cstring == nil doesn't compile

[demotomohiro]

mytests/testcstring.nim:

var c: cstring
discard c == nil

$ ./bin/nimony c mytests/testcstring.nim 
bin/nimsem  --isSystem m nifcache/sys9azlf.1.nif nifcache/sys9azlf.2.nif nifcache/sys9azlf.2.idx.nif
bin/nimsem  m nifcache/tes6cgtz1.1.nif nifcache/tes6cgtz1.2.nif nifcache/tes6cgtz1.2.idx.nif
Traceback (most recent call last)
src/nimony/nimsem.nim(120) nimsem
src/nimony/nimsem.nim(117) handleCmdLine
src/nimony/nimsem.nim(50) singleModule
src/nimony/sem.nim(5558) semcheck
src/nimony/sem.nim(749) semStmt
src/nimony/sem.nim(5270) semExpr
src/nimony/sem.nim(3493) semDiscard
src/nimony/sem.nim(5344) semExpr
src/nimony/sem.nim(1648) semCall
nim-2.3.1/lib/system/iterators_1.nim(1480) resolveOverloads
src/nimony/sembasics.nim(157) buildErr
mytests/testcstring.nim(2, 11) Error: Type mismatch at [position]
[1] expected: (u +64) but got: (cstring)
[1] expected: (i +16) but got: (cstring)
[1] expected: (i +64) but got: (cstring)
[1] (cstring) does not match constraint Enum.0.sys9azlf
[1] expected: (ref T.27.sys9azlf) but got: (cstring)
[1] expected: (ptr T.28.sys9azlf) but got: (cstring)
[1] expected: string.0.sys9azlf but got: (cstring)
[1] expected: (u +32) but got: (cstring)
[1] expected: (pointer) but got: (cstring)
[1] expected: (set T.26.sys9azlf) but got: (cstring)
[1] expected: string.0.sys9azlf but got: (cstring)
[1] expected: (bool) but got: (cstring)
[1] expected: (f +32) but got: (cstring)
[1] expected: (c +8) but got: (cstring)
[1] expected: (i +8) but got: (cstring)
[1] expected: (i +32) but got: (cstring)
[1] expected: (u +8) but got: (cstring)
[1] expected: (u +16) but got: (cstring)
[1] expected: (f +64) but got: (cstring)
Type mismatch at [position]
[1] expected: (u +64) but got: (cstring)
[1] expected: (i +16) but got: (cstring)
[1] expected: (i +64) but got: (cstring)
[1] (cstring) does not match constraint Enum.0.sys9azlf
[1] expected: (ref T.27.sys9azlf) but got: (cstring)
[1] expected: (ptr T.28.sys9azlf) but got: (cstring)
[1] expected: string.0.sys9azlf but got: (cstring)
[1] expected: (u +32) but got: (cstring)
[1] expected: (pointer) but got: (cstring)
[1] expected: (set T.26.sys9azlf) but got: (cstring)
[1] expected: string.0.sys9azlf but got: (cstring)
[1] expected: (bool) but got: (cstring)
[1] expected: (f +32) but got: (cstring)
[1] expected: (c +8) but got: (cstring)
[1] expected: (i +8) but got: (cstring)
[1] expected: (i +32) but got: (cstring)
[1] expected: (u +8) but got: (cstring)
[1] expected: (u +16) but got: (cstring)
[1] expected: (f +64) but got: (cstring)

[Araq]

I think that's just a missing == proc in system.nim.

[demotomohiro]

I added following lines to system.nim, but I got the different error.

proc `==`*(x, y: cstring): bool {.magic: "EqCString", noSideEffect.}
  ## Checks for equality between two `cstring` variables.

$ ./bin/nimony c mytests/testcstring.nim 
bin/nimsem  --isSystem m nifcache/sys9azlf.1.nif nifcache/sys9azlf.2.nif nifcache/sys9azlf.2.idx.nif
bin/nimsem  m nifcache/tes6cgtz1.1.nif nifcache/tes6cgtz1.2.nif nifcache/tes6cgtz1.2.idx.nif
cc -c   -I/home/player/worktmpfs/nif/vendor/mimalloc/include vendor/mimalloc/src/static.c -o nifcache/static.o
bin/hexer --bits:64 nifcache/tes6cgtz1.2.nif
bin/nifc c --compileOnly --isMain nifcache/tes6cgtz1.c.nif
[Error] expected declaration for `imp` but got: )
Traceback (most recent call last)
src/nifc/nifc.nim(207) nifc
src/nifc/nifc.nim(165) handleCmdLine
src/nifc/nifc.nim(66) generateBackend
src/nifc/codegen.nim(661) generateCode
src/nifc/codegen.nim(636) traverseCode
src/nifc/codegen.nim(614) genToplevel
src/nifc/codegen.nim(593) genImp
src/nifc/codegen.nim(157) error

[Araq]

But it shouldn't be a magic, you can implement it in pure Nim... Nimony should complain about a wrong magic though.

[demotomohiro]

I thought it should be implemented as magic because mEqCString is declared in TMagic enum type in src/nimony/magics.nim.

[Araq]

Usually doc/tags.md is the best indicator for how things should be. It has no eqcstring tag or anything like it.