Simple code with compiletime eval not working

[ASVIEST]

import std/syncio

proc foo(): int = 
  var myvar = 21
  myvar * 2

const bar = foo()
echo bar

It produces error:

a.nim(7, 16) Error: cannot evaluate expression at compile time: foo()

/home/asvi/nim/nimo4/nimony/src/hexer/hexer.nim(110) hexer
/home/asvi/nim/nimo4/nimony/src/hexer/hexer.nim(105) handleCmdLine
/home/asvi/nim/nimo4/nimony/src/hexer/dce2.nim(200) deadCodeElimination
/home/asvi/nim/nimo4/nimony/src/hexer/dce2.nim(67) markLive
/home/asvi/.local/share/grabnim/nim-devel/lib/std/assertions.nim(41) failedAssertImpl
/home/asvi/.local/share/grabnim/nim-devel/lib/std/assertions.nim(34) raiseAssert
Error: unhandled exception: /home/asvi/nim/nimo4/nimony/src/hexer/dce2.nim(67, 15) `sowner in result` sowner is not in result for string.0.sysvq0asl [AssertionDefect]
make: /home/asvi/nim/nimo4/nimony/bin/hexer d --bits:64 nimcache/wriwhv7qv.x.nif nimcache/syn1lfpjv.x.nif nimcache/mat7cnfv21.x.nif nimcache/for2ybv4p1.x.nif nimcache/atxA1E66DB28FCD6D5164E4A15FD14E8E4DA33B7E66.x.nif
FAILURE: /home/asvi/nim/nimo4/nimony/bin/nifmake --base:'' -j run nimcache/atxA1E66DB28FCD6D5164E4A15FD14E8E4DA33B7E66.exec.build.nif

make: /home/asvi/nim/nimo4/nimony/bin/nimsem m --isMain nimcache/atxy29s.p.nif
FAILURE: /home/asvi/nim/nimo4/nimony/bin/nifmake --base:'' -j run nimcache/atxy29s.build.nif
Error: execution of an external program failed: '/home/asvi/nim/nimo4/nimony/bin/nimony c -r a.nim'

[Araq]

Interesting, a somewhat harder test tmyops.nim is always green.

[ASVIEST]

Apparently this error occurs for any return type except string (and its derivatives). That is, even something like this causes an error:

proc foo(): bool = true
const bar = foo()