loplugin:redundantfcast look for redundant copies in return statements

Change-Id: I5f416c865dfe1c36018784246a8007452eb42008
Reviewed-on: https://gerrit.libreoffice.org/50996
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

2 files changed, 49 insertions, 0 deletions

diff --git a/compilerplugins/clang/redundantfcast.cxx b/compilerplugins/clang/redundantfcast.cxx
index 811c6d48647c..89e5618e19da 100644
--- a/compilerplugins/clang/redundantfcast.cxx
+++ b/compilerplugins/clang/redundantfcast.cxx
@@ -21,6 +21,45 @@ public:
     {
     }
 
+    bool TraverseFunctionDecl(FunctionDecl* functionDecl)
+    {
+        auto prev = m_CurrentFunctionDecl;
+        m_CurrentFunctionDecl = functionDecl;
+        auto rv = RecursiveASTVisitor<RedundantFCast>::TraverseFunctionDecl(functionDecl);
+        m_CurrentFunctionDecl = prev;
+        return rv;
+    }
+
+    bool VisitReturnStmt(ReturnStmt const* returnStmt)
+    {
+        if (ignoreLocation(returnStmt))
+            return true;
+        Expr const* expr = returnStmt->getRetValue();
+        if (!expr)
+            return true;
+        if (auto exprWithCleanups = dyn_cast<ExprWithCleanups>(expr))
+            expr = exprWithCleanups->getSubExpr();
+        if (auto cxxConstructExpr = dyn_cast<CXXConstructExpr>(expr))
+        {
+            if (cxxConstructExpr->getNumArgs() != 1)
+                return true;
+            expr = cxxConstructExpr->getArg(0);
+        }
+        if (auto materializeTemporaryExpr = dyn_cast<MaterializeTemporaryExpr>(expr))
+            expr = materializeTemporaryExpr->GetTemporaryExpr();
+        auto cxxFunctionalCastExpr = dyn_cast<CXXFunctionalCastExpr>(expr);
+        if (!cxxFunctionalCastExpr)
+            return true;
+        auto const t1 = cxxFunctionalCastExpr->getTypeAsWritten();
+        auto const t2 = compat::getSubExprAsWritten(cxxFunctionalCastExpr)->getType();
+        if (t1.getCanonicalType().getTypePtr() != t2.getCanonicalType().getTypePtr())
+            return true;
+        report(DiagnosticsEngine::Warning, "redundant functional cast from %0 to %1",
+               cxxFunctionalCastExpr->getExprLoc())
+            << t2 << t1 << cxxFunctionalCastExpr->getSourceRange();
+        return true;
+    }
+
     /* Check for the creation of unnecessary temporaries when calling a method that takes a param by const & */
     bool VisitCallExpr(CallExpr const* callExpr)
     {
@@ -104,6 +143,7 @@ private:
             TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
         }
     }
+    FunctionDecl const* m_CurrentFunctionDecl;
 };
 
 static loplugin::Plugin::Registration<RedundantFCast> reg("redundantfcast");
diff --git a/compilerplugins/clang/test/redundantfcast.cxx b/compilerplugins/clang/test/redundantfcast.cxx
index 609b787347e1..da7e8be5a027 100644
--- a/compilerplugins/clang/test/redundantfcast.cxx
+++ b/compilerplugins/clang/test/redundantfcast.cxx
@@ -56,4 +56,13 @@ int main()
         foo)); // expected-error@-1 {{redundant functional cast from 'Foo' to 'Foo' [loplugin:redundantfcast]}}
 }
 
+class Class1
+{
+    Foo foo;
+    Foo func2()
+    {
+        return Foo(
+            foo); // expected-error@-1 {{redundant functional cast from 'Foo' to 'Foo' [loplugin:redundantfcast]}}
+    }
+};
 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */