Method assertSubtypeOf

src/chap14/TypeInfo.java:25–31

(TypeInfo type, TypeEnv env, ASTree where)

        return type() == superType || superType == ANY;
    }
    public void assertSubtypeOf(TypeInfo type, TypeEnv env, ASTree where)
        throws TypeException
    {
        if (!subtypeOf(type))
            throw new TypeException("type mismatch: cannot convert from "
                                    + this + " to " + type, where);
    }
    public TypeInfo union(TypeInfo right, TypeEnv tenv) {
        if (match(right))
            return type();