internal error in genRdVar in vmgen.nim

[jibal]

nim 1.2 on Windows

This code

import regex, strformat

proc p =
  for i in 1..1:
    const rx = re(&"")

produces this error message:

Error: internal error: (filename: "vmgen.nim", line: 1642, column: 22)

Note that this is the regex module from nimble ... it compiles regular expressions at compile time.

In reducing my actual code to a minimal failing case, I found that the iterator and the content of the string don't matter, but const, the calls to re and & (or fmt), as well as being inside a proc, are all necessary to produce the failure.

[nitely]

It seems related to static[T]. Here's a reduced case:

import strformat
proc re(s: static string): string = s
proc p =
  const rx = re(&"")

[ghost]

I think it might not be related to static:

proc p =
  const rx = block:
    var fmtRes_14356029 = "" 
    fmtRes_14356029

fails as well

[ghost]

Is this a duplicate of #12172 ?

[timotheecour]

probably not because top example produces
Error: internal error: /Users/timothee/git_clone/nim/Nim_prs/compiler/vmgen.nim(1632, 23)

whereas #12172 gives a different error

note: top example a bit reduced (without iterator):

import regex, strformat
proc p =
  const rx = re(&"")

[jibal]

I think it might not be related to static

AFAICS, your example has nothing to do with this defect, which is about a specific error message (a failure at a specific line in the compiler).

[jibal]

top example a bit reduced (without iterator):

nitely previously posted a reduced case without the iterator and without importing regex:

import strformat
proc re(s: static string): string = s
proc p =
  const rx = re(&"")

[nitely]

@jibal btw, here is a workaround:

import strformat
import regex
proc reCt(s: string): Regex {.compileTime.} = re(s)
proc p =
  const rx = reCt(&"")

[timotheecour]

here's the most straightforward way to circumvent this bug:

when true: # gitissue
  import strformat
  proc re(s: static string): string = s
  proc p =
    # const rx = re(&"") # BUG
    const rx = re(static(&"")) # ok

that might help for PR that would fix this