Cannot refer constant from a class

[yhara]

A = 1
class B
  def foo; A; end
end

Error: Error { msg: "constant `ConstFullname("::A")' was not found", backtrace: stack backtrace:

[yhara]

Currently A = 1 is inserted into main_exprs and thus cannot be referred from toplevel_defs (eg. class definition).

A should be detected as a constant in prior to convert_toplevel_defs.