compiler/wordrecg.nim


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#
#
#           The Nim Compiler
#        (c) Copyright 2015 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

# This module contains a word recognizer, i.e. a simple
# procedure which maps special words to an enumeration.
# It is primarily needed because Pascal's case statement
# does not support strings. Without this the code would
# be slow and unreadable.

from strutils import cmpIgnoreStyle

# Keywords must be kept sorted and within a range

type
  TSpecialWord* = enum
    wInvalid,

    wAddr, wAnd, wAs, wAsm, wAtomic,
    wBind, wBlock, wBreak, wCase, wCast, wConcept, wConst,
    wContinue, wConverter, wDefer, wDiscard, wDistinct, wDiv, wDo,
    wElif, wElse, wEnd, wEnum, wExcept, wExport,
    wFinally, wFor, wFrom, wFunc, wGeneric, wIf, wImport, wIn,
    wInclude, wInterface, wIs, wIsnot, wIterator, wLet,
    wMacro, wMethod, wMixin, wMod, wNil,
    wNot, wNotin, wObject, wOf, wOr, wOut, wProc, wPtr, wRaise, wRef, wReturn,
    wShl, wShr, wStatic, wTemplate, wTry, wTuple, wType, wUsing, wVar,
    wWhen, wWhile, wWith, wWithout, wXor, wYield,

    wColon, wColonColon, wEquals, wDot, wDotDot,
    wStar, wMinus,
    wMagic, wThread, wFinal, wProfiler, wMemTracker, wObjChecks,
    wIntDefine, wStrDefine,

    wDestroy,

    wImmediate, wConstructor, wDestructor, wDelegator, wOverride,
    wImportCpp, wImportObjC,
    wImportCompilerProc,
    wImportc, wExportc, wExportNims, wIncompleteStruct, wRequiresInit,
    wAlign, wNodecl, wPure, wSideeffect, wHeader,
    wNosideeffect, wGcSafe, wNoreturn, wMerge, wLib, wDynlib,
    wCompilerproc, wProcVar, wBase, wUsed,
    wFatal, wError, wWarning, wHint, wLine, wPush, wPop, wDefine, wUndef,
    wLinedir, wStacktrace, wLinetrace, wLink, wCompile,
    wLinksys, wDeprecated, wVarargs, wCallconv, wBreakpoint, wDebugger,
    wNimcall, wStdcall, wCdecl, wSafecall, wSyscall, wInline, wNoInline,
    wFastcall, wClosure, wNoconv, wOn, wOff, wChecks, wRangechecks,
    wBoundchecks, wOverflowchecks, wNilchecks,
    wFloatchecks, wNanChecks, wInfChecks,
    wAssertions, wPatterns, wWarnings,
    wHints, wOptimization, wRaises, wWrites, wReads, wSize, wEffects, wTags,
    wDeadCodeElim, wSafecode, wNoForward, wNoRewrite,
    wPragma,
    wCompileTime, wNoInit,
    wPassc, wPassl, wBorrow, wDiscardable,
    wFieldChecks,
    wWatchPoint, wSubsChar,
    wAcyclic, wShallow, wUnroll, wLinearScanEnd, wComputedGoto,
    wInjectStmt, wExperimental,
    wWrite, wGensym, wInject, wDirty, wInheritable, wThreadVar, wEmit,
    wAsmNoStackFrame,
    wImplicitStatic, wGlobal, wCodegenDecl, wUnchecked, wGuard, wLocks,
    wPartial,

    wAuto, wBool, wCatch, wChar, wClass,
    wConst_cast, wDefault, wDelete, wDouble, wDynamic_cast,
    wExplicit, wExtern, wFalse, wFloat, wFriend,
    wGoto, wInt, wLong, wMutable, wNamespace, wNew, wOperator,
    wPrivate, wProtected, wPublic, wRegister, wReinterpret_cast,
    wShort, wSigned, wSizeof, wStatic_cast, wStruct, wSwitch,
    wThis, wThrow, wTrue, wTypedef, wTypeid, wTypename,
    wUnion, wPacked, wUnsigned, wVirtual, wVoid, wVolatile, wWchar_t,

    wAlignas, wAlignof, wConstexpr, wDecltype, wNullptr, wNoexcept,
    wThread_local, wStatic_assert, wChar16_t, wChar32_t,

    wStdIn, wStdOut, wStdErr,

    wInOut, wByCopy, wByRef, wOneWay,
    wBitsize,

  TSpecialWords* = set[TSpecialWord]

const
  oprLow* = ord(wColon)
  oprHigh* = ord(wDotDot)

  nimKeywordsLow* = ord(wAsm)
  nimKeywordsHigh* = ord(wYield)

  ccgKeywordsLow* = ord(wAuto)
  ccgKeywordsHigh* = ord(wOneWay)

  cppNimSharedKeywords* = {
    wAsm, wBreak, wCase, wConst, wContinue, wDo, wElse, wEnum, wExport,
    wFor, wIf, wReturn, wStatic, wTemplate, wTry, wWhile, wUsing}

  specialWords*: array[low(TSpecialWord)..high(TSpecialWord), string] = ["",

    "addr", "and", "as", "asm", "atomic",
    "bind", "block", "break", "case", "cast",
    "concept", "const", "continue", "converter",
    "defer", "discard", "distinct", "div", "do",
    "elif", "else", "end", "enum", "except", "export",
    "finally", "for", "from", "func", "generic", "if",
    "import", "in", "include", "interface", "is", "isnot", "iterator",
    "let",
    "macro", "method", "mixin", "mod", "nil", "not", "notin",
    "object", "of", "or",
    "out", "proc", "ptr", "raise", "ref", "return",
    "shl", "shr", "static",
    "template", "try", "tuple", "type", "using", "var",
    "when", "while", "with", "without", "xor",
    "yield",

    ":", "::", "=", ".", "..",
    "*", "-",
    "magic", "thread", "final", "profiler", "memtracker", "objchecks", "intdefine", "strdefine",

    "destroy",

    "immediate", "constructor", "destructor", "delegator", "override",
    "importcpp", "importobjc",
    "importcompilerproc", "importc", "exportc", "exportnims",
    "incompletestruct",
    "requiresinit", "align", "nodecl", "pure", "sideeffect",
    "header", "nosideeffect", "gcsafe", "noreturn", "merge", "lib", "dynlib",
    "compilerproc", "procvar", "base", "used",
    "fatal", "error", "warning", "hint", "line",
    "push", "pop", "define", "undef", "linedir", "stacktrace", "linetrace",
    "link", "compile", "linksys", "deprecated", "varargs",
    "callconv", "breakpoint", "debugger", "nimcall", "stdcall",
    "cdecl", "safecall", "syscall", "inline", "noinline", "fastcall", "closure",
    "noconv", "on", "off", "checks", "rangechecks", "boundchecks",
    "overflowchecks", "nilchecks",
    "floatchecks", "nanchecks", "infchecks",

    "assertions", "patterns", "warnings", "hints",
    "optimization", "raises", "writes", "reads", "size", "effects", "tags",
    "deadcodeelim", "safecode", "noforward", "norewrite",
    "pragma",
    "compiletime", "noinit",
    "passc", "passl", "borrow", "discardable", "fieldchecks",
    "watchpoint",
    "subschar", "acyclic", "shallow", "unroll", "linearscanend",
    "computedgoto", "injectstmt", "experimental",
    "write", "gensym", "inject", "dirty", "inheritable", "threadvar", "emit",
    "asmnostackframe", "implicitstatic", "global", "codegendecl", "unchecked",
    "guard", "locks", "partial",

    "auto", "bool", "catch", "char", "class",
    "const_cast", "default", "delete", "double",
    "dynamic_cast", "explicit", "extern", "false",
    "float", "friend", "goto", "int", "long", "mutable",
    "namespace", "new", "operator",
    "private", "protected", "public", "register", "reinterpret_cast",
    "short", "signed", "sizeof", "static_cast", "struct", "switch",
    "this", "throw", "true", "typedef", "typeid",
    "typename", "union", "packed", "unsigned", "virtual", "void", "volatile",
    "wchar_t",

    "alignas", "alignof", "constexpr", "decltype", "nullptr", "noexcept",
    "thread_local", "static_assert", "char16_t", "char32_t",

    "stdin", "stdout", "stderr",

    "inout", "bycopy", "byref", "oneway",
    "bitsize",
    ]

proc findStr*(a: openArray[string], s: string): int =
  for i in countup(low(a), high(a)):
    if cmpIgnoreStyle(a[i], s) == 0:
      return i
  result = - 1
#
#
#           The Nim Compiler
#        (c) Copyright 2013 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

## this module does the semantic checking of statements
#  included from sem.nim

const
  errNoSymbolToBorrowFromFound = "no symbol to borrow from found"
  errDiscardValueX = "value of type '$1' has to be discarded"
  errInvalidDiscard = "statement returns no value that can be discarded"
  errInvalidControlFlowX = "invalid control flow: $1"
  errSelectorMustBeOfCertainTypes = "selector must be of an ordinal type, float or string"
  errExprCannotBeRaised = "only a 'ref object' can be raised"
  errBreakOnlyInLoop = "'break' only allowed in loop construct"
  errExceptionAlreadyHandled = "exception already handled"
  errYieldNotAllowedHere = "'yield' only allowed in an iterator"
  errYieldNotAllowedInTryStmt = "'yield' cannot be used within 'try' in a non-inlined iterator"
  errInvalidNumberOfYieldExpr = "invalid number of 'yield' expressions"
  errCannotReturnExpr = "current routine cannot return an expression"
  errGenericLambdaNotAllowed = "A nested proc can have generic parameters only when " &
    "it is used as an operand to another routine and the types " &
    "of the generic paramers can be inferred from the expected signature."
  errCannotInferTypeOfTheLiteral = "cannot infer the type of the $1"
  errCannotInferReturnType = "cannot infer the return type of the proc"
  errCannotInferStaticParam = "cannot infer the value of the static param '$1'"
  errProcHasNoConcreteType = "'$1' doesn't have a concrete type, due to unspecified generic parameters."
  errLetNeedsInit = "'let' symbol requires an initialization"
  errThreadvarCannotInit = "a thread var cannot be initialized explicitly; this would only run for the main thread"
  errImplOfXexpected = "implementation of '$1' expected"
  errRecursiveDependencyX = "recursive dependency: '$1'"
  errPragmaOnlyInHeaderOfProcX = "pragmas are only allowed in the header of a proc; redefinition of $1"

var enforceVoidContext = PType(kind: tyStmt) # XXX global variable here

proc semDiscard(c: PContext, n: PNode): PNode =
  result = n
  checkSonsLen(n, 1, c.config)
  if n.sons[0].kind != nkEmpty:
    n.sons[0] = semExprWithType(c, n.sons[0])
    if isEmptyType(n.sons[0].typ) or n.sons[0].typ.kind == tyNone or n.sons[0].kind == nkTypeOfExpr:
      localError(c.config, n.info, errInvalidDiscard)

