This is a V2 fixture for pub module_mut: struct fields.
It demonstrates a field that is public for reading, but mutable only from the
module that declares the struct. A separate pub mut: field is included to show
the difference with a publicly mutable field.
The sources are stored as .vv2 so shared V1/vfmt paths do not parse V2-only
syntax directly. To try it manually, copy the files to temporary .v files and
compile them with -v2.
Expected behavior:
counter.value can be read from main;counter.value is changed through state.Counter.inc(), inside module
state;counter.label can be changed from main because it is under pub mut:;counter.value++ must be rejected.