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##[
Represents absolute paths, but using a symbolic variables (eg $nimr) which can be
resolved at runtime; this avoids hardcoding at compile time absolute paths so
that the project root can be relocated.

xxx consider some refactoring with $nim/testament/lib/stdtest/specialpaths.nim;
specialpaths is simpler because it doesn't need variables to be relocatable at
runtime (eg for use in testament)

interpolation variables:
  $nimr: such that `$nimr/lib/system.nim` exists (avoids confusion with $nim binary)
         in compiler, it's obtainable via getPrefixDir(); for other tools (eg koch),
        this could be getCurrentDir() or getAppFilename().parentDir.parentDir,
        depending on use case

Unstable API
]##

import std/[os,strutils]

const
  docCss* = "$nimr/doc/nimdoc.css"
  docHackNim* = "$nimr/tools/dochack/dochack.nim"
  docHackJs* = docHackNim.changeFileExt("js")
  docHackJsFname* = docHackJs.lastPathPart
  theindexFname* = "theindex.html"
  nimdocOutCss* = "nimdoc.out.css"
    # `out` to make it easier to use with gitignore in user's repos
  htmldocsDirname* = "htmldocs"
  dotdotMangle* = "_._"  ## refs #13223
    # if this changes, make sure it's consistent with `esc` and `escapeLink`
    # lots of other obvious options won't work, see #14454; `_` could work too

proc interp*(path: string, nimr: string): string =
  result = path % ["nimr", nimr]
  doAssert '$' notin result, $(path, nimr, result) # avoids un-interpolated variables in output

proc getDocHacksJs*(nimr: string, nim = getCurrentCompilerExe(), forceRebuild = false): string =
  ## return absolute path to dochack.js, rebuilding if it doesn't exist or if
  ## `forceRebuild`.
  let docHackJs2 = docHackJs.interp(nimr = nimr)
  if forceRebuild or not docHackJs2.fileExists:
    let cmd =  "$nim js -d:release $file" % ["nim", nim.quoteShell, "file", docHackNim.interp(nimr = nimr).quoteShell]
    echo "getDocHacksJs: cmd: " & cmd
    doAssert execShellCmd(cmd) == 0, $(cmd)
  doAssert docHackJs2.fileExists
  result = docHackJs2
n484'>484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998
#
#
#           The Nim Compiler
#        (c) Copyright 2015 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

import
  intsets, ast, astalgo, msgs, renderer, magicsys, types, idents, trees,
  wordrecg, strutils, options, guards, writetracking, configuration,
  modulegraphs

when defined(useDfa):
  import dfa

# Second semantic checking pass over the AST. Necessary because the old
# way had some inherent problems. Performs:
#
# * effect+exception tracking
# * "usage before definition" checking

# ------------------------ exception and tag tracking -------------------------

discard """
  exception tracking:

  a() # raises 'x', 'e'
  try:
    b() # raises 'e'
  except e:
    # must not undo 'e' here; hrm
    c()

 --> we need a stack of scopes for this analysis

  # XXX enhance the algorithm to care about 'dirty' expressions:
  lock a[i].L:
    inc i # mark 'i' dirty
    lock a[j].L:
      access a[i], a[j]  # --> reject a[i]
"""

type
  TEffects = object
    exc: PNode  # stack of exceptions
    tags: PNode # list of tags
    bottom, inTryStmt: int
    owner: PSym
    init: seq[int] # list of initialized variables
    guards: TModel # nested guards
    locked: seq[PNode] # locked locations
    gcUnsafe, isRecursive, isToplevel, hasSideEffect, inEnforcedGcSafe: bool
    maxLockLevel, currLockLevel: TLockLevel
    config: ConfigRef
    graph: ModuleGraph
  PEffects = var TEffects

proc `<`(a, b: TLockLevel): bool {.borrow.}
proc `<=`(a, b: TLockLevel): bool {.borrow.}
proc `==`(a, b: TLockLevel): bool {.borrow.}
proc max(a, b: TLockLevel): TLockLevel {.borrow.}

proc isLocalVar(a: PEffects, s: PSym): bool =
  s.kind in {skVar, skResult} and sfGlobal notin s.flags and
    s.owner == a.owner and s.typ != nil

proc getLockLevel(t: PType): TLockLevel =
  var t = t
  # tyGenericInst(TLock {tyGenericBody}, tyStatic, tyObject):
  if t.kind == tyGenericInst and t.len == 3: t = t.sons[1]
  if t.kind == tyStatic and t.n != nil and t.n.kind in {nkCharLit..nkInt64Lit}:
    result = t.n.intVal.TLockLevel

proc lockLocations(a: PEffects; pragma: PNode) =
  if pragma.kind != nkExprColonExpr:
    localError(a.config, pragma.info, "locks pragma without argument")
    return
  var firstLL = TLockLevel(-1'i16)
  for x in pragma[1]:
    let thisLL = getLockLevel(x.typ)
    if thisLL != 0.TLockLevel:
      if thisLL < 0.TLockLevel or thisLL > MaxLockLevel.TLockLevel:
        localError(a.config, x.info, "invalid lock level: " & $thisLL)
      elif firstLL < 0.TLockLevel: firstLL = thisLL
      elif firstLL != thisLL:
        localError(a.config, x.info,
          "multi-lock requires the same static lock level for every operand")
      a.maxLockLevel = max(a.maxLockLevel, firstLL)
    a.locked.add x
  if firstLL >= 0.TLockLevel and firstLL != a.currLockLevel:
    if a.currLockLevel > 0.TLockLevel and a.currLockLevel <= firstLL:
      localError(a.config, pragma.info, "invalid nested locking")
    a.currLockLevel = firstLL

proc guardGlobal(a: PEffects; n: PNode; guard: PSym) =
  # check whether the corresponding lock is held:
  for L in a.locked:
    if L.kind == nkSym and L.sym == guard: return
  # we allow accesses nevertheless in top level statements for
  # easier initialization:
  #if a.isTopLevel:
  #  message(n.info, warnUnguardedAccess, renderTree(n))
  #else:
  if not a.isTopLevel:
    localError(a.config, n.info, "unguarded access: " & renderTree(n))

