loplugin:trivialdestructor: Only warn about definitions

Change-Id: I666e72a5c95b48cd5bc0cb775de3ec6a6c82fe39
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/131574
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

compilerplugins/clang/test/trivialdestructor.cxx

@@ -0,0 +1,28 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+struct S1
+{
+    // expected-note@+1 {{previous declaration is here [loplugin:trivialdestructor]}}
+    ~S1();
+};
+
+// expected-error@+1 {{no need for explicit destructor decl [loplugin:trivialdestructor]}}
+S1::~S1() {}
+
+struct S2
+{
+    // expected-note@+1 {{previous declaration is here [loplugin:trivialdestructor]}}
+    ~S2();
+};
+
+// expected-error@+1 {{no need for explicit destructor decl [loplugin:trivialdestructor]}}
+S2::~S2() = default;
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */

compilerplugins/clang/trivialdestructor.cxx

@@ -45,6 +45,8 @@ bool TrivialDestructor::VisitCXXDestructorDecl(CXXDestructorDecl const* destruct
 {
     if (ignoreLocation(destructorDecl))
         return true;
+    if (!destructorDecl->isThisDeclarationADefinition())
+        return true;
     if (!destructorDecl->hasTrivialBody())
         return true;
     if (destructorDecl->isVirtual())
@@ -62,12 +64,15 @@ bool TrivialDestructor::VisitCXXDestructorDecl(CXXDestructorDecl const* destruct
     report(DiagnosticsEngine::Warning, "no need for explicit destructor decl",
            destructorDecl->getLocation())
         << destructorDecl->getSourceRange();
-    if (destructorDecl->getCanonicalDecl() != destructorDecl)
+    for (FunctionDecl const* d2 = destructorDecl;;)
     {
-        destructorDecl = destructorDecl->getCanonicalDecl();
-        report(DiagnosticsEngine::Warning, "no need for explicit destructor decl",
-               destructorDecl->getLocation())
-            << destructorDecl->getSourceRange();
+        d2 = d2->getPreviousDecl();
+        if (d2 == nullptr)
+        {
+            break;
+        }
+        report(DiagnosticsEngine::Note, "previous declaration is here", d2->getLocation())
+            << d2->getSourceRange();
     }
     return true;
 }

solenv/CompilerTest_compilerplugins_clang.mk

@@ -94,6 +94,7 @@ $(eval $(call gb_CompilerTest_add_exception_objects,compilerplugins_clang, \
     compilerplugins/clang/test/stringstatic \
     compilerplugins/clang/test/stringview \
     compilerplugins/clang/test/stringviewparam \
+    compilerplugins/clang/test/trivialdestructor \
     compilerplugins/clang/test/typedefparam \
     compilerplugins/clang/test/typeidcomparison \
     compilerplugins/clang/test/unnecessarycatchthrow \