[clang-tidy] Fix false positives in readability-redundant-inline-specifier (#135391)

The out-of-line explicitly-defaulted definition is not the first
declaration, so it is not implicitly inline.

Alt. reference:
9.5.2 (3) Explicitly-defaulted functions in
[N4950](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/n4950.pdf).
or https://timsong-cpp.github.io/cppwp/n4861/dcl.fct.def.default#3

Fixes #130745

---------

Signed-off-by: Björn Svensson <[email protected]>

Author: bjosv

clang-tools-extra/clang-tidy/readability/RedundantInlineSpecifierCheck.cpp

@@ -72,11 +72,13 @@ static SourceLocation getInlineTokenLocation(SourceRange RangeLocation,
 }
 
 void RedundantInlineSpecifierCheck::registerMatchers(MatchFinder *Finder) {
+  const auto IsPartOfRecordDecl = hasAncestor(recordDecl());
   Finder->addMatcher(
       functionDecl(isInlineSpecified(),
-                   anyOf(isConstexpr(), isDeleted(), isDefaulted(),
+                   anyOf(isConstexpr(), isDeleted(),
+                         allOf(isDefaulted(), IsPartOfRecordDecl),
                          isInternalLinkage(StrictMode),
-                         allOf(isDefinition(), hasAncestor(recordDecl()))))
+                         allOf(isDefinition(), IsPartOfRecordDecl)))
           .bind("fun_decl"),
       this);
 
@@ -88,7 +90,6 @@ void RedundantInlineSpecifierCheck::registerMatchers(MatchFinder *Finder) {
         this);
 
   if (getLangOpts().CPlusPlus17) {
-    const auto IsPartOfRecordDecl = hasAncestor(recordDecl());
     Finder->addMatcher(
         varDecl(
             isInlineSpecified(),

clang-tools-extra/docs/ReleaseNotes.rst

@@ -313,6 +313,10 @@ Changes in existing checks
   <clang-tidy/checks/readability/qualified-auto>` check by adding the option
   `AllowedTypes`, that excludes specified types from adding qualifiers.
 
+- Improved :doc:`readability-redundant-inline-specifier
+  <clang-tidy/checks/readability/redundant-inline-specifier>` check by fixing
+  false positives on out-of-line explicitly defaulted functions.
+
 - Improved :doc:`readability-redundant-smartptr-get
   <clang-tidy/checks/readability/redundant-smartptr-get>` check by fixing
   some false positives involving smart pointers to arrays.

clang-tools-extra/test/clang-tidy/checkers/readability/redundant-inline-specifier.cpp

@@ -149,3 +149,13 @@ class A
   // CHECK-FIXES-STRICT: static float test4;
 };
 }
+
+namespace ns {
+class B
+{
+public:
+  ~B();
+};
+
+inline B::~B() = default;
+}