Eiffel：或和中的局部声明编译失败

Question

编译器抱怨未知标识符，似乎它无法识别我的多个声明中的任何一个，我哪里错了？

if attached {INTEGER_REF} field.item as l_int
        or attached {INTEGER_64} field.item as l_int
        or ( attached {TUPLE} field.item as l_tuple and then attached {INTEGER_64} l_tuple.item (1) as l_int ) then
    Result.put_integer (l_int.to_integer_64, primary_key_db_column_name)
elseif attached {STRING} field.item as l_s then
    Result.put_string (l_s, primary_key_db_column_name)
end

更新

因为这似乎是一个有效的表达式，我认为如果在我的或的每个分支中都声明了一个 l_int 我应该能够在然后范围。

但是这个表达式似乎是有效的

if attached a.b as l_b and then attached l_b.c as l_c then
    l_c.is_available_in_this_scope
    l_b.is_available_in_this_scope
else
    io.putstring ("you are wrong dear and either l_b and l_c are not available!")
end

虽然这个不是！

if attached a.b as l_b and then attached l_b.c as l_c
        or attached a.x as l_b and then attached l_x.d as l_c then
    l_c.is_available_in_this_scope -- Compiler complain about l_c
    l_b.is_available_in_this_scope -- Compiler complain about l_b
else
    io.putstring ("you are wrong dear and either l_b and l_c are not available!")
end

用我的代码

这个编译

    if attached {INTEGER_REF} field.item as l_int then
        Result.put_integer (l_int.to_integer_64, primary_key_db_column_name)
    elseif attached {INTEGER_64} field.item as l_int then
        Result.put_integer (l_int, primary_key_db_column_name)
    elseif attached {TUPLE} field.item as l_tuple and then attached {INTEGER_64} l_tuple.item (1) as l_int then
        Result.put_integer (l_int, primary_key_db_column_name)
    elseif attached {STRING} field.item as l_s then
        Result.put_string (l_s, primary_key_db_column_name)
    else
        logger.write_error ("to_json-> Type not found in matching:" + field.item.out)
        check
            not_found_item_type: False
        end
    end

虽然这个不是

if attached {INTEGER_REF} field.item as l_int then
    Result.put_integer (l_int.to_integer_64, primary_key_db_column_name)
elseif attached {INTEGER_64} field.item as l_int
        or attached {TUPLE} field.item as l_tuple and then attached {INTEGER_64} l_tuple.item (1) as l_int then
    Result.put_integer (l_int, primary_key_db_column_name) -- Unknown identifier `l_int`
elseif attached {STRING} field.item as l_s then
    Result.put_string (l_s, primary_key_db_column_name)
else
    logger.write_error ("to_json-> Type not found in matching:" + field.item.out)
    check
        not_found_item_type: False
    end
end

Answer 1

首先，您不能对同一范围内的多个对象测试局部变量使用相同的标识符 (l_int)。

Answer 2

对象测试有范围。用 OT 表示对象测试，其范围为

if OT         then A else B end
if OT and ... then A else B end
if OT or  ... then C else B end

只是A。因此对于析取，作用域为空，不能在任何分支中使用对应的对象test local

如果一个条件中有两个对象测试，它们的范围可能重叠也可能不重叠：

if OT1 and      OT2 then A else B end
if OT1 and then OT2 then A else B end
if OT1 or       OT2 then C else B end

这里和之前一样，OT1的对象test局部变量的作用域是A。另外，对于and then，范围包括OT2，特别是OT2可以使用OT1的局部。同理，OT2不能使用OT1.

的同一个对象test local

对于析取，OT1和OT2的object test locals的范围都是空的。为了提供更多信息，具有助记名称的相同代码如下所示：

if attached e1 as x and      attached e2_without_x as y then use_x_and_y else B end
if attached e1 as x and then attached e2_with_x    as y then use_x_and_y else B end
if attached e1 as x or       attached e2_without_x as y then no_x_no_y   else B end

如果所有涉及的表达式的类型都相同（事实并非如此，因为有类型 INTEGER_64 和 INTEGER_REF):

if attached
       if attached {INTEGER_64_REF} field.item as i then
           i
       elseif
           attached {TUPLE} field.item as t and then
           t.count > 0 and then
           attached {INTEGER_64_REF} t.item (1) as i
       then
           i
       else
           Void
       end
   as j
then
   -- Use j
...

但这变得太麻烦了，使用多个分支或临时局部变量看起来是更好的选择。

Eiffel：或和中的局部声明编译失败

Eiffel: local declaration in or and and failed to compile

eiffel

compiler-errors

更新

用我的代码