Hello,
Some modifiers are implementation properties, like strictfp, native, and
synchronized -- they not part of the "interface" of the method per se,
but still useful to apply and query in some circumstances. The
"mandated" property can have a similar character as partially a function
of the particulars of how the record was declared.
The mandated information about records is used by the printing
processor, javac -Xprint, to provide a more source-faithful
representation of a record by eliding the mandated elements. The
regression tests
test/langtools/tools/javac/processing/model/element/TestRecordDesugar.java
also looks at mandated vs explicit for record elements. At present, the
test is only run against the source version of a record as the the
information isn't (yet) available to the same degree from class file.
Cheers,
-Joe
PS Lack of consistent mandated information around method parameters has
made it difficult to address several long-standing issue in the core
reflection API.
On 10/10/2019 10:41 AM, Alex Buckley wrote:
Enum types are specified such that a `values` method is always
implicitly declared. (If you declare one explicitly, you have two
method declarations with override-equivalent signatures, which is an
error per JLS 8.4.) Accordingly, the corresponding method in the class
file should always be marked as mandated. Sadly we don't have room for
an ACC_MANDATED flag in `method_info`, but morally the method is
mandated and Core Reflection should expose that fact.
Record types are specified more sensitively: a component's accessor is
implicitly declared if and only if it isn't explicitly declared. (Same
deal as the default constructor of a class.) If a component's accessor
is explicitly declared, then there's nothing more to say; if it's
implicitly declared, then it should be marked as mandated.
I wouldn't characterize this as member descriptor v. member
implementation, because that sounds like "the signature" v. "the
body". Fundamentally, the topic at hand is component accessors, which
are non-abstract methods of non-abstract classes; for such methods of
such classes, EITHER you declare both the signature and the body (in
which case there's an explicit declaration of both signature and body)
OR you declare neither (in which case there's an implicit declaration
of both signature and body). Ordinary consumers of the record type are
happy because they can be assured that component accessors are always
declared (i.e., the compiler will always find the signature, the VM
will always link the descriptor, and the subsequent execution of the
linked method will always do something useful), while reflective
consumers of the record type are happy because they can tell whether a
component accessor (the signature and body as one undivided entity)
was declared explicitly or implicitly. You say "random", I say
"accurate".
Alex
On 10/10/2019 9:09 AM, Brian Goetz wrote:
Under that interpretation, that leaves record members in a funny
place, since a given mandated member (e.g., an accessor for a
component) _might_ have been explicit in the source, or might not
have been. Should ACC_MANDATED describe the member descriptor (“spec
mandates a member with this descriptor”) or only the implementation
(“the source didn’t have it, but its here in the byte code”)? In the
latter interpretation, the presence of ACC_MANDATED on a mandated
member would basically be random, based on implementation-of-the-day,
which seems wrong.
On Oct 10, 2019, at 12:06 PM, Joe Darcy <joe.da...@oracle.com> wrote:
A mandated construct is one that is mandated by the specification,
but not explicitly declared. Constructs of that sort have been in
the platform since the beginning, such as default constructors.
ACC_MANDATED was added to the platform only more recently and has
some exposure through javax.lang.model.
I recommend going forward ACC_MANDATED to be used more widely, on
all the mandated structures, including the values methods on enum
types, etc.
Cheers,
-Joe
On 10/10/2019 8:50 AM, Brian Goetz wrote:
We should match the behavior of methods like `Enum::values`.
On Oct 10, 2019, at 10:15 AM, Remi Forax <fo...@univ-mlv.fr> wrote:
Hi all,
fields and methods of a record are marked ACC_MANDATED which
contradict JLS 13.1.12 that explains that you can not use
ACC_MANDATED on field and method.
regards,
Rémi
