[[@LINE-1]]:1: warning: consider using 'std::string_view' to 
avoid unnecessary copying and allocations [modernize-use-string-view]
+  return "literal";
+}
+
 // ==========================================================
 // Negative tests
 // ==========================================================
 
+std::string toString() {
+  return "ignored by default options";
+}
+
+std::string ToString() {
+  return "ignored by default options";
+}
+
+std::string to_string() {
+  return "ignored by default options";
+}
+
 std::string localVariable() {
   std::string s = "local variable";
   // TODO: extract and return literal
@@ -166,8 +180,9 @@ std::string mixedReturns(bool flag) {
   return s;
 }
 
-std::string ternary(bool flag) {
-  return flag ? "true" : "false";
+std::string stringTernary(bool flag) {
+  // TODO: extract literals
+  return flag ? std::string("true") : std::string("false");
 }
 
 std::string_view alreadyGood() {
@@ -178,18 +193,6 @@ std::wstring_view alreadyGoodW() {
   return L"alreadyGood";
 }
 
-std::u8string_view alreadyGoodU8() {
-  return u8"alreadyGood";
-}
-
-std::u16string_view alreadyGoodU16() {
-  return u"alreadyGood";
-}
-
-std::u32string_view alreadyGoodU32() {
-  return U"alreadyGood";
-}
-
 std::string simpleLiteralS() {
   // TODO: replace ""s to literal and return string_view
   using namespace std::literals::string_literals;
@@ -224,7 +227,7 @@ std::string returnConstVar() {
 }
 
 std::string passStringView(std::string_view sv) {
-  // Can be unsafe or intentional, like converting string_view into string
+  // TODO: Can be unsafe or intentional, like converting string_view into 
string
   return std::string(sv);
 }
 
@@ -234,6 +237,20 @@ std::string explicitConstruction() {
   return std::string("explicitConstruction");
 }
 
+std::string explicitConstructionWithInitList() {
+  // Cannot be std::string_view: returning address of local temporary object
+  // TODO: extract and return literal
+  return std::string{"explicitConstruction"};
+}
+
+std::string explicitConstructionEmpty() {
+  return std::string("");
+}
+
+std::string explicitConstructionWithInitListEmpty() {
+  return std::string{""};
+}
+
 struct B {
   virtual ~B() = default;
   virtual std::string virtMethod1() { return "B::virtual1"; }
@@ -252,7 +269,7 @@ std::string C::virtMethod2() { return "C::virtual"; }
 std::string lambda() {
   // TODO: extract and return literal from lambda
   return []() {
-     return "lambda";
+    return "lambda";
   }();
 }
 
@@ -336,4 +353,21 @@ std::string safeFunctionWithLambda() {
   };
   // TODO: fix hasDescendant(returnStmt(hasReturnValue... which is too strict
   return "safe literal";
+}
+
+using Handle = std::wstring;
+
+#ifdef HANDLE_SUPPORTED
+Handle handle_or_string();
+#else
+std::string handle_or_string();
+#endif
+
+#ifdef HANDLE_SUPPORTED
+Handle
+#else
+std::string
+#endif
+my_function() {
+  return handle_or_string();
 }
\ No newline at end of file

>From 4bcf80ab010c3a07c83f885be59048ce292f6e35 Mon Sep 17 00:00:00 2001
From: Zinovy Nis <[email protected]>
Date: Mon, 22 Dec 2025 07:55:28 +0300
Subject: [PATCH 4/6] Update
 clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst

Co-authored-by: EugeneZelenko <[email protected]>
---
 .../docs/clang-tidy/checks/modernize/use-string-view.rst        | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git 
a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst 
b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
index 1eac38be8af2a..c435c68852769 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
@@ -61,7 +61,7 @@ Options
 .. option:: IgnoredFunctions
 
    A semicolon-separated list of the names of functions or methods to be
-   ignored. Regular expressions are accepted, e.g. ``[Rr]ef(erence)?$`` matches
+   ignored. Regular expressions are accepted, e.g. `[Rr]ef(erence)?$` matches
    every type with suffix ``Ref``, ``ref``, ``Reference`` and ``reference``.
    The default is {``toString$;ToString$;to_string$;to_s$``}. If a
    name in the list contains the sequence `::` it is matched against the

>From f33310be2d8da2c54221cb315c10ebc7be5afc11 Mon Sep 17 00:00:00 2001
From: Zinovy Nis <[email protected]>
Date: Mon, 22 Dec 2025 07:55:54 +0300
Subject: [PATCH 5/6] Update
 clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst

Co-authored-by: EugeneZelenko <[email protected]>
---
 .../docs/clang-tidy/checks/modernize/use-string-view.rst        | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git 
a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst 
b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
index c435c68852769..f1455660bcf54 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
@@ -63,7 +63,7 @@ Options
    A semicolon-separated list of the names of functions or methods to be
    ignored. Regular expressions are accepted, e.g. `[Rr]ef(erence)?$` matches
    every type with suffix ``Ref``, ``ref``, ``Reference`` and ``reference``.
-   The default is {``toString$;ToString$;to_string$;to_s$``}. If a
+   The default is {`toString$;ToString$;to_string$;to_s$`}. If a
    name in the list contains the sequence `::` it is matched against the
    qualified type name (i.e. ``namespace::Type``), otherwise it is matched
    against only the type name (i.e. ``Type``).

>From 62b36f5880d59b0d390c58c6a6308c5b36292f22 Mon Sep 17 00:00:00 2001
From: Zinovy Nis <[email protected]>
Date: Mon, 22 Dec 2025 13:33:25 +0300
Subject: [PATCH 6/6] Update
 clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst

Co-authored-by: Baranov Victor <[email protected]>
---
 .../docs/clang-tidy/checks/modernize/use-string-view.rst         | 1 +
 1 file changed, 1 insertion(+)

diff --git 
a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst 
b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
index f1455660bcf54..f025bfff3a7d8 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/modernize/use-string-view.rst
@@ -67,3 +67,4 @@ Options
    name in the list contains the sequence `::` it is matched against the
    qualified type name (i.e. ``namespace::Type``), otherwise it is matched
    against only the type name (i.e. ``Type``).
+   The default is `toString$;ToString$;to_string$`.

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