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>

4 files changed, 37 insertions, 0 deletions

diff --git a/compilerplugins/clang/check.cxx b/compilerplugins/clang/check.cxx
index 22f58ebd7ac9..f7647ac8c9c9 100644
--- a/compilerplugins/clang/check.cxx
+++ b/compilerplugins/clang/check.cxx
@@ -103,6 +103,16 @@ TypeCheck TypeCheck::Pointer() const {
     return TypeCheck();
 }
 
+TerminalCheck TypeCheck::Enum() const {
+    if (!type_.isNull()) {
+        auto const t = type_->getAs<clang::EnumType>();
+        if (t != nullptr) {
+            return TerminalCheck(true);
+        }
+    }
+    return TerminalCheck(false);
+}
+
 TypeCheck TypeCheck::Typedef() const {
     if (!type_.isNull()) {
         if (auto const t = type_->getAs<clang::TypedefType>()) {
diff --git a/compilerplugins/clang/check.hxx b/compilerplugins/clang/check.hxx
index 8c3edf773ea1..cf91dfd2aee2 100644
--- a/compilerplugins/clang/check.hxx
+++ b/compilerplugins/clang/check.hxx
@@ -53,6 +53,8 @@ public:
 
     TypeCheck Pointer() const;
 
+    TerminalCheck Enum() const;
+
     TypeCheck LvalueReference() const;
 
     template<std::size_t N> inline ContextCheck Class(char const (& id)[N])
diff --git a/compilerplugins/clang/redundantcast.cxx b/compilerplugins/clang/redundantcast.cxx
index 0525fa51f584..4bef116f481b 100644
--- a/compilerplugins/clang/redundantcast.cxx
+++ b/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;
diff --git a/compilerplugins/clang/test/redundantcast.cxx b/compilerplugins/clang/test/redundantcast.cxx
index e8be3013cd86..a7516c1a058f 100644
--- a/compilerplugins/clang/test/redundantcast.cxx
+++ b/compilerplugins/clang/test/redundantcast.cxx
@@ -10,6 +10,8 @@
 void f1(char *) {}
 void f2(char const *) {}
 
+enum Enum1 { X };
+
 int main() {
     char * p1;
     char const * p2;
@@ -27,6 +29,9 @@ int main() {
     f2(const_cast<char * const>(p2)); // expected-error {{redundant const_cast from 'const char *' to 'char *', result is implictly cast to 'const char *' [loplugin:redundantcast]}}
     f2(const_cast<char const *>(p2)); // expected-error {{redundant const_cast from 'const char *' to 'const char *' [loplugin:redundantcast]}}
     f2(const_cast<char const * const>(p2)); // expected-error {{redundant const_cast from 'const char *' to 'const char *const' [loplugin:redundantcast]}}
+
+    Enum1 e = (Enum1)Enum1::X; // expected-error {{redundant cstyle enum cast from 'Enum1' to 'Enum1' [loplugin:redundantcast]}}
+    (void)e;
 }
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */