Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -1115,6 +1115,11 @@
   bool LHSFloat = LHSType->isRealFloatingType();
   bool RHSFloat = RHSType->isRealFloatingType();
 
+  // FIXME: Implement Floating-fixedpoint conversion. (Bug 46268)
+  // Reference N1169 4.1.4 (Type conversion, usual arithmetic conversions).
+  if ((LHSType->isFixedPointType() && RHSType->isRealFloatingType()) ||
+      (LHSType->isRealFloatingType() && RHSType->isFixedPointType()))
+    return QualType();
   // If we have two real floating types, convert the smaller operand
   // to the bigger result.
   if (LHSFloat && RHSFloat) {