[BUG] - Recursive Section Member Reference Isn't Accepted as Valid

[bgribaudo]

Expected behavior
The M language specification and the existing Power Query SDK allow a section member to use an exclusive identifier reference to refer to itself (e.g. the SumConsecutive(x - 1) reference in the below example).

section SomeSection;

SumConsecutive = (x) => if x <= 0 then 0 else x + SumConsecutive(x - 1);

Actual behavior
The parser considers the above-mentioned reference an error, complaining that it "cannot find the name 'SumConsecutive'".

To Reproduce
In VSCode, create a new Power Query document. Paste in the above M code. The error shown in the screenshot will then be displayed.

Additional context
Power Query / M Language extension version: v0.1.42

Thank you for your help with this, and for the VSCode extension!

[JordanBoltonMN]

I don't believe this is a bug. Recursive functions should have the @ prefix, and if you add that prefix then the parser doesn't experience an error.

Thoughts?

[bgribaudo]

Hi @JordanBoltonMN,

Thanks for taking a look at this!

Recursive functions should have the @ prefix[....]

I believe this is only true when the identifier being referenced is a record field or let expression variable.

From the language specification's discussion on Identifier references:

It is an error for an exclusive-identifier-reference to refer to an identifier that is currently being initialized if the referenced identifier is defined inside a record-initializer-expression or let-expression.

In this issue, the referenced identifier is a section member, so based on the above quote from the language specification (and as discussed in MicrosoftDocs/query-docs#9 (comment)), I believe an exclusive identifier reference (no @) should be considered valid in this case.

[JordanBoltonMN]

I believe you're right in that it's not a requirement on section members. If I had to guess this was a bug in the C# parser that went unnoticed, but in any case it's been shipped for who knows how long so it's now a feature. I'll have to update the scope generation for section members to include both @name and name.

[bgribaudo]

Thank you, @JordanBoltonMN!