comptime need a way detect a field is shared or not

[kbkpbot]

Describe the feature

When use generic/comptime , it need some way to detect a struct field is shared or not.

Use Case

a sample code, share.v :

import encoding.binary

struct MyS {
	a int
	cache shared map[u64]string
}

fn main() {
	mut s := MyS{}
	
	b := binary.encode_binary(s)!
	dump(b)
}

v share.v

compile this will just issue a error message :

$ v share.v
/media/HD/github/kbkpbot/v/vlib/encoding/binary/serialize.v:69:29: error: `value` is `shared` and must be `rlock`ed or `lock`ed to be passed as non-mut argument
   67 |                 encode_map(mut s, value)!
   68 |             } $else {
   69 |                 encode_primitive(mut s, value)!
      |                                         ~~~~~
   70 |             }
   71 |         }

Proposed Solution

introduce something like

$if field is shared {
} $else {
}

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

Version used

V 0.4.12 ac2e7d7.4b5f337

Environment details (OS name and version, etc.)

V full version	V 0.4.12 ac2e7d7.4b5f337
OS	linux, Ubuntu 24.04.3 LTS
Processor	8 cpus, 64bit, little endian, Intel(R) Core(TM) i7-9700 CPU @ 3.00GHz
Memory	11.73GB/15.51GB
V executable	/media/HD/github/kbkpbot/v/v
V last modified time	2025-10-26 13:12:30
V home dir	OK, value: /media/HD/github/kbkpbot/v
VMODULES	OK, value: /home/mars/.vmodules
VTMP	OK, value: /tmp/v_1000
Current working dir	OK, value: /home/mars/v/bug/table
Git version	git version 2.43.0
V git status	weekly.2025.42-63-gac2e7d7f-dirty
.git/config present	true
cc version	cc (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0
gcc version	gcc (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0
clang version	Ubuntu clang version 18.1.3 (1ubuntu1)
tcc version	tcc version 0.9.28rc 2025-02-13 HEAD@f8bd136d (x86_64 Linux)
tcc git status	thirdparty-linux-amd64 696c1d84
emcc version	N/A
glibc version	ldd (Ubuntu GLIBC 2.39-0ubuntu8.6) 2.39

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[kbkpbot]

and this is not work yet:

import encoding.binary

struct MyS {
	a int
	cache shared map[u64]string
}

fn main() {
	mut s := MyS{}
	
	rlock s.cache {
		b := binary.encode_binary(s)!
		dump(b)
	}
}