Compiler crash when trying to create a closure within a loop over `os.walkDir` which captures an outside varaible

[Quelklef]

Example

import os
for unused_var in walkDir("."):
  let outside = "x"
  let closure = proc(): string = outside

Current Output

Hint: used config file '/playground/nim/config/nim.cfg' [Conf]
Hint: system [Processing]
Hint: widestrs [Processing]
Hint: io [Processing]
Hint: in [Processing]
Hint: os [Processing]
Hint: strutils [Processing]
Hint: parseutils [Processing]
Hint: math [Processing]
Hint: bitops [Processing]
Hint: macros [Processing]
Hint: algorithm [Processing]
Hint: unicode [Processing]
Hint: pathnorm [Processing]
Hint: osseps [Processing]
Hint: posix [Processing]
Hint: times [Processing]
Hint: options [Processing]
Hint: typetraits [Processing]
/usercode/in.nim(5, 7) Hint: 'closure' is declared but not used [XDeclaredButNotUsed]
Hint: gcc -c  -w   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_assertions.nim.c.o /usercode/nimcache/stdlib_assertions.nim.c [Exec]
Hint: gcc -c  -w   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_system.nim.c.o /usercode/nimcache/stdlib_system.nim.c [Exec]
Hint: gcc -c  -w   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_pathnorm.nim.c.o /usercode/nimcache/stdlib_pathnorm.nim.c [Exec]
Hint: gcc -c  -w   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_times.nim.c.o /usercode/nimcache/stdlib_times.nim.c [Exec]
Hint: gcc -c  -w   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_os.nim.c.o /usercode/nimcache/stdlib_os.nim.c [Exec]
Hint: gcc -c  -w   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/@min.nim.c.o /usercode/nimcache/@min.nim.c [Exec]
/usercode/nimcache/@min.nim.c: In function 'colonanonymous___joSqnaeyrUqFaMMdrvJu0A':
/usercode/nimcache/@min.nim.c:495:22: error: 'outside__XaBgCwy9aLkuI2Qj5G8ldCA_2' undeclared (first use in this function)
  result = copyString(outside__XaBgCwy9aLkuI2Qj5G8ldCA_2);
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usercode/nimcache/@min.nim.c:495:22: note: each undeclared identifier is reported only once for each function it appears in
Error: execution of an external program failed: 'gcc -c  -w   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/@min.nim.c.o /usercode/nimcache/@min.nim.c'

Expected Output

No compiler crash

Possible Solution

• Uncertain.

Additional Information

• No bug if a custom string iterator is used rather than walkDir
• Running Ubuntu 18.04.3
• No bug if outside is declared globally

$ nim -v
Nim Compiler Version 0.3.5 [Linux: amd64]
git hash: cbd78ec1f68e78a88e4a83a5009bc4c8c28c79b3

[Quelklef]

It's not clear to me why walkDir is special, but the os module was pretty resistant to me trying to crack it open and find out.