[clang-tidy] Fix nested namespaces in `readability-static-definition-…

…in-anonymous-namespace` check

The check previously inspected only the immediate parent namespace.
`static` in a named namespace within an unnamed namespace is still
redundant.
We will use `Decl::isInAnonymousNamespace()` method that traverses the
namespaces hierarchy recursively.

Differential Revision: https://reviews.llvm.org/D118010

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

@@ -17,12 +17,16 @@ namespace clang {
 namespace tidy {
 namespace readability {
 
+AST_MATCHER(NamedDecl, isInAnonymousNamespace) {
+  return Node.isInAnonymousNamespace();
+}
+
 void StaticDefinitionInAnonymousNamespaceCheck::registerMatchers(
     MatchFinder *Finder) {
   Finder->addMatcher(
       namedDecl(anyOf(functionDecl(isDefinition(), isStaticStorageClass()),
                       varDecl(isDefinition(), isStaticStorageClass())),
-                hasParent(namespaceDecl(isAnonymous())))
+                isInAnonymousNamespace())
           .bind("static-def"),
       this);
 }

clang-tools-extra/docs/clang-tidy/checks/readability-static-definition-in-anonymous-namespace.rst

@@ -12,7 +12,10 @@ visibility of definitions to a single translation unit.
 
   namespace {
     static int a = 1; // Warning.
-    static const b = 1; // Warning.
+    static const int b = 1; // Warning.
+    namespace inner {
+      static int c = 1; // Warning.
+    }
   }
 
 The check will apply a fix by removing the redundant ``static`` qualifier.

clang-tools-extra/test/clang-tidy/checkers/readability-static-definition-in-anonymous-namespace.cpp

@@ -36,6 +36,21 @@ DEFINE_STATIC int h = 1;
 DEFINE_STATIC_VAR(i);
 // CHECK-FIXES: {{^}}DEFINE_STATIC_VAR(i);
 
+namespace inner {
+int a = 1;
+const int b = 1;
+static int c = 1;
+// CHECK-MESSAGES: :[[@LINE-1]]:12: warning: 'c' is a static definition in anonymous namespace; static is redundant here [readability-static-definition-in-anonymous-namespace]
+// CHECK-FIXES: {{^}}int c = 1;
+namespace deep_inner {
+int a = 1;
+const int b = 1;
+static int c = 1;
+// CHECK-MESSAGES: :[[@LINE-1]]:12: warning: 'c' is a static definition in anonymous namespace; static is redundant here [readability-static-definition-in-anonymous-namespace]
+// CHECK-FIXES: {{^}}int c = 1;
+} // namespace deep_inner
+} // namespace inner
+
 } // namespace
 
 namespace N {