[Help-bash] Why does `declare` in a function in a subshell interfere with a read-only variable in the parent shell?

[Peng Yu]

HI,

The following code shows declare cannot tell whether it is in a
subshell while it is called in a function.

It always yields an error when it sees a read-only variable, even the
read-only variable is from a parent shell.

I am not sure this makes sense. Should this behavior be fixed? Thanks.

$ cat ./x.sh
#!/usr/bin/env bash
# vim: set noexpandtab tabstop=2:

set -v
declare x=42
readonly x
function f {
    declare x
}
f
(
    declare x
)
(
    function f {
        declare x
    }
    f
)
12:43:41@/tmp$ ./x.sh
declare x=42
readonly x
function f {
    declare x
}
f
./x.sh: line 8: declare: x: readonly variable
(
    declare x
)
(
    function f {
        declare x
    }
    f
)
./x.sh: line 16: declare: x: readonly variable

-- 
Regards,
Peng