loplugin:redundantcast improvements for floating-integer conversions

Change-Id: I63dbf18f144a792ae775fe6706da81657f790016
Reviewed-on: https://gerrit.libreoffice.org/54416
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Tested-by: Stephan Bergmann <sbergman@redhat.com>

2 files changed, 27 insertions, 0 deletions

diff --git a/compilerplugins/clang/redundantcast.cxx b/compilerplugins/clang/redundantcast.cxx
index 0faadc5a541a..66b81941e579 100644
--- a/compilerplugins/clang/redundantcast.cxx
+++ b/compilerplugins/clang/redundantcast.cxx
@@ -248,6 +248,23 @@ bool RedundantCast::VisitImplicitCastExpr(const ImplicitCastExpr * expr) {
             }
         }
         break;
+    case CK_FloatingToIntegral:
+    case CK_IntegralToFloating:
+        if (auto e = dyn_cast<ExplicitCastExpr>(expr->getSubExpr()->IgnoreParenImpCasts())) {
+            if ((isa<CXXStaticCastExpr>(e) || isa<CXXFunctionalCastExpr>(e))
+                && (e->getSubExprAsWritten()->getType().getCanonicalType().getTypePtr()
+                    == expr->getType().getCanonicalType().getTypePtr()))
+            {
+                report(
+                    DiagnosticsEngine::Warning,
+                    ("suspicious %select{static_cast|functional cast}0 from %1 to %2, result is"
+                     " implicitly cast to %3"),
+                    e->getExprLoc())
+                    << isa<CXXFunctionalCastExpr>(e) << e->getSubExprAsWritten()->getType()
+                    << e->getTypeAsWritten() << expr->getType() << expr->getSourceRange();
+            }
+        }
+        break;
     default:
         break;
     }
diff --git a/compilerplugins/clang/test/redundantcast.cxx b/compilerplugins/clang/test/redundantcast.cxx
index 70fcdf3340cb..713a3be1433c 100644
--- a/compilerplugins/clang/test/redundantcast.cxx
+++ b/compilerplugins/clang/test/redundantcast.cxx
@@ -374,6 +374,15 @@ void testOverloadResolution() {
     (void) NonOverloadMemFn(&Overload::nonOverload); // expected-error {{redundant functional cast from 'void (Overload::*)()' to 'NonOverloadMemFn' (aka 'void (Overload::*)()') [loplugin:redundantcast]}}
 };
 
+void testIntermediaryStaticCast() {
+    int n = 0;
+    n = static_cast<double>(n); // expected-error {{suspicious static_cast from 'int' to 'double', result is implicitly cast to 'int' [loplugin:redundantcast]}}
+    n = double(n); // expected-error {{suspicious functional cast from 'int' to 'double', result is implicitly cast to 'int' [loplugin:redundantcast]}}
+    double d = 0.0;
+    d = static_cast<int>(d) + 1.0; // expected-error {{suspicious static_cast from 'double' to 'int', result is implicitly cast to 'double' [loplugin:redundantcast]}}
+    d = int(d) + 1.0; // expected-error {{suspicious functional cast from 'double' to 'int', result is implicitly cast to 'double' [loplugin:redundantcast]}}
+};
+
 int main() {
     testConstCast();
     testStaticCast();
@@ -382,6 +391,7 @@ int main() {
     testCStyleCastOfTemplateMethodResult(nullptr);
     testReinterpretConstCast();
     testDynamicCast();
+    testIntermediaryStaticCast();
 }
 
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