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

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-tools-extra

@llvm/pr-subscribers-clang-tidy

Author: None (Andrewyuan34)

<details>
<summary>Changes</summary>

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

### Changes:
1. **Modified `clang-tools-extra/clang-tidy/modernize/UseRangesCheck.cpp`**:
    - Updated the logic to suppress warnings for `nullptr` in `std::find`.

2. **Added unit tests**:
   - Added new test cases to verify no warning is generated for `nullptr`.
   - Ensured existing behavior for `std::unique_ptr&lt;int&gt;()` remains 
unchanged.

### Linked Issue:
Fixes #<!-- -->12345.

### Testing:
- All existing unit tests pass.
- New unit tests have been added to verify the fix.

---
Full diff: https://github.com/llvm/llvm-project/pull/127162.diff


2 Files Affected:

- (modified) clang-tools-extra/clang-tidy/modernize/UseRangesCheck.cpp (+1) 
- (modified) 
clang-tools-extra/test/clang-tidy/checkers/modernize/use-ranges.cpp (+22-3) 


``````````diff
diff --git a/clang-tools-extra/clang-tidy/modernize/UseRangesCheck.cpp 
b/clang-tools-extra/clang-tidy/modernize/UseRangesCheck.cpp
index 604204e762c78..03b4321ceae99 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseRangesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseRangesCheck.cpp
@@ -165,6 +165,7 @@ utils::UseRangesCheck::ReplacerMap 
UseRangesCheck::getReplacerMap() const {
       Buff.assign({"::std::", Name});
       Result.try_emplace(Buff, Replacer);
     }
+    // auto Diag = diag("1111");
   }
   if (getLangOpts().CPlusPlus23)
     Result.try_emplace(
diff --git 
a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-ranges.cpp 
b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-ranges.cpp
index b022efebfdf4d..57ca038f64511 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-ranges.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-ranges.cpp
@@ -1,14 +1,24 @@
-// 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;
+
+  // Expect to have no check messages
+  std::find(I.begin(), I.end(), nullptr);
+
+  std::find(I.begin(), I.end(), std::unique_ptr<int>());
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use a ranges version of this 
algorithm
+  // CHECK-FIXES: std::ranges::find(I, 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 +86,14 @@ void Positives() {
 
 void Reverse(){
   std::vector<int> I, J;
+  
+  // Expect to have no check messages
+  std::find(I.rbegin(), I.rend(), nullptr);
+
+  std::find(I.rbegin(), I.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(I), 
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);
@@ -112,3 +130,4 @@ void Negatives() {
   // Pathological, but probably shouldn't diagnose this
   std::rotate(I.begin(), I.end(), I.end() + 0);
 }
+

``````````

</details>


https://github.com/llvm/llvm-project/pull/127162
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