# 'guard*' are checks which are concerned with 'guard' annotations
# (var x{.guard: y.}: int)
proc guardDotAccess(a: PEffects; n: PNode) =
  let ri = n.sons[1]
  if ri.kind != nkSym or ri.sym.kind != skField: return
  var g = ri.sym.guard
  if g.isNil or a.isTopLevel: return
  # fixup guard:
  if g.kind == skUnknown:
    var field: PSym = nil
    var ty = n.sons[0].typ.skipTypes(abstractPtrs)
    if ty.kind == tyTuple and not ty.n.isNil:
      field = lookupInRecord(ty.n, g.name)
    else:
      while ty != nil and ty.kind == tyObject:
        field = lookupInRecord(ty.n, g.name)
        if field != nil: break
        ty = ty.sons[0]
        if ty == nil: break
        ty = ty.skipTypes(skipPtrs)
    if field == nil:
      localError(a.config, n.info, "invalid guard field: " & g.name.s)
      return
    g = field
    #ri.sym.guard = field
    # XXX unfortunately this is not correct for generic instantiations!
  if g.kind == skField:
    let dot = newNodeI(nkDotExpr, n.info, 2)
    dot.sons[0] = n.sons[0]
    dot.sons[1] = newSymNode(g)
    dot.typ = g.typ
    for L in a.locked:
      #if a.guards.sameSubexprs(dot, L): return
      if guards.sameTree(dot, L): return
    localError(a.config, n.info, "unguarded access: " & renderTree(n))
  else:
    guardGlobal(a, n, g)

proc makeVolatile(a: PEffects; s: PSym) {.inline.} =
  template compileToCpp(a): untyped =
    a.config.cmd == cmdCompileToCpp or sfCompileToCpp in getModule(a.owner).flags
  if a.inTryStmt > 0 and not compileToCpp(a):
    incl(s.flags, sfVolatile)

proc initVar(a: PEffects, n: PNode; volatileCheck: bool) =
  if n.kind != nkSym: return
  let s = n.sym
  if isLocalVar(a, s):
    if volatileCheck: makeVolatile(a, s)
    for x in a.init:
      if x == s.id: return
    a.init.add s.id

proc initVarViaNew(a: PEffects, n: PNode) =
  if n.kind != nkSym: return
  let s = n.sym
  if {tfNeedsInit, tfNotNil} * s.typ.flags <= {tfNotNil}:
    # 'x' is not nil, but that doesn't mean its "not nil" children
    # are initialized:
    initVar(a, n, volatileCheck=true)
  elif isLocalVar(a, s):
    makeVolatile(a, s)

proc warnAboutGcUnsafe(n: PNode; conf: ConfigRef) =
  #assert false
  message(conf, n.info, warnGcUnsafe, renderTree(n))

proc markGcUnsafe(a: PEffects; reason: PSym) =
  if not a.inEnforcedGcSafe:
    a.gcUnsafe = true
    if a.owner.kind in routineKinds: a.owner.gcUnsafetyReason = reason

proc markGcUnsafe(a: PEffects; reason: PNode) =
  if not a.inEnforcedGcSafe:
    a.gcUnsafe = true
    if a.owner.kind in routineKinds:
      if reason.kind == nkSym:
        a.owner.gcUnsafetyReason = reason.sym
      else:
        a.owner.gcUnsafetyReason = newSym(skUnknown, getIdent("<unknown>"),
                                          a.owner, reason.info, {})

when true:
  template markSideEffect(a: PEffects; reason: typed) =
    a.hasSideEffect = true
else:
  template markSideEffect(a: PEffects; reason: typed) =
    a.hasSideEffect = true
    markGcUnsafe(a, reason)

proc listGcUnsafety(s: PSym; onlyWarning: bool; cycleCheck: var IntSet; conf: ConfigRef) =
  let u = s.gcUnsafetyReason
  if u != nil and not cycleCheck.containsOrIncl(u.id):
    let msgKind = if onlyWarning: warnGcUnsafe2 else: errGenerated
    case u.kind
    of skLet, skVar:
      message(conf, s.info, msgKind,
        ("'$#' is not GC-safe as it accesses '$#'" &
        " which is a global using GC'ed memory") % [s.name.s, u.name.s])
    of routineKinds:
      # recursive call *always* produces only a warning so the full error
      # message is printed:
      listGcUnsafety(u, true, cycleCheck, conf)
      message(conf, s.info, msgKind,
        "'$#' is not GC-safe as it calls '$#'" %
        [s.name.s, u.name.s])
    of skParam, skForVar:
      message(conf, s.info, msgKind,
        "'$#' is not GC-safe as it performs an indirect call via '$#'" %
        [s.name.s, u.name.s])
    else:
      message(conf, u.info, msgKind,
        "'$#' is not GC-safe as it performs an indirect call here" % s.name.s)

proc listGcUnsafety(s: PSym; onlyWarning: bool; conf: ConfigRef) =
  var cycleCheck = initIntSet()
  listGcUnsafety(s, onlyWarning, cycleCheck, conf)

