Invalid utf8 string warning in '\xc0' literal

[mike-ward]

Describe the bug

v -e "println('\xc0')"
01JM7GKNS7A628B6A71RG4R7EW.vsh:1:12: warning: invalid utf8 string, please check your file's encoding is utf8
    1 | println('\xc0')
      |            ~~~

Reproduction Steps

see description

Expected Behavior

Should not produce warning.

Current Behavior

see description

Possible Solution

From Discord:

JalonSolov — Yesterday at 5:49 PM
This is likely the culprit... just merged today... #23721

Additional Information/Context

tcn — Yesterday at 5:20 PM
ran this in termux
same error

V version

V 0.4.9 2015aa3

Environment details (OS name and version, etc.)

V full version	V 0.4.9 da3112e.2015aa3
OS	macos, macOS, 15.3, 24D60
Processor	8 cpus, 64bit, little endian, Apple M2
Memory	0.17GB/8GB
V executable	/Users/mike/Documents/github/v/v
V last modified time	2025-02-16 13:45:01
V home dir	OK, value: /Users/mike/Documents/github/v
VMODULES	OK, value: /Users/mike/.vmodules
VTMP	OK, value: /tmp/v_501
Current working dir	OK, value: /Users/mike/Documents/github/kite
Git version	git version 2.48.1
V git status	weekly.2025.06-61-g2015aa3c
.git/config present	true
cc version	Apple clang version 16.0.0 (clang-1600.0.26.6)
gcc version	Apple clang version 16.0.0 (clang-1600.0.26.6)
clang version	Apple clang version 16.0.0 (clang-1600.0.26.6)
tcc version	tcc version 0.9.28rc 2024-02-05 HEAD@105d70f7 (AArch64 Darwin)
tcc git status	thirdparty-macos-arm64 713692d4
emcc version	N/A
glibc version	N/A

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[huly-for-github]

Connected to Huly®: V_0.6-22157

[spytheman]

@kbkpbot, @medvednikov what are your opinions on that?

Should V's literals be checked at compile time, to contain only valid utf8 sequences, or not?

[kbkpbot]

Because V's string encoding in UTF8 default, I think it is user's responsibility to make sure their string literals are valid utf8 sequences.
I think we should keep this warning message.

If user try to build a string with invalid UTF8 sequence, he can first use a []u8 construct the string, and then use something like tos convert it to V's string.