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Clarify instantiation of objects with abstract methods #1355

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Clarify instantiation of objects with abstract methods #1355

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Clarify instantiation of objects with abstract methods
jaehyun1ee Dec 4, 2024
ec2d6f3
Delete parameter name restriction, add abstract method overload restr…
jaehyun1ee Dec 10, 2024
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jaehyun1ee Dec 12, 2024
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13 changes: 9 additions & 4 deletions p4-16/spec/P4-16-spec.adoc
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Expand Up @@ -2765,7 +2765,7 @@ either by the number of arguments or by the names of the arguments,
when calls are specifying argument names. Argument type information
is not used in disambiguating calls.

Notice that overloading of parsers, controls, or packages is not allowed:
Notice that overloading of abstract methods, parsers, controls, or packages is not allowed:
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I would just point out this forbids overloading of abstract methods completely, i.e. also by the number of arguments. I am OK with that, but I wanted to highlight that.

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Yes, it was intended because allowing overload via only the arity, and only for abstract methods, would be too complex. But in some future, if someone finds such a feature useful, we might consider lift this restriction then.


[source,p4]
----
Expand Down Expand Up @@ -5415,10 +5415,15 @@ include::grammar.adoc[tag=objDeclarations]
include::grammar.adoc[tag=objDeclaration]
----

Abstract method implementations must use the same number of parameters, and
the same parameter directions as those declared in the extern object declaration.
Note that overloading of abstract methods is not allowed, thus an
implementation could be matched to a declaration only with the method name.

The abstract methods can only use the supplied arguments or refer to
values that are in the top-level scope. When calling another method
of the same instance the `this` keyword is used to indicate the
current object instance:
values that are in the same initializer block or the top-level scope.
When calling another method of the same instance the `this` keyword is
used to indicate the current object instance:

[source,p4]
----
Expand Down