remove old bootstrap symbols < 0.20.0

[timotheecour]

cleanup old bootstrap stuff, eg:

• when declared(echo)
• instances with when (NimMajor, NimMinor, NimPatch) < (0, 19, 9):
• instances w since
• these:

      if version.startsWith "Nim Compiler Version 0.19.0":
        extraOption.add " -d:nimBoostrapCsources0_19_0"
        # remove this when csources get updated

    # Nim versions < (1, 1) expect Nim's exception type to have a 'raiseId' field for
    # C++ interop. Later Nim versions do this differently and removed the 'raiseId' field.
    # Thus we always bootstrap the first iteration with "c" and not with "cpp" as
    # a workaround.
    let defaultCommand = if useCpp and i > 0: "cpp" else: "c"

• cleanup when defined(nimNewRoof): ... else: dead code for old defined symbols
• Requires --nilseqs:on since 0.19.
  => --nilseqs is now a deprecated noop nim-lang/Nim#17211

example

$nim_0200_X is the nim used for bootstrap (built from csources via sh build_all.sh)
$nim_0200_X -v
Nim Compiler Version 0.20.0 [MacOSX: amd64]

$nim_csources_local_X = $nim_0200_X
$nim_0200_X c -r --skipusercfg --skipparentcfg main
every symbol from condsyms.nim that passes this test can be removed:
$nim_0200_X c -r --skipusercfg --skipparentcfg main

doAssert defined(nimHasNilSeqs)
doAssert defined(nimNoNilSeqs2)
doAssert defined(nimNoNilSeqs)
doAssert defined(nimNewRoof)

nimHasStyleChecks

echo 'echo defined(nimHasStyleChecks)' | $nim_csources_local_X c -r -
false
defined in 0.20.2

note

the only thing that should be kept is the reference in condsyms.nim so that if some user has when defined(nimHasFoo), it'll still work

[ringabout]

• when declared(echo)
• instances with when (NimMajor, NimMinor, NimPatch) < (0, 19, 9):
• instances w since
• cleanup when defined(nimNewRoof): ... else: dead code for old defined symbols

[timotheecour]

instances with when (NimMajor, NimMinor, NimPatch) < (0, 19, 9):

• only this i guess:
  tests/tuples/tuple_with_nil.nim:15:31: when (NimMajor, NimMinor, NimPatch) > (0, 10, 2):
  (EDIT: done)

[timotheecour]

this snippet gives an idea of how many times each condsym symbol is used:

# D20201203T131231
import std/[strformat,os,osproc,strutils,parseutils,sugar]
import pkg/regex
proc main() =
  let s = readFile("compiler/condsyms.nim")
  let a = collect(newSeq):
    for m in findAll(s, re"""defineSymbol\(\"(?P<name>\w+)\"\)"""):
      m.group(0, s)[0]
  echo a
  var tot = 0
  for ai in a:
    if ai == "nimnode": continue # skip special case otherwise matches NimNode etc
    let cmd = fmt"rg -i {ai} . | wc -l"
    var (outp, code) = execCmdEx(cmd)
    doAssert code == 0
    let num = outp.strip.parseInt
    tot += num
    echo (ai, num)
  echo (a.len, tot)
main()

results:

("nimhygiene", 9)
("niminheritable", 2)
("nimmixin", 1)
("nimeffects", 1)
("nimbabel", 2)
("nimcomputedgoto", 2)
("nimunion", 2)
("nimnewshared", 2)
("nimNewTypedesc", 2)
("nimrequiresnimframe", 1)
("nimparsebiggestfloatmagic", 1)
("nimalias", 1)
("nimlocks", 2)
("nimvarargstyped", 2)
("nimtypedescfixed", 2)
("nimKnowsNimvm", 1)
("nimArrIdx", 2)
("nimHasalignOf", 3)
("nimDistros", 1)
("nimHasCppDefine", 2)
("nimGenericInOutFlags", 1)
("nimHasOpt", 1)
("nimNoArrayToCstringConversion", 8)
("nimNewRoof", 3)
("nimHasRunnableExamples", 2)
("nimNewDot", 2)
("nimHasNilChecks", 2)
("nimSymKind", 7)
("nimVmEqIdent", 2)
("nimNoNil", 31)
("nimNoZeroTerminator", 2)
("nimNotNil", 1)
("nimVmExportFixed", 2)
("nimHasSymOwnerInMacro", 2)
("nimNewRuntime", 2)
("nimIncrSeqV3", 7)
("nimAshr", 3)
("nimNoNilSeqs", 28)
("nimNoNilSeqs2", 3)
("nimHasUserErrors", 2)
("nimUncheckedArrayTyp", 2)
("nimHasTypeof", 4)
("nimErrorProcCanHaveBody", 2)
("nimHasInstantiationOfInMacro", 2)
("nimHasHotCodeReloading", 4)
("nimHasNilSeqs", 1)
("nimHasSignatureHashInMacro", 2)
("nimHasDefault", 3)
("nimMacrosSizealignof", 2)
("nimNoZeroExtendMagic", 3)
("nimMacrosGetNodeId", 2)
("nimFixedOwned", 2)
("nimHasStyleChecks", 38)
("nimToOpenArrayCString", 6)
("nimHasUsed", 4)
("nimFixedForwardGeneric", 2)
("nimnomagic64", 1)
("nimNewShiftOps", 1)
("nimHasCursor", 2)
("nimAlignPragma", 3)
("nimHasExceptionsQuery", 2)
("nimHasIsNamedTuple", 2)
("nimHashOrdinalFixed", 2)
("nimHasLibFFIEnabled", 1)
("nimHasSinkInference", 8)
("nimNewIntegerOps", 2)
("nimHasInvariant", 5)
("nimHasStacktraceMsgs", 2)
("nimDoesntTrackDefects", 4)
("nimHasLentIterators", 2)
("nimHasDeclaredMagic", 3)
("nimHasStacktracesModule", 1)
("nimHasEffectTraitsModule", 2)
("nimHasCastPragmaBlocks", 1)
("nimHasDeclaredLocs", 1)
(76, 276)

[timotheecour]

• remove --nilseqs:on + associated logic to support it · Issue #293 · nim-lang/RFCs