proc semBreakOrContinue(c: PContext, n: PNode): PNode =
  result = n
  checkSonsLen(n, 1, c.config)
  if n.sons[0].kind != nkEmpty:
    if n.kind != nkContinueStmt:
      var s: PSym
      case n.sons[0].kind
      of nkIdent: s = lookUp(c, n.sons[0])
      of nkSym: s = n.sons[0].sym
      else: illFormedAst(n, c.config)
      s = getGenSym(c, s)
      if s.kind == skLabel and s.owner.id == c.p.owner.id:
        var x = newSymNode(s)
        x.info = n.info
        incl(s.flags, sfUsed)
        n.sons[0] = x
        suggestSym(c.config, x.info, s, c.graph.usageSym)
        styleCheckUse(x.info, s)
      else:
        localError(c.config, n.info, errInvalidControlFlowX % s.name.s)
    else:
      localError(c.config, n.info, errGenerated, "'continue' cannot have a label")
  elif (c.p.nestedLoopCounter <= 0) and (c.p.nestedBlockCounter <= 0):
    localError(c.config, n.info, errInvalidControlFlowX %
               renderTree(n, {renderNoComments}))

proc semAsm(c: PContext, n: PNode): PNode =
  checkSonsLen(n, 2, c.config)
  var marker = pragmaAsm(c, n.sons[0])
  if marker == '\0': marker = '`' # default marker
  result = semAsmOrEmit(c, n, marker)

proc semWhile(c: PContext, n: PNode): PNode =
  result = n
  checkSonsLen(n, 2, c.config)
  openScope(c)
  n.sons[0] = forceBool(c, semExprWithType(c, n.sons[0]))
  inc(c.p.nestedLoopCounter)
  n.sons[1] = semStmt(c, n.sons[1])
  dec(c.p.nestedLoopCounter)
  closeScope(c)
  if n.sons[1].typ == enforceVoidContext:
    result.typ = enforceVoidContext

proc toCover(t: PType): BiggestInt =
  var t2 = skipTypes(t, abstractVarRange-{tyTypeDesc})
  if t2.kind == tyEnum and enumHasHoles(t2):
    result = sonsLen(t2.n)
  else:
    result = lengthOrd(skipTypes(t, abstractVar-{tyTypeDesc}))

proc semProc(c: PContext, n: PNode): PNode

proc semExprBranch(c: PContext, n: PNode): PNode =
  result = semExpr(c, n)
  if result.typ != nil:
    # XXX tyGenericInst here?
    if result.typ.kind in {tyVar, tyLent}: result = newDeref(result)

proc semExprBranchScope(c: PContext, n: PNode): PNode =
  openScope(c)
  result = semExprBranch(c, n)
  closeScope(c)

const
  skipForDiscardable = {nkIfStmt, nkIfExpr, nkCaseStmt, nkOfBranch,
    nkElse, nkStmtListExpr, nkTryStmt, nkFinally, nkExceptBranch,
    nkElifBranch, nkElifExpr, nkElseExpr, nkBlockStmt, nkBlockExpr}

proc implicitlyDiscardable(n: PNode): bool =
  var n = n
  while n.kind in skipForDiscardable: n = n.lastSon
  result = isCallExpr(n) and n.sons[0].kind == nkSym and
           sfDiscardable in n.sons[0].sym.flags

proc fixNilType(c: PContext; n: PNode) =
  if isAtom(n):
    if n.kind != nkNilLit and n.typ != nil:
      localError(c.config, n.info, errDiscardValueX % n.typ.typeToString)
  elif n.kind in {nkStmtList, nkStmtListExpr}:
    n.kind = nkStmtList
    for it in n: fixNilType(c, it)
  n.typ = nil

proc discardCheck(c: PContext, result: PNode) =
  if c.matchedConcept != nil: return
  if result.typ != nil and result.typ.kind notin {tyStmt, tyVoid}:
    if implicitlyDiscardable(result):
      var n = result
      result.typ = nil
      while n.kind in skipForDiscardable:
        n = n.lastSon
        n.typ = nil
    elif result.typ.kind != tyError and c.config.cmd != cmdInteractive:
      var n = result
      while n.kind in skipForDiscardable: n = n.lastSon
      var s = "expression '" & $n & "' is of type '" &
          result.typ.typeToString & "' and has to be discarded"
      if result.info.line != n.info.line or
          result.info.fileIndex != n.info.fileIndex:
        s.add "; start of expression here: " & $result.info
      if result.typ.kind == tyProc:
        s.add "; for a function call use ()"
      localError(c.config, n.info, s)

proc semIf(c: PContext, n: PNode): PNode =
  result = n
  var typ = commonTypeBegin
  var hasElse = false
  for i in countup(0, sonsLen(n) - 1):
    var it = n.sons[i]
    if it.len == 2:
      when newScopeForIf: openScope(c)
      it.sons[0] = forceBool(c, semExprWithType(c, it.sons[0]))
      when not newScopeForIf: openScope(c)
      it.sons[1] = semExprBranch(c, it.sons[1])
      typ = commonType(typ, it.sons[1])
      closeScope(c)
    elif it.len == 1:
      hasElse = true
      it.sons[0] = semExprBranchScope(c, it.sons[0])
      typ = commonType(typ, it.sons[0])
    else: illFormedAst(it, c.config)
  if isEmptyType(typ) or typ.kind in {tyNil, tyExpr} or not hasElse:
    for it in n: discardCheck(c, it.lastSon)
    result.kind = nkIfStmt
    # propagate any enforced VoidContext:
    if typ == enforceVoidContext: result.typ = enforceVoidContext
  else:
    for it in n:
      let j = it.len-1
      if not endsInNoReturn(it.sons[j]):
        it.sons[j] = fitNode(c, typ, it.sons[j], it.sons[j].info)
    result.kind = nkIfExpr
    result.typ = typ

proc semCase(c: PContext, n: PNode): PNode =
  result = n
  checkMinSonsLen(n, 2, c.config)
  openScope(c)
  n.sons[0] = semExprWithType(c, n.sons[0])
  var chckCovered = false
  var covered: BiggestInt = 0
  var typ = commonTypeBegin
  var hasElse = false
  let caseTyp = skipTypes(n.sons[0].typ, abstractVarRange-{tyTypeDesc})
  case caseTyp.kind
  of tyInt..tyInt64, tyChar, tyEnum, tyUInt..tyUInt32, tyBool:
    chckCovered = true
  of tyFloat..tyFloat128, tyString, tyError:
    discard
  else:
    localError(c.config, n.info, errSelectorMustBeOfCertainTypes)
    return
  for i in countup(1, sonsLen(n) - 1):
    var x = n.sons[i]
    when defined(nimsuggest):
      if c.config.ideCmd == ideSug and exactEquals(gTrackPos, x.info) and caseTyp.kind == tyEnum:
        suggestEnum(c, x, caseTyp)
    case x.kind
    of nkOfBranch:
      checkMinSonsLen(x, 2, c.config)
      semCaseBranch(c, n, x, i, covered)
      var last = sonsLen(x)-1
      x.sons[last] = semExprBranchScope(c, x.sons[last])
      typ = commonType(typ, x.sons[last])
    of nkElifBranch:
      chckCovered = false
      checkSonsLen(x, 2, c.config)
      when newScopeForIf: openScope(c)
      x.sons[0] = forceBool(c, semExprWithType(c, x.sons[0]))
      when not newScopeForIf: openScope(c)
      x.sons[1] = semExprBranch(c, x.sons[1])
      typ = commonType(typ, x.sons[1])
      closeScope(c)
    of nkElse:
      chckCovered = false
      checkSonsLen(x, 1, c.config)
      x.sons[0] = semExprBranchScope(c, x.sons[0])
      typ = commonType(typ, x.sons[0])
      hasElse = true
    else:
      illFormedAst(x, c.config)
  if chckCovered:
    if covered == toCover(n.sons[0].typ):
      hasElse = true
    else:
      localError(c.config, n.info, "not all cases are covered")
  closeScope(c)
  if isEmptyType(typ) or typ.kind in {tyNil, tyExpr} or not hasElse:
    for i in 1..n.len-1: discardCheck(c, n.sons[i].lastSon)
    # propagate any enforced VoidContext:
    if typ == enforceVoidContext:
      result.typ = enforceVoidContext
  else:
    for i in 1..n.len-1:
      var it = n.sons[i]
      let j = it.len-1
      if not endsInNoReturn(it.sons[j]):
        it.sons[j] = fitNode(c, typ, it.sons[j], it.sons[j].info)
    result.typ = typ

proc semTry(c: PContext, n: PNode): PNode =

  var check = initIntSet()
  template semExceptBranchType(typeNode: PNode): bool =
    # returns true if exception type is imported type
    let typ = semTypeNode(c, typeNode, nil).toObject()
    var is_imported = false
    if isImportedException(typ, c.config):
      is_imported = true
    elif not isException(typ):
      localError(c.config, typeNode.info, errExprCannotBeRaised)

    if containsOrIncl(check, typ.id):
      localError(c.config, typeNode.info, errExceptionAlreadyHandled)
    typeNode = newNodeIT(nkType, typeNode.info, typ)
    is_imported

  result = n
  inc c.p.inTryStmt
  checkMinSonsLen(n, 2, c.config)

  var typ = commonTypeBegin
  n[0] = semExprBranchScope(c, n[0])
  typ = commonType(typ, n[0].typ)

  var last = sonsLen(n) - 1
  for i in countup(1, last):
    let a = n.sons[i]
    checkMinSonsLen(a, 1, c.config)
    openScope(c)
    if a.kind == nkExceptBranch:

      if a.len == 2 and a[0].kind == nkBracket:
        # rewrite ``except [a, b, c]: body`` -> ```except a, b, c: body```
        a.sons[0..0] = a[0].sons

      if a.len == 2 and a[0].isInfixAs():
        # support ``except Exception as ex: body``
        let is_imported = semExceptBranchType(a[0][1])
        let symbol = newSymG(skLet, a[0][2], c)
        symbol.typ = if is_imported: a[0][1].typ
                     else: a[0][1].typ.toRef()
        addDecl(c, symbol)
        # Overwrite symbol in AST with the symbol in the symbol table.
        a[0][2] = newSymNode(symbol, a[0][2].info)

      else:
        # support ``except KeyError, ValueError, ... : body``
        var is_native, is_imported: bool
        for j in 0..a.len-2:
          let tmp = semExceptBranchType(a[j])
          if tmp: is_imported = true
          else: is_native = true

        if is_native and is_imported:
          localError(c.config, a[0].info, "Mix of imported and native exception types is not allowed in one except branch")

    elif a.kind != nkFinally:
      illFormedAst(n, c.config)

