"surprising" Javascript UTF-8 cstring len behaviour

[zevv]

What is the semantics of len() on unicode cstrings in javascript? Is the following behaviour expected?

let s1 = "♜♞♝♛♚♝♞♜"
const s2 = "♜♞♝♛♚♝♞♜"

echo "lit   string  ", "♜♞♝♛♚♝♞♜".len
echo "lit   cstring ", "♜♞♝♛♚♝♞♜".cstring.len
echo "let   string  ", s1.len
echo "let   cstring ", s1.cstring.len
echo "const string  ", s2.len
echo "const cstring ", s2.cstring.len

native:

lit   string  24
lit   cstring 24
let   string  24
let   cstring 24
const string  24
const cstring 24

Javascript:

lit   string  24
lit   cstring 24
let   string  24
let   cstring 8
const string  24
const cstring 24

[Araq]

cstring is mapped to JS strings and so len should return what JS's length returns.

[zevv]

Fair enough, but the behaviour is different for consts and literals then for variables - which might surprise some users, me included.

[krux02]

I can confirm, this is a bug. Only the value of the let expression is correct.

var s1_245005 = makeNimstrLit("\xE2\x99\x9C\xE2\x99\x9E\xE2\x99\x9D\xE2\x99\x9B\xE2\x99\x9A\xE2\x99\x9D\xE2\x99\x9E\xE2\x99\x9C");
rawEcho(makeNimstrLit("lit   string  "), makeNimstrLit("24"));
rawEcho(makeNimstrLit("lit   cstring "), makeNimstrLit("24"));
rawEcho(makeNimstrLit("let   string  "), cstrToNimstr(((s1_245005 != null ? s1_245005.length : 0))+""));
rawEcho(makeNimstrLit("let   cstring "), cstrToNimstr(((toJSStr(s1_245005) != null ? toJSStr(s1_245005).length : 0))+""));
rawEcho(makeNimstrLit("const string  "), makeNimstrLit("24"));
rawEcho(makeNimstrLit("const cstring "), makeNimstrLit("24"));

In the other cases Nim thinks in can calculate the size at compile time when in fact it can't. When I tried to resolve this bug, I found out that in semMagic the magic to calculate the length of the cstring is mLengthArray, not mLengthStr as it should be, at least by the overloads that are in system.nim.