[clang-tidy][modernize-use-starts-ends-with] Fix minor mistake in error message

[nicovank]

In one of the cases recently added to this check in #110448, the error message is no longer accurate as the comparison is not with zero. #116033 brought my attention to this as it may add another comparison without zero.

Remove the [!=] 0 part of the diagnostic. This is in line with some other checks e.g. modernize-use-emplace.

> cat tmp.cpp
#include <string>
bool f(std::string u, std::string v) {
  return u.rfind(v) == u.size() - v.size();
}

# Before.
> ./build/bin/clang-tidy -checks="-*,modernize-use-starts-ends-with" tmp.cpp -- -std=c++20
tmp.cpp:3:12: warning: use ends_with instead of rfind() == 0 [modernize-use-starts-ends-with]
    3 |   return u.rfind(v) == u.size() - v.size();
      |            ^~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~
      |            ends_with( )

# After.
> ./build/bin/clang-tidy -checks="-*,modernize-use-starts-ends-with" tmp.cpp -- -std=c++20
tmp.cpp:3:12: warning: use ends_with instead of rfind [modernize-use-starts-ends-with]
    3 |   return u.rfind(v) == u.size() - v.size();
      |            ^~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~
      |            ends_with( )

[llvmbot]

@llvm/pr-subscribers-clang-tidy

@llvm/pr-subscribers-clang-tools-extra

Author: Nicolas van Kempen (nicovank)

Changes

In one of the cases recently added to this check in #110448, the error message is no longer accurate as the comparison is not with zero. #116033 brought my attention to this as it may add another comparison without zero.

Remove the [!=] 0 part of the diagnostic. This is in line with some other checks e.g. modernize-use-emplace.

> cat tmp.cpp
#include <string>
bool f(std::string u, std::string v) {
  return u.rfind(v) == u.size() - v.size();
}

# Before.
> ./build/bin/clang-tidy -checks="-*,modernize-use-starts-ends-with" tmp.cpp -- -std=c++20
tmp.cpp:3:12: warning: use ends_with instead of rfind() == 0 [modernize-use-starts-ends-with]
    3 |   return u.rfind(v) == u.size() - v.size();
      |            ^~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~
      |            ends_with( )

# After.
> ./build/bin/clang-tidy -checks="-*,modernize-use-starts-ends-with" tmp.cpp -- -std=c++20
tmp.cpp:3:12: warning: use ends_with instead of rfind [modernize-use-starts-ends-with]
    3 |   return u.rfind(v) == u.size() - v.size();
      |            ^~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~
      |            ends_with( )

---

Full diff: https://github.com/llvm/llvm-project/pull/116132.diff

3 Files Affected:

• (modified) clang-tools-extra/clang-tidy/modernize/UseStartsEndsWithCheck.cpp (+3-6)
• (modified) clang-tools-extra/docs/ReleaseNotes.rst (+1-1)
• (modified) clang-tools-extra/test/clang-tidy/checkers/modernize/use-starts-ends-with.cpp (+4-4)

diff --git a/clang-tools-extra/clang-tidy/modernize/UseStartsEndsWithCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseStartsEndsWithCheck.cpp
index 1231f954298adc..4d8f6dbc2cc11b 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseStartsEndsWithCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseStartsEndsWithCheck.cpp
@@ -189,11 +189,8 @@ void UseStartsEndsWithCheck::check(const MatchFinder::MatchResult &Result) {
   if (ComparisonExpr->getBeginLoc().isMacroID())
     return;
 
-  const bool Neg = ComparisonExpr->getOpcode() == BO_NE;
-
-  auto Diagnostic =
-      diag(FindExpr->getExprLoc(), "use %0 instead of %1() %select{==|!=}2 0")
-      << ReplacementFunction->getName() << FindFun->getName() << Neg;
+  auto Diagnostic = diag(FindExpr->getExprLoc(), "use %0 instead of %1")
+                    << ReplacementFunction->getName() << FindFun->getName();
 
   // Remove possible arguments after search expression and ' [!=]= .+' suffix.
   Diagnostic << FixItHint::CreateReplacement(
@@ -215,7 +212,7 @@ void UseStartsEndsWithCheck::check(const MatchFinder::MatchResult &Result) {
       (ReplacementFunction->getName() + "(").str());
 
   // Add possible negation '!'.
-  if (Neg)
+  if (ComparisonExpr->getOpcode() == BO_NE)
     Diagnostic << FixItHint::CreateInsertion(FindExpr->getBeginLoc(), "!");
 }
 
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index db971f08ca3dbc..a6c2ced1a56783 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -244,7 +244,7 @@ Changes in existing checks
 
 - Improved :doc:`modernize-use-starts-ends-with
   <clang-tidy/checks/modernize/use-starts-ends-with>` check to handle two cases
-  that can be replaced with ``ends_with``
+  that can be replaced with ``ends_with``. Minor change to error message.
 
 - Improved :doc:`modernize-use-std-format
   <clang-tidy/checks/modernize/use-std-format>` check to support replacing
diff --git a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-starts-ends-with.cpp b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-starts-ends-with.cpp
index 91477241e82e54..788de297a01c01 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-starts-ends-with.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-starts-ends-with.cpp
@@ -36,7 +36,7 @@ void test(std::string s, std::string_view sv, sub_string ss, sub_sub_string sss,
           string_like sl, string_like_camel slc, prefer_underscore_version puv,
           prefer_underscore_version_flip puvf) {
   s.find("a") == 0;
-  // CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with instead of find() == 0
+  // CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with instead of find
   // CHECK-FIXES: s.starts_with("a");
 
   (((((s)).find("a")))) == ((0));
@@ -68,7 +68,7 @@ void test(std::string s, std::string_view sv, sub_string ss, sub_sub_string sss,
   // CHECK-FIXES: !s.starts_with("a");
 
   s.rfind("a", 0) == 0;
-  // CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with instead of rfind() == 0
+  // CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with instead of rfind
   // CHECK-FIXES: s.starts_with("a");
 
   s.rfind(s, 0) == 0;
@@ -149,11 +149,11 @@ void test(std::string s, std::string_view sv, sub_string ss, sub_sub_string sss,
   // CHECK-FIXES: puvf.starts_with("a");
 
   s.compare(0, 1, "a") == 0;
-  // CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with instead of compare() == 0
+  // CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with instead of compare
   // CHECK-FIXES: s.starts_with("a");
 
   s.compare(0, 1, "a") != 0;
-  // CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with instead of compare() != 0
+  // CHECK-MESSAGES: :[[@LINE-1]]:{{[0-9]+}}: warning: use starts_with instead of compare
   // CHECK-FIXES: !s.starts_with("a");
 
   s.compare(0, strlen("a"), "a") == 0;

[nicovank]

Incorporated in #116033.