Poor error message for `spawn` when a procedure (without calling it) is passed

[k0pernicus]

Nim version: 0.18.0 [MacOSX: amd64]

I experimented the behaviour of spawn and parallel for a project, and I got an issue passing an anonymous procedure to spawn.

The following code demonstrates the expected behaviour:

proc my_proc(x: uint32) =
    echo x
proc print_parallel_ok(r: uint32) =
    for x in 0..r:
        spawn my_proc x

The compiler compiles the code, and running it is ok.

Otherwise, the following demonstrates the error:

proc print_parallel_nok(r: uint32) =
    for x in 0..r:
        spawn (proc (x: uint32) = echo x)

Here, instead of using a named procedure, I passed an anonymous procedure to spawn.

The error, passing an anonymous procedure to spawn is: expression 'spawn proc (x: uint32) = echo [x], nimCreateFlowVar' is of type 'FlowVar[proc (x: uint32){.gcsafe, locks: 0.}]' and has to be discarded.
Also, if I add a discard, I get an internal compiler error.

[k0pernicus]

So, my code (using anonymous procedure) was not OK.
In the code, I passed a procedure pointer to spawn, instead of calling the anonymous procedure.

The following code works fine now:

proc print_parallel_nok(r: uint32) =
    for x in 0..r:
        spawn (proc (x: uint32) = echo x)(x)

But, it still remains that the error message may be improved