proc useVar(a: PEffects, n: PNode) =
  let s = n.sym
  if isLocalVar(a, s):
    if s.id notin a.init:
      if {tfNeedsInit, tfNotNil} * s.typ.flags != {}:
        message(a.config, n.info, warnProveInit, s.name.s)
      else:
        message(a.config, n.info, warnUninit, s.name.s)
      # prevent superfluous warnings about the same variable:
      a.init.add s.id
  if {sfGlobal, sfThread} * s.flags != {} and s.kind in {skVar, skLet} and
      s.magic != mNimVm:
    if s.guard != nil: guardGlobal(a, n, s.guard)
    if {sfGlobal, sfThread} * s.flags == {sfGlobal} and
        (tfHasGCedMem in s.typ.flags or s.typ.isGCedMem):
      #if warnGcUnsafe in gNotes: warnAboutGcUnsafe(n)
      markGcUnsafe(a, s)
      markSideEffect(a, s)
    else:
      markSideEffect(a, s)


type
  TIntersection = seq[tuple[id, count: int]] # a simple count table

proc addToIntersection(inter: var TIntersection, s: int) =
  for j in 0..<inter.len:
    if s == inter[j].id:
      inc inter[j].count
      return
  inter.add((id: s, count: 1))

proc throws(tracked, n: PNode) =
  if n.typ == nil or n.typ.kind != tyError: tracked.add n

proc getEbase(g: ModuleGraph; info: TLineInfo): PType =
  result = g.sysTypeFromName(info, "Exception")

proc excType(g: ModuleGraph; n: PNode): PType =
  # reraise is like raising E_Base:
  let t = if n.kind == nkEmpty or n.typ.isNil: getEbase(g, n.info) else: n.typ
  result = skipTypes(t, skipPtrs)

proc createRaise(g: ModuleGraph; n: PNode): PNode =
  result = newNode(nkType)
  result.typ = getEbase(g, n.info)
  if not n.isNil: result.info = n.info

proc createTag(g: ModuleGraph; n: PNode): PNode =
  result = newNode(nkType)
  result.typ = g.sysTypeFromName(n.info, "RootEffect")
  if not n.isNil: result.info = n.info

proc addEffect(a: PEffects, e: PNode, useLineInfo=true) =
  assert e.kind != nkRaiseStmt
  var aa = a.exc
  for i in a.bottom ..< aa.len:
    if sameType(a.graph.excType(aa[i]), a.graph.excType(e)):
      if not useLineInfo or a.config.cmd == cmdDoc: return
      elif aa[i].info == e.info: return
  throws(a.exc, e)

proc addTag(a: PEffects, e: PNode, useLineInfo=true) =
  var aa = a.tags
  for i in 0 ..< aa.len:
    if sameType(aa[i].typ.skipTypes(skipPtrs), e.typ.skipTypes(skipPtrs)):
      if not useLineInfo or a.config.cmd == cmdDoc: return
      elif aa[i].info == e.info: return
  throws(a.tags, e)

proc mergeEffects(a: PEffects, b, comesFrom: PNode) =
  if b.isNil:
    addEffect(a, createRaise(a.graph, comesFrom))
  else:
    for effect in items(b): addEffect(a, effect, useLineInfo=comesFrom != nil)

proc mergeTags(a: PEffects, b, comesFrom: PNode) =
  if b.isNil:
    addTag(a, createTag(a.graph, comesFrom))
  else:
    for effect in items(b): addTag(a, effect, useLineInfo=comesFrom != nil)

proc listEffects(a: PEffects) =
  for e in items(a.exc):  message(a.config, e.info, hintUser, typeToString(e.typ))
  for e in items(a.tags): message(a.config, e.info, hintUser, typeToString(e.typ))
  #if a.maxLockLevel != 0:
  #  message(e.info, hintUser, "lockLevel: " & a.maxLockLevel)

proc catches(tracked: PEffects, e: PType) =
  let e = skipTypes(e, skipPtrs)
  var L = tracked.exc.len
  var i = tracked.bottom
  while i < L:
    # r supertype of e?
    if safeInheritanceDiff(tracked.graph.excType(tracked.exc[i]), e) <= 0:
      tracked.exc.sons[i] = tracked.exc.sons[L-1]
      dec L
    else:
      inc i
  if not isNil(tracked.exc.sons):
    setLen(tracked.exc.sons, L)
  else:
    assert L == 0

proc catchesAll(tracked: PEffects) =
  if not isNil(tracked.exc.sons):
    setLen(tracked.exc.sons, tracked.bottom)

proc track(tracked: PEffects, n: PNode)
proc trackTryStmt(tracked: PEffects, n: PNode) =
  let oldBottom = tracked.bottom
  tracked.bottom = tracked.exc.len

  let oldState = tracked.init.len
  var inter: TIntersection = @[]

  inc tracked.inTryStmt
  track(tracked, n.sons[0])
  dec tracked.inTryStmt
  for i in oldState..<tracked.init.len:
    addToIntersection(inter, tracked.init[i])

  var branches = 1
  var hasFinally = false
  for i in 1 ..< n.len:
    let b = n.sons[i]
    let blen = sonsLen(b)
    if b.kind == nkExceptBranch:
      inc branches
      if blen == 1:
        catchesAll(tracked)
      else:
        for j in countup(0, blen - 2):
          if b.sons[j].isInfixAs():
            assert(b.sons[j][1].kind == nkType)
            catches(tracked, b.sons[j][1].typ)
          else:
            assert(b.sons[j].kind == nkType)
            catches(tracked, b.sons[j].typ)
      setLen(tracked.init, oldState)
      track(tracked, b.sons[blen-1])
      for i in oldState..<tracked.init.len:
        addToIntersection(inter, tracked.init[i])
    else:
      assert b.kind == nkFinally
      setLen(tracked.init, oldState)
      track(tracked, b.sons[blen-1])
      hasFinally = true

  tracked.bottom = oldBottom
  if not hasFinally:
    setLen(tracked.init, oldState)
  for id, count in items(inter):
    if count == branches: tracked.init.add id

proc isIndirectCall(n: PNode, owner: PSym): bool =
  # we don't count f(...) as an indirect call if 'f' is an parameter.
  # Instead we track expressions of type tyProc too. See the manual for
  # details:
  if n.kind != nkSym:
    result = true
  elif n.sym.kind == skParam:
    result = owner != n.sym.owner or owner == nil
  elif n.sym.kind notin routineKinds:
    result = true

