loplugin:redundantcast handle dynamic_cast

Change-Id: I7855c76e820efce96778b1c19ec71dffcc4b4abb
Reviewed-on: https://gerrit.libreoffice.org/43621
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/compilerplugins/clang/redundantcast.cxx b/compilerplugins/clang/redundantcast.cxx
index 30914a460dc4..c28878e9e536 100644
--- a/compilerplugins/clang/redundantcast.cxx
+++ b/compilerplugins/clang/redundantcast.cxx
@@ -128,6 +128,8 @@ public:
 
     bool VisitCXXFunctionalCastExpr(CXXFunctionalCastExpr const * expr);
 
+    bool VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr);
+
     bool VisitCallExpr(CallExpr const * expr);
 
     bool VisitCXXDeleteExpr(CXXDeleteExpr const * expr);
@@ -676,6 +678,28 @@ bool RedundantCast::VisitCXXFunctionalCastExpr(CXXFunctionalCastExpr const * exp
     return true;
 }
 
+bool RedundantCast::VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr) {
+    if (ignoreLocation(expr)) {
+        return true;
+    }
+    // ignore dynamic_cast<T1>(static_cast<T1>(void*)), it's necessary
+    if (auto subStaticCast = dyn_cast<CXXStaticCastExpr>(expr->getSubExpr())) {
+        if (loplugin::TypeCheck(subStaticCast->getSubExpr()->getType()).Pointer().Void())
+            return true;
+    }
+    // so far this only deals with dynamic casting from T to T
+    auto const sub = compat::getSubExprAsWritten(expr);
+    auto const t1 = expr->getTypeAsWritten();
+    auto const t2 = sub->getType();
+    if (t1.getCanonicalType() != t2.getCanonicalType())
+        return true;
+    report(
+        DiagnosticsEngine::Warning,
+        "redundant dynamic cast from %0 to %1", expr->getExprLoc())
+        << t2 << t1 << expr->getSourceRange();
+    return true;
+}
+
 bool RedundantCast::VisitCallExpr(CallExpr const * expr) {
     if (ignoreLocation(expr)) {
         return true;