-,---- Stack trace -- - - -
-| base_attr_nullable_alt1::Foo::run (alt/base_attr_nullable_alt1.nit:36)
-| base_attr_nullable_alt1::Foo::init (alt/base_attr_nullable_alt1.nit:48)
-| new Foo base_attr_nullable_alt1::Foo::init (alt/base_attr_nullable_alt1.nit:48)
-| base_attr_nullable_alt1::Sys::main (alt/base_attr_nullable_alt1.nit:81)
-`------------------- - - -