proc isForwardedProc(n: PNode): bool =
  result = n.kind == nkSym and sfForward in n.sym.flags

proc trackPragmaStmt(tracked: PEffects, n: PNode) =
  for i in countup(0, sonsLen(n) - 1):
    var it = n.sons[i]
    if whichPragma(it) == wEffects:
      # list the computed effects up to here:
      listEffects(tracked)

proc effectSpec(n: PNode, effectType: TSpecialWord): PNode =
  for i in countup(0, sonsLen(n) - 1):
    var it = n.sons[i]
    if it.kind == nkExprColonExpr and whichPragma(it) == effectType:
      result = it.sons[1]
      if result.kind notin {nkCurly, nkBracket}:
        result = newNodeI(nkCurly, result.info)
        result.add(it.sons[1])
      return

proc documentEffect(n, x: PNode, effectType: TSpecialWord, idx: int): PNode =
  let spec = effectSpec(x, effectType)
  if isNil(spec):
    let s = n.sons[namePos].sym

    let actual = s.typ.n.sons[0]
    if actual.len != effectListLen: return
    let real = actual.sons[idx]

    # warning: hack ahead:
    var effects = newNodeI(nkBracket, n.info, real.len)
    for i in 0 ..< real.len:
      var t = typeToString(real[i].typ)
      if t.startsWith("ref "): t = substr(t, 4)
      effects.sons[i] = newIdentNode(getIdent(t), n.info)
      # set the type so that the following analysis doesn't screw up:
      effects.sons[i].typ = real[i].typ

    result = newNode(nkExprColonExpr, n.info, @[
      newIdentNode(getIdent(specialWords[effectType]), n.info), effects])

proc documentWriteEffect(n: PNode; flag: TSymFlag; pragmaName: string): PNode =
  let s = n.sons[namePos].sym
  let params = s.typ.n

  var effects = newNodeI(nkBracket, n.info)
  for i in 1 ..< params.len:
    if params[i].kind == nkSym and flag in params[i].sym.flags:
      effects.add params[i]

  if effects.len > 0:
    result = newNode(nkExprColonExpr, n.info, @[
      newIdentNode(getIdent(pragmaName), n.info), effects])

proc documentNewEffect(n: PNode): PNode =
  let s = n.sons[namePos].sym
  if tfReturnsNew in s.typ.flags:
    result = newIdentNode(getIdent("new"), n.info)

proc documentRaises*(n: PNode) =
  if n.sons[namePos].kind != nkSym: return
  let pragmas = n.sons[pragmasPos]
  let p1 = documentEffect(n, pragmas, wRaises, exceptionEffects)
  let p2 = documentEffect(n, pragmas, wTags, tagEffects)
  let p3 = documentWriteEffect(n, sfWrittenTo, "writes")
  let p4 = documentNewEffect(n)
  let p5 = documentWriteEffect(n, sfEscapes, "escapes")

  if p1 != nil or p2 != nil or p3 != nil or p4 != nil or p5 != nil:
    if pragmas.kind == nkEmpty:
      n.sons[pragmasPos] = newNodeI(nkPragma, n.info)
    if p1 != nil: n.sons[pragmasPos].add p1
    if p2 != nil: n.sons[pragmasPos].add p2
    if p3 != nil: n.sons[pragmasPos].add p3
    if p4 != nil: n.sons[pragmasPos].add p4
    if p5 != nil: n.sons[pragmasPos].add p5

template notGcSafe(t): untyped = {tfGcSafe, tfNoSideEffect} * t.flags == {}

proc importedFromC(n: PNode): bool =
  # when imported from C, we assume GC-safety.
  result = n.kind == nkSym and sfImportc in n.sym.flags

proc getLockLevel(s: PSym): TLockLevel =
  result = s.typ.lockLevel
  if result == UnspecifiedLockLevel:
    if {sfImportc, sfNoSideEffect} * s.flags != {} or
       tfNoSideEffect in s.typ.flags:
      result = 0.TLockLevel
    else:
      result = UnknownLockLevel
      #message(s.info, warnUser, "FOR THIS " & s.name.s)

proc mergeLockLevels(tracked: PEffects, n: PNode, lockLevel: TLockLevel) =
  if lockLevel >= tracked.currLockLevel:
    # if in lock section:
    if tracked.currLockLevel > 0.TLockLevel:
      localError tracked.config, n.info, errGenerated,
        "expected lock level < " & $tracked.currLockLevel &
        " but got lock level " & $lockLevel
    tracked.maxLockLevel = max(tracked.maxLockLevel, lockLevel)

proc propagateEffects(tracked: PEffects, n: PNode, s: PSym) =
  let pragma = s.ast.sons[pragmasPos]
  let spec = effectSpec(pragma, wRaises)
  mergeEffects(tracked, spec, n)

  let tagSpec = effectSpec(pragma, wTags)
  mergeTags(tracked, tagSpec, n)

  if notGcSafe(s.typ) and sfImportc notin s.flags:
    if warnGcUnsafe in tracked.config.notes: warnAboutGcUnsafe(n, tracked.config)
    markGcUnsafe(tracked, s)
  if tfNoSideEffect notin s.typ.flags:
    markSideEffect(tracked, s)
  mergeLockLevels(tracked, n, s.getLockLevel)

proc procVarcheck(n: PNode; conf: ConfigRef) =
  if n.kind in nkSymChoices:
    for x in n: procVarCheck(x, conf)
  elif n.kind == nkSym and n.sym.magic != mNone and n.sym.kind in routineKinds:
    localError(conf, n.info, "'$1' cannot be passed to a procvar" % n.sym.name.s)