    # last child of an nkExcept/nkFinally branch is a statement:
    a[^1] = semExprBranchScope(c, a[^1])
    if a.kind != nkFinally: typ = commonType(typ, a[^1])
    else: dec last
    closeScope(c)

  dec c.p.inTryStmt
  if isEmptyType(typ) or typ.kind in {tyNil, tyExpr}:
    discardCheck(c, n.sons[0])
    for i in 1..n.len-1: discardCheck(c, n.sons[i].lastSon)
    if typ == enforceVoidContext:
      result.typ = enforceVoidContext
  else:
    if n.lastSon.kind == nkFinally: discardCheck(c, n.lastSon.lastSon)
    n.sons[0] = fitNode(c, typ, n.sons[0], n.sons[0].info)
    for i in 1..last:
      var it = n.sons[i]
      let j = it.len-1
      it.sons[j] = fitNode(c, typ, it.sons[j], it.sons[j].info)
    result.typ = typ

proc fitRemoveHiddenConv(c: PContext, typ: PType, n: PNode): PNode =
  result = fitNode(c, typ, n, n.info)
  if result.kind in {nkHiddenStdConv, nkHiddenSubConv}:
    let r1 = result.sons[1]
    if r1.kind in {nkCharLit..nkUInt64Lit} and typ.skipTypes(abstractRange).kind in {tyFloat..tyFloat128}:
      result = newFloatNode(nkFloatLit, BiggestFloat r1.intVal)
      result.info = n.info
      result.typ = typ
    else:
      changeType(c, r1, typ, check=true)
      result = r1
  elif not sameType(result.typ, typ):
    changeType(c, result, typ, check=false)

proc findShadowedVar(c: PContext, v: PSym): PSym =
  for scope in walkScopes(c.currentScope.parent):
    if scope == c.topLevelScope: break
    let shadowed = strTableGet(scope.symbols, v.name)
    if shadowed != nil and shadowed.kind in skLocalVars:
      return shadowed

proc identWithin(n: PNode, s: PIdent): bool =
  for i in 0 .. n.safeLen-1:
    if identWithin(n.sons[i], s): return true
  result = n.kind == nkSym and n.sym.name.id == s.id

proc semIdentDef(c: PContext, n: PNode, kind: TSymKind): PSym =
  if isTopLevel(c):
    result = semIdentWithPragma(c, kind, n, {sfExported})
    incl(result.flags, sfGlobal)
    #if kind in {skVar, skLet}:
    #  echo "global variable here ", n.info, " ", result.name.s
  else:
    result = semIdentWithPragma(c, kind, n, {})
    if result.owner.kind == skModule:
      incl(result.flags, sfGlobal)
  suggestSym(c.config, n.info, result, c.graph.usageSym)
  styleCheckDef(result)

proc checkNilable(c: PContext; v: PSym) =
  if {sfGlobal, sfImportC} * v.flags == {sfGlobal} and
      {tfNotNil, tfNeedsInit} * v.typ.flags != {}:
    if v.ast.isNil:
      message(c.config, v.info, warnProveInit, v.name.s)
    elif tfNotNil in v.typ.flags and tfNotNil notin v.ast.typ.flags:
      message(c.config, v.info, warnProveInit, v.name.s)

include semasgn

proc addToVarSection(c: PContext; result: PNode; orig, identDefs: PNode) =
  let L = identDefs.len
  let value = identDefs[L-1]
  if result.kind == nkStmtList:
    let o = copyNode(orig)
    o.add identDefs
    result.add o
  else:
    result.add identDefs

proc isDiscardUnderscore(v: PSym): bool =
  if v.name.s == "_":
    v.flags.incl(sfGenSym)
    result = true

proc semUsing(c: PContext; n: PNode): PNode =
  result = c.graph.emptyNode
  if not isTopLevel(c): localError(c.config, n.info, errXOnlyAtModuleScope % "using")
  for i in countup(0, sonsLen(n)-1):
    var a = n.sons[i]
    if c.config.cmd == cmdIdeTools: suggestStmt(c, a)
    if a.kind == nkCommentStmt: continue
    if a.kind notin {nkIdentDefs, nkVarTuple, nkConstDef}: illFormedAst(a, c.config)
    checkMinSonsLen(a, 3, c.config)
    var length = sonsLen(a)
    if a.sons[length-2].kind != nkEmpty:
      let typ = semTypeNode(c, a.sons[length-2], nil)
      for j in countup(0, length-3):
        let v = semIdentDef(c, a.sons[j], skParam)
        v.typ = typ
        strTableIncl(c.signatures, v)
    else:
      localError(c.config, a.info, "'using' section must have a type")
    var def: PNode
    if a.sons[length-1].kind != nkEmpty:
      localError(c.config, a.info, "'using' sections cannot contain assignments")

proc hasEmpty(typ: PType): bool =
  if typ.kind in {tySequence, tyArray, tySet}:
    result = typ.lastSon.kind == tyEmpty
  elif typ.kind == tyTuple:
    for s in typ.sons:
      result = result or hasEmpty(s)

proc makeDeref(n: PNode): PNode =
  var t = n.typ
  if t.kind in tyUserTypeClasses and t.isResolvedUserTypeClass:
    t = t.lastSon
  t = skipTypes(t, {tyGenericInst, tyAlias, tySink})
  result = n
  if t.kind in {tyVar, tyLent}:
    result = newNodeIT(nkHiddenDeref, n.info, t.sons[0])
    addSon(result, n)
    t = skipTypes(t.sons[0], {tyGenericInst, tyAlias, tySink})
  while t.kind in {tyPtr, tyRef}:
    var a = result
    let baseTyp = t.lastSon
    result = newNodeIT(nkHiddenDeref, n.info, baseTyp)
    addSon(result, a)
    t = skipTypes(baseTyp, {tyGenericInst, tyAlias, tySink})

proc fillPartialObject(c: PContext; n: PNode; typ: PType) =
  if n.len == 2:
    let x = semExprWithType(c, n[0])
    let y = considerQuotedIdent(c.config, n[1])
    let obj = x.typ.skipTypes(abstractPtrs)
    if obj.kind == tyObject and tfPartial in obj.flags:
      let field = newSym(skField, getIdent(y.s), obj.sym, n[1].info)
      field.typ = skipIntLit(typ)
      field.position = sonsLen(obj.n)
      addSon(obj.n, newSymNode(field))
      n.sons[0] = makeDeref x
      n.sons[1] = newSymNode(field)
      n.typ = field.typ
    else:
      localError(c.config, n.info, "implicit object field construction " &
        "requires a .partial object, but got " & typeToString(obj))
  else:
    localError(c.config, n.info, "nkDotNode requires 2 children")

proc setVarType(c: PContext; v: PSym, typ: PType) =
  if v.typ != nil and not sameTypeOrNil(v.typ, typ):
    localError(c.config, v.info, "inconsistent typing for reintroduced symbol '" &
        v.name.s & "': previous type was: " & typeToString(v.typ) &
        "; new type is: " & typeToString(typ))
  v.typ = typ

proc semVarOrLet(c: PContext, n: PNode, symkind: TSymKind): PNode =
  var b: PNode
  result = copyNode(n)
  var hasCompileTime = false
  for i in countup(0, sonsLen(n)-1):
    var a = n.sons[i]
    if c.config.cmd == cmdIdeTools: suggestStmt(c, a)
    if a.kind == nkCommentStmt: continue
    if a.kind notin {nkIdentDefs, nkVarTuple, nkConstDef}: illFormedAst(a, c.config)
    checkMinSonsLen(a, 3, c.config)
    var length = sonsLen(a)
    var typ: PType
    if a.sons[length-2].kind != nkEmpty:
      typ = semTypeNode(c, a.sons[length-2], nil)
    else:
      typ = nil
    var def: PNode = c.graph.emptyNode
    if a.sons[length-1].kind != nkEmpty:
      def = semExprWithType(c, a.sons[length-1], {efAllowDestructor})
      if def.typ.kind == tyTypeDesc and c.p.owner.kind != skMacro:
        # prevent the all too common 'var x = int' bug:
        localError(c.config, def.info, "'typedesc' metatype is not valid here; typed '=' instead of ':'?")
        def.typ = errorType(c)
      if typ != nil:
        if typ.isMetaType:
          def = inferWithMetatype(c, typ, def)
          typ = def.typ
        else:
          # BUGFIX: ``fitNode`` is needed here!
          # check type compatibility between def.typ and typ
          def = fitNode(c, typ, def, def.info)
          #changeType(def.skipConv, typ, check=true)
      else:
        typ = skipIntLit(def.typ)
        if typ.kind in tyUserTypeClasses and typ.isResolvedUserTypeClass:
          typ = typ.lastSon
        if hasEmpty(typ):
          localError(c.config, def.info, errCannotInferTypeOfTheLiteral %
                     ($typ.kind).substr(2).toLowerAscii)
        elif typ.kind == tyProc and tfUnresolved in typ.flags:
          localError(c.config, def.info, errProcHasNoConcreteType % def.renderTree)
    else:
      if symkind == skLet: localError(c.config, a.info, errLetNeedsInit)

    # this can only happen for errornous var statements:
    if typ == nil: continue
    typeAllowedCheck(c.config, a.info, typ, symkind, if c.matchedConcept != nil: {taConcept} else: {})
    liftTypeBoundOps(c, typ, a.info)
    var tup = skipTypes(typ, {tyGenericInst, tyAlias, tySink})
    if a.kind == nkVarTuple:
      if tup.kind != tyTuple:
        localError(c.config, a.info, errXExpected, "tuple")
      elif length-2 != sonsLen(tup):
        localError(c.config, a.info, errWrongNumberOfVariables)
      b = newNodeI(nkVarTuple, a.info)
      newSons(b, length)
      b.sons[length-2] = a.sons[length-2] # keep type desc for doc generator
      b.sons[length-1] = def
      addToVarSection(c, result, n, b)
    elif tup.kind == tyTuple and def.kind in {nkPar, nkTupleConstr} and
        a.kind == nkIdentDefs and a.len > 3:
      message(c.config, a.info, warnEachIdentIsTuple)

    for j in countup(0, length-3):
      if a[j].kind == nkDotExpr:
        fillPartialObject(c, a[j],
          if a.kind != nkVarTuple: typ else: tup.sons[j])
        addToVarSection(c, result, n, a)
        continue
      var v = semIdentDef(c, a.sons[j], symkind)
      if sfGenSym notin v.flags and not isDiscardUnderscore(v):
        addInterfaceDecl(c, v)
      when oKeepVariableNames:
        if c.inUnrolledContext > 0: v.flags.incl(sfShadowed)
        else:
          let shadowed = findShadowedVar(c, v)
          if shadowed != nil:
            shadowed.flags.incl(sfShadowed)
            if shadowed.kind == skResult and sfGenSym notin v.flags:
              message(c.config, a.info, warnResultShadowed)
            # a shadowed variable is an error unless it appears on the right
            # side of the '=':
            if warnShadowIdent in c.config.notes and not identWithin(def, v.name):
              message(c.config, a.info, warnShadowIdent, v.name.s)
      if a.kind != nkVarTuple:
        if def.kind != nkEmpty:
          # this is needed for the evaluation pass and for the guard checking:
          v.ast = def
          if sfThread in v.flags: localError(c.config, def.info, errThreadvarCannotInit)
        setVarType(c, v, typ)
        b = newNodeI(nkIdentDefs, a.info)
        if importantComments(c.config):
          # keep documentation information:
          b.comment = a.comment
        addSon(b, newSymNode(v))
        addSon(b, a.sons[length-2])      # keep type desc for doc generator
        addSon(b, copyTree(def))
        addToVarSection(c, result, n, b)
      else:
        if def.kind in {nkPar, nkTupleConstr}: v.ast = def[j]
        # bug #7663, for 'nim check' this can be a non-tuple:
        if tup.kind == tyTuple: setVarType(c, v, tup.sons[j])
        else: v.typ = tup
        b.sons[j] = newSymNode(v)
      checkNilable(c, v)
      if sfCompileTime in v.flags: hasCompileTime = true
  if hasCompileTime:
    vm.setupCompileTimeVar(c.module, c.cache, c.graph, result)

proc semConst(c: PContext, n: PNode): PNode =
  result = copyNode(n)
  for i in countup(0, sonsLen(n) - 1):
    var a = n.sons[i]
    if c.config.cmd == cmdIdeTools: suggestStmt(c, a)
    if a.kind == nkCommentStmt: continue
    if a.kind != nkConstDef: illFormedAst(a, c.config)
    checkSonsLen(a, 3, c.config)
    var v = semIdentDef(c, a.sons[0], skConst)
    var typ: PType = nil
    if a.sons[1].kind != nkEmpty: typ = semTypeNode(c, a.sons[1], nil)

    var def = semConstExpr(c, a.sons[2])
    if def == nil:
      localError(c.config, a.sons[2].info, errConstExprExpected)
      continue
    # check type compatibility between def.typ and typ:
    if typ != nil:
      def = fitRemoveHiddenConv(c, typ, def)
    else:
      typ = def.typ
    if typ == nil:
      localError(c.config, a.sons[2].info, errConstExprExpected)
      continue
    if typeAllowed(typ, skConst) != nil and def.kind != nkNilLit:
      localError(c.config, a.info, "invalid type for const: " & typeToString(typ))
      continue
    setVarType(c, v, typ)
    v.ast = def               # no need to copy
    if sfGenSym notin v.flags: addInterfaceDecl(c, v)
    var b = newNodeI(nkConstDef, a.info)
    if importantComments(c.config): b.comment = a.comment
    addSon(b, newSymNode(v))
    addSon(b, a.sons[1])
    addSon(b, copyTree(def))
    addSon(result, b)

include semfields

proc addForVarDecl(c: PContext, v: PSym) =
  if warnShadowIdent in c.config.notes:
    let shadowed = findShadowedVar(c, v)
    if shadowed != nil:
      # XXX should we do this here?
      #shadowed.flags.incl(sfShadowed)
      message(c.config, v.info, warnShadowIdent, v.name.s)
  addDecl(c, v)

proc symForVar(c: PContext, n: PNode): PSym =
  let m = if n.kind == nkPragmaExpr: n.sons[0] else: n
  result = newSymG(skForVar, m, c)
  styleCheckDef(result)

proc semForVars(c: PContext, n: PNode): PNode =
  result = n
  var length = sonsLen(n)
  let iterBase = n.sons[length-2].typ
  var iter = skipTypes(iterBase, {tyGenericInst, tyAlias, tySink})
  # length == 3 means that there is one for loop variable
  # and thus no tuple unpacking:
  if iter.kind != tyTuple or length == 3:
    if length == 3:
      var v = symForVar(c, n.sons[0])
      if getCurrOwner(c).kind == skModule: incl(v.flags, sfGlobal)
      # BUGFIX: don't use `iter` here as that would strip away
      # the ``tyGenericInst``! See ``tests/compile/tgeneric.nim``
      # for an example:
      v.typ = iterBase
      n.sons[0] = newSymNode(v)
      if sfGenSym notin v.flags: addForVarDecl(c, v)
    else:
      localError(c.config, n.info, errWrongNumberOfVariables)
  elif length-2 != sonsLen(iter):
    localError(c.config, n.info, errWrongNumberOfVariables)
  else:
    for i in countup(0, length - 3):
      var v = symForVar(c, n.sons[i])
      if getCurrOwner(c).kind == skModule: incl(v.flags, sfGlobal)
      v.typ = iter.sons[i]
      n.sons[i] = newSymNode(v)
      if sfGenSym notin v.flags and not isDiscardUnderscore(v):
        addForVarDecl(c, v)
  inc(c.p.nestedLoopCounter)
  openScope(c)
  n.sons[length-1] = semStmt(c, n.sons[length-1])
  closeScope(c)
  dec(c.p.nestedLoopCounter)

proc implicitIterator(c: PContext, it: string, arg: PNode): PNode =
  result = newNodeI(nkCall, arg.info)
  result.add(newIdentNode(it.getIdent, arg.info))
  if arg.typ != nil and arg.typ.kind in {tyVar, tyLent}:
    result.add newDeref(arg)
  else:
    result.add arg
  result = semExprNoDeref(c, result, {efWantIterator})

proc isTrivalStmtExpr(n: PNode): bool =
  for i in 0 .. n.len-2:
    if n[i].kind notin {nkEmpty, nkCommentStmt}:
      return false
  result = true

proc handleForLoopMacro(c: PContext; n: PNode): PNode =
  let iterExpr = n[^2]
  if iterExpr.kind in nkCallKinds:
    # we transform
    # n := for a, b, c in m(x, y, z): Y
    # to
    # m(n)
    let forLoopStmt = magicsys.getCompilerProc(c.graph, "ForLoopStmt")
    if forLoopStmt == nil: return

    let headSymbol = iterExpr[0]
    var o: TOverloadIter
    var match: PSym = nil
    var symx = initOverloadIter(o, c, headSymbol)
    while symx != nil:
      if symx.kind in {skTemplate, skMacro}:
        if symx.typ.len == 2 and symx.typ[1] == forLoopStmt.typ:
          if match == nil:
            match = symx
          else:
            localError(c.config, n.info, errAmbiguousCallXYZ % [
              getProcHeader(match), getProcHeader(symx), $iterExpr])
      symx = nextOverloadIter(o, c, headSymbol)

    if match == nil: return
    var callExpr = newNodeI(nkCall, n.info)
    callExpr.add newSymNode(match)
    callExpr.add n
    case match.kind
    of skMacro: result = semMacroExpr(c, callExpr, callExpr, match, {})
    of skTemplate: result = semTemplateExpr(c, callExpr, match, {})
    else: result = nil

proc semFor(c: PContext, n: PNode): PNode =
  checkMinSonsLen(n, 3, c.config)
  var length = sonsLen(n)
  result = handleForLoopMacro(c, n)
  if result != nil: return result
  openScope(c)
  result = n
  n.sons[length-2] = semExprNoDeref(c, n.sons[length-2], {efWantIterator})
  var call = n.sons[length-2]
  if call.kind == nkStmtListExpr and isTrivalStmtExpr(call):
    call = call.lastSon
    n.sons[length-2] = call
  let isCallExpr = call.kind in nkCallKinds
  if isCallExpr and call[0].kind == nkSym and
      call[0].sym.magic in {mFields, mFieldPairs, mOmpParFor}:
    if call.sons[0].sym.magic == mOmpParFor:
      result = semForVars(c, n)
      result.kind = nkParForStmt
    else:
      result = semForFields(c, n, call.sons[0].sym.magic)
  elif isCallExpr and call.sons[0].typ.callConv == ccClosure and
      tfIterator in call.sons[0].typ.flags:
    # first class iterator:
    result = semForVars(c, n)
  elif not isCallExpr or call.sons[0].kind != nkSym or
      call.sons[0].sym.kind != skIterator:
    if length == 3:
      n.sons[length-2] = implicitIterator(c, "items", n.sons[length-2])
    elif length == 4:
      n.sons[length-2] = implicitIterator(c, "pairs", n.sons[length-2])
    else:
      localError(c.config, n.sons[length-2].info, "iterator within for loop context expected")
    result = semForVars(c, n)
  else:
    result = semForVars(c, n)
  # propagate any enforced VoidContext:
  if n.sons[length-1].typ == enforceVoidContext:
    result.typ = enforceVoidContext
  closeScope(c)

proc semRaise(c: PContext, n: PNode): PNode =
  result = n
  checkSonsLen(n, 1, c.config)
  if n[0].kind != nkEmpty:
    n[0] = semExprWithType(c, n[0])
    let typ = n[0].typ
    if not isImportedException(typ, c.config):
      if typ.kind != tyRef or typ.lastSon.kind != tyObject:
        localError(c.config, n.info, errExprCannotBeRaised)
      if not isException(typ.lastSon):
        localError(c.config, n.info, "raised object of type $1 does not inherit from Exception",
                          [typeToString(typ)])

proc addGenericParamListToScope(c: PContext, n: PNode) =
  if n.kind != nkGenericParams: illFormedAst(n, c.config)
  for i in countup(0, sonsLen(n)-1):
    var a = n.sons[i]
    if a.kind == nkSym: addDecl(c, a.sym)
    else: illFormedAst(a, c.config)

proc typeSectionTypeName(c: PContext; n: PNode): PNode =
  if n.kind == nkPragmaExpr:
    if n.len == 0: illFormedAst(n, c.config)
    result = n.sons[0]
  else:
    result = n
  if result.kind != nkSym: illFormedAst(n, c.config)


proc typeSectionLeftSidePass(c: PContext, n: PNode) =
  # process the symbols on the left side for the whole type section, before
  # we even look at the type definitions on the right
  for i in countup(0, sonsLen(n) - 1):
    var a = n.sons[i]
    when defined(nimsuggest):
      if c.config.cmd == cmdIdeTools:
        inc c.inTypeContext
        suggestStmt(c, a)
        dec c.inTypeContext
    if a.kind == nkCommentStmt: continue
    if a.kind != nkTypeDef: illFormedAst(a, c.config)
    checkSonsLen(a, 3, c.config)
    let name = a.sons[0]
    var s: PSym
    if name.kind == nkDotExpr and a[2].kind == nkObjectTy:
      let pkgName = considerQuotedIdent(c.config, name[0])
      let typName = considerQuotedIdent(c.config, name[1])
      let pkg = c.graph.packageSyms.strTableGet(pkgName)
      if pkg.isNil or pkg.kind != skPackage:
        localError(c.config, name.info, "unknown package name: " & pkgName.s)
      else:
        let typsym = pkg.tab.strTableGet(typName)
        if typsym.isNil:
          s = semIdentDef(c, name[1], skType)
          s.typ = newTypeS(tyObject, c)
          s.typ.sym = s
          s.flags.incl sfForward
          pkg.tab.strTableAdd s
          addInterfaceDecl(c, s)
        elif typsym.kind == skType and sfForward in typsym.flags:
          s = typsym
          addInterfaceDecl(c, s)
        else:
          localError(c.config, name.info, typsym.name.s & " is not a type that can be forwarded")
          s = typsym
    else:
      s = semIdentDef(c, name, skType)
      s.typ = newTypeS(tyForward, c)
      s.typ.sym = s             # process pragmas:
      if name.kind == nkPragmaExpr:
        pragma(c, s, name.sons[1], typePragmas)
      if sfForward in s.flags:
        # check if the symbol already exists:
        let pkg = c.module.owner
        if not isTopLevel(c) or pkg.isNil:
          localError(c.config, name.info, "only top level types in a package can be 'package'")
        else:
          let typsym = pkg.tab.strTableGet(s.name)
          if typsym != nil:
            if sfForward notin typsym.flags or sfNoForward notin typsym.flags:
              typeCompleted(typsym)
              typsym.info = s.info
            else:
              localError(c.config, name.info, "cannot complete type '" & s.name.s & "' twice; " &
                      "previous type completion was here: " & $typsym.info)
            s = typsym
      # add it here, so that recursive types are possible:
      if sfGenSym notin s.flags: addInterfaceDecl(c, s)

    if name.kind == nkPragmaExpr:
      a.sons[0].sons[0] = newSymNode(s)
    else:
      a.sons[0] = newSymNode(s)

proc checkCovariantParamsUsages(c: PContext; genericType: PType) =
  var body = genericType[^1]

  proc traverseSubTypes(c: PContext; t: PType): bool =
    template error(msg) = localError(c.config, genericType.sym.info, msg)
    result = false
    template subresult(r) =
      let sub = r
      result = result or sub

    case t.kind
    of tyGenericParam:
      t.flags.incl tfWeakCovariant
      return true
    of tyObject:
      for field in t.n:
        subresult traverseSubTypes(c, field.typ)
    of tyArray:
      return traverseSubTypes(c, t[1])
    of tyProc:
      for subType in t.sons:
        if subType != nil:
          subresult traverseSubTypes(c, subType)
      if result:
        error("non-invariant type param used in a proc type: " & $t)
    of tySequence:
      return traverseSubTypes(c, t[0])
    of tyGenericInvocation:
      let targetBody = t[0]
      for i in 1 ..< t.len:
        let param = t[i]
        if param.kind == tyGenericParam:
          if tfCovariant in param.flags:
            let formalFlags = targetBody[i-1].flags
            if tfCovariant notin formalFlags:
              error("covariant param '" & param.sym.name.s &
                    "' used in a non-covariant position")
            elif tfWeakCovariant in formalFlags:
              param.flags.incl tfWeakCovariant
            result = true
          elif tfContravariant in param.flags:
            let formalParam = targetBody[i-1].sym
            if tfContravariant notin formalParam.typ.flags:
              error("contravariant param '" & param.sym.name.s &
                    "' used in a non-contravariant position")
            result = true
        else:
          subresult traverseSubTypes(c, param)
    of tyAnd, tyOr, tyNot, tyStatic, tyBuiltInTypeClass, tyCompositeTypeClass:
      error("non-invariant type parameters cannot be used with types such '" & $t & "'")
    of tyUserTypeClass, tyUserTypeClassInst:
      error("non-invariant type parameters are not supported in concepts")
    of tyTuple:
      for fieldType in t.sons:
        subresult traverseSubTypes(c, fieldType)
    of tyPtr, tyRef, tyVar, tyLent:
      if t.base.kind == tyGenericParam: return true
      return traverseSubTypes(c, t.base)
    of tyDistinct, tyAlias, tySink:
      return traverseSubTypes(c, t.lastSon)
    of tyGenericInst:
      internalAssert c.config, false
    else:
      discard
  discard traverseSubTypes(c, body)

proc typeSectionRightSidePass(c: PContext, n: PNode) =
  for i in countup(0, sonsLen(n) - 1):
    var a = n.sons[i]
    if a.kind == nkCommentStmt: continue
    if a.kind != nkTypeDef: illFormedAst(a, c.config)
    checkSonsLen(a, 3, c.config)
    let name = typeSectionTypeName(c, a.sons[0])
    var s = name.sym
    if s.magic == mNone and a.sons[2].kind == nkEmpty:
      localError(c.config, a.info, errImplOfXexpected % s.name.s)
    if s.magic != mNone: processMagicType(c, s)
    if a.sons[1].kind != nkEmpty:
      # We have a generic type declaration here. In generic types,
      # symbol lookup needs to be done here.
      openScope(c)
      pushOwner(c, s)
      if s.magic == mNone: s.typ.kind = tyGenericBody
      # XXX for generic type aliases this is not correct! We need the
      # underlying Id really:
      #
      # type
      #   TGObj[T] = object
      #   TAlias[T] = TGObj[T]
      #
      s.typ.n = semGenericParamList(c, a.sons[1], s.typ)
      a.sons[1] = s.typ.n
      s.typ.size = -1 # could not be computed properly
      # we fill it out later. For magic generics like 'seq', it won't be filled
      # so we use tyNone instead of nil to not crash for strange conversions
      # like: mydata.seq
      rawAddSon(s.typ, newTypeS(tyNone, c))
      s.ast = a
      inc c.inGenericContext
      var body = semTypeNode(c, a.sons[2], nil)
      dec c.inGenericContext
      if body != nil:
        body.sym = s
        body.size = -1 # could not be computed properly
        s.typ.sons[sonsLen(s.typ) - 1] = body
        if tfCovariant in s.typ.flags:
          checkCovariantParamsUsages(c, s.typ)
          # XXX: This is a temporary limitation:
          # The codegen currently produces various failures with
          # generic imported types that have fields, but we need
          # the fields specified in order to detect weak covariance.
          # The proper solution is to teach the codegen how to handle
          # such types, because this would offer various interesting
          # possibilities such as instantiating C++ generic types with
          # garbage collected Nim types.
          if sfImportc in s.flags:
            var body = s.typ.lastSon
            if body.kind == tyObject:
              # erases all declared fields
              body.n.sons = nil

      popOwner(c)
      closeScope(c)
    elif a.sons[2].kind != nkEmpty:
      # process the type's body:
      pushOwner(c, s)
      var t = semTypeNode(c, a.sons[2], s.typ)
      if s.typ == nil:
        s.typ = t
      elif t != s.typ and (s.typ == nil or s.typ.kind != tyAlias):
        # this can happen for e.g. tcan_alias_specialised_generic:
        assignType(s.typ, t)
        #debug s.typ
      s.ast = a
      popOwner(c)
    let aa = a.sons[2]
    if aa.kind in {nkRefTy, nkPtrTy} and aa.len == 1 and
       aa.sons[0].kind == nkObjectTy:
      # give anonymous object a dummy symbol:
      var st = s.typ
      if st.kind == tyGenericBody: st = st.lastSon
      internalAssert c.config, st.kind in {tyPtr, tyRef}
      internalAssert c.config, st.lastSon.sym == nil
      incl st.flags, tfRefsAnonObj
      let obj = newSym(skType, getIdent(s.name.s & ":ObjectType"),
                              getCurrOwner(c), s.info)
      obj.typ = st.lastSon
      st.lastSon.sym = obj


proc checkForMetaFields(c: PContext; n: PNode) =
  template checkMeta(t) =
    if t != nil and t.isMetaType and tfGenericTypeParam notin t.flags:
      localError(c.config, n.info, errTIsNotAConcreteType % t.typeToString)

  if n.isNil: return
  case n.kind
  of nkRecList, nkRecCase:
    for s in n: checkForMetaFields(c, s)
  of nkOfBranch, nkElse:
    checkForMetaFields(c, n.lastSon)
  of nkSym:
    let t = n.sym.typ
    case t.kind
    of tySequence, tySet, tyArray, tyOpenArray, tyVar, tyLent, tyPtr, tyRef,
       tyProc, tyGenericInvocation, tyGenericInst, tyAlias, tySink:
      let start = int ord(t.kind in {tyGenericInvocation, tyGenericInst})
      for i in start ..< t.sons.len:
        checkMeta(t.sons[i])
    else:
      checkMeta(t)
  else:
    internalAssert c.config, false

proc typeSectionFinalPass(c: PContext, n: PNode) =
  for i in countup(0, sonsLen(n) - 1):
    var a = n.sons[i]
    if a.kind == nkCommentStmt: continue
    let name = typeSectionTypeName(c, a.sons[0])
    var s = name.sym
    # compute the type's size and check for illegal recursions:
    if a.sons[1].kind == nkEmpty:
      var x = a[2]
      while x.kind in {nkStmtList, nkStmtListExpr} and x.len > 0:
        x = x.lastSon
      if x.kind notin {nkObjectTy, nkDistinctTy, nkEnumTy, nkEmpty} and
          s.typ.kind notin {tyObject, tyEnum}:
        # type aliases are hard:
        var t = semTypeNode(c, x, nil)
        assert t != nil
        if s.typ != nil and s.typ.kind notin {tyAlias, tySink}:
          if t.kind in {tyProc, tyGenericInst} and not t.isMetaType:
            assignType(s.typ, t)
            s.typ.id = t.id
          elif t.kind in {tyObject, tyEnum, tyDistinct}:
            assert s.typ != nil
            assignType(s.typ, t)
            s.typ.id = t.id     # same id
      checkConstructedType(c.config, s.info, s.typ)
      if s.typ.kind in {tyObject, tyTuple} and not s.typ.n.isNil:
        checkForMetaFields(c, s.typ.n)
  instAllTypeBoundOp(c, n.info)


proc semAllTypeSections(c: PContext; n: PNode): PNode =
  proc gatherStmts(c: PContext; n: PNode; result: PNode) {.nimcall.} =
    case n.kind
    of nkIncludeStmt:
      for i in 0..<n.len:
        var f = checkModuleName(c.config, n.sons[i])
        if f != InvalidFileIDX:
          if containsOrIncl(c.includedFiles, f.int):
            localError(c.config, n.info, errRecursiveDependencyX % f.toFilename)
          else:
            let code = gIncludeFile(c.graph, c.module, f, c.cache)
            gatherStmts c, code, result
            excl(c.includedFiles, f.int)
    of nkStmtList:
      for i in 0 ..< n.len:
        gatherStmts(c, n.sons[i], result)
    of nkTypeSection:
      incl n.flags, nfSem
      typeSectionLeftSidePass(c, n)
      result.add n
    else:
      result.add n

  result = newNodeI(nkStmtList, n.info)
  gatherStmts(c, n, result)

  template rec(name) =
    for i in 0 ..< result.len:
      if result[i].kind == nkTypeSection:
        name(c, result[i])

  rec typeSectionRightSidePass
  rec typeSectionFinalPass
  when false:
    # too beautiful to delete:
    template rec(name; setbit=false) =
      proc `name rec`(c: PContext; n: PNode) {.nimcall.} =
        if n.kind == nkTypeSection:
          when setbit: incl n.flags, nfSem
          name(c, n)
        elif n.kind == nkStmtList:
          for i in 0 ..< n.len:
            `name rec`(c, n.sons[i])
      `name rec`(c, n)
    rec typeSectionLeftSidePass, true
    rec typeSectionRightSidePass
    rec typeSectionFinalPass

proc semTypeSection(c: PContext, n: PNode): PNode =
  ## Processes a type section. This must be done in separate passes, in order
  ## to allow the type definitions in the section to reference each other
  ## without regard for the order of their definitions.
  if sfNoForward notin c.module.flags or nfSem notin n.flags:
    inc c.inTypeContext
    typeSectionLeftSidePass(c, n)
    typeSectionRightSidePass(c, n)
    typeSectionFinalPass(c, n)
    dec c.inTypeContext
  result = n

proc semParamList(c: PContext, n, genericParams: PNode, s: PSym) =
  s.typ = semProcTypeNode(c, n, genericParams, nil, s.kind)
  if s.kind notin {skMacro, skTemplate}:
    if s.typ.sons[0] != nil and s.typ.sons[0].kind == tyStmt:
      localError(c.config, n.info, "invalid return type: 'stmt'")

proc addParams(c: PContext, n: PNode, kind: TSymKind) =
  for i in countup(1, sonsLen(n)-1):
    if n.sons[i].kind == nkSym: addParamOrResult(c, n.sons[i].sym, kind)
    else: illFormedAst(n, c.config)

proc semBorrow(c: PContext, n: PNode, s: PSym) =
  # search for the correct alias:
  var b = searchForBorrowProc(c, c.currentScope.parent, s)
  if b != nil:
    # store the alias:
    n.sons[bodyPos] = newSymNode(b)
  else:
    localError(c.config, n.info, errNoSymbolToBorrowFromFound)

proc addResult(c: PContext, t: PType, info: TLineInfo, owner: TSymKind) =
  if t != nil:
    var s = newSym(skResult, getIdent"result", getCurrOwner(c), info)
    s.typ = t
    incl(s.flags, sfUsed)
    addParamOrResult(c, s, owner)
    c.p.resultSym = s

proc addResultNode(c: PContext, n: PNode) =
  if c.p.resultSym != nil: addSon(n, newSymNode(c.p.resultSym))

proc copyExcept(n: PNode, i: int): PNode =
  result = copyNode(n)
  for j in 0..<n.len:
    if j != i: result.add(n.sons[j])

proc lookupMacro(c: PContext, n: PNode): PSym =
  if n.kind == nkSym:
    result = n.sym
    if result.kind notin {skMacro, skTemplate}: result = nil
  else:
    result = searchInScopes(c, considerQuotedIdent(c.config, n), {skMacro, skTemplate})

proc semProcAnnotation(c: PContext, prc: PNode;
                       validPragmas: TSpecialWords): PNode =
  var n = prc.sons[pragmasPos]
  if n == nil or n.kind == nkEmpty: return
  for i in countup(0, n.len-1):
    var it = n.sons[i]
    var key = if it.kind in nkPragmaCallKinds and it.len >= 1: it.sons[0] else: it
    let m = lookupMacro(c, key)
    if m == nil:
      if key.kind == nkIdent and key.ident.id == ord(wDelegator):
        if considerQuotedIdent(c.config, prc.sons[namePos]).s == "()":
          prc.sons[namePos] = newIdentNode(c.cache.idDelegator, prc.info)
          prc.sons[pragmasPos] = copyExcept(n, i)
        else:
          localError(c.config, prc.info, "only a call operator can be a delegator")
      continue
    elif sfCustomPragma in m.flags:
      continue # semantic check for custom pragma happens later in semProcAux

    # we transform ``proc p {.m, rest.}`` into ``m(do: proc p {.rest.})`` and
    # let the semantic checker deal with it:
    var x = newNodeI(nkCall, n.info)
    x.add(newSymNode(m))
    prc.sons[pragmasPos] = copyExcept(n, i)
    if prc[pragmasPos].kind != nkEmpty and prc[pragmasPos].len == 0:
      prc.sons[pragmasPos] = c.graph.emptyNode

    if it.kind in nkPragmaCallKinds and it.len > 1:
      # pass pragma arguments to the macro too:
      for i in 1..<it.len:
        x.add(it.sons[i])
    x.add(prc)

    # recursion assures that this works for multiple macro annotations too:
    result = semExpr(c, x)
    # since a proc annotation can set pragmas, we process these here again.
    # This is required for SqueakNim-like export pragmas.
    if result.kind in procDefs and result[namePos].kind == nkSym and
        result[pragmasPos].kind != nkEmpty:
      pragma(c, result[namePos].sym, result[pragmasPos], validPragmas)
    return

proc setGenericParamsMisc(c: PContext; n: PNode): PNode =
  let orig = n.sons[genericParamsPos]
  # we keep the original params around for better error messages, see
  # issue https://github.com/nim-lang/Nim/issues/1713
  result = semGenericParamList(c, orig)
  if n.sons[miscPos].kind == nkEmpty:
    n.sons[miscPos] = newTree(nkBracket, c.graph.emptyNode, orig)
  else:
    n.sons[miscPos].sons[1] = orig
  n.sons[genericParamsPos] = result

proc semLambda(c: PContext, n: PNode, flags: TExprFlags): PNode =
  # XXX semProcAux should be good enough for this now, we will eventually
  # remove semLambda
  result = semProcAnnotation(c, n, lambdaPragmas)
  if result != nil: return result
  result = n
  checkSonsLen(n, bodyPos + 1, c.config)
  var s: PSym
  if n[namePos].kind != nkSym:
    s = newSym(skProc, c.cache.idAnon, getCurrOwner(c), n.info)
    s.ast = n
    n.sons[namePos] = newSymNode(s)
  else:
    s = n[namePos].sym
  pushOwner(c, s)
  openScope(c)
  var gp: PNode
  if n.sons[genericParamsPos].kind != nkEmpty:
    gp = setGenericParamsMisc(c, n)
  else:
    gp = newNodeI(nkGenericParams, n.info)

  if n.sons[paramsPos].kind != nkEmpty:
    semParamList(c, n.sons[paramsPos], gp, s)
    # paramsTypeCheck(c, s.typ)
    if sonsLen(gp) > 0 and n.sons[genericParamsPos].kind == nkEmpty:
      # we have a list of implicit type parameters:
      n.sons[genericParamsPos] = gp
  else:
    s.typ = newProcType(c, n.info)
  if n.sons[pragmasPos].kind != nkEmpty:
    pragma(c, s, n.sons[pragmasPos], lambdaPragmas)
  s.options = c.config.options
  if n.sons[bodyPos].kind != nkEmpty:
    if sfImportc in s.flags:
      localError(c.config, n.sons[bodyPos].info, errImplOfXNotAllowed % s.name.s)
    #if efDetermineType notin flags:
    # XXX not good enough; see tnamedparamanonproc.nim
    if gp.len == 0 or (gp.len == 1 and tfRetType in gp[0].typ.flags):
      pushProcCon(c, s)
      addResult(c, s.typ.sons[0], n.info, skProc)
      addResultNode(c, n)
      let semBody = hloBody(c, semProcBody(c, n.sons[bodyPos]))
      n.sons[bodyPos] = transformBody(c.graph, c.module, semBody, s)
      popProcCon(c)
    elif efOperand notin flags:
      localError(c.config, n.info, errGenericLambdaNotAllowed)
    sideEffectsCheck(c, s)
  else:
    localError(c.config, n.info, errImplOfXexpected % s.name.s)
  closeScope(c)           # close scope for parameters
  popOwner(c)
  result.typ = s.typ

proc semInferredLambda(c: PContext, pt: TIdTable, n: PNode): PNode =
  var n = n

  let original = n.sons[namePos].sym
  let s = original #copySym(original, false)
  #incl(s.flags, sfFromGeneric)
  #s.owner = original

  n = replaceTypesInBody(c, pt, n, original)
  result = n
  s.ast = result
  n.sons[namePos].sym = s
  n.sons[genericParamsPos] = c.graph.emptyNode
  # for LL we need to avoid wrong aliasing
  let params = copyTree n.typ.n
  n.sons[paramsPos] = params
  s.typ = n.typ
  for i in 1..<params.len:
    if params[i].typ.kind in {tyTypeDesc, tyGenericParam,
                              tyFromExpr}+tyTypeClasses:
      localError(c.config, params[i].info, "cannot infer type of parameter: " &
                 params[i].sym.name.s)
    #params[i].sym.owner = s
  openScope(c)
  pushOwner(c, s)
  addParams(c, params, skProc)
  pushProcCon(c, s)
  addResult(c, n.typ.sons[0], n.info, skProc)
  addResultNode(c, n)
  let semBody = hloBody(c, semProcBody(c, n.sons[bodyPos]))
  n.sons[bodyPos] = transformBody(c.graph, c.module, semBody, s)
  popProcCon(c)
  popOwner(c)
  closeScope(c)

  # alternative variant (not quite working):
  # var prc = arg[0].sym
  # let inferred = c.semGenerateInstance(c, prc, m.bindings, arg.info)
  # result = inferred.ast
  # result.kind = arg.kind

proc activate(c: PContext, n: PNode) =
  # XXX: This proc is part of my plan for getting rid of
  # forward declarations. stay tuned.
  when false:
    # well for now it breaks code ...
    case n.kind
    of nkLambdaKinds:
      discard semLambda(c, n, {})
    of nkCallKinds:
      for i in 1 ..< n.len: activate(c, n[i])
    else:
      discard

proc maybeAddResult(c: PContext, s: PSym, n: PNode) =
  if s.typ.sons[0] != nil and not
      (s.kind == skIterator and s.typ.callConv != ccClosure):
    addResult(c, s.typ.sons[0], n.info, s.kind)
    addResultNode(c, n)

proc semOverride(c: PContext, s: PSym, n: PNode) =
  case s.name.s.normalize
  of "=destroy":
    let t = s.typ
    var noError = false
    if t.len == 2 and t.sons[0] == nil and t.sons[1].kind == tyVar:
      var obj = t.sons[1].sons[0]
      while true:
        incl(obj.flags, tfHasAsgn)
        if obj.kind in {tyGenericBody, tyGenericInst}: obj = obj.lastSon
        elif obj.kind == tyGenericInvocation: obj = obj.sons[0]
        else: break
      if obj.kind in {tyObject, tyDistinct}:
        if obj.destructor.isNil:
          obj.destructor = s
        else:
          localError(c.config, n.info, errGenerated,
            "cannot bind another '" & s.name.s & "' to: " & typeToString(obj))
        noError = true
    if not noError and sfSystemModule notin s.owner.flags:
      localError(c.config, n.info, errGenerated,
        "signature for '" & s.name.s & "' must be proc[T: object](x: var T)")
    incl(s.flags, sfUsed)
  of "deepcopy", "=deepcopy":
    if s.typ.len == 2 and
        s.typ.sons[1].skipTypes(abstractInst).kind in {tyRef, tyPtr} and
        sameType(s.typ.sons[1], s.typ.sons[0]):
      # Note: we store the deepCopy in the base of the pointer to mitigate
      # the problem that pointers are structural types:
      var t = s.typ.sons[1].skipTypes(abstractInst).lastSon.skipTypes(abstractInst)
      while true:
        if t.kind == tyGenericBody: t = t.lastSon
        elif t.kind == tyGenericInvocation: t = t.sons[0]
        else: break
      if t.kind in {tyObject, tyDistinct, tyEnum}:
        if t.deepCopy.isNil: t.deepCopy = s
        else:
          localError(c.config, n.info, errGenerated,
                     "cannot bind another 'deepCopy' to: " & typeToString(t))
      else:
        localError(c.config, n.info, errGenerated,
                   "cannot bind 'deepCopy' to: " & typeToString(t))
    else:
      localError(c.config, n.info, errGenerated,
                 "signature for 'deepCopy' must be proc[T: ptr|ref](x: T): T")
    incl(s.flags, sfUsed)
  of "=", "=sink":
    if s.magic == mAsgn: return
    incl(s.flags, sfUsed)
    let t = s.typ
    if t.len == 3 and t.sons[0] == nil and t.sons[1].kind == tyVar:
      var obj = t.sons[1].sons[0]
      while true:
        incl(obj.flags, tfHasAsgn)
        if obj.kind == tyGenericBody: obj = obj.lastSon
        elif obj.kind == tyGenericInvocation: obj = obj.sons[0]
        else: break
      var objB = t.sons[2]
      while true:
        if objB.kind == tyGenericBody: objB = objB.lastSon
        elif objB.kind in {tyGenericInvocation, tyGenericInst}:
          objB = objB.sons[0]
        else: break
      if obj.kind in {tyObject, tyDistinct} and sameType(obj, objB):
        let opr = if s.name.s == "=": addr(obj.assignment) else: addr(obj.sink)
        if opr[].isNil:
          opr[] = s
        else:
          localError(c.config, n.info, errGenerated,
                     "cannot bind another '" & s.name.s & "' to: " & typeToString(obj))
        return
    if sfSystemModule notin s.owner.flags:
      localError(c.config, n.info, errGenerated,
                "signature for '" & s.name.s & "' must be proc[T: object](x: var T; y: T)")
  else:
    if sfOverriden in s.flags:
      localError(c.config, n.info, errGenerated,
                 "'destroy' or 'deepCopy' expected for 'override'")

proc cursorInProcAux(n: PNode): bool =
  if inCheckpoint(n.info) != cpNone: return true
  for i in 0..<n.safeLen:
    if cursorInProcAux(n[i]): return true

proc cursorInProc(n: PNode): bool =
  if n.info.fileIndex == gTrackPos.fileIndex:
    result = cursorInProcAux(n)

type
  TProcCompilationSteps = enum
    stepRegisterSymbol,
    stepDetermineType,

proc hasObjParam(s: PSym): bool =
  var t = s.typ
  for col in countup(1, sonsLen(t)-1):
    if skipTypes(t.sons[col], skipPtrs).kind == tyObject:
      return true

proc finishMethod(c: PContext, s: PSym) =
  if hasObjParam(s):
    methodDef(c.graph, s, false)

proc semMethodPrototype(c: PContext; s: PSym; n: PNode) =
  if isGenericRoutine(s):
    let tt = s.typ
    var foundObj = false
    # we start at 1 for now so that tparsecombnum continues to compile.
    # XXX Revisit this problem later.
    for col in countup(1, sonsLen(tt)-1):
      let t = tt.sons[col]
      if t != nil and t.kind == tyGenericInvocation:
        var x = skipTypes(t.sons[0], {tyVar, tyLent, tyPtr, tyRef, tyGenericInst,
                                      tyGenericInvocation, tyGenericBody,
                                      tyAlias, tySink})
        if x.kind == tyObject and t.len-1 == n.sons[genericParamsPos].len:
          foundObj = true
          x.methods.safeAdd((col,s))
    if not foundObj:
      message(c.config, n.info, warnDeprecated, "generic method not attachable to object type")
  else:
    # why check for the body? bug #2400 has none. Checking for sfForward makes
    # no sense either.
    # and result.sons[bodyPos].kind != nkEmpty:
    if hasObjParam(s):
      methodDef(c.graph, s, fromCache=false)
    else:
      localError(c.config, n.info, "'method' needs a parameter that has an object type")

proc semProcAux(c: PContext, n: PNode, kind: TSymKind,
                validPragmas: TSpecialWords,
                phase = stepRegisterSymbol): PNode =
  result = semProcAnnotation(c, n, validPragmas)
  if result != nil: return result
  result = n
  checkSonsLen(n, bodyPos + 1, c.config)
  var s: PSym
  var typeIsDetermined = false
  var isAnon = false
  if n[namePos].kind != nkSym:
    assert phase == stepRegisterSymbol

    if n[namePos].kind == nkEmpty:
      s = newSym(kind, c.cache.idAnon, getCurrOwner(c), n.info)
      incl(s.flags, sfUsed)
      isAnon = true
    else:
      s = semIdentDef(c, n.sons[0], kind)
    n.sons[namePos] = newSymNode(s)
    s.ast = n
    #s.scope = c.currentScope
    when false:
      # disable for now
      if sfNoForward in c.module.flags and
         sfSystemModule notin c.module.flags:
        addInterfaceOverloadableSymAt(c, c.currentScope, s)
        s.flags.incl sfForward
        return
  else:
    s = n[namePos].sym
    s.owner = getCurrOwner(c)
    typeIsDetermined = s.typ == nil
    s.ast = n
    #s.scope = c.currentScope

  # before compiling the proc body, set as current the scope
  # where the proc was declared
  let oldScope = c.currentScope
  #c.currentScope = s.scope
  pushOwner(c, s)
  openScope(c)
  var gp: PNode
  if n.sons[genericParamsPos].kind != nkEmpty:
    gp = setGenericParamsMisc(c, n)
  else:
    gp = newNodeI(nkGenericParams, n.info)
  # process parameters:
  if n.sons[paramsPos].kind != nkEmpty:
    semParamList(c, n.sons[paramsPos], gp, s)
    if sonsLen(gp) > 0:
      if n.sons[genericParamsPos].kind == nkEmpty:
        # we have a list of implicit type parameters:
        n.sons[genericParamsPos] = gp
        # check for semantics again:
        # semParamList(c, n.sons[ParamsPos], nil, s)
  else:
    s.typ = newProcType(c, n.info)
  if tfTriggersCompileTime in s.typ.flags: incl(s.flags, sfCompileTime)
  if n.sons[patternPos].kind != nkEmpty:
    n.sons[patternPos] = semPattern(c, n.sons[patternPos])
  if s.kind == skIterator:
    s.typ.flags.incl(tfIterator)
  elif s.kind == skFunc:
    incl(s.flags, sfNoSideEffect)
    incl(s.typ.flags, tfNoSideEffect)
  var proto = searchForProc(c, oldScope, s)
  if proto == nil or isAnon:
    if s.kind == skIterator:
      if s.typ.callConv != ccClosure:
        s.typ.callConv = if isAnon: ccClosure else: ccInline
    else:
      s.typ.callConv = lastOptionEntry(c).defaultCC
    # add it here, so that recursive procs are possible:
    if sfGenSym in s.flags: discard
    elif kind in OverloadableSyms:
      if not typeIsDetermined:
        addInterfaceOverloadableSymAt(c, oldScope, s)
    else:
      if not typeIsDetermined:
        addInterfaceDeclAt(c, oldScope, s)
    if n.sons[pragmasPos].kind != nkEmpty:
      pragma(c, s, n.sons[pragmasPos], validPragmas)
    else:
      implicitPragmas(c, s, n, validPragmas)
  else:
    if n.sons[pragmasPos].kind != nkEmpty:
      pragma(c, s, n.sons[pragmasPos], validPragmas)
      # To ease macro generation that produce forwarded .async procs we now
      # allow a bit redudancy in the pragma declarations. The rule is
      # a prototype's pragma list must be a superset of the current pragma
      # list.
      # XXX This needs more checks eventually, for example that external
      # linking names do agree:
      if proto.typ.callConv != s.typ.callConv or proto.typ.flags < s.typ.flags:
        localError(c.config, n.sons[pragmasPos].info, errPragmaOnlyInHeaderOfProcX %
          ("'" & proto.name.s & "' from " & $proto.info))
    if sfForward notin proto.flags:
      wrongRedefinition(c, n.info, proto.name.s)
    excl(proto.flags, sfForward)
    closeScope(c)         # close scope with wrong parameter symbols
    openScope(c)          # open scope for old (correct) parameter symbols
    if proto.ast.sons[genericParamsPos].kind != nkEmpty:
      addGenericParamListToScope(c, proto.ast.sons[genericParamsPos])
    addParams(c, proto.typ.n, proto.kind)
    proto.info = s.info       # more accurate line information
    s.typ = proto.typ
    s = proto
    n.sons[genericParamsPos] = proto.ast.sons[genericParamsPos]
    n.sons[paramsPos] = proto.ast.sons[paramsPos]
    n.sons[pragmasPos] = proto.ast.sons[pragmasPos]
    if n.sons[namePos].kind != nkSym: internalError(c.config, n.info, "semProcAux")
    n.sons[namePos].sym = proto
    if importantComments(c.config) and not isNil(proto.ast.comment):
      n.comment = proto.ast.comment
    proto.ast = n             # needed for code generation
    popOwner(c)
    pushOwner(c, s)
  s.options = c.config.options
  if sfOverriden in s.flags or s.name.s[0] == '=': semOverride(c, s, n)
  if s.name.s[0] in {'.', '('}:
    if s.name.s in [".", ".()", ".="] and {destructor, dotOperators} * c.features == {}:
      localError(c.config, n.info, "the overloaded " & s.name.s &
        " operator has to be enabled with {.experimental: \"dotOperators\".}")
    elif s.name.s == "()" and callOperator notin c.features:
      localError(c.config, n.info, "the overloaded " & s.name.s &
        " operator has to be enabled with {.experimental: \"callOperator\".}")

  if n.sons[bodyPos].kind != nkEmpty:
    # for DLL generation it is annoying to check for sfImportc!
    if sfBorrow in s.flags:
      localError(c.config, n.sons[bodyPos].info, errImplOfXNotAllowed % s.name.s)
    let usePseudoGenerics = kind in {skMacro, skTemplate}
    # Macros and Templates can have generic parameters, but they are
    # only used for overload resolution (there is no instantiation of
    # the symbol, so we must process the body now)
    if not usePseudoGenerics and c.config.ideCmd in {ideSug, ideCon} and not
        cursorInProc(n.sons[bodyPos]):
      discard "speed up nimsuggest"
      if s.kind == skMethod: semMethodPrototype(c, s, n)
    else:
      pushProcCon(c, s)
      if n.sons[genericParamsPos].kind == nkEmpty or usePseudoGenerics:
        if not usePseudoGenerics: paramsTypeCheck(c, s.typ)

        c.p.wasForwarded = proto != nil
        maybeAddResult(c, s, n)
        if s.kind == skMethod: semMethodPrototype(c, s, n)

        if lfDynamicLib notin s.loc.flags:
          # no semantic checking for importc:
          let semBody = hloBody(c, semProcBody(c, n.sons[bodyPos]))
          # unfortunately we cannot skip this step when in 'system.compiles'
          # context as it may even be evaluated in 'system.compiles':
          n.sons[bodyPos] = transformBody(c.graph, c.module, semBody, s)
      else:
        if s.typ.sons[0] != nil and kind != skIterator:
          addDecl(c, newSym(skUnknown, getIdent"result", nil, n.info))

        openScope(c)
        n.sons[bodyPos] = semGenericStmt(c, n.sons[bodyPos])
        closeScope(c)
        fixupInstantiatedSymbols(c, s)
        if s.kind == skMethod: semMethodPrototype(c, s, n)
      if sfImportc in s.flags:
        # so we just ignore the body after semantic checking for importc:
        n.sons[bodyPos] = c.graph.emptyNode
      popProcCon(c)
  else:
    if s.kind == skMethod: semMethodPrototype(c, s, n)
    if proto != nil: localError(c.config, n.info, errImplOfXexpected % proto.name.s)
    if {sfImportc, sfBorrow} * s.flags == {} and s.magic == mNone:
      incl(s.flags, sfForward)
    elif sfBorrow in s.flags: semBorrow(c, n, s)
  sideEffectsCheck(c, s)
  closeScope(c)           # close scope for parameters
  # c.currentScope = oldScope
  popOwner(c)
  if n.sons[patternPos].kind != nkEmpty:
    c.patterns.add(s)
  if isAnon:
    n.kind = nkLambda
    result.typ = s.typ
  if isTopLevel(c) and s.kind != skIterator and
      s.typ.callConv == ccClosure:
    localError(c.config, s.info, "'.closure' calling convention for top level routines is invalid")

proc determineType(c: PContext, s: PSym) =
  if s.typ != nil: return
  #if s.magic != mNone: return
  #if s.ast.isNil: return
  discard semProcAux(c, s.ast, s.kind, {}, stepDetermineType)

proc semIterator(c: PContext, n: PNode): PNode =
  # gensym'ed iterator?
  let isAnon = n[namePos].kind == nkEmpty
  if n[namePos].kind == nkSym:
    # gensym'ed iterators might need to become closure iterators:
    n[namePos].sym.owner = getCurrOwner(c)
    n[namePos].sym.kind = skIterator
  result = semProcAux(c, n, skIterator, iteratorPragmas)
  # bug #7093: if after a macro transformation we don't have an
  # nkIteratorDef aynmore, return. The iterator then might have been
  # sem'checked already. (Or not, if the macro skips it.)
  if result.kind != n.kind: return
  var s = result.sons[namePos].sym
  var t = s.typ
  if t.sons[0] == nil and s.typ.callConv != ccClosure:
    localError(c.config, n.info, "iterator needs a return type")
  if isAnon and s.typ.callConv == ccInline:
    localError(c.config, n.info, "inline iterators are not first-class / cannot be assigned to variables")
  # iterators are either 'inline' or 'closure'; for backwards compatibility,
  # we require first class iterators to be marked with 'closure' explicitly
  # -- at least for 0.9.2.
  if s.typ.callConv == ccClosure:
    incl(s.typ.flags, tfCapturesEnv)
  else:
    s.typ.callConv = ccInline
  if n.sons[bodyPos].kind == nkEmpty and s.magic == mNone:
    localError(c.config, n.info, errImplOfXexpected % s.name.s)

proc semProc(c: PContext, n: PNode): PNode =
  result = semProcAux(c, n, skProc, procPragmas)

proc semFunc(c: PContext, n: PNode): PNode =
  result = semProcAux(c, n, skFunc, procPragmas)

proc semMethod(c: PContext, n: PNode): PNode =
  if not isTopLevel(c): localError(c.config, n.info, errXOnlyAtModuleScope % "method")
  result = semProcAux(c, n, skMethod, methodPragmas)
  # macros can transform converters to nothing:
  if namePos >= result.safeLen: return result
  # bug #7093: if after a macro transformation we don't have an
  # nkIteratorDef aynmore, return. The iterator then might have been
  # sem'checked already. (Or not, if the macro skips it.)
  if result.kind != nkMethodDef: return
  var s = result.sons[namePos].sym
  # we need to fix the 'auto' return type for the dispatcher here (see tautonotgeneric
  # test case):
  let disp = getDispatcher(s)
  # auto return type?
  if disp != nil and disp.typ.sons[0] != nil and disp.typ.sons[0].kind == tyExpr:
    let ret = s.typ.sons[0]
    disp.typ.sons[0] = ret
    if disp.ast[resultPos].kind == nkSym:
      if isEmptyType(ret): disp.ast.sons[resultPos] = c.graph.emptyNode
      else: disp.ast[resultPos].sym.typ = ret

proc semConverterDef(c: PContext, n: PNode): PNode =
  if not isTopLevel(c): localError(c.config, n.info, errXOnlyAtModuleScope % "converter")
  checkSonsLen(n, bodyPos + 1, c.config)
  result = semProcAux(c, n, skConverter, converterPragmas)
  # macros can transform converters to nothing:
  if namePos >= result.safeLen: return result
  # bug #7093: if after a macro transformation we don't have an
  # nkIteratorDef aynmore, return. The iterator then might have been
  # sem'checked already. (Or not, if the macro skips it.)
  if result.kind != nkConverterDef: return
  var s = result.sons[namePos].sym
  var t = s.typ
  if t.sons[0] == nil: localError(c.config, n.info, errXNeedsReturnType % "converter")
  if sonsLen(t) != 2: localError(c.config, n.info, "a converter takes exactly one argument")
  addConverter(c, s)

proc semMacroDef(c: PContext, n: PNode): PNode =
  checkSonsLen(n, bodyPos + 1, c.config)
  result = semProcAux(c, n, skMacro, macroPragmas)
  # macros can transform macros to nothing:
  if namePos >= result.safeLen: return result
  # bug #7093: if after a macro transformation we don't have an
  # nkIteratorDef aynmore, return. The iterator then might have been
  # sem'checked already. (Or not, if the macro skips it.)
  if result.kind != nkMacroDef: return
  var s = result.sons[namePos].sym
  var t = s.typ
  var allUntyped = true
  for i in 1 .. t.n.len-1:
    let param = t.n.sons[i].sym
    if param.typ.kind != tyExpr: allUntyped = false
  if allUntyped: incl(s.flags, sfAllUntyped)
  if t.sons[0] == nil: localError(c.config, n.info, "macro needs a return type")
  if n.sons[bodyPos].kind == nkEmpty:
    localError(c.config, n.info, errImplOfXexpected % s.name.s)

proc evalInclude(c: PContext, n: PNode): PNode =
  result = newNodeI(nkStmtList, n.info)
  addSon(result, n)
  for i in countup(0, sonsLen(n) - 1):
    var f = checkModuleName(c.config, n.sons[i])
    if f != InvalidFileIDX:
      if containsOrIncl(c.includedFiles, f.int):
        localError(c.config, n.info, errRecursiveDependencyX % f.toFilename)
      else:
        addSon(result, semStmt(c, gIncludeFile(c.graph, c.module, f, c.cache)))
        excl(c.includedFiles, f.int)

proc setLine(n: PNode, info: TLineInfo) =
  for i in 0 ..< safeLen(n): setLine(n.sons[i], info)
  n.info = info

proc semPragmaBlock(c: PContext, n: PNode): PNode =
  let pragmaList = n.sons[0]
  pragma(c, nil, pragmaList, exprPragmas)
  result = semExpr(c, n.sons[1])
  n.sons[1] = result
  for i in 0 ..< pragmaList.len:
    case whichPragma(pragmaList.sons[i])
    of wLine: setLine(result, pragmaList.sons[i].info)
    of wLocks, wGcSafe:
      result = n
      result.typ = n.sons[1].typ
    of wNoRewrite:
      incl(result.flags, nfNoRewrite)
    else: discard

proc semStaticStmt(c: PContext, n: PNode): PNode =
  #echo "semStaticStmt"
  #writeStackTrace()
  inc c.inStaticContext
  let a = semStmt(c, n.sons[0])
  dec c.inStaticContext
  n.sons[0] = a
  evalStaticStmt(c.module, c.cache, c.graph, a, c.p.owner)
  result = newNodeI(nkDiscardStmt, n.info, 1)
  result.sons[0] = c.graph.emptyNode

proc usesResult(n: PNode): bool =
  # nkStmtList(expr) properly propagates the void context,
  # so we don't need to process that all over again:
  if n.kind notin {nkStmtList, nkStmtListExpr,
                   nkMacroDef, nkTemplateDef} + procDefs:
    if isAtom(n):
      result = n.kind == nkSym and n.sym.kind == skResult
    elif n.kind == nkReturnStmt:
      result = true
    else:
      for c in n:
        if usesResult(c): return true

proc inferConceptStaticParam(c: PContext, inferred, n: PNode) =
  var typ = inferred.typ
  let res = semConstExpr(c, n)
  if not sameType(res.typ, typ.base):
    localError(c.config, n.info,
      "cannot infer the concept parameter '%s', due to a type mismatch. " &
      "attempt to equate '%s' and '%s'.",
      [inferred.renderTree, $res.typ, $typ.base])
  typ.n = res

proc semStmtList(c: PContext, n: PNode, flags: TExprFlags): PNode =
  # these must be last statements in a block:
  const
    LastBlockStmts = {nkRaiseStmt, nkReturnStmt, nkBreakStmt, nkContinueStmt}
  result = n
  result.kind = nkStmtList
  var length = sonsLen(n)
  var voidContext = false
  var last = length-1
  # by not allowing for nkCommentStmt etc. we ensure nkStmtListExpr actually
  # really *ends* in the expression that produces the type: The compiler now
  # relies on this fact and it's too much effort to change that. And arguably
  #  'R(); #comment' shouldn't produce R's type anyway.
  #while last > 0 and n.sons[last].kind in {nkPragma, nkCommentStmt,
  #                                         nkNilLit, nkEmpty}:
  #  dec last
  for i in countup(0, length - 1):
    var expr = semExpr(c, n.sons[i], flags)
    n.sons[i] = expr
    if c.matchedConcept != nil and expr.typ != nil and
        (nfFromTemplate notin n.flags or i != last):
      case expr.typ.kind
      of tyBool:
        if expr.kind == nkInfix and
            expr[0].kind == nkSym and
            expr[0].sym.name.s == "==":
          if expr[1].typ.isUnresolvedStatic:
            inferConceptStaticParam(c, expr[1], expr[2])
            continue
          elif expr[2].typ.isUnresolvedStatic:
            inferConceptStaticParam(c, expr[2], expr[1])
            continue

        let verdict = semConstExpr(c, n[i])
        if verdict.intVal == 0:
          localError(c.config, result.info, "concept predicate failed")
      of tyUnknown: continue
      else: discard
    if n.sons[i].typ == enforceVoidContext: #or usesResult(n.sons[i]):
      voidContext = true
      n.typ = enforceVoidContext
    if i == last and (length == 1 or efWantValue in flags):
      n.typ = n.sons[i].typ
      if not isEmptyType(n.typ): n.kind = nkStmtListExpr
    elif i != last or voidContext:
      discardCheck(c, n.sons[i])
    else:
      n.typ = n.sons[i].typ
      if not isEmptyType(n.typ): n.kind = nkStmtListExpr
    if n.sons[i].kind in LastBlockStmts or
        n.sons[i].kind in nkCallKinds and n.sons[i][0].kind == nkSym and
        sfNoReturn in n.sons[i][0].sym.flags:
      for j in countup(i + 1, length - 1):
        case n.sons[j].kind
        of nkPragma, nkCommentStmt, nkNilLit, nkEmpty, nkBlockExpr,
            nkBlockStmt, nkState: discard
        else: localError(c.config, n.sons[j].info, "unreachable statement after 'return'")
    else: discard

  if result.len == 1 and
     # concept bodies should be preserved as a stmt list:
     c.matchedConcept == nil and
     # also, don't make life complicated for macros.
     # they will always expect a proper stmtlist:
     nfBlockArg notin n.flags and
     result.sons[0].kind != nkDefer:
    result = result.sons[0]

  when defined(nimfix):
    if result.kind == nkCommentStmt and not result.comment.isNil and
        not (result.comment[0] == '#' and result.comment[1] == '#'):
      # it is an old-style comment statement: we replace it with 'discard ""':
      prettybase.replaceComment(result.info)

proc semStmt(c: PContext, n: PNode): PNode =
  # now: simply an alias:
  result = semExprNoType(c, n)