loplugin:redundantcast find redundant c-style enum casts

Change-Id: I2dab376d87804521aed6b6bd41ad7762830fa349
Reviewed-on: https://gerrit.libreoffice.org/35467
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

compilerplugins/clang/redundantcast.cxx

@@ -138,6 +138,8 @@ public:
 
     bool VisitCXXDeleteExpr(CXXDeleteExpr const * expr);
 
+    bool VisitCStyleCastExpr(CStyleCastExpr const * expr);
+
     bool VisitBinSub(BinaryOperator const * expr)
     { return visitBinOp(expr); }
 
@@ -288,6 +290,24 @@ bool RedundantCast::VisitImplicitCastExpr(const ImplicitCastExpr * expr) {
     return true;
 }
 
+bool RedundantCast::VisitCStyleCastExpr(CStyleCastExpr const * expr) {
+    if (ignoreLocation(expr)) {
+        return true;
+    }
+    if (isInUnoIncludeFile(compiler.getSourceManager().getSpellingLoc(expr->getLocStart()))) {
+        return true;
+    }
+    auto t1 = getSubExprAsWritten(expr)->getType();
+    auto t2 = expr->getTypeAsWritten();
+    if (loplugin::TypeCheck(t1).Enum() && loplugin::TypeCheck(t2).Enum() && t1 == t2) {
+        report(
+            DiagnosticsEngine::Warning,
+            "redundant cstyle enum cast from %0 to %1", expr->getExprLoc())
+            << t1 << t2 << expr->getSourceRange();
+    }
+    return true;
+}
+
 bool RedundantCast::VisitCXXStaticCastExpr(CXXStaticCastExpr const * expr) {
     if (ignoreLocation(expr)) {
         return true;