[vim/vim] Vim9: inconsistent type checking when passing output of funcref to "get()" (#8644)

[lacygoill]

Describe the bug

In Vim9 script, passing the output of a funcref to get() might give an error in compiled code, but not at the script level, which is inconsistent.

To Reproduce

Run this shell command:

vim -Nu NONE -S <(cat <<'EOF'
    vim9script
    var Getqflist: func = function('getqflist', [{id: 0}])
    Getqflist()->get('id', 0)
EOF
)

No error is given.

Now, run the same code in a :def function:

vim -Nu NONE -S <(cat <<'EOF'
    vim9script
    def Func(): number
        var Getqflist: func = function('getqflist', [{id: 0}])
        return Getqflist()->get('id', 0)
    enddef
    defcompile
EOF
)

E1013 is given:

E1013: Argument 1: type mismatch, expected list<any> but got unknown

Expected behavior

I think the second command should not give an error, to be consistent with what happens at the script level.

IOW, if Vim doesn't know what the output of a function is, it should be treated as any. Does that make sense? Or would this lead to other issues?

Environment

• Vim version: 8.2 Included patches: 1-3223
• OS: Ubuntu 20.04.2 LTS
• Terminal: XTerm(353)

Additional context

As a workaround, we can declare the return type of the funcref with list<any>:

var Getqflist: func: list<any> = function('getqflist', [{id: 0}])
                     ^-------^

Test:

vim9script
def Func(): number
    var Getqflist: func: list<any> = function('getqflist', [{id: 0}])
    return Getqflist()->get('id', 0)
enddef
defcompile
echo 'no error'

no error

---

If it is a regression, then it was introduced in 8.2.3221.

cc @yegappan via #8632

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[Yegappan Lakshmanan]

Hi,

The argument type check for the get() function already accepts the "any" type

for the first argument. But in this case, the type is "unknown". To support this,

we need to disable the type check for the first argument of get().

- Yegappan

[vim-dev ML]

Hi,

On Mon, Jul 26, 2021 at 8:11 AM lacygoill ***@***.***> wrote:

> *Describe the bug*

>
> In Vim9 script, passing the output of a funcref to get() might give an
> error in compiled code, but not at the script level, which is inconsistent.
>

> *To Reproduce*

>
> Run this shell command:
>
> vim -Nu NONE -S <(cat <<'EOF'
> vim9script
> var Getqflist: func = function('getqflist', [{id: 0}])
> Getqflist()->get('id', 0)
> EOF
> )
>
> No error is given.
>
> Now, run the same code in a :def function:
>
> vim -Nu NONE -S <(cat <<'EOF'
> vim9script
> def Func(): number
> var Getqflist: func = function('getqflist', [{id: 0}])
> return Getqflist()->get('id', 0)
> enddef
> defcompile
> EOF
> )
>
> E1013 is given:
>
> E1013: Argument 1: type mismatch, expected list<any> but got unknown
>

> *Expected behavior*

>
> I think the second command should not give an error, to be consistent with
> what happens at the script level.
>
> IOW, if Vim doesn't know what the output of a function is, it should be
> treated as any. Does that make sense? Or would this lead to other issues?
>

The argument type check for the get() function already accepts the "any"
type
for the first argument. But in this case, the type is "unknown". To support
this,
we need to disable the type check for the first argument of get().

- Yegappan

> *Environment*
>
> - Vim version: 8.2 Included patches: 1-3223
> - OS: Ubuntu 20.04.2 LTS
> - Terminal: XTerm(353)
>
> *Additional context*

>
> As a workaround, we can declare the return type of the funcref with
> list<any>:
>
> var Getqflist: func: list<any> = function('getqflist', [{id: 0}])
> ^-------^
>
> Test:
>

> vim9scriptdef Func(): number

> var Getqflist: func: list<any> = function('getqflist', [{id: 0}])
> return Getqflist()->get('id', 0)enddefdefcompileecho 'no error'
>
> no error
>

> ------------------------------
>
> *If* it is a regression, then it was introduced in 8.2.3221
> <https://github.com/vim/vim/releases/tag/v8.2.3221>.
>
> cc @yegappan <https://github.com/yegappan> via #8632
> <https://github.com/vim/vim/pull/8632>

[lacygoill]

Closed #8644.

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[lacygoill]

To support this, we need to disable the type check for the first argument of get().

Since we can pass the output of such a funcref to any other function, that would mean disable type checking entirely, which is not possible. So, closing the issue.

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[lacygoill]

I re-open because maybe Vim should not infer the return type as unknown; maybe it should be any.

Also, this comment might be relevant (in particular the end "may also have caused some bugs"):

Note that I recently made :def functions return void
instead of zero, and for lambda make the return type unknown until it is
compiled. These changes have improved some things, but may also have
caused some bugs.

Source.

Feel free to close the issue, if it can't be fixed. We certainly don't want to disable type checking entirely for get(), nor for any other builtin function.

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[lacygoill]

Reopened #8644.

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[Bram Moolenaar]

Closed #8644 via f723701.

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