Add a couple of FIXME's

Author: bjorn3

src/value_and_place.rs

@@ -85,6 +85,7 @@ impl<'tcx> CValue<'tcx> {
     }
 
     pub(crate) fn by_val(value: Value, layout: TyAndLayout<'tcx>) -> CValue<'tcx> {
+        // FIXME assert type of value matches the layout
         CValue(CValueInner::ByVal(value), layout)
     }
 
@@ -93,6 +94,7 @@ impl<'tcx> CValue<'tcx> {
         extra: Value,
         layout: TyAndLayout<'tcx>,
     ) -> CValue<'tcx> {
+        // FIXME assert type of value and extra matches the layout
         CValue(CValueInner::ByValPair(value, extra), layout)
     }