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Const values don't short circuit. #19773

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treeform opened this issue May 6, 2022 · 2 comments
Open

Const values don't short circuit. #19773

treeform opened this issue May 6, 2022 · 2 comments

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@treeform
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treeform commented May 6, 2022

If you have a const string it will not short-circuit and will not compile:

Example

const s1 = ""
if s1.len == 0 or s1[0] == '/':
  echo "root"

Current Output

Error: index out of bounds, the container is empty""[0]

Expected Output

root

I would expect it to work similar to let or var.

let s2 = ""
if s2.len == 0 or s2[0] == '/':
  echo "root"

var s3 = ""
if s3.len == 0 or s3[0] == '/':
  echo "root"

output:

root
root

That works fine.

The const make it work more like some sort of substitution:

if "".len == 0 or ""[0] == '/':
  echo "root"

output:

Error: index out of bounds, the container is emptys1[0]

Same thing happens with static values:

proc foo(s2: static string) =
  if s2.len == 0 or s2[0] == '/':
    echo "root"
foo ""

output:

Error: index out of bounds, the container is emptys1[0]

$ nim -v
Nim Compiler Version 1.7.1 [Linux: amd64]
Compiled at 2022-05-05
Copyright (c) 2006-2022 by Andreas Rumpf

git hash: 278ecad973c6581aeea0a6ff9372109b0dd6df5e
active boot switches: -d:release

Related issue: related #19492
@ghost
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ghost commented May 6, 2022

See #14631 and #13541 as well

@ringabout ringabout removed their assignment Aug 6, 2022
@ringabout
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It seems very hard to make semcheck short circuir, I have no idea.

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@treeform @ringabout