1 files changed, 83 insertions, 0 deletions
diff --git a/compilerplugins/clang/doubleconvert.cxx b/compilerplugins/clang/doubleconvert.cxx
new file mode 100644
index 000000000..6f9cc88df
--- /dev/null
+++ b/compilerplugins/clang/doubleconvert.cxx
@@ -0,0 +1,83 @@
+/* -*- 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/.
+ */
+
+#ifndef LO_CLANG_SHARED_PLUGINS
+
+#include "check.hxx"
+#include "plugin.hxx"
+
+/**
+ * Look for places where we are converting from type A through a conversion operator and back to type A,
+ * which is redundant. At the moment only look for Color, to aid my ColorData->Color conversion
+ */
+namespace
+{
+class DoubleConvert final : public loplugin::FilteringPlugin<DoubleConvert>
+{
+public:
+    explicit DoubleConvert(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+    void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+    bool VisitCXXConstructExpr(CXXConstructExpr const*);
+};
+
+/**
+ The AST looks like:
+
+ CXXOperatorCallExpr 0x8e5b840 'class Color' lvalue
+|-ImplicitCastExpr 0x8e5b828 'class Color &(*)(class Color &&) noexcept' <FunctionToPointerDecay>
+| `-DeclRefExpr 0x8e5b800 'class Color &(class Color &&) noexcept' lvalue CXXMethod 0x8e59a08 'operator=' 'class Color &(class Color &&) noexcept'
+|-DeclRefExpr 0x8e5b678 'class Color' lvalue Var 0x8e5b5d0 'col2' 'class Color'
+`-MaterializeTemporaryExpr 0x8e5b7e8 'class Color' xvalue
+  `-CXXConstructExpr 0x8e5b7b0 'class Color' 'void (ColorData)'
+    `-ImplicitCastExpr 0x8e5b798 'ColorData':'unsigned int' <IntegralCast>
+      `-CXXFunctionalCastExpr 0x8e5b770 'sal_Int32':'int' functional cast to sal_Int32 <NoOp>
+        `-ImplicitCastExpr 0x8e5b758 'sal_Int32':'int' <UserDefinedConversion>
+          `-CXXMemberCallExpr 0x8e5b730 'sal_Int32':'int'
+            `-MemberExpr 0x8e5b6f8 '<bound member function type>' .operator int 0x8e51048
+              `-ImplicitCastExpr 0x8e5b6e0 'const class Color' lvalue <NoOp>
+                `-DeclRefExpr 0x8e5b6b0 'class Color' lvalue Var 0x8e5b518 'col1' 'class Color'
+*/
+bool DoubleConvert::VisitCXXConstructExpr(CXXConstructExpr const* cxxConstruct)
+{
+    if (ignoreLocation(cxxConstruct))
+        return true;
+    if (cxxConstruct->getNumArgs() == 0)
+        return true;
+    auto cxxMemberCallExpr
+        = dyn_cast<CXXMemberCallExpr>(cxxConstruct->getArg(0)->IgnoreParenCasts());
+    if (!cxxMemberCallExpr)
+        return true;
+    if (!isa_and_nonnull<CXXConversionDecl>(cxxMemberCallExpr->getMethodDecl()))
+        return true;
+    if (cxxConstruct->getType().getCanonicalType().getTypePtr()
+        != cxxMemberCallExpr->getImplicitObjectArgument()
+               ->getType()
+               .getCanonicalType()
+               .getTypePtr())
+        return true;
+    if (!loplugin::TypeCheck(cxxConstruct->getType().getCanonicalType())
+             .Class("Color")
+             .GlobalNamespace())
+        return true;
+
+    report(DiagnosticsEngine::Warning, "redundant double conversion", cxxConstruct->getExprLoc())
+        << cxxConstruct->getSourceRange();
+    return true;
+}
+
+static loplugin::Plugin::Registration<DoubleConvert> doubleconvert("doubleconvert");
+}
+
+#endif // LO_CLANG_SHARED_PLUGINS
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */