new loplugin unnecessaryparen

Change-Id: Ic883a07b30069ca6342d7521c8ad890f4326f0ec
Reviewed-on: https://gerrit.libreoffice.org/39549
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

compilerplugins/clang/test/unnecessaryparen.cxx

@@ -0,0 +1,20 @@
+/* -*- 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/.
+ */
+
+bool foo(int);
+
+int main()
+{
+    int x = 1;
+    x = ((2)); // expected-error {{parentheses around parentheses [loplugin:unnecessaryparen]}}
+
+    if ((foo(1))) foo(2); // expected-error {{parentheses immediately inside if [loplugin:unnecessaryparen]}}
+};
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */

compilerplugins/clang/unnecessaryparen.cxx

@@ -0,0 +1,84 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * 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/.
+ */
+
+#include <cassert>
+#include <string>
+#include <iostream>
+#include <fstream>
+#include <set>
+
+#include <clang/AST/CXXInheritance.h>
+#include "compat.hxx"
+#include "plugin.hxx"
+
+/**
+look for unnecessary parentheses
+*/
+
+namespace {
+
+class UnnecessaryParen:
+    public RecursiveASTVisitor<UnnecessaryParen>, public loplugin::Plugin
+{
+public:
+    explicit UnnecessaryParen(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override
+    {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitParenExpr(const ParenExpr *);
+    bool VisitIfStmt(const IfStmt *);
+};
+
+bool UnnecessaryParen::VisitParenExpr(const ParenExpr* parenExpr)
+{
+    if (ignoreLocation(parenExpr))
+        return true;
+    if (parenExpr->getLocStart().isMacroID())
+        return true;
+
+    auto subParenExpr = dyn_cast<ParenExpr>(parenExpr->getSubExpr());
+    if (subParenExpr) {
+        if (subParenExpr->getLocStart().isMacroID())
+            return true;
+        report(
+            DiagnosticsEngine::Warning, "parentheses around parentheses",
+            parenExpr->getLocStart())
+            << parenExpr->getSourceRange();
+    }
+    return true;
+}
+
+bool UnnecessaryParen::VisitIfStmt(const IfStmt* ifStmt)
+{
+    if (ignoreLocation(ifStmt))
+        return true;
+
+    if (auto parenExpr = dyn_cast<ParenExpr>(ifStmt->getCond())) {
+        if (parenExpr->getLocStart().isMacroID())
+            return true;
+        // assignments need extra parentheses or they generate a compiler warning
+        auto binaryOp = dyn_cast<BinaryOperator>(parenExpr->getSubExpr());
+        if (binaryOp && binaryOp->getOpcode() == BO_Assign)
+            return true;
+        report(
+            DiagnosticsEngine::Warning, "parentheses immediately inside if",
+            ifStmt->getLocStart())
+            << ifStmt->getSourceRange();
+    }
+    return true;
+}
+
+loplugin::Plugin::Registration< UnnecessaryParen > X("unnecessaryparen", true);
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */