new loplugin simplifydynamiccast

simplify dynamic_cast followed by static_cast

Change-Id: I965afcf05d1675094cfde53d3590a0fd00f26279
Reviewed-on: https://gerrit.libreoffice.org/44460
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Noel Grandin <noel.grandin@collabora.co.uk>

2 files changed, 150 insertions, 0 deletions

diff --git a/compilerplugins/clang/simplifydynamiccast.cxx b/compilerplugins/clang/simplifydynamiccast.cxx
new file mode 100644
index 000000000000..f305f8cbeaef
--- /dev/null
+++ b/compilerplugins/clang/simplifydynamiccast.cxx
@@ -0,0 +1,116 @@
+/* -*- 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"
+
+namespace
+{
+class SimplifyDynamicCast : public RecursiveASTVisitor<SimplifyDynamicCast>, public loplugin::Plugin
+{
+public:
+    explicit SimplifyDynamicCast(loplugin::InstantiationData const& data)
+        : Plugin(data)
+    {
+    }
+
+    virtual void run() override
+    {
+        //        StringRef fn( compiler.getSourceManager().getFileEntryForID(
+        //                          compiler.getSourceManager().getMainFileID())->getName() );
+        //        if (loplugin::isSamePathname(fn, WORKDIR "/YaccTarget/unoidl/source/sourceprovider-parser.cxx"))
+        //             return;
+
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool TraverseIfStmt(IfStmt*);
+    bool VisitCXXStaticCastExpr(CXXStaticCastExpr const*);
+
+private:
+    std::vector<QualType> dynamicCastVec;
+    std::vector<Decl const*> dynamicCastSubExprVec;
+    std::vector<IfStmt const*> ifVec;
+};
+
+bool SimplifyDynamicCast::TraverseIfStmt(IfStmt* ifStmt)
+{
+    auto condExpr = ifStmt->getCond()->IgnoreParenImpCasts();
+    auto dynamicCastExpr = dyn_cast<CXXDynamicCastExpr>(condExpr);
+    if (!dynamicCastExpr)
+    {
+        if (auto binaryOp = dyn_cast<BinaryOperator>(condExpr))
+        {
+            if (binaryOp->getOpcode() == BO_NE)
+                dynamicCastExpr
+                    = dyn_cast<CXXDynamicCastExpr>(binaryOp->getLHS()->IgnoreParenImpCasts());
+        }
+    }
+    Decl const* subExprDecl = nullptr;
+    if (dynamicCastExpr)
+    {
+        auto subExprDeclRefExpr
+            = dyn_cast<DeclRefExpr>(dynamicCastExpr->getSubExpr()->IgnoreParenImpCasts());
+        if (!subExprDeclRefExpr)
+            dynamicCastExpr = nullptr;
+        else
+            subExprDecl = subExprDeclRefExpr->getDecl();
+    }
+    if (dynamicCastExpr)
+    {
+        auto qt = dynamicCastExpr->getTypeAsWritten();
+        dynamicCastVec.push_back(qt);
+        dynamicCastSubExprVec.push_back(subExprDecl);
+        ifVec.push_back(ifStmt);
+    }
+    bool ret = RecursiveASTVisitor::TraverseIfStmt(ifStmt);
+    if (dynamicCastExpr)
+    {
+        dynamicCastVec.pop_back();
+        dynamicCastSubExprVec.pop_back();
+        ifVec.pop_back();
+    }
+    return ret;
+}
+
+bool SimplifyDynamicCast::VisitCXXStaticCastExpr(CXXStaticCastExpr const* staticCastExpr)
+{
+    if (ignoreLocation(staticCastExpr))
+        return true;
+    if (dynamicCastVec.empty())
+        return true;
+
+    auto qt = staticCastExpr->getTypeAsWritten();
+    auto it = std::find(dynamicCastVec.begin(), dynamicCastVec.end(), qt);
+    if (it == dynamicCastVec.end())
+        return true;
+    int idx = it - dynamicCastVec.begin();
+    auto subExprDecl = dyn_cast<DeclRefExpr>(staticCastExpr->getSubExpr()->IgnoreParenImpCasts());
+    if (!subExprDecl)
+        return true;
+    if (dynamicCastSubExprVec[idx] != subExprDecl->getDecl())
+        return true;
+    report(DiagnosticsEngine::Warning, "simplify, use var in if", staticCastExpr->getLocStart())
+        << staticCastExpr->getSourceRange();
+    auto ifStmt = ifVec[idx];
+    report(DiagnosticsEngine::Note, "if here", ifStmt->getLocStart()) << ifStmt->getSourceRange();
+    return true;
+}
+
+loplugin::Plugin::Registration<SimplifyDynamicCast> X("simplifydynamiccast", true);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/compilerplugins/clang/test/simplifydynamiccast.cxx b/compilerplugins/clang/test/simplifydynamiccast.cxx
new file mode 100644
index 000000000000..111734f0a511
--- /dev/null
+++ b/compilerplugins/clang/test/simplifydynamiccast.cxx
@@ -0,0 +1,34 @@
+/* -*- 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 ClassA
+{
+    virtual ~ClassA() {}
+};
+
+struct ClassB : public ClassA
+{
+    void foo() {}
+};
+
+void f1(ClassA* p1)
+{
+    if (dynamic_cast<ClassB*>(p1)) // expected-note {{if here [loplugin:simplifydynamiccast]}}
+    {
+        static_cast<ClassB*>(p1)
+            ->foo(); // expected-error@-1 {{simplify, use var in if [loplugin:simplifydynamiccast]}}
+    }
+    if (dynamic_cast<ClassB*>(p1) != nullptr)
+    { // expected-note@-1 {{if here [loplugin:simplifydynamiccast]}}
+        static_cast<ClassB*>(p1)
+            ->foo(); // expected-error@-1 {{simplify, use var in if [loplugin:simplifydynamiccast]}}
+    }
+};
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */