Spec change documents for Value Objects
Dan Smith
daniel.smith at oracle.com
Thu May 19 23:14:07 UTC 2022
On Apr 27, 2022, at 5:01 PM, Dan Smith <daniel.smith at oracle.com<mailto:daniel.smith at oracle.com>> wrote:
Please see these two spec change documents for JLS and JVMS changes in support of the Value Objects feature.
Here's a revision, including some additional language checks that I missed in the first iteration.
http://cr.openjdk.java.net/~dlsmith/jep8277163/jep8277163-20220519/specs/value-objects-jls.html
http://cr.openjdk.java.net/~dlsmith/jep8277163/jep8277163-20220519/specs/value-objects-jvms.html
----------
Diff of the changes:
diff --git a/closed/src/java.se/share/specs/value-objects-jls.md<http://java.se/share/specs/value-objects-jls.md> b/closed/src/java.se/share/specs/value-objects-jls.md<http://java.se/share/specs/value-objects-jls.md>
index 3e8e44aa2c..392242efb9 100644
--- a/closed/src/java.se/share/specs/value-objects-jls.md<http://java.se/share/specs/value-objects-jls.md>
+++ b/closed/src/java.se/share/specs/value-objects-jls.md<http://java.se/share/specs/value-objects-jls.md>
@@ -501,9 +501,9 @@ It is permitted for the class declaration to redundantly specify the `final`
modifier.
The `identity` and `value` modifiers limit the set of classes that can extend
-an `abstract` class ([8.1.4]).
+a non-`final` class ([8.1.4]).
-Special restrictions apply to the field declarations ([8.3.1.2]), method
+Special restrictions apply to the field declarations ([8.3.1]), method
declarations ([8.4.3.6]), and constructors ([8.8.7]) of a class that is not an
`identity` class.
@@ -524,6 +524,61 @@ Should there be?
+#### 8.1.3 Inner Classes and Enclosing Instances {#jls-8.1.3}
+
+...
+
+An inner class *C* is a *direct inner class of a class or interface O* if *O* is
+the immediately enclosing class or interface declaration of *C* and the
+declaration of *C* does not occur in a static context.
+
+> If an inner class is a local class or an anonymous class, it may be declared
+> in a static context, and in that case is not considered an inner class of any
+> enclosing class or interface.
+
+A class *C* is an *inner class of class or interface O* if it is either a direct
+inner class of *O* or an inner class of an inner class of *O*.
+
+> It is unusual, but possible, for the immediately enclosing class or interface
+> declaration of an inner class to be an interface.
+> This only occurs if the class is a local or anonymous class declared in a
+> `default` or `static` method body ([9.4]).
+
+A class or interface *O* is the *zeroth lexically enclosing class or interface
+declaration of itself*.
+
+A class *O* is the *n'th lexically enclosing class declaration of a class C* if
+it is the immediately enclosing class declaration of the *n-1*'th lexically
+enclosing class declaration of *C*.
+
+An instance *i* of a direct inner class *C* of a class or interface *O* is
+associated with an instance of *O*, known as the *immediately enclosing instance
+of i*.
+The immediately enclosing instance of an object, if any, is determined when the
+object is created ([15.9.2]).
+
+An object *o* is the *zeroth lexically enclosing instance of itself*.
+
+An object *o* is the *n'th lexically enclosing instance of an instance i* if it
+is the immediately enclosing instance of the *n-1*'th lexically enclosing
+instance of *i*.
+
+An instance of an inner local class or an anonymous class whose declaration
+occurs in a static context has no immediately enclosing instance.
+Also, an instance of a `static` nested class ([8.1.1.4]) has no immediately
+enclosing instance.
+
+**It is a compile-time error if an inner class has an immediately enclosing
+instance but is declared an `abstract` `value` class ([8.1.1.1], [8.1.1.5]).**
+
+> **If an abstract class is declared with neither the `value` nor the `identity`
+> modifier, but it is an inner class and has an immediately enclosing instance,
+> it is implicitly an `identity` class, per [8.1.1.5].**
+
+...
+
+
+
#### 8.1.4 Superclasses and Subclasses {#jls-8.1.4}
The optional `extends` clause in a normal class declaration specifies the
@@ -761,8 +816,110 @@ instance method.**
+### 8.6 Instance Initializers {#jls-8.6}
+
+An *instance initializer* declared in a class is executed when an instance of
+the class is created ([12.5], [15.9], [8.8.7.1]).
+
+*InstanceInitializer:*
+: *Block*
+
+**It is a compile-time error for an `abstract` `value` class to declare an
+instance initializer.**
+
+> **If an abstract class is declared with neither the `value` nor the `identity`
+> modifier, but it declares an instance initializer, it is implicitly an
+> `identity` class, per [8.1.1.5].**
+
+It is a compile-time error if an instance initializer cannot complete normally
+([14.22]).
+
+It is a compile-time error if a `return` statement ([14.17]) appears anywhere
+within an instance initializer.
+
+An instance initializer is permitted to refer to the current object using the
+keyword `this` ([15.8.3]) or the keyword `super` ([15.11.2], [15.12]), and to
+use any type variables in scope.
+
+Restrictions on how an instance initializer may refer to instance variables,
+even when the instance variables are in scope, are specified in [8.3.3].
+
+Exception checking for an instance initializer is specified in [11.2.3].
+
+
+
### 8.8 Constructor Declarations {#jls-8.8}
+A *constructor* is used in the creation of an object that is an instance of a
+class ([12.5], [15.9]).
+
+*ConstructorDeclaration:*
+: {*ConstructorModifier*} *ConstructorDeclarator* [*Throws*] *ConstructorBody*
+
+*ConstructorDeclarator:*
+: [*TypeParameters*] *SimpleTypeName*\
+ `(` [*ReceiverParameter* `,`] [*FormalParameterList*] `)`
+
+*SimpleTypeName:*
+: *TypeIdentifier*
+
+The rules in this section apply to constructors in all class declarations,
+including enum declarations and record declarations.
+However, special rules apply to enum declarations with regard to constructor
+modifiers, constructor bodies, and default constructors; these rules are stated
+in [8.9.2].
+Special rules also apply to record declarations with regard to constructors, as
+stated in [8.10.4].
+
+The *SimpleTypeName* in the *ConstructorDeclarator* must be the simple name of
+the class that contains the constructor declaration, or a compile-time error
+occurs.
+
+In all other respects, a constructor declaration looks just like a method
+declaration that has no result ([8.4.5]).
+
+Constructor declarations are not members.
+They are never inherited and therefore are not subject to hiding or overriding.
+
+**It is a compile-time error for an `abstract` `value` class to declare a
+nontrivial constructor ([8.1.1.5]).**
+
+> **If an abstract class is declared with neither the `value` nor the `identity`
+> modifier, but it declares a nontrivial constructor, it is implicitly an
+> `identity` class, per [8.1.1.5].**
+
+:::editorial
+It's not ideal to define a new term just for the purpose of this rule. But the
+list of things to check is long, and we don't want to repeat it. Perhaps it
+would be helpful to somehow overlap this definition with the discussion of
+default constructors in [8.8.9].
+:::
+
+Constructors are invoked by class instance creation expressions ([15.9]), by the
+conversions and concatenations caused by the string concatenation operator `+`
+([15.18.1]), and by explicit constructor invocations from other constructors
+([8.8.7]).
+Access to constructors is governed by access modifiers ([6.6]), so it is
+possible to prevent class instantiation by declaring an inaccessible constructor
+([8.8.10]).
+
+Constructors are never invoked by method invocation expressions ([15.12]).
+
+:::example
+
+Example 8.8-1. Constructor Declarations
+
+```
+class Point {
+ int x, y;
+ Point(int x, int y) { this.x = x; this.y = y; }
+}
+```
+
+:::
+
+
+
#### 8.8.7 Constructor Body {#jls-8.8.7}
The first statement of a constructor body may be an explicit invocation of
@@ -2231,7 +2388,7 @@ synchronization.