proc notNilCheck(tracked: PEffects, n: PNode, paramType: PType) =
  let n = n.skipConv
  if paramType.isNil or paramType.kind != tyTypeDesc:
    procVarcheck skipConvAndClosure(n), tracked.config
  #elif n.kind in nkSymChoices:
  #  echo "came here"
  let paramType = paramType.skipTypesOrNil(abstractInst)
  if paramType != nil and tfNotNil in paramType.flags and
      n.typ != nil and tfNotNil notin n.typ.flags:
    if n.kind == nkAddr:
      # addr(x[]) can't be proven, but addr(x) can:
      if not containsNode(n, {nkDerefExpr, nkHiddenDeref}): return
    elif (n.kind == nkSym and n.sym.kind in routineKinds) or
         (n.kind in procDefs+{nkObjConstr, nkBracket, nkClosure, nkStrLit..nkTripleStrLit}) or
         (n.kind in nkCallKinds and n[0].kind == nkSym and n[0].sym.magic == mArrToSeq):
      # 'p' is not nil obviously:
      return
    case impliesNotNil(tracked.guards, n)
    of impUnknown:
      message(tracked.config, n.info, errGenerated,
              "cannot prove '$1' is not nil" % n.renderTree)
    of impNo:
      message(tracked.config, n.info, errGenerated,
              "'$1' is provably nil" % n.renderTree)
    of impYes: discard

proc assumeTheWorst(tracked: PEffects; n: PNode; op: PType) =
  addEffect(tracked, createRaise(tracked.graph, n))
  addTag(tracked, createTag(tracked.graph, n))
  let lockLevel = if op.lockLevel == UnspecifiedLockLevel: UnknownLockLevel
                  else: op.lockLevel
  #if lockLevel == UnknownLockLevel:
  #  message(n.info, warnUser, "had to assume the worst here")
  mergeLockLevels(tracked, n, lockLevel)

proc isOwnedProcVar(n: PNode; owner: PSym): bool =
  # XXX prove the soundness of this effect system rule
  result = n.kind == nkSym and n.sym.kind == skParam and owner == n.sym.owner

proc trackOperand(tracked: PEffects, n: PNode, paramType: PType) =
  let a = skipConvAndClosure(n)
  let op = a.typ
  if op != nil and op.kind == tyProc and n.skipConv.kind != nkNilLit:
    internalAssert tracked.config, op.n.sons[0].kind == nkEffectList
    var effectList = op.n.sons[0]
    let s = n.skipConv
    if s.kind == nkSym and s.sym.kind in routineKinds:
      propagateEffects(tracked, n, s.sym)
    elif effectList.len == 0:
      if isForwardedProc(n):
        # we have no explicit effects but it's a forward declaration and so it's
        # stated there are no additional effects, so simply propagate them:
        propagateEffects(tracked, n, n.sym)
      elif not isOwnedProcVar(a, tracked.owner):
        # we have no explicit effects so assume the worst:
        assumeTheWorst(tracked, n, op)
      # assume GcUnsafe unless in its type; 'forward' does not matter:
      if notGcSafe(op) and not isOwnedProcVar(a, tracked.owner):
        if warnGcUnsafe in tracked.config.notes: warnAboutGcUnsafe(n, tracked.config)
        markGcUnsafe(tracked, a)
      elif tfNoSideEffect notin op.flags and not isOwnedProcVar(a, tracked.owner):
        markSideEffect(tracked, a)
    else:
      mergeEffects(tracked, effectList.sons[exceptionEffects], n)
      mergeTags(tracked, effectList.sons[tagEffects], n)
      if notGcSafe(op):
        if warnGcUnsafe in tracked.config.notes: warnAboutGcUnsafe(n, tracked.config)
        markGcUnsafe(tracked, a)
      elif tfNoSideEffect notin op.flags:
        markSideEffect(tracked, a)
  if paramType != nil and paramType.kind == tyVar:
    if n.kind == nkSym and isLocalVar(tracked, n.sym):
      makeVolatile(tracked, n.sym)
  if paramType != nil and paramType.kind == tyProc and tfGcSafe in paramType.flags:
    let argtype = skipTypes(a.typ, abstractInst)
    # XXX figure out why this can be a non tyProc here. See httpclient.nim for an
    # example that triggers it.
    if argtype.kind == tyProc and notGcSafe(argtype) and not tracked.inEnforcedGcSafe:
      localError(tracked.config, n.info, $n & " is not GC safe")
  notNilCheck(tracked, n, paramType)

proc breaksBlock(n: PNode): bool =
  # sematic check doesn't allow statements after raise, break, return or
  # call to noreturn proc, so it is safe to check just the last statements
  var it = n
  while it.kind in {nkStmtList, nkStmtListExpr} and it.len > 0:
    it = it.lastSon

  result = it.kind in {nkBreakStmt, nkReturnStmt, nkRaiseStmt} or
    it.kind in nkCallKinds and it[0].kind == nkSym and sfNoReturn in it[0].sym.flags

proc trackCase(tracked: PEffects, n: PNode) =
  track(tracked, n.sons[0])
  let oldState = tracked.init.len
  let oldFacts = tracked.guards.s.len
  let stringCase = skipTypes(n.sons[0].typ,
        abstractVarRange-{tyTypeDesc}).kind in {tyFloat..tyFloat128, tyString}
  let interesting = not stringCase and interestingCaseExpr(n.sons[0]) and
        warnProveField in tracked.config.notes
  var inter: TIntersection = @[]
  var toCover = 0
  for i in 1..<n.len:
    let branch = n.sons[i]
    setLen(tracked.init, oldState)
    if interesting:
      setLen(tracked.guards.s, oldFacts)
      addCaseBranchFacts(tracked.guards, n, i)
    for i in 0 ..< branch.len:
      track(tracked, branch.sons[i])
    if not breaksBlock(branch.lastSon): inc toCover
    for i in oldState..<tracked.init.len:
      addToIntersection(inter, tracked.init[i])

