Merge pull request #8949 from nim-lang/araq-for-loop-expressions

For loop expressions

compiler/docgen.nim

@@ -16,7 +16,7 @@ import
   wordrecg, syntaxes, renderer, lexer, packages/docutils/rstast,
   packages/docutils/rst, packages/docutils/rstgen,
   packages/docutils/highlite, sempass2, json, xmltree, cgi,
-  typesrenderer, astalgo, modulepaths, lineinfos, sequtils
+  typesrenderer, astalgo, modulepaths, lineinfos, sequtils, intsets
 
 type
   TSections = array[TSymKind, Rope]
@@ -32,6 +32,8 @@ type
     conf*: ConfigRef
     cache*: IdentCache
     exampleCounter: int
+    emitted: IntSet # we need to track which symbols have been emitted
+                    # already. See bug #3655
 
   PDoc* = ref TDocumentor ## Alias to type less.
 
@@ -119,6 +121,7 @@ proc newDocumentor*(filename: string; cache: IdentCache; conf: ConfigRef): PDoc
   initStrTable result.types
   result.onTestSnippet = proc (d: var RstGenerator; filename, cmd: string; status: int; content: string) =
     localError(conf, newLineInfo(conf, d.filename, -1, -1), warnUser, "only 'rst2html' supports the ':test:' attribute")
+  result.emitted = initIntSet()
 
 proc dispA(conf: ConfigRef; dest: var Rope, xml, tex: string, args: openArray[Rope]) =
   if conf.cmd != cmdRst2tex: addf(dest, xml, args)
@@ -377,7 +380,7 @@ when false:
       else:
         result = n.comment.substr(2).replace("\n##", "\n").strip
 
-proc isVisible(n: PNode): bool =
+proc isVisible(d: PDoc; n: PNode): bool =
   result = false
   if n.kind == nkPostfix:
     if n.len == 2 and n.sons[0].kind == nkIdent:
@@ -388,8 +391,10 @@ proc isVisible(n: PNode): bool =
     # exception tracking information here. Instead we copy over the comment
     # from the proc header.
     result = {sfExported, sfFromGeneric, sfForward}*n.sym.flags == {sfExported}
+    if result and containsOrIncl(d.emitted, n.sym.id):
+      result = false
   elif n.kind == nkPragmaExpr:
-    result = isVisible(n.sons[0])
+    result = isVisible(d, n.sons[0])
 
 proc getName(d: PDoc, n: PNode, splitAfter = -1): string =
   case n.kind
@@ -520,7 +525,7 @@ proc docstringSummary(rstText: string): string =
 
 
 proc genItem(d: PDoc, n, nameNode: PNode, k: TSymKind) =
-  if not isVisible(nameNode): return
+  if not isVisible(d, nameNode): return
   let
     name = getName(d, nameNode)
     nameRope = name.rope
@@ -601,7 +606,7 @@ proc genItem(d: PDoc, n, nameNode: PNode, k: TSymKind) =
     d.types.strTableAdd nameNode.sym
 
 proc genJsonItem(d: PDoc, n, nameNode: PNode, k: TSymKind): JsonNode =
-  if not isVisible(nameNode): return
+  if not isVisible(d, nameNode): return
   var
     name = getName(d, nameNode)
     comm = $genRecComment(d, n)

compiler/parser.nim

@@ -537,7 +537,7 @@ proc parsePar(p: var TParser): PNode =
   flexComment(p, result)
   if p.tok.tokType in {tkDiscard, tkInclude, tkIf, tkWhile, tkCase,
                        tkTry, tkDefer, tkFinally, tkExcept, tkFor, tkBlock,
-                       tkConst, tkLet, tkWhen, tkVar,
+                       tkConst, tkLet, tkWhen, tkVar, tkFor,
                        tkMixin}:
     # XXX 'bind' used to be an expression, so we exclude it here;
     # tests/reject/tbind2 fails otherwise.
@@ -1112,7 +1112,7 @@ proc parseProcExpr(p: var TParser; isExpr: bool; kind: TNodeKind): PNode =
 
 proc isExprStart(p: TParser): bool =
   case p.tok.tokType
-  of tkSymbol, tkAccent, tkOpr, tkNot, tkNil, tkCast, tkIf,
+  of tkSymbol, tkAccent, tkOpr, tkNot, tkNil, tkCast, tkIf, tkFor,
      tkProc, tkFunc, tkIterator, tkBind, tkBuiltInMagics,
      tkParLe, tkBracketLe, tkCurlyLe, tkIntLit..tkCharLit, tkVar, tkRef, tkPtr,
      tkTuple, tkObject, tkWhen, tkCase, tkOut:
@@ -1152,16 +1152,35 @@ proc parseTypeDescKAux(p: var TParser, kind: TNodeKind,
     result.addSon list
     parseSymbolList(p, list)
 
+proc parseFor(p: var TParser): PNode =
+  #| forStmt = 'for' (identWithPragma ^+ comma