[8.1.1.4]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.1.1.4
[8.1.1.5]: #jls-8.1.1.5
[8.1.2]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.1.2
-[8.1.3]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.1.3
+[8.1.3]: #jls-8.1.3
[8.1.4]: #jls-8.1.4
[8.1.5]: #jls-8.1.5
[8.1.6]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.1.6
@@ -2260,9 +2417,9 @@ synchronization.
[8.4.8.3]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.4.8.3
[8.4.9]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.4.9
[8.5]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.5
-[8.6]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.6
+[8.6]: #jls-8.6
[8.7]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.7
-[8.8]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.8
+[8.8]: #jls-8.8
[8.8.1]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.8.1
[8.8.2]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.8.2
[8.8.3]: https://docs.oracle.com/javase/specs/jls/se18/html/jls-8.html#jls-8.8.3
diff --git a/closed/src/java.se/share/specs/value-objects-jvms.md<http://java.se/share/specs/value-objects-jvms.md> b/closed/src/java.se/share/specs/value-objects-jvms.md<http://java.se/share/specs/value-objects-jvms.md>
index fe747ad3bd..70e24541ce 100644
--- a/closed/src/java.se/share/specs/value-objects-jvms.md<http://java.se/share/specs/value-objects-jvms.md>
+++ b/closed/src/java.se/share/specs/value-objects-jvms.md<http://java.se/share/specs/value-objects-jvms.md>
@@ -1561,6 +1561,70 @@ Attribute Location `class`
+#### 4.7.6 The `InnerClasses` Attribute {#jvms-4.7.6}
+
+...
+
+inner_class_access_flags
+
+: The value of the `inner_class_access_flags` item is a mask of flags used
+ to denote access permissions to and properties of class or interface *C*
+ as declared in the source code from which this `class` file was
+ compiled.
+ It is used by a compiler to recover the original information when source
+ code is not available.
+ The flags are specified in [Table 4.7.6-A].
+
+ ::: {.table #jvms-4.7.6-300-D.1-D.1}
+
+ Table 4.7.6-A. Nested class access and property flags
+
+ ----------------------------------------------------------------------------
+ Flag Name Value Interpretation
+ ------------------------ ----------- ---------------------------------------
+ `ACC_PUBLIC` 0x0001 Marked or implicitly `public` in
+ source.
+
+ `ACC_PRIVATE` 0x0002 Marked `private` in source.
+
+ `ACC_PROTECTED` 0x0004 Marked `protected` in source.
+
+ `ACC_STATIC` 0x0008 Marked or implicitly `static` in
+ source.
+
+ `ACC_FINAL` 0x0010 Marked or implicitly `final` in
+ source.
+
+ **`ACC_IDENTITY`** **0x0020** **Declared as an `identity` class or
+ interface.**
+
+ **`ACC_VALUE`** **0x0040** **Declared as a `value` class or
+ interface.**
+
+ `ACC_INTERFACE` 0x0200 Was an `interface` in source.
+
+ `ACC_ABSTRACT` 0x0400 Marked or implicitly `abstract` in
+ source.
+
+ `ACC_SYNTHETIC` 0x1000 Declared synthetic; not present in the
+ source code.
+
+ `ACC_ANNOTATION` 0x2000 Declared as an annotation interface.
+
+ `ACC_ENUM` 0x4000 Declared as an `enum` class.
+ ----------------------------------------------------------------------------
+
+ :::
+
+ All bits of the `inner_class_access_flags` item not assigned in [Table
+ 4.7.6-A] are reserved for future use.
+ They should be set to zero in generated `class` files and should be
+ ignored by Java Virtual Machine implementations.
+
+...
+
+
+
#### **4.7.31 The `Preload` Attribute** {#jvms-4.7.31}
:::inserted
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