feedback

Author: hjanuschka

clang-tools-extra/clang-tidy/readability/UseSpanFirstLastCheck.h

@@ -13,8 +13,8 @@
 
 namespace clang::tidy::readability {
 
-/// Suggests using clearer std::span member functions first()/last() instead of
-/// equivalent subspan() calls where applicable.
+/// Suggests using clearer 'std::span' member functions 'first()'/'last()'
+/// instead of equivalent 'subspan()' calls where applicable.
 ///
 /// For example:
 /// \code
@@ -33,9 +33,9 @@ class UseSpanFirstLastCheck : public ClangTidyCheck {
 
   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.CPlusPlus20; 
-	}
+  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+    return LangOpts.CPlusPlus20;
+  }
 
 private:
   void handleSubspanCall(const ast_matchers::MatchFinder::MatchResult &Result,
@@ -44,4 +44,4 @@ class UseSpanFirstLastCheck : public ClangTidyCheck {
 
 } // namespace clang::tidy::readability
 
-#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_USESPANFIRSTLASTCHECK_H
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_USESPANFIRSTLASTCHECK_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -142,13 +142,15 @@ New checks
   Finds cases when an uninstantiated virtual member function in a template class 
   causes cross-compiler incompatibility.
 
-New check aliases
-^^^^^^^^^^^^^^^^^
+- New :doc:`readability-use-span-first-last
+  <clang-tidy/checks/readability/readability-use-span-first-last>` check.
 
-- New check `readability-use-span-first-last` has been added that suggests using
-  ``std::span::first()`` and ``std::span::last()`` member functions instead of
+  Suggests using ``std::span::first()`` and ``std::span::last()`` member functions instead of
   equivalent ``subspan()``.
 
+New check aliases
+^^^^^^^^^^^^^^^^^
+
 - New alias :doc:`cert-arr39-c <clang-tidy/checks/cert/arr39-c>` to
   :doc:`bugprone-sizeof-expression
   <clang-tidy/checks/bugprone/sizeof-expression>` was added.

clang-tools-extra/docs/clang-tidy/checks/readability/use-span-first-last.rst

@@ -9,12 +9,13 @@ to C++20 to provide more expressive alternatives to common subspan operations.
 
 Covered scenarios:
 
-==================================== ==================================
-Expression                           Replacement
------------------------------------- ----------------------------------
-``s.subspan(0, n)``                  ``s.first(n)``
-``s.subspan(s.size() - n)``          ``s.last(n)``
-==================================== ==================================
+========================== ====================
+Expression                 Replacement
+------------------------- --------------------
+``s.subspan(0, n)``       ``s.first(n)``
+``s.subspan(s.size() - n)`` ``s.last(n)``
+========================== ====================
+
 
 Non-zero offset with count (like ``subspan(1, n)``) or offset-only calls 
 (like ``subspan(n)``) have no clearer equivalent using ``first()`` or 

clang-tools-extra/test/clang-tidy/checkers/readability/use-span-first-last.cpp

@@ -48,4 +48,24 @@ void test() {
 
   auto sub4 = s.subspan(1, 2);  // No warning
   auto sub5 = s.subspan(2);     // No warning
-}
+
+
+#define ZERO 0
+#define TWO 2
+#define SIZE_MINUS(s, n) s.size() - n
+#define MAKE_SUBSPAN(obj, n) obj.subspan(0, n)
+#define MAKE_LAST_N(obj, n) obj.subspan(obj.size() - n)
+
+  auto sub6 = s.subspan(SIZE_MINUS(s, 2));
+  // CHECK-MESSAGES: :[[@LINE-1]]:15: warning: prefer 'span::last()' over 'subspan()'
+  // CHECK-FIXES: auto sub6 = s.last(2);
+
+  auto sub7 = MAKE_SUBSPAN(s, 3);
+  // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: prefer 'span::first()' over 'subspan()'
+  // CHECK-FIXES: auto sub7 = s.first(3);
+
+  auto sub8 = MAKE_LAST_N(s, 2);
+  // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: prefer 'span::last()' over 'subspan()'
+  // CHECK-FIXES: auto sub8 = s.last(2);
+
+}