streams cannot compile with taint mode enabled

[Sam647254]

streams from the standard library fails to compile when compiling with taint mode enabled.

Example

import streams

Then compile with --taintMode:on

Current Output

Compilation fails with the following:

/mnt/c/Users/Sam/Documents/Nim/lib/pure/streams.nim(904, 11) Error: type mismatch: got <TaintedString, int literal(0)>
but expected one of:
proc setLen[T](s: var seq[T]; newlen: Natural)
  first type mismatch at position: 1
  required type for s: var seq[T]
  but expression 'line' is of type: TaintedString
proc setLen(s: var string; newlen: Natural)
  first type mismatch at position: 1
  required type for s: var string
  but expression 'line' is of type: TaintedString

Expected Output

(should compile successfully)

Possible Solution

Going to the line of code in the error message reveals:

    when nimvm: #Bug #12282
      line.setLen(0)
    else:
      line.string.setLen(0)

The easiest solution may be to borrow setLen (and add, which is used later in streams) from string.

Additional Information

• The issue is essentially identical to httpclient import causes compiler error with taint mode #12789 but happening in streams instead of httpclient (in fact, I encountered this when trying to reproduce that issue)

$ nim -v
Nim Compiler Version 1.1.1 [Linux: amd64]
Compiled at 2019-12-26

[timotheecour]

is taintMode really useful or should it become a (deprecated) no-op?

[Sam647254]

nim-lang/RFCs#24
It has been discussed two years ago (as of this comment), but it still appears to be undecided.

[Araq]

IMHO it should be removed for good.