Returning a proc named result is accepted by the compiler but segfaults

[deech]

Example

proc p(): proc() =
  proc result = echo "hello world"

(p())()

Current Output

nim c -r --verbosity\:0 --hint\[Processing\]\:off --excessiveStackTrace\:on /home/deech/Nim/functest.nim
/home/deech/Nim/functest.nim(2, 8) Hint: 'result' is declared but not used [XDeclaredButNotUsed]
Traceback (most recent call last)
/home/deech/Nim/functest.nim(4) functest
SIGSEGV: Illegal storage access. (Attempt to read from nil?)
Segmentation fault
Error: execution of an external program failed: '/home/deech/Nim/functest '

Expected Output

hello world

Additional Information

Changing it to this works but the compiler should catch the above:

proc p(): proc() =
  result = proc () = echo "hello world"

(p())()

Nim Compiler Version 1.5.1 [Linux: amd64]
Compiled at 2021-07-12
Copyright (c) 2006-2021 by Andreas Rumpf

git hash: 195300a938c7c8dd4ec7db3ca7cc76dddeab953e
active boot switches: -d:release

[Araq]

No bug here, you don't return the inner proc at all so you return a "nil" proc which crashes when you try to call it.

[Araq]

See also nim-lang/RFCs#378 (upvote it) :-)

[deech]

I think the bug here is that in the first example result is manually initialized but the compiler doesn't see that proc result() ... and result = proc () ... are equivalent.

[Araq]

that proc result() ... and result = proc () ... are equivalent.

They are not equivalent at all. In one case you declare a proc named result (i.e. the builtin result is shadowed), in the other case you assign an anon proc to result.