  setLen(tracked.init, oldState)
  if not stringCase or lastSon(n).kind == nkElse:
    for id, count in items(inter):
      if count >= toCover: tracked.init.add id
    # else we can't merge
  setLen(tracked.guards.s, oldFacts)

proc trackIf(tracked: PEffects, n: PNode) =
  track(tracked, n.sons[0].sons[0])
  let oldFacts = tracked.guards.s.len
  addFact(tracked.guards, n.sons[0].sons[0])
  let oldState = tracked.init.len

  var inter: TIntersection = @[]
  var toCover = 0
  track(tracked, n.sons[0].sons[1])
  if not breaksBlock(n.sons[0].sons[1]): inc toCover
  for i in oldState..<tracked.init.len:
    addToIntersection(inter, tracked.init[i])

  for i in 1..<n.len:
    let branch = n.sons[i]
    setLen(tracked.guards.s, oldFacts)
    for j in 0..i-1:
      addFactNeg(tracked.guards, n.sons[j].sons[0])
    if branch.len > 1:
      addFact(tracked.guards, branch.sons[0])
    setLen(tracked.init, oldState)
    for i in 0 ..< branch.len:
      track(tracked, branch.sons[i])
    if not breaksBlock(branch.lastSon): inc toCover
    for i in oldState..<tracked.init.len:
      addToIntersection(inter, tracked.init[i])
  setLen(tracked.init, oldState)
  if lastSon(n).len == 1:
    for id, count in items(inter):
      if count >= toCover: tracked.init.add id
    # else we can't merge as it is not exhaustive
  setLen(tracked.guards.s, oldFacts)

proc trackBlock(tracked: PEffects, n: PNode) =
  if n.kind in {nkStmtList, nkStmtListExpr}:
    var oldState = -1
    for i in 0..<n.len:
      if hasSubnodeWith(n.sons[i], nkBreakStmt):
        # block:
        #   x = def
        #   if ...: ... break # some nested break
        #   y = def
        # --> 'y' not defined after block!
        if oldState < 0: oldState = tracked.init.len
      track(tracked, n.sons[i])
    if oldState > 0: setLen(tracked.init, oldState)
  else:
    track(tracked, n)

proc isTrue*(n: PNode): bool =
  n.kind == nkSym and n.sym.kind == skEnumField and n.sym.position != 0 or
    n.kind == nkIntLit and n.intVal != 0

proc paramType(op: PType, i: int): PType =
  if op != nil and i < op.len: result = op.sons[i]

proc cstringCheck(tracked: PEffects; n: PNode) =
  if n.sons[0].typ.kind == tyCString and (let a = skipConv(n[1]);
      a.typ.kind == tyString and a.kind notin {nkStrLit..nkTripleStrLit}):
    message(tracked.config, n.info, warnUnsafeCode, renderTree(n))

