Nimsuggest - Methods marked with {.base.} trigger error on chk

[richardhallett]

Description

When working with dynamic dispatch base methods, IDE integrations which use nimsuggest and/or nimsuggest via the CLI trigger an error on the following code:

type
  Expression = ref object of RootObj ## abstract base class for an expression
  Literal = ref object of Expression
    x: int
  PlusExpr = ref object of Expression
    a, b: Expression

# watch out: 'eval' relies on dynamic binding
method eval(e: Expression): int {.base.} =
  # override this base method
  quit "to override!"

method eval(e: Literal): int = e.x
method eval(e: PlusExpr): int = eval(e.a) + eval(e.b)

proc newLit(x: int): Literal = Literal(x: x)
proc newPlus(a, b: Expression): PlusExpr = PlusExpr(a: a, b: b)

echo eval(newPlus(newPlus(newLit(1), newLit(2)), newLit(4)))

This code is directly lifted from tutorial https://nim-lang.org/docs/tut2.html#object-oriented-programming-dynamic-dispatch

The error in question is
method is not a base

When running nimsuggest chk on this code it reports (path was changed for privacy reasons)

> chk "example.nim"
chk	skUnknown		Hint	???	0	-1	">> (toplevel): import(dirty): /home/user/example/example.nim [Processing]"	0
chk	skUnknown		Error	/home/user/example/example.nim 9	7	"method is not a base"	0

Nim Version

Nim Compiler Version 2.0.4 [Linux: amd64]
Compiled at 2024-03-28
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: b47747d
active boot switches: -d:release -d:danger --gc:markAndSweep

Current Output

No response

Expected Output

No response

Possible Solution

No response

Additional Information

This manifested for me initially with the VSCode extension https://github.com/nim-lang/vscode-nim but own investigation appeared to be in nimsuggest

[jmgomez]

Cant be reproed in the v4 of the protocol. Tools should use that one instead as it has many other enhancements

nimsuggest --v4 example.nim

[Seanld]

I had the same problem as OP, but I guess the problem is that I was using nimlsp, the author of which hasn't kept it up to date with the latest nimsuggest protocol updates (as far as I can tell, even V3 hasn't been implemented). So the answer was to switch to nimlangserver. After switching, the {.base.} error is gone.

[richardhallett]

So I can confirm if I run with explicit --v4 as above then yes it appears to work as expected.
So perhaps the error is instead within the handling by nimlangserver? However based upon what @Seanld said this worked for them.

For me running either vscode integration or neovim with nimlangserver still shows errors.

I've tried to see if I can find the protocol being chosen but my best guess is:
https://github.com/nim-lang/langserver/blob/97ffd6da89c658abaf6043e29ac6aeab1afda8f9/suggestapi.nim#L268

Running:
nimsuggest --info:protocolVer
Returns:
4

As an aside Why is the default protocol still v2? If v4 is generally better, shouldn't that be the default?