[clang-tidy] Fix invalid fixit from modernize-use-ranges for nullptr used with std::unique_ptr (#127162)

This PR fixes issue #124815 by correcting the handling of `nullptr` with
`std::unique_ptr` in the `modernize-use-ranges` check.

Updated the logic to suppress warnings for `nullptr` in `std::find`.

Author: Andrewyuan34

clang-tools-extra/clang-tidy/utils/UseRangesCheck.cpp

@@ -215,6 +215,19 @@ void UseRangesCheck::check(const MatchFinder::MatchResult &Result) {
     const auto *Call = Result.Nodes.getNodeAs<CallExpr>(Buffer);
     if (!Call)
       continue;
+
+    // FIXME: This check specifically handles `CXXNullPtrLiteralExpr`, but
+    // a more general solution might be needed.
+    if (Function->getName() == "find") {
+      const unsigned ValueArgIndex = 2;
+      if (Call->getNumArgs() <= ValueArgIndex)
+        continue;
+      const Expr *ValueExpr =
+          Call->getArg(ValueArgIndex)->IgnoreParenImpCasts();
+      if (isa<CXXNullPtrLiteralExpr>(ValueExpr))
+        return;
+    }
+
     auto Diag = createDiag(*Call);
     if (auto ReplaceName = Replacer->getReplaceName(*Function))
       Diag << FixItHint::CreateReplacement(Call->getCallee()->getSourceRange(),

clang-tools-extra/docs/ReleaseNotes.rst

@@ -131,6 +131,10 @@ Changes in existing checks
 - Improved :doc:`misc-redundant-expression
   <clang-tidy/checks/misc/redundant-expression>` check by providing additional
   examples and fixing some macro related false positives.
+  
+- Improved :doc:`modernize-use-ranges
+  <clang-tidy/checks/modernize/use-ranges>` check by updating suppress 
+  warnings logic for ``nullptr`` in ``std::find``.
 
 - Improved :doc:`misc-use-internal-linkage
   <clang-tidy/checks/misc/use-internal-linkage>` check by fix false positives

clang-tools-extra/test/clang-tidy/checkers/modernize/use-ranges.cpp

@@ -1,14 +1,25 @@
-// RUN: %check_clang_tidy -std=c++20 %s modernize-use-ranges %t -- -- -I %S/Inputs/use-ranges/
-// RUN: %check_clang_tidy -std=c++23 %s modernize-use-ranges %t -check-suffixes=,CPP23 -- -I %S/Inputs/use-ranges/
+// RUN: %check_clang_tidy -std=c++20 %s modernize-use-ranges %t -- -- -I %S/Inputs/
+// RUN: %check_clang_tidy -std=c++23 %s modernize-use-ranges %t -check-suffixes=,CPP23 -- -I %S/Inputs/
+// Example: ./check_clang_tidy.py -std=c++20 checkers/modernize/use-ranges.cpp modernize-use-ranges temp.txt -- -- -I ~/llvm-project/clang-tools-extra/test/clang-tidy/checkers/modernize/Inputs/
 
 // CHECK-FIXES: #include <algorithm>
 // CHECK-FIXES-CPP23: #include <numeric>
 // CHECK-FIXES: #include <ranges>
 
-#include "fake_std.h"
+#include "use-ranges/fake_std.h"
+#include "smart-ptr/unique_ptr.h"
 
 void Positives() {
   std::vector<int> I, J;
+  std::vector<std::unique_ptr<int>> K;
+
+  // Expect to have no check messages
+  std::find(K.begin(), K.end(), nullptr);
+
+  std::find(K.begin(), K.end(), std::unique_ptr<int>());
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use a ranges version of this algorithm
+  // CHECK-FIXES: std::ranges::find(K, std::unique_ptr<int>());
+
   std::find(I.begin(), I.end(), 0);
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use a ranges version of this algorithm
   // CHECK-FIXES: std::ranges::find(I, 0);
@@ -76,6 +87,15 @@ void Positives() {
 
 void Reverse(){
   std::vector<int> I, J;
+  std::vector<std::unique_ptr<int>> K;
+  
+  // Expect to have no check messages
+  std::find(K.rbegin(), K.rend(), nullptr);
+
+  std::find(K.rbegin(), K.rend(), std::unique_ptr<int>());
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use a ranges version of this algorithm
+  // CHECK-FIXES: std::ranges::find(std::ranges::reverse_view(K), std::unique_ptr<int>());
+
   std::find(I.rbegin(), I.rend(), 0);
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use a ranges version of this algorithm
   // CHECK-FIXES: std::ranges::find(std::ranges::reverse_view(I), 0);