proc track(tracked: PEffects, n: PNode) =
  case n.kind
  of nkSym:
    useVar(tracked, n)
  of nkRaiseStmt:
    n.sons[0].info = n.info
    #throws(tracked.exc, n.sons[0])
    addEffect(tracked, n.sons[0], useLineInfo=false)
    for i in 0 ..< safeLen(n):
      track(tracked, n.sons[i])
  of nkCallKinds:
    # p's effects are ours too:
    let a = n.sons[0]
    let op = a.typ
    # XXX: in rare situations, templates and macros will reach here after
    # calling getAst(templateOrMacro()). Currently, templates and macros
    # are indistinguishable from normal procs (both have tyProc type) and
    # we can detect them only by checking for attached nkEffectList.
    if op != nil and op.kind == tyProc and op.n.sons[0].kind == nkEffectList:
      if a.kind == nkSym:
        if a.sym == tracked.owner: tracked.isRecursive = true
        # even for recursive calls we need to check the lock levels (!):
        mergeLockLevels(tracked, n, a.sym.getLockLevel)
        if sfSideEffect in a.sym.flags: markSideEffect(tracked, a)
      else:
        mergeLockLevels(tracked, n, op.lockLevel)
      var effectList = op.n.sons[0]
      if a.kind == nkSym and a.sym.kind == skMethod:
        propagateEffects(tracked, n, a.sym)
      elif effectList.len == 0:
        if isForwardedProc(a):
          propagateEffects(tracked, n, a.sym)
        elif isIndirectCall(a, tracked.owner):
          assumeTheWorst(tracked, n, op)
      else:
        mergeEffects(tracked, effectList.sons[exceptionEffects], n)
        mergeTags(tracked, effectList.sons[tagEffects], n)
        if notGcSafe(op) and not importedFromC(a):
          # and it's not a recursive call:
          if not (a.kind == nkSym and a.sym == tracked.owner):
            if warnGcUnsafe in tracked.config.notes: warnAboutGcUnsafe(n, tracked.config)
            markGcUnsafe(tracked, a)
        if tfNoSideEffect notin op.flags and not importedFromC(a):
          # and it's not a recursive call:
          if not (a.kind == nkSym and a.sym == tracked.owner):
            markSideEffect(tracked, a)
    if a.kind != nkSym or a.sym.magic != mNBindSym:
      for i in 1 ..< len(n): trackOperand(tracked, n.sons[i], paramType(op, i))
    if a.kind == nkSym and a.sym.magic in {mNew, mNewFinalize, mNewSeq}:
      # may not look like an assignment, but it is:
      let arg = n.sons[1]
      initVarViaNew(tracked, arg)
      if arg.typ.len != 0 and {tfNeedsInit} * arg.typ.lastSon.flags != {}:
        if a.sym.magic == mNewSeq and n[2].kind in {nkCharLit..nkUInt64Lit} and
            n[2].intVal == 0:
          # var s: seq[notnil];  newSeq(s, 0)  is a special case!
          discard
        else:
          message(tracked.config, arg.info, warnProveInit, $arg)
    for i in 0 ..< safeLen(n):
      track(tracked, n.sons[i])
  of nkDotExpr:
    guardDotAccess(tracked, n)
    for i in 0 ..< len(n): track(tracked, n.sons[i])
  of nkCheckedFieldExpr:
    track(tracked, n.sons[0])
    if warnProveField in tracked.config.notes:
      checkFieldAccess(tracked.guards, n, tracked.config)
  of nkTryStmt: trackTryStmt(tracked, n)
  of nkPragma: trackPragmaStmt(tracked, n)
  of nkAsgn, nkFastAsgn:
    track(tracked, n.sons[1])
    initVar(tracked, n.sons[0], volatileCheck=true)
    invalidateFacts(tracked.guards, n.sons[0])
    track(tracked, n.sons[0])
    addAsgnFact(tracked.guards, n.sons[0], n.sons[1])
    notNilCheck(tracked, n.sons[1], n.sons[0].typ)
    when false: cstringCheck(tracked, n)
  of nkVarSection, nkLetSection:
    for child in n:
      let last = lastSon(child)
      if last.kind != nkEmpty: track(tracked, last)
      if child.kind == nkIdentDefs and last.kind != nkEmpty:
        for i in 0 .. child.len-3:
          initVar(tracked, child.sons[i], volatileCheck=false)
          addAsgnFact(tracked.guards, child.sons[i], last)
          notNilCheck(tracked, last, child.sons[i].typ)
      # since 'var (a, b): T = ()' is not even allowed, there is always type
      # inference for (a, b) and thus no nil checking is necessary.
  of nkConstSection:
    for child in n:
      let last = lastSon(child)
      track(tracked, last)
  of nkCaseStmt: trackCase(tracked, n)
  of nkWhen, nkIfStmt, nkIfExpr: trackIf(tracked, n)
  of nkBlockStmt, nkBlockExpr: trackBlock(tracked, n.sons[1])
  of nkWhileStmt:
    track(tracked, n.sons[0])
    # 'while true' loop?
    if isTrue(n.sons[0]):
      trackBlock(tracked, n.sons[1])
    else:
      # loop may never execute:
      let oldState = tracked.init.len
      let oldFacts = tracked.guards.s.len
      addFact(tracked.guards, n.sons[0])
      track(tracked, n.sons[1])
      setLen(tracked.init, oldState)
      setLen(tracked.guards.s, oldFacts)
  of nkForStmt, nkParForStmt:
    # we are very conservative here and assume the loop is never executed:
    let oldState = tracked.init.len
    for i in 0 ..< len(n):
      track(tracked, n.sons[i])
    setLen(tracked.init, oldState)
  of nkObjConstr:
    when false: track(tracked, n.sons[0])
    let oldFacts = tracked.guards.s.len
    for i in 1 ..< len(n):
      let x = n.sons[i]
      track(tracked, x)
      if x.sons[0].kind == nkSym and sfDiscriminant in x.sons[0].sym.flags:
        addDiscriminantFact(tracked.guards, x)
    setLen(tracked.guards.s, oldFacts)
  of nkPragmaBlock:
    let pragmaList = n.sons[0]
    let oldLocked = tracked.locked.len
    let oldLockLevel = tracked.currLockLevel
    var enforcedGcSafety = false
    for i in 0 ..< pragmaList.len:
      let pragma = whichPragma(pragmaList.sons[i])
      if pragma == wLocks:
        lockLocations(tracked, pragmaList.sons[i])
      elif pragma == wGcSafe:
        enforcedGcSafety = true
    if enforcedGcSafety: tracked.inEnforcedGcSafe = true
    track(tracked, n.lastSon)
    if enforcedGcSafety: tracked.inEnforcedGcSafe = false
    setLen(tracked.locked, oldLocked)
    tracked.currLockLevel = oldLockLevel
  of nkTypeSection, nkProcDef, nkConverterDef, nkMethodDef, nkIteratorDef,
      nkMacroDef, nkTemplateDef, nkLambda, nkDo, nkFuncDef:
    discard
  of nkCast, nkHiddenStdConv, nkHiddenSubConv, nkConv:
    if n.len == 2: track(tracked, n.sons[1])
  of nkObjUpConv, nkObjDownConv, nkChckRange, nkChckRangeF, nkChckRange64:
    if n.len == 1: track(tracked, n.sons[0])
  else:
    for i in 0 ..< safeLen(n): track(tracked, n.sons[i])

proc subtypeRelation(g: ModuleGraph; spec, real: PNode): bool =
  result = safeInheritanceDiff(g.excType(real), spec.typ) <= 0

proc checkRaisesSpec(g: ModuleGraph; spec, real: PNode, msg: string, hints: bool;
                     effectPredicate: proc (g: ModuleGraph; a, b: PNode): bool {.nimcall.}) =
  # check that any real exception is listed in 'spec'; mark those as used;
  # report any unused exception
  var used = initIntSet()
  for r in items(real):
    block search:
      for s in 0 ..< spec.len:
        if effectPredicate(g, spec[s], r):
          used.incl(s)
          break search
      # XXX call graph analysis would be nice here!
      pushInfoContext(spec.info)
      localError(g.config, r.info, errGenerated, msg & typeToString(r.typ))
      popInfoContext()
  # hint about unnecessarily listed exception types:
  if hints:
    for s in 0 ..< spec.len:
      if not used.contains(s):
        message(g.config, spec[s].info, hintXDeclaredButNotUsed, renderTree(spec[s]))

proc checkMethodEffects*(g: ModuleGraph; disp, branch: PSym) =
  ## checks for consistent effects for multi methods.
  let actual = branch.typ.n.sons[0]
  if actual.len != effectListLen: return

