是协变量返回类型覆盖根据jls？

问题描述

我相信所有的jls都是真理。

考虑来自jls的下一个片段：

转到子签名声明：

关于同一签名：

哪个规则允许使用协变返回类型？我看不到。

@ rgettman answer

 返回类型为R1的方法声明d1是返回类型可替换的， iff任何以下是真的：
 ... 
  - 如果R1是引用类型，则下列之一为真：
 ---- R1，适用于类型参数的d2（§8.4.4），是R2的一个子类型。 
 ... 
  

和子签名要求：

对我来说看起来像是矛盾。

解决方案

这些规则都不允许协变返回类型。方法的签名引用方法名称及其参数的类型和顺序，但不引用返回类型。

：

这是指，其中规定：

（强调我）

我加粗的部分允许协变返回类型。

just say, that point of my question is learn to understand jls.

I believe that all in jls is truth.

consider next snippet from jls:

go to subsignature declaration:

about same signature:

Which rule does allow to use covariant return type ? I don't see it.

P.S. after @rgettman answer

A method declaration d1 with return type R1 is return-type-substitutable for another method d2 with return type R2 iff any of the following is true:
...
--If R1 is a reference type then one of the following is true:
----R1, adapted to the type parameters of d2 (§8.4.4), is a subtype of R2.
...

and subsignature requirement:

For me it is looks like contradiction.

解决方案

Neither of these rules allows covariant return types. Signatures of a method refer to the method name and the types and order of its arguments, but not to the return type.

From JLS, Section 8.4.8.3:

That refers to Section 8.4.5, which states:

(emphasis mine)

That part I bolded allows covariant return types.

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