Equality on types with Any as LHS does not work

[Akirathan]

Any == Boolean returns a function Any.type.== instead of False. This is because it resolves as Any.type.== Any Boolean method call (which expects 3 arguments rather than 2). Note that Boolean == Any returns False as expected, because it resolves to Any.== Boolean Any

May be related to #4077

Related pending test: https://github.com/enso-org/enso/blob/develop/test/Tests/src/Semantic/Equals_Spec.enso#L172

[JaroslavTulach]

If we implement #6300 then Any == Boolean should treat == as an instance invocation of == on Any and this issue should be resolved.

[wdanilo]

Why Any == Boolean resolves to Any.type.==? What is the logic behind this resolution?

[Akirathan]

Why Any == Boolean resolves to Any.type.==? What is the logic behind this resolution?

When the engine executes Any == Boolean, it invokes MethodResolverNode.execute(self=Any, type=Any.type, symbol=UnresolvedSymbol<==>), which invokes UnresolvedSymbol(==).resolveFor(Any.type), which finds Any.type.== because == is both a static and instance method, as are all the other methods. And Any.type.== expects 3 arguments, as opposed to Any.==. Therefore, it returns a curried function.

This problem is related to #6216. This is also the reason why, e.g., Boolean == Vector will resolve to Any.==

Note that, however, Boolean == Vector will correctly resolve to Any.== Boolean.type Vector.type, as it transitively calls into UnresolvedSymbol(==).resolveFor(Boolean.type) and Boolean.type has Any as its parent, therefore, the instance method Any.== is found.

I know this is all really kind of a mess. This is why there is a huge discussion in #6216 that should resolve this, and all the related problems with instance VS static methods, once and for all.

[JaroslavTulach]

... huge discussion in #6216 that should resolve this, and all the related problems with instance VS static methods, ...

The discussion in #6216 is huge and touches a lot of important topics including syntax of the Enso language. As such I'd like to reword your conclusion Pavel:

#6300 is a small and non-controversial subset of the #6216 discussion with as limited scope as possible - only methods defined on Any would resolve differently for the Type objects - e.g. as instance methods. As == is defined on Any, it would resolve as an instance method and that's enough to fix the #5612 problem.

once and for all.

Not only #6300 solves this problem, but there are other "duplicates" it solves as well. As such #6300 got a "go" yesterday. However I wouldn't say it fixes "everything for once and all" - that's the goal for #6216 which remains open for discussion.

[JaroslavTulach]

#6300 got integrated, but alas, Any == Boolean still resolves to a function, not False.

Additions to #6300

Every instance method defined on Any has default self argument set to the type. My_Type_Without_To_Text.to_text becomes Any.to_text self=My_Type_Without_To_Text. If one wants the static method, one would write My_Type_Without_To_Text.to_text... and the result would be a function with one (defaulted) self argument.

To invoke any instance method (defined on Any) one could:

• My_Type.m - a shortcut for My_Type.m self=My_Type
• My_Type.m self=other - one could define different self as a named argument
• My_Type.m other - first argument of the function is going to be self, so this has the same meaning as the previous line
• My_Type.m... - returns a function with defaulted self argument

Current behavior on Any is:

Any.to_text
>>> org.enso.interpreter.runtime.callable.function.Function - that's wrong, we need defaulted self
Any.to_text self=Boolean
>>> Boolean - good
> Any.to_text Boolean
>>> Boolean - good
> Any.to_text...
>>> org.enso.interpreter.runtime.callable.function.Function - that's correct

the same would work for == as well:

> Any == Boolean
>>> org.enso.interpreter.runtime.callable.function.Function - that's wrong, we need defaulted self
> Any.== self=Any Boolean
>>> false - good
> Any.== Any Boolean
>>> false - good
> Any.== self=Boolean Boolean
>>> true - good
> Any.==...
>>> org.enso.interpreter.runtime.callable.function.Function - that's correct

Nothing from the above is new, all the code already parses and runs somehow. For example following code already behaves as needed:

> f = Any.==...
> f
>>> org.enso.interpreter.runtime.callable.function.Function
> f self=Boolean Boolean
>>> true
> f Boolean Boolean
>>> true
> f Any Boolean
>>> false

What doesn't work is:

> f Boolean
>>> org.enso.interpreter.runtime.callable.function.Function - with defaulted self, this'd be false
> f Any
>>> org.enso.interpreter.runtime.callable.function.Function - this should be true

We just need to provide the defaulted self argument for instance methods defined on Any. Then we have a chance to resolve the Any == Boolean as well as Any.to_text still returning function.

[hubertp]

I wasn't aware of this ticket. Will add it to my list of follow ups.

[enso-bot]

Pavel Marek reports a new STANDUP for today (2023-06-14):

Progress: - Looking at relevant discussions, fiddling around

• Scatching a solution in a draft PR It should be finished by 2023-06-20.

[enso-bot]

Pavel Marek reports a new STANDUP for yesterday (2023-06-15):

Progress: Writing some tests, gathering information from relevant issues. It should be finished by 2023-06-20.

[enso-bot]

Pavel Marek reports a new STANDUP for today (2023-06-16):

Progress: - Finally understood the specification that is desired.

• Tweaking InvokeMethodNode such that the static method calls on Any are handled specifically - mostly a self default argument is prepended. It should be finished by 2023-06-20.

[JaroslavTulach]

• a self default argument is prepended

I believe you need to append (not prepend) the default self argument. That's syntactically impossible in Enso language (there is a check in IR passes that self is always the first argument), but internally achievable - there should be no problem in having self as the last argument in the runtime, I believe.

[enso-bot]

Pavel Marek reports a new STANDUP for today (2023-06-19):

Progress: - Still hacking InvokeMethodNode to build a new InvokeFunctionNode for static method calls on Any.

• Still bumping into issues with consistency of FunctionSchema of a method on Any.type versus the call argument informations. It should be finished by 2023-06-20.

[enso-bot]

Pavel Marek reports a new STANDUP for today (2023-06-20):

Progress: - More progress on the Any static method calls.

• Seems pretty complicated now, as a node replacement is required.
• Import/export discussion, private keyword introduction proposal. It should be finished by 2023-06-20.

[enso-bot]

Pavel Marek reports a new 🔴 DELAY for yesterday (2023-06-21):

Summary: There is 3 days delay in implementation of the Equality on types with Any as LHS does not work (#5612) task.
It will cause 0 days delay for the delivery of this weekly plan.

I introduced a hack and I am not sure it will be accepted by reviewers.

Delay Cause: A slight delay of PR reviews.

[enso-bot]

Pavel Marek reports a new STANDUP for yesterday (2023-06-21):

Progress: - Resolved more issues, tests seem to be passing now. It should be finished by 2023-06-23.

[enso-bot]

Pavel Marek reports a new STANDUP for today (2023-06-22):

Progress: - Integrated all the PR review, all tests are passing.

• Should be merged today, or tomorrow. It should be finished by 2023-06-23.