  let p = disp.ast.sons[pragmasPos]
  let raisesSpec = effectSpec(p, wRaises)
  if not isNil(raisesSpec):
    checkRaisesSpec(g, raisesSpec, actual.sons[exceptionEffects],
      "can raise an unlisted exception: ", hints=off, subtypeRelation)
  let tagsSpec = effectSpec(p, wTags)
  if not isNil(tagsSpec):
    checkRaisesSpec(g, tagsSpec, actual.sons[tagEffects],
      "can have an unlisted effect: ", hints=off, subtypeRelation)
  if sfThread in disp.flags and notGcSafe(branch.typ):
    localError(g.config, branch.info, "base method is GC-safe, but '$1' is not" %
                                branch.name.s)
  if branch.typ.lockLevel > disp.typ.lockLevel:
    when true:
      message(g.config, branch.info, warnLockLevel,
        "base method has lock level $1, but dispatcher has $2" %
          [$branch.typ.lockLevel, $disp.typ.lockLevel])
    else:
      # XXX make this an error after bigbreak has been released:
      localError(g.config, branch.info,
        "base method has lock level $1, but dispatcher has $2" %
          [$branch.typ.lockLevel, $disp.typ.lockLevel])

proc setEffectsForProcType*(g: ModuleGraph; t: PType, n: PNode) =
  var effects = t.n.sons[0]
  if t.kind != tyProc or effects.kind != nkEffectList: return

  let
    raisesSpec = effectSpec(n, wRaises)
    tagsSpec = effectSpec(n, wTags)
  if not isNil(raisesSpec) or not isNil(tagsSpec):
    internalAssert g.config, effects.len == 0
    newSeq(effects.sons, effectListLen)
    if not isNil(raisesSpec):
      effects.sons[exceptionEffects] = raisesSpec
    if not isNil(tagsSpec):
      effects.sons[tagEffects] = tagsSpec

proc initEffects(g: ModuleGraph; effects: PNode; s: PSym; t: var TEffects) =
  newSeq(effects.sons, effectListLen)
  effects.sons[exceptionEffects] = newNodeI(nkArgList, s.info)
  effects.sons[tagEffects] = newNodeI(nkArgList, s.info)
  effects.sons[usesEffects] = ast.emptyNode
  effects.sons[writeEffects] = ast.emptyNode

  t.exc = effects.sons[exceptionEffects]
  t.tags = effects.sons[tagEffects]
  t.owner = s
  t.init = @[]
  t.guards.s = @[]
  t.guards.o = initOperators(g)
  t.locked = @[]
  t.graph = g
  t.config = g.config

proc trackProc*(g: ModuleGraph; s: PSym, body: PNode) =
  var effects = s.typ.n.sons[0]
  if effects.kind != nkEffectList: return
  # effects already computed?
  if sfForward in s.flags: return
  if effects.len == effectListLen: return

  var t: TEffects
  initEffects(g, effects, s, t)
  track(t, body)
  if not isEmptyType(s.typ.sons[0]) and
      {tfNeedsInit, tfNotNil} * s.typ.sons[0].flags != {} and
      s.kind in {skProc, skFunc, skConverter, skMethod}:
    var res = s.ast.sons[resultPos].sym # get result symbol
    if res.id notin t.init:
      message(g.config, body.info, warnProveInit, "result")
  let p = s.ast.sons[pragmasPos]
  let raisesSpec = effectSpec(p, wRaises)
  if not isNil(raisesSpec):
    checkRaisesSpec(g, raisesSpec, t.exc, "can raise an unlisted exception: ",
                    hints=on, subtypeRelation)
    # after the check, use the formal spec:
    effects.sons[exceptionEffects] = raisesSpec

  let tagsSpec = effectSpec(p, wTags)
  if not isNil(tagsSpec):
    checkRaisesSpec(g, tagsSpec, t.tags, "can have an unlisted effect: ",
                    hints=off, subtypeRelation)
    # after the check, use the formal spec:
    effects.sons[tagEffects] = tagsSpec

  if sfThread in s.flags and t.gcUnsafe:
    if optThreads in g.config.globalOptions and optThreadAnalysis in g.config.globalOptions:
      #localError(s.info, "'$1' is not GC-safe" % s.name.s)
      listGcUnsafety(s, onlyWarning=false, g.config)
    else:
      listGcUnsafety(s, onlyWarning=true, g.config)
      #localError(s.info, warnGcUnsafe2, s.name.s)
  if sfNoSideEffect in s.flags and t.hasSideEffect:
    when false:
      listGcUnsafety(s, onlyWarning=false, g.config)
    else:
      localError(g.config, s.info, "'$1' can have side effects" % s.name.s)
  if not t.gcUnsafe:
    s.typ.flags.incl tfGcSafe
  if not t.hasSideEffect and sfSideEffect notin s.flags:
    s.typ.flags.incl tfNoSideEffect
  if s.typ.lockLevel == UnspecifiedLockLevel:
    s.typ.lockLevel = t.maxLockLevel
  elif t.maxLockLevel > s.typ.lockLevel:
    #localError(s.info,
    message(g.config, s.info, warnLockLevel,
      "declared lock level is $1, but real lock level is $2" %
        [$s.typ.lockLevel, $t.maxLockLevel])
  when defined(useDfa):
    if s.kind == skFunc:
      dataflowAnalysis(s, body)
      when false: trackWrites(s, body)

proc trackTopLevelStmt*(g: ModuleGraph; module: PSym; n: PNode) =
  if n.kind in {nkPragma, nkMacroDef, nkTemplateDef, nkProcDef, nkFuncDef,
                nkTypeSection, nkConverterDef, nkMethodDef, nkIteratorDef}:
    return
  var effects = newNode(nkEffectList, n.info)
  var t: TEffects
  initEffects(g, effects, module, t)
  t.isToplevel = true
  track(t, n)