path: root/compiler/renderer.nim

#
#
#           The Nimrod Compiler
#        (c) Copyright 2012 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

# This module implements the renderer of the standard Nimrod representation.

import 
  lexer, options, idents, strutils, ast, msgs, lists

type 
  TRenderFlag* = enum 
    renderNone, renderNoBody, renderNoComments, renderDocComments, 
    renderNoPragmas, renderIds
  TRenderFlags* = set[TRenderFlag]
  TRenderTok*{.final.} = object 
    kind*: TTokType
    length*: int16

  TRenderTokSeq* = seq[TRenderTok]
  TSrcGen*{.final.} = object 
    indent*: int
    lineLen*: int
    pos*: int              # current position for iteration over the buffer
    idx*: int              # current token index for iteration over the buffer
    tokens*: TRenderTokSeq
    buf*: string
    pendingNL*: int        # negative if not active; else contains the
                           # indentation value
    comStack*: seq[PNode]  # comment stack
    flags*: TRenderFlags


proc renderModule*(n: PNode, filename: string, renderFlags: TRenderFlags = {})
proc renderTree*(n: PNode, renderFlags: TRenderFlags = {}): string
proc initTokRender*(r: var TSrcGen, n: PNode, renderFlags: TRenderFlags = {})
proc getNextTok*(r: var TSrcGen, kind: var TTokType, literal: var string)
# implementation
# We render the source code in a two phases: The first
# determines how long the subtree will likely be, the second
# phase appends to a buffer that will be the output.

const 
  IndentWidth = 2
  longIndentWid = 4
  MaxLineLen = 80
  LineCommentColumn = 30

proc InitSrcGen(g: var TSrcGen, renderFlags: TRenderFlags) = 
  g.comStack = @[]
  g.tokens = @[]
  g.indent = 0
  g.lineLen = 0
  g.pos = 0
  g.idx = 0
  g.buf = ""
  g.flags = renderFlags
  g.pendingNL = - 1

proc addTok(g: var TSrcGen, kind: TTokType, s: string) = 
  var length = len(g.tokens)
  setlen(g.tokens, length + 1)
  g.tokens[length].kind = kind
  g.tokens[length].length = int16(len(s))
  add(g.buf, s)

proc addPendingNL(g: var TSrcGen) = 
  if g.pendingNL >= 0: 
    addTok(g, tkInd, "\n" & repeatChar(g.pendingNL))
    g.lineLen = g.pendingNL
    g.pendingNL = - 1

proc putNL(g: var TSrcGen, indent: int) = 
  if g.pendingNL >= 0: addPendingNL(g)
  else: addTok(g, tkInd, "\n")
  g.pendingNL = indent
  g.lineLen = indent

proc putNL(g: var TSrcGen) = 
  putNL(g, g.indent)

proc optNL(g: var TSrcGen, indent: int) = 
  g.pendingNL = indent
  g.lineLen = indent          # BUGFIX
  
proc optNL(g: var TSrcGen) = 
  optNL(g, g.indent)

proc indentNL(g: var TSrcGen) = 
  inc(g.indent, indentWidth)
  g.pendingNL = g.indent
  g.lineLen = g.indent

proc Dedent(g: var TSrcGen) = 
  dec(g.indent, indentWidth)
  assert(g.indent >= 0)
  if g.pendingNL > indentWidth: 
    Dec(g.pendingNL, indentWidth)
    Dec(g.lineLen, indentWidth)

proc put(g: var TSrcGen, kind: TTokType, s: string) = 
  addPendingNL(g)
  if len(s) > 0: 
    addTok(g, kind, s)
    inc(g.lineLen, len(s))

proc putLong(g: var TSrcGen, kind: TTokType, s: string, lineLen: int) = 
  # use this for tokens over multiple lines.
  addPendingNL(g)
  addTok(g, kind, s)
  g.lineLen = lineLen

proc toNimChar(c: Char): string = 
  case c
  of '\0': result = "\\0"
  of '\x01'..'\x1F', '\x80'..'\xFF': result = "\\x" & strutils.toHex(ord(c), 2)
  of '\'', '\"', '\\': result = '\\' & c
  else: result = c & ""
  
proc makeNimString(s: string): string = 
  result = "\""
  for i in countup(0, len(s)-1): add(result, toNimChar(s[i]))
  add(result, '\"')

proc putComment(g: var TSrcGen, s: string) = 
  var i = 0
  var comIndent = 1
  var isCode = (len(s) >= 2) and (s[1] != ' ')
  var ind = g.lineLen
  var com = ""
  while true: 
    case s[i]
    of '\0': 
      break 
    of '\x0D': 
      put(g, tkComment, com)
      com = ""
      inc(i)
      if s[i] == '\x0A': inc(i)
      optNL(g, ind)
    of '\x0A': 
      put(g, tkComment, com)
      com = ""
      inc(i)
      optNL(g, ind)
    of '#': 
      add(com, s[i])
      inc(i)
      comIndent = 0
      while s[i] == ' ': 
        add(com, s[i])
        inc(i)
        inc(comIndent)
    of ' ', '\x09': 
      add(com, s[i])
      inc(i)
    else: 
      # we may break the comment into a multi-line comment if the line
      # gets too long:
      # compute length of the following word:
      var j = i
      while s[j] > ' ': inc(j)
      if not isCode and (g.lineLen + (j - i) > MaxLineLen): 
        put(g, tkComment, com)
        optNL(g, ind)
        com = '#' & repeatChar(comIndent)
      while s[i] > ' ': 
        add(com, s[i])
        inc(i)
  put(g, tkComment, com)
  optNL(g)

proc maxLineLength(s: string): int = 
  result = 0
  var i = 0
  var lineLen = 0
  while true: 
    case s[i]
    of '\0': 
      break 
    of '\x0D': 
      inc(i)
      if s[i] == '\x0A': inc(i)
      result = max(result, lineLen)
      lineLen = 0
    of '\x0A': 
      inc(i)
      result = max(result, lineLen)
      lineLen = 0
    else: 
      inc(lineLen)
      inc(i)

proc putRawStr(g: var TSrcGen, kind: TTokType, s: string) = 
  var i = 0
  var hi = len(s) - 1
  var str = ""
  while i <= hi: 
    case s[i]
    of '\x0D': 
      put(g, kind, str)
      str = ""
      inc(i)
      if (i <= hi) and (s[i] == '\x0A'): inc(i)
      optNL(g, 0)
    of '\x0A': 
      put(g, kind, str)
      str = ""
      inc(i)
      optNL(g, 0)
    else: 
      add(str, s[i])
      inc(i)
  put(g, kind, str)

proc containsNL(s: string): bool = 
  for i in countup(0, len(s) - 1): 
    case s[i]
    of '\x0D', '\x0A': 
      return true
    else: 
      nil
  result = false

proc pushCom(g: var TSrcGen, n: PNode) = 
  var length = len(g.comStack)
  setlen(g.comStack, length + 1)
  g.comStack[length] = n

proc popAllComs(g: var TSrcGen) = 
  setlen(g.comStack, 0)

proc popCom(g: var TSrcGen) = 
  setlen(g.comStack, len(g.comStack) - 1)

const 
  Space = " "

proc shouldRenderComment(g: var TSrcGen, n: PNode): bool = 
  result = false
  if n.comment != nil: 
    result = not (renderNoComments in g.flags) or
        (renderDocComments in g.flags) and startsWith(n.comment, "##")
  
proc gcom(g: var TSrcGen, n: PNode) = 
  assert(n != nil)
  if shouldRenderComment(g, n): 
    if (g.pendingNL < 0) and (len(g.buf) > 0) and (g.buf[len(g.buf)] != ' '): 
      put(g, tkSpaces, Space) 
      # Before long comments we cannot make sure that a newline is generated,
      # because this might be wrong. But it is no problem in practice.
    if (g.pendingNL < 0) and (len(g.buf) > 0) and
        (g.lineLen < LineCommentColumn): 
      var ml = maxLineLength(n.comment)
      if ml + LineCommentColumn <= maxLineLen: 
        put(g, tkSpaces, repeatChar(LineCommentColumn - g.lineLen))
    putComment(g, n.comment)  #assert(g.comStack[high(g.comStack)] = n);
  
proc gcoms(g: var TSrcGen) = 
  for i in countup(0, high(g.comStack)): gcom(g, g.comStack[i])
  popAllComs(g)

proc lsub(n: PNode): int
proc litAux(n: PNode, x: biggestInt, size: int): string = 
  if nfBase2 in n.flags: result = "0b" & toBin(x, size * 8)
  elif nfBase8 in n.flags: result = "0o" & toOct(x, size * 3)
  elif nfBase16 in n.flags: result = "0x" & toHex(x, size * 2)
  else: result = $(x)
  
proc atom(n: PNode): string = 
  var f: float32
  case n.kind
  of nkEmpty: result = ""
  of nkIdent: result = n.ident.s
  of nkSym: result = n.sym.name.s
  of nkStrLit: result = makeNimString(n.strVal)
  of nkRStrLit: result = "r\"" & replace(n.strVal, "\"", "\"\"")  & '\"'
  of nkTripleStrLit: result = "\"\"\"" & n.strVal & "\"\"\""
  of nkCharLit: result = '\'' & toNimChar(chr(int(n.intVal))) & '\''
  of nkIntLit: result = litAux(n, n.intVal, 4)
  of nkInt8Lit: result = litAux(n, n.intVal, 1) & "\'i8"
  of nkInt16Lit: result = litAux(n, n.intVal, 2) & "\'i16"
  of nkInt32Lit: result = litAux(n, n.intVal, 4) & "\'i32"
  of nkInt64Lit: result = litAux(n, n.intVal, 8) & "\'i64"
  of nkFloatLit: 
    if n.flags * {nfBase2, nfBase8, nfBase16} == {}: result = $(n.floatVal)
    else: result = litAux(n, (cast[PInt64](addr(n.floatVal)))[] , 8)
  of nkFloat32Lit: 
    if n.flags * {nfBase2, nfBase8, nfBase16} == {}: 
      result = $(n.floatVal) & "\'f32"
    else: 
      f = n.floatVal
      result = litAux(n, (cast[PInt32](addr(f)))[] , 4) & "\'f32"
  of nkFloat64Lit: 
    if n.flags * {nfBase2, nfBase8, nfBase16} == {}: 
      result = $(n.floatVal) & "\'f64"
    else: 
      result = litAux(n, (cast[PInt64](addr(n.floatVal)))[] , 8) & "\'f64"
  of nkNilLit: result = "nil"
  of nkType: 
    if (n.typ != nil) and (n.typ.sym != nil): result = n.typ.sym.name.s
    else: result = "[type node]"
  else: InternalError("rnimsyn.atom " & $n.kind)
  
proc lcomma(n: PNode, start: int = 0, theEnd: int = - 1): int = 
  assert(theEnd < 0)
  result = 0
  for i in countup(start, sonsLen(n) + theEnd): 
    inc(result, lsub(n.sons[i]))
    inc(result, 2)            # for ``, ``
  if result > 0: 
    dec(result, 2)            # last does not get a comma!
  
proc lsons(n: PNode, start: int = 0, theEnd: int = - 1): int = 
  assert(theEnd < 0)
  result = 0
  for i in countup(start, sonsLen(n) + theEnd): inc(result, lsub(n.sons[i]))
  
proc lsub(n: PNode): int = 
  # computes the length of a tree
  if isNil(n): return 0
  if n.comment != nil: return maxLineLen + 1
  case n.kind
  of nkEmpty: result = 0
  of nkTripleStrLit: 
    if containsNL(n.strVal): result = maxLineLen + 1
    else: result = len(atom(n))
  of succ(nkEmpty)..pred(nkTripleStrLit), succ(nkTripleStrLit)..nkNilLit: 
    result = len(atom(n))
  of nkCall, nkBracketExpr, nkCurlyExpr, nkConv:
    result = lsub(n.sons[0]) + lcomma(n, 1) + 2
  of nkHiddenStdConv, nkHiddenSubConv, nkHiddenCallConv: result = lsub(n[1])
  of nkCast: result = lsub(n.sons[0]) + lsub(n.sons[1]) + len("cast[]()")
  of nkAddr: result = lsub(n.sons[0]) + len("addr()")
  of nkStaticExpr: result = lsub(n.sons[0]) + len("static_")
  of nkHiddenAddr, nkHiddenDeref: result = lsub(n.sons[0])
  of nkCommand: result = lsub(n.sons[0]) + lcomma(n, 1) + 1
  of nkExprEqExpr, nkAsgn, nkFastAsgn: result = lsons(n) + 3
  of nkPar, nkCurly, nkBracket, nkClosure: result = lcomma(n) + 2
  of nkTableConstr:
    result = if n.len > 0: lcomma(n) + 2 else: len("{:}")
  of nkSymChoice: result = lsons(n) + len("()") + sonsLen(n) - 1
  of nkTupleTy: result = lcomma(n) + len("tuple[]")
  of nkDotExpr: result = lsons(n) + 1
  of nkBind: result = lsons(n) + len("bind_")
  of nkBindStmt: result = lcomma(n) + len("bind_")
  of nkCheckedFieldExpr: result = lsub(n.sons[0])
  of nkLambda: result = lsons(n) + len("proc__=_")
  of nkDo: result = lsons(n) + len("do__:_")
  of nkConstDef, nkIdentDefs: 
    result = lcomma(n, 0, - 3)
    var L = sonsLen(n)
    if n.sons[L - 2].kind != nkEmpty: result = result + lsub(n.sons[L - 2]) + 2
    if n.sons[L - 1].kind != nkEmpty: result = result + lsub(n.sons[L - 1]) + 3
  of nkVarTuple: result = lcomma(n, 0, - 3) + len("() = ") + lsub(lastSon(n))
  of nkChckRangeF: result = len("chckRangeF") + 2 + lcomma(n)
  of nkChckRange64: result = len("chckRange64") + 2 + lcomma(n)
  of nkChckRange: result = len("chckRange") + 2 + lcomma(n)
  of nkObjDownConv, nkObjUpConv, nkStringToCString, nkCStringToString: 
    result = 2
    if sonsLen(n) >= 1: result = result + lsub(n.sons[0])
    result = result + lcomma(n, 1)
  of nkExprColonExpr: result = lsons(n) + 2
  of nkInfix: result = lsons(n) + 2
  of nkPrefix: result = lsons(n) + 1
  of nkPostfix: result = lsons(n)
  of nkCallStrLit: result = lsons(n)
  of nkPragmaExpr: result = lsub(n.sons[0]) + lcomma(n, 1)
  of nkRange: result = lsons(n) + 2
  of nkDerefExpr: result = lsub(n.sons[0]) + 2
  of nkAccQuoted: result = lsons(n) + 2
  of nkIfExpr: 
    result = lsub(n.sons[0].sons[0]) + lsub(n.sons[0].sons[1]) + lsons(n, 1) +
        len("if_:_")
  of nkElifExpr: result = lsons(n) + len("_elif_:_")
  of nkElseExpr: result = lsub(n.sons[0]) + len("_else:_") # type descriptions
  of nkTypeOfExpr: result = lsub(n.sons[0]) + len("type_")
  of nkRefTy: result = lsub(n.sons[0]) + len("ref_")
  of nkPtrTy: result = lsub(n.sons[0]) + len("ptr_")
  of nkVarTy: result = lsub(n.sons[0]) + len("var_")
  of nkDistinctTy: result = lsub(n.sons[0]) + len("Distinct_")
  of nkTypeDef: result = lsons(n) + 3
  of nkOfInherit: result = lsub(n.sons[0]) + len("of_")
  of nkProcTy: result = lsons(n) + len("proc_")
  of nkEnumTy: 
    if sonsLen(n) > 0:
      result = lsub(n.sons[0]) + lcomma(n, 1) + len("enum_")
    else:
      result = len("enum")
  of nkEnumFieldDef: result = lsons(n) + 3
  of nkVarSection, nkLetSection: 
    if sonsLen(n) > 1: result = maxLineLen + 1
    else: result = lsons(n) + len("var_")
  of nkReturnStmt: result = lsub(n.sons[0]) + len("return_")
  of nkRaiseStmt: result = lsub(n.sons[0]) + len("raise_")
  of nkYieldStmt: result = lsub(n.sons[0]) + len("yield_")
  of nkDiscardStmt: result = lsub(n.sons[0]) + len("discard_")
  of nkBreakStmt: result = lsub(n.sons[0]) + len("break_")
  of nkContinueStmt: result = lsub(n.sons[0]) + len("continue_")
  of nkPragma: result = lcomma(n) + 4
  of nkCommentStmt: result = len(n.comment)
  of nkOfBranch: result = lcomma(n, 0, - 2) + lsub(lastSon(n)) + len("of_:_")
  of nkElifBranch: result = lsons(n) + len("elif_:_")
  of nkElse: result = lsub(n.sons[0]) + len("else:_")
  of nkFinally: result = lsub(n.sons[0]) + len("finally:_")
  of nkGenericParams: result = lcomma(n) + 2
  of nkFormalParams: 
    result = lcomma(n, 1) + 2
    if n.sons[0].kind != nkEmpty: result = result + lsub(n.sons[0]) + 2
  of nkExceptBranch: 
    result = lcomma(n, 0, -2) + lsub(lastSon(n)) + len("except_:_")
  else: result = maxLineLen + 1
  
proc fits(g: TSrcGen, x: int): bool = 
  result = x + g.lineLen <= maxLineLen

type 
  TSubFlag = enum 
    rfLongMode, rfNoIndent, rfInConstExpr
  TSubFlags = set[TSubFlag]
  TContext = tuple[spacing: int, flags: TSubFlags]

const 
  emptyContext: TContext = (spacing: 0, flags: {})

proc initContext(c: var TContext) = 
  c.spacing = 0
  c.flags = {}

proc gsub(g: var TSrcGen, n: PNode, c: TContext)
proc gsub(g: var TSrcGen, n: PNode) = 
  var c: TContext
  initContext(c)
  gsub(g, n, c)

proc hasCom(n: PNode): bool = 
  result = false
  if n.comment != nil: return true
  case n.kind
  of nkEmpty..nkNilLit: nil
  else: 
    for i in countup(0, sonsLen(n) - 1): 
      if hasCom(n.sons[i]): return true
  
proc putWithSpace(g: var TSrcGen, kind: TTokType, s: string) = 
  put(g, kind, s)
  put(g, tkSpaces, Space)

proc gcommaAux(g: var TSrcGen, n: PNode, ind: int, start: int = 0, 
               theEnd: int = - 1) = 
  for i in countup(start, sonsLen(n) + theEnd): 
    var c = i < sonsLen(n) + theEnd
    var sublen = lsub(n.sons[i]) + ord(c)
    if not fits(g, sublen) and (ind + sublen < maxLineLen): optNL(g, ind)
    gsub(g, n.sons[i])
    if c: 
      putWithSpace(g, tkComma, ",")
      if hasCom(n.sons[i]): 
        gcoms(g)
        optNL(g, ind)

proc gcomma(g: var TSrcGen, n: PNode, c: TContext, start: int = 0, 
            theEnd: int = - 1) = 
  var ind: int
  if rfInConstExpr in c.flags: 
    ind = g.indent + indentWidth
  else: 
    ind = g.lineLen
    if ind > maxLineLen div 2: ind = g.indent + longIndentWid
  gcommaAux(g, n, ind, start, theEnd)

proc gcomma(g: var TSrcGen, n: PNode, start: int = 0, theEnd: int = - 1) = 
  var ind = g.lineLen
  if ind > maxLineLen div 2: ind = g.indent + longIndentWid
  gcommaAux(g, n, ind, start, theEnd)

proc gsons(g: var TSrcGen, n: PNode, c: TContext, start: int = 0, 
           theEnd: int = - 1) = 
  for i in countup(start, sonsLen(n) + theEnd): gsub(g, n.sons[i], c)

proc gsection(g: var TSrcGen, n: PNode, c: TContext, kind: TTokType, 
              k: string) = 
  if sonsLen(n) == 0: return # empty var sections are possible
  putWithSpace(g, kind, k)
  gcoms(g)
  indentNL(g)
  for i in countup(0, sonsLen(n) - 1): 
    optNL(g)
    gsub(g, n.sons[i], c)
    gcoms(g)
  dedent(g)

proc longMode(n: PNode, start: int = 0, theEnd: int = - 1): bool = 
  result = n.comment != nil
  if not result: 
    # check further
    for i in countup(start, sonsLen(n) + theEnd): 
      if (lsub(n.sons[i]) > maxLineLen): 
        result = true
        break 

proc gstmts(g: var TSrcGen, n: PNode, c: TContext) = 
  if n.kind == nkEmpty: return 
  if (n.kind == nkStmtList) or (n.kind == nkStmtListExpr): 
    indentNL(g)
    for i in countup(0, sonsLen(n) - 1): 
      optNL(g)
      gsub(g, n.sons[i])
      gcoms(g)
    dedent(g)
  else: 
    if rfLongMode in c.flags: indentNL(g)
    gsub(g, n)
    gcoms(g)
    optNL(g)
    if rfLongMode in c.flags: dedent(g)
  
proc gif(g: var TSrcGen, n: PNode) = 
  var c: TContext
  gsub(g, n.sons[0].sons[0])
  initContext(c)
  putWithSpace(g, tkColon, ":")
  if longMode(n) or (lsub(n.sons[0].sons[1]) + g.lineLen > maxLineLen): 
    incl(c.flags, rfLongMode)
  gcoms(g)                    # a good place for comments
  gstmts(g, n.sons[0].sons[1], c)
  var length = sonsLen(n)
  for i in countup(1, length - 1): 
    optNL(g)
    gsub(g, n.sons[i], c)

proc gwhile(g: var TSrcGen, n: PNode) = 
  var c: TContext
  putWithSpace(g, tkWhile, "while")
  gsub(g, n.sons[0])
  putWithSpace(g, tkColon, ":")
  initContext(c)
  if longMode(n) or (lsub(n.sons[1]) + g.lineLen > maxLineLen): 
    incl(c.flags, rfLongMode)
  gcoms(g)                    # a good place for comments
  gstmts(g, n.sons[1], c)

proc gpragmaBlock(g: var TSrcGen, n: PNode) = 
  var c: TContext
  gsub(g, n.sons[0])
  putWithSpace(g, tkColon, ":")
  initContext(c)
  if longMode(n) or (lsub(n.sons[1]) + g.lineLen > maxLineLen):
    incl(c.flags, rfLongMode)
  gcoms(g)                    # a good place for comments
  gstmts(g, n.sons[1], c)

proc gtry(g: var TSrcGen, n: PNode) = 
  var c: TContext
  put(g, tkTry, "try")
  putWithSpace(g, tkColon, ":")
  initContext(c)
  if longMode(n) or (lsub(n.sons[0]) + g.lineLen > maxLineLen): 
    incl(c.flags, rfLongMode)
  gcoms(g)                    # a good place for comments
  gstmts(g, n.sons[0], c)
  gsons(g, n, c, 1)

proc gfor(g: var TSrcGen, n: PNode) = 
  var c: TContext
  var length = sonsLen(n)
  putWithSpace(g, tkFor, "for")
  initContext(c)
  if longMode(n) or
      (lsub(n.sons[length - 1]) + lsub(n.sons[length - 2]) + 6 + g.lineLen >
      maxLineLen): 
    incl(c.flags, rfLongMode)
  gcomma(g, n, c, 0, - 3)
  put(g, tkSpaces, Space)
  putWithSpace(g, tkIn, "in")
  gsub(g, n.sons[length - 2], c)
  putWithSpace(g, tkColon, ":")
  gcoms(g)
  gstmts(g, n.sons[length - 1], c)

proc gmacro(g: var TSrcGen, n: PNode) = 
  var c: TContext
  initContext(c)
  gsub(g, n.sons[0])
  putWithSpace(g, tkColon, ":")
  if longMode(n) or (lsub(n.sons[1]) + g.lineLen > maxLineLen): 
    incl(c.flags, rfLongMode)
  gcoms(g)
  gsons(g, n, c, 1)

proc gcase(g: var TSrcGen, n: PNode) = 
  var c: TContext
  initContext(c)
  var length = sonsLen(n)
  var last = if n.sons[length-1].kind == nkElse: -2 else: -1
  if longMode(n, 0, last): incl(c.flags, rfLongMode)
  putWithSpace(g, tkCase, "case")
  gsub(g, n.sons[0])
  gcoms(g)
  optNL(g)
  gsons(g, n, c, 1, last)
  if last == - 2: 
    initContext(c)
    if longMode(n.sons[length - 1]): incl(c.flags, rfLongMode)
    gsub(g, n.sons[length - 1], c)

proc gproc(g: var TSrcGen, n: PNode) = 
  var c: TContext
  gsub(g, n.sons[0])
  gsub(g, n.sons[1])
  gsub(g, n.sons[2])
  gsub(g, n.sons[3])
  if not (renderNoBody in g.flags): 
    if n.sons[4].kind != nkEmpty: 
      put(g, tkSpaces, Space)
      putWithSpace(g, tkEquals, "=")
      indentNL(g)
      gcoms(g)
      dedent(g)
      initContext(c)
      gstmts(g, n.sons[4], c)
      putNL(g)
    else: 
      indentNL(g)
      gcoms(g)
      dedent(g)

proc gblock(g: var TSrcGen, n: PNode) = 
  var c: TContext
  initContext(c)
  if n.sons[0].kind != nkEmpty:
    putWithSpace(g, tkBlock, "block")
    gsub(g, n.sons[0])
  else:
    put(g, tkBlock, "block")
  putWithSpace(g, tkColon, ":")
  if longMode(n) or (lsub(n.sons[1]) + g.lineLen > maxLineLen): 
    incl(c.flags, rfLongMode)
  gcoms(g)
  # XXX I don't get why this is needed here! gstmts should already handle this!
  indentNL(g)
  gstmts(g, n.sons[1], c)
  dedent(g)

proc gstaticStmt(g: var TSrcGen, n: PNode) = 
  var c: TContext
  putWithSpace(g, tkStatic, "static")
  putWithSpace(g, tkColon, ":")
  initContext(c)
  if longMode(n) or (lsub(n.sons[0]) + g.lineLen > maxLineLen): 
    incl(c.flags, rfLongMode)
  gcoms(g)                    # a good place for comments
  gstmts(g, n.sons[0], c)

proc gasm(g: var TSrcGen, n: PNode) = 
  putWithSpace(g, tkAsm, "asm")
  gsub(g, n.sons[0])
  gcoms(g)
  gsub(g, n.sons[1])

proc gident(g: var TSrcGen, n: PNode) = 
  var t: TTokType
  var s = atom(n)
  if (s[0] in lexer.SymChars): 
    if (n.kind == nkIdent): 
      if (n.ident.id < ord(tokKeywordLow) - ord(tkSymbol)) or
          (n.ident.id > ord(tokKeywordHigh) - ord(tkSymbol)): 
        t = tkSymbol
      else: 
        t = TTokType(n.ident.id + ord(tkSymbol))
    else: 
      t = tkSymbol
  else: 
    t = tkOpr
  put(g, t, s)
  if n.kind == nkSym and renderIds in g.flags: put(g, tkIntLit, $n.sym.id)

proc doParamsAux(g: var TSrcGen, params: PNode) =
  if params.len > 1:
    put(g, tkParLe, "(")
    gcomma(g, params, 1)
    put(g, tkParRi, ")")
  
  if params.sons[0].kind != nkEmpty: 
    putWithSpace(g, tkOpr, "->")
    gsub(g, params.sons[0])

proc gsub(g: var TSrcGen, n: PNode, c: TContext) = 
  if isNil(n): return
  var 
    L: int
    a: TContext
  if n.comment != nil: pushCom(g, n)
  case n.kind                 # atoms:
  of nkTripleStrLit: putRawStr(g, tkTripleStrLit, n.strVal)
  of nkEmpty: nil
  of nkType: put(g, tkInvalid, atom(n))
  of nkSym, nkIdent: gident(g, n)
  of nkIntLit: put(g, tkIntLit, atom(n))
  of nkInt8Lit: put(g, tkInt8Lit, atom(n))
  of nkInt16Lit: put(g, tkInt16Lit, atom(n))
  of nkInt32Lit: put(g, tkInt32Lit, atom(n))
  of nkInt64Lit: put(g, tkInt64Lit, atom(n))
  of nkFloatLit: put(g, tkFloatLit, atom(n))
  of nkFloat32Lit: put(g, tkFloat32Lit, atom(n))
  of nkFloat64Lit: put(g, tkFloat64Lit, atom(n))
  of nkStrLit: put(g, tkStrLit, atom(n))
  of nkRStrLit: put(g, tkRStrLit, atom(n))
  of nkCharLit: put(g, tkCharLit, atom(n))
  of nkNilLit: put(g, tkNil, atom(n))    # complex expressions
  of nkCall, nkConv, nkDotCall: 
    if sonsLen(n) >= 1: gsub(g, n.sons[0])
    put(g, tkParLe, "(")
    gcomma(g, n, 1)
    put(g, tkParRi, ")")
  of nkCallStrLit: 
    gsub(g, n.sons[0])
    if n.sons[1].kind == nkRStrLit: 
      put(g, tkRStrLit, '\"' & replace(n[1].strVal, "\"", "\"\"") & '\"')
    else: 
      gsub(g, n.sons[1])
  of nkHiddenStdConv, nkHiddenSubConv, nkHiddenCallConv: gsub(g, n.sons[0])
  of nkCast: 
    put(g, tkCast, "cast")
    put(g, tkBracketLe, "[")
    gsub(g, n.sons[0])
    put(g, tkBracketRi, "]")
    put(g, tkParLe, "(")
    gsub(g, n.sons[1])
    put(g, tkParRi, ")")
  of nkAddr: 
    put(g, tkAddr, "addr")
    put(g, tkParLe, "(")
    gsub(g, n.sons[0])
    put(g, tkParRi, ")")
  of nkStaticExpr:
    put(g, tkStatic, "static")
    put(g, tkSpaces, space)
    gsub(g, n.sons[0])
  of nkBracketExpr: 
    gsub(g, n.sons[0])
    put(g, tkBracketLe, "[")
    gcomma(g, n, 1)
    put(g, tkBracketRi, "]")
  of nkCurlyExpr:
    gsub(g, n.sons[0])
    put(g, tkCurlyLe, "{")
    gcomma(g, n, 1)
    put(g, tkCurlyRi, "}")
  of nkPragmaExpr: 
    gsub(g, n.sons[0])
    gcomma(g, n, 1)
  of nkCommand: 
    gsub(g, n.sons[0])
    put(g, tkSpaces, space)
    gcomma(g, n, 1)
  of nkExprEqExpr, nkAsgn, nkFastAsgn: 
    gsub(g, n.sons[0])
    put(g, tkSpaces, Space)
    putWithSpace(g, tkEquals, "=")
    gsub(g, n.sons[1])
  of nkChckRangeF: 
    put(g, tkSymbol, "chckRangeF")
    put(g, tkParLe, "(")
    gcomma(g, n)
    put(g, tkParRi, ")")
  of nkChckRange64: 
    put(g, tkSymbol, "chckRange64")
    put(g, tkParLe, "(")
    gcomma(g, n)
    put(g, tkParRi, ")")
  of nkChckRange: 
    put(g, tkSymbol, "chckRange")
    put(g, tkParLe, "(")
    gcomma(g, n)
    put(g, tkParRi, ")")
  of nkObjDownConv, nkObjUpConv, nkStringToCString, nkCStringToString: 
    if sonsLen(n) >= 1: gsub(g, n.sons[0])
    put(g, tkParLe, "(")
    gcomma(g, n, 1)
    put(g, tkParRi, ")")
  of nkSymChoice: 
    put(g, tkParLe, "(")
    for i in countup(0, sonsLen(n) - 1): 
      if i > 0: put(g, tkOpr, "|")
      gsub(g, n.sons[i], c)
    put(g, tkParRi, ")")
  of nkPar, nkClosure: 
    put(g, tkParLe, "(")
    gcomma(g, n, c)
    put(g, tkParRi, ")")
  of nkCurly: 
    put(g, tkCurlyLe, "{")
    gcomma(g, n, c)
    put(g, tkCurlyRi, "}")
  of nkTableConstr:
    put(g, tkCurlyLe, "{")
    if n.len > 0: gcomma(g, n, c)
    else: put(g, tkColon, ":")
    put(g, tkCurlyRi, "}")
  of nkBracket:
    put(g, tkBracketLe, "[")
    gcomma(g, n, c)
    put(g, tkBracketRi, "]")
  of nkDotExpr: 
    gsub(g, n.sons[0])
    put(g, tkDot, ".")
    gsub(g, n.sons[1])
  of nkBind: 
    putWithSpace(g, tkBind, "bind")
    gsub(g, n.sons[0])
  of nkCheckedFieldExpr, nkHiddenAddr, nkHiddenDeref: 
    gsub(g, n.sons[0])
  of nkLambda:
    putWithSpace(g, tkLambda, "proc")
    gsub(g, n.sons[paramsPos])
    gsub(g, n.sons[pragmasPos])
    put(g, tkSpaces, Space)
    putWithSpace(g, tkEquals, "=")
    gsub(g, n.sons[bodyPos])
  of nkDo:
    putWithSpace(g, tkDo, "do")
    doParamsAux(g, n.sons[paramsPos])
    gsub(g, n.sons[pragmasPos])
    put(g, tkColon, ":")
    gsub(g, n.sons[bodyPos])
  of nkConstDef, nkIdentDefs: 
    gcomma(g, n, 0, - 3)
    var L = sonsLen(n)
    if n.sons[L - 2].kind != nkEmpty: 
      putWithSpace(g, tkColon, ":")
      gsub(g, n.sons[L - 2])
    if n.sons[L - 1].kind != nkEmpty: 
      put(g, tkSpaces, Space)
      putWithSpace(g, tkEquals, "=")
      gsub(g, n.sons[L - 1], c)
  of nkVarTuple: 
    put(g, tkParLe, "(")
    gcomma(g, n, 0, - 3)
    put(g, tkParRi, ")")
    put(g, tkSpaces, Space)
    putWithSpace(g, tkEquals, "=")
    gsub(g, lastSon(n), c)
  of nkExprColonExpr: 
    gsub(g, n.sons[0])
    putWithSpace(g, tkColon, ":")
    gsub(g, n.sons[1])
  of nkInfix: 
    gsub(g, n.sons[1])
    put(g, tkSpaces, Space)
    gsub(g, n.sons[0])        # binary operator
    if not fits(g, lsub(n.sons[2]) + lsub(n.sons[0]) + 1): 
      optNL(g, g.indent + longIndentWid)
    else: 
      put(g, tkSpaces, Space)
    gsub(g, n.sons[2])
  of nkPrefix: 
    gsub(g, n.sons[0])
    put(g, tkSpaces, space)
    gsub(g, n.sons[1])
  of nkPostfix: 
    gsub(g, n.sons[1])
    gsub(g, n.sons[0])
  of nkRange: 
    gsub(g, n.sons[0])
    put(g, tkDotDot, "..")
    gsub(g, n.sons[1])
  of nkDerefExpr: 
    gsub(g, n.sons[0])
    putWithSpace(g, tkOpr, "^") 
    # unfortunately this requires a space, because ^. would be only one opr
  of nkAccQuoted:
    put(g, tkAccent, "`")
    if n.len > 0: gsub(g, n.sons[0])
    for i in 1 .. <n.len:
      put(g, tkSpaces, Space)
      gsub(g, n.sons[i])
    put(g, tkAccent, "`")
  of nkIfExpr: 
    putWithSpace(g, tkIf, "if")
    gsub(g, n.sons[0].sons[0])
    putWithSpace(g, tkColon, ":")
    gsub(g, n.sons[0].sons[1])
    gsons(g, n, emptyContext, 1)
  of nkElifExpr: 
    putWithSpace(g, tkElif, " elif")
    gsub(g, n.sons[0])
    putWithSpace(g, tkColon, ":")
    gsub(g, n.sons[1])
  of nkElseExpr: 
    put(g, tkElse, " else")
    putWithSpace(g, tkColon, ":")
    gsub(g, n.sons[0])
  of nkTypeOfExpr: 
    putWithSpace(g, tkType, "type")
    gsub(g, n.sons[0])
  of nkRefTy: 
    if sonsLen(n) > 0:
      putWithSpace(g, tkRef, "ref")
      gsub(g, n.sons[0])
    else:
      put(g, tkRef, "ref")
  of nkPtrTy: 
    if sonsLen(n) > 0:
      putWithSpace(g, tkPtr, "ptr")
      gsub(g, n.sons[0])
    else:
      put(g, tkPtr, "ptr")
  of nkVarTy: 
    if sonsLen(n) > 0:
      putWithSpace(g, tkVar, "var")
      gsub(g, n.sons[0])
    else:
      put(g, tkVar, "var")
  of nkDistinctTy: 
    if sonsLen(n) > 0:
      putWithSpace(g, tkDistinct, "distinct")
      gsub(g, n.sons[0])
    else:
      put(g, tkDistinct, "distinct")
  of nkTypeDef: 
    gsub(g, n.sons[0])
    gsub(g, n.sons[1])
    put(g, tkSpaces, Space)
    if n.sons[2].kind != nkEmpty: 
      putWithSpace(g, tkEquals, "=")
      gsub(g, n.sons[2])
  of nkObjectTy: 
    if sonsLen(n) > 0:
      putWithSpace(g, tkObject, "object")
      gsub(g, n.sons[0])
      gsub(g, n.sons[1])
      gcoms(g)
      gsub(g, n.sons[2])
    else:
      put(g, tkObject, "object")
  of nkRecList: 
    indentNL(g)
    for i in countup(0, sonsLen(n) - 1): 
      optNL(g)
      gsub(g, n.sons[i], c)
      gcoms(g)
    dedent(g)
    putNL(g)
  of nkOfInherit: 
    putWithSpace(g, tkOf, "of")
    gsub(g, n.sons[0])
  of nkProcTy: 
    if sonsLen(n) > 0:
      putWithSpace(g, tkProc, "proc")
      gsub(g, n.sons[0])
      gsub(g, n.sons[1])
    else:
      put(g, tkProc, "proc")
  of nkEnumTy: 
    if sonsLen(n) > 0:
      putWithSpace(g, tkEnum, "enum")
      gsub(g, n.sons[0])
      gcoms(g)
      indentNL(g)
      gcommaAux(g, n, g.indent, 1)
      gcoms(g)                  # BUGFIX: comment for the last enum field
      dedent(g)
    else:
      put(g, tkEnum, "enum")
  of nkEnumFieldDef: 
    gsub(g, n.sons[0])
    put(g, tkSpaces, Space)
    putWithSpace(g, tkEquals, "=")
    gsub(g, n.sons[1])
  of nkStmtList, nkStmtListExpr: gstmts(g, n, emptyContext)
  of nkIfStmt: 
    putWithSpace(g, tkIf, "if")
    gif(g, n)
  of nkWhen, nkRecWhen: 
    putWithSpace(g, tkWhen, "when")
    gif(g, n)
  of nkWhileStmt: gwhile(g, n)
  of nkPragmaBlock: gpragmaBlock(g, n)
  of nkCaseStmt, nkRecCase: gcase(g, n)
  of nkMacroStmt: gmacro(g, n)
  of nkTryStmt: gtry(g, n)
  of nkForStmt: gfor(g, n)
  of nkBlockStmt, nkBlockExpr: gblock(g, n)
  of nkStaticStmt: gstaticStmt(g, n)
  of nkAsmStmt: gasm(g, n)
  of nkProcDef: 
    putWithSpace(g, tkProc, "proc")
    gproc(g, n)
  of nkConverterDef:
    putWithSpace(g, tkConverter, "converter")
    gproc(g, n)
  of nkMethodDef: 
    putWithSpace(g, tkMethod, "method")
    gproc(g, n)
  of nkIteratorDef: 
    putWithSpace(g, tkIterator, "iterator")
    gproc(g, n)
  of nkMacroDef: 
    putWithSpace(g, tkMacro, "macro")
    gproc(g, n)
  of nkTemplateDef: 
    putWithSpace(g, tkTemplate, "template")
    gproc(g, n)
  of nkTypeSection: 
    gsection(g, n, emptyContext, tkType, "type")
  of nkConstSection: 
    initContext(a)
    incl(a.flags, rfInConstExpr)
    gsection(g, n, a, tkConst, "const")
  of nkVarSection, nkLetSection:
    L = sonsLen(n)
    if L == 0: return
    if n.kind == nkVarSection: putWithSpace(g, tkVar, "var")
    else: putWithSpace(g, tkLet, "let")
    if L > 1: 
      gcoms(g)
      indentNL(g)
      for i in countup(0, L - 1): 
        optNL(g)
        gsub(g, n.sons[i])
        gcoms(g)
      dedent(g)
    else: 
      gsub(g, n.sons[0])
  of nkReturnStmt: 
    putWithSpace(g, tkReturn, "return")
    gsub(g, n.sons[0])
  of nkRaiseStmt: 
    putWithSpace(g, tkRaise, "raise")
    gsub(g, n.sons[0])
  of nkYieldStmt: 
    putWithSpace(g, tkYield, "yield")
    gsub(g, n.sons[0])
  of nkDiscardStmt: 
    putWithSpace(g, tkDiscard, "discard")
    gsub(g, n.sons[0])
  of nkBreakStmt: 
    putWithSpace(g, tkBreak, "break")
    gsub(g, n.sons[0])
  of nkContinueStmt: 
    putWithSpace(g, tkContinue, "continue")
    gsub(g, n.sons[0])
  of nkPragma: 
    if not (renderNoPragmas in g.flags): 
      put(g, tkCurlyDotLe, "{.")
      gcomma(g, n, emptyContext)
      put(g, tkCurlyDotRi, ".}")
  of nkImportStmt: 
    putWithSpace(g, tkImport, "import")
    gcoms(g)
    indentNL(g)
    gcommaAux(g, n, g.indent)
    dedent(g)
    putNL(g)
  of nkFromStmt: 
    putWithSpace(g, tkFrom, "from")
    gsub(g, n.sons[0])
    put(g, tkSpaces, Space)
    putWithSpace(g, tkImport, "import")
    gcomma(g, n, emptyContext, 1)
    putNL(g)
  of nkIncludeStmt: 
    putWithSpace(g, tkInclude, "include")
    gcoms(g)
    indentNL(g)
    gcommaAux(g, n, g.indent)
    dedent(g)
    putNL(g)
  of nkCommentStmt: 
    gcoms(g)
    optNL(g)
  of nkOfBranch: 
    optNL(g)
    putWithSpace(g, tkOf, "of")
    gcomma(g, n, c, 0, - 2)
    putWithSpace(g, tkColon, ":")
    gcoms(g)
    gstmts(g, lastSon(n), c)
  of nkBindStmt: 
    putWithSpace(g, tkBind, "bind")
    gcomma(g, n, c)
  of nkElifBranch: 
    optNL(g)
    putWithSpace(g, tkElif, "elif")
    gsub(g, n.sons[0])
    putWithSpace(g, tkColon, ":")
    gcoms(g)
    gstmts(g, n.sons[1], c)
  of nkElse: 
    optNL(g)
    put(g, tkElse, "else")
    putWithSpace(g, tkColon, ":")
    gcoms(g)
    gstmts(g, n.sons[0], c)
  of nkFinally: 
    optNL(g)
    put(g, tkFinally, "finally")
    putWithSpace(g, tkColon, ":")
    gcoms(g)
    gstmts(g, n.sons[0], c)
  of nkExceptBranch: 
    optNL(g)
    putWithSpace(g, tkExcept, "except")
    gcomma(g, n, 0, - 2)
    putWithSpace(g, tkColon, ":")
    gcoms(g)
    gstmts(g, lastSon(n), c)
  of nkGenericParams: 
    put(g, tkBracketLe, "[")
    gcomma(g, n)
    put(g, tkBracketRi, "]")
  of nkFormalParams: 
    put(g, tkParLe, "(")
    gcomma(g, n, 1)
    put(g, tkParRi, ")")
    if n.sons[0].kind != nkEmpty: 
      putWithSpace(g, tkColon, ":")
      gsub(g, n.sons[0])
  of nkTupleTy: 
    put(g, tkTuple, "tuple")
    if sonsLen(n) > 0:
      put(g, tkBracketLe, "[")
      gcomma(g, n)
      put(g, tkBracketRi, "]")
  else: 
    #nkNone, nkMetaNode, nkExplicitTypeListCall: 
    InternalError(n.info, "rnimsyn.gsub(" & $n.kind & ')')

proc renderTree(n: PNode, renderFlags: TRenderFlags = {}): string = 
  var g: TSrcGen
  initSrcGen(g, renderFlags)
  gsub(g, n)
  result = g.buf

proc renderModule(n: PNode, filename: string, 
                  renderFlags: TRenderFlags = {}) =
  var
    f: tfile
    g: TSrcGen
  initSrcGen(g, renderFlags)
  for i in countup(0, sonsLen(n) - 1):
    gsub(g, n.sons[i])
    optNL(g)
    case n.sons[i].kind
    of nkTypeSection, nkConstSection, nkVarSection, nkLetSection,
       nkCommentStmt: putNL(g)
    else: nil
  gcoms(g)
  if optStdout in gGlobalOptions:
    write(stdout, g.buf)
  elif open(f, filename, fmWrite):
    write(f, g.buf)
    close(f)
  else:
    rawMessage(errCannotOpenFile, filename)    

proc initTokRender(r: var TSrcGen, n: PNode, renderFlags: TRenderFlags = {}) = 
  initSrcGen(r, renderFlags)
  gsub(r, n)

proc getNextTok(r: var TSrcGen, kind: var TTokType, literal: var string) = 
  if r.idx < len(r.tokens): 
    kind = r.tokens[r.idx].kind
    var length = r.tokens[r.idx].length
    literal = substr(r.buf, r.pos + 0, r.pos + 0 + length - 1)
    inc(r.pos, length)
    inc(r.idx)
  else: 
    kind = tkEof