improve redundantcast loplugin

to find c-style casts where the expression is a templated method

Change-Id: Ifbd1e2cdc72d906fc95a7ec0f9408c3f6d2a836b
Reviewed-on: https://gerrit.libreoffice.org/42275
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

2 files changed, 15 insertions, 0 deletions

diff --git a/compilerplugins/clang/redundantcast.cxx b/compilerplugins/clang/redundantcast.cxx
index 19393e0c6449..32f7e8bd7fd9 100644
--- a/compilerplugins/clang/redundantcast.cxx
+++ b/compilerplugins/clang/redundantcast.cxx
@@ -294,6 +294,9 @@ bool RedundantCast::VisitCStyleCastExpr(CStyleCastExpr const * expr) {
     }
     auto t1 = compat::getSubExprAsWritten(expr)->getType();
     auto t2 = expr->getTypeAsWritten();
+    if (auto templateType = dyn_cast<SubstTemplateTypeParmType>(t1)) {
+        t1 = templateType->desugar();
+    }
     if (t1 != t2) {
         return true;
     }
diff --git a/compilerplugins/clang/test/redundantcast.cxx b/compilerplugins/clang/test/redundantcast.cxx
index 9eda22a04b0f..db1268b8b87b 100644
--- a/compilerplugins/clang/test/redundantcast.cxx
+++ b/compilerplugins/clang/test/redundantcast.cxx
@@ -290,11 +290,23 @@ void testCStyleCast() {
     (void)e;
 }
 
+template<typename T>
+struct EnumItemInterface {
+    T GetValue() { return static_cast<T>(0); }
+};
+class Enum1Item : public EnumItemInterface<Enum1> {
+};
+bool testCStyleCastOfTemplateMethodResult(Enum1Item* item) {
+    return (Enum1)item->GetValue() == Enum1::X; // expected-error {{redundant cstyle cast from 'Enum1' to 'Enum1' [loplugin:redundantcast]}}
+}
+
+
 int main() {
     testConstCast();
     testStaticCast();
     testFunctionalCast();
     testCStyleCast();
+    testCStyleCastOfTemplateMethodResult(nullptr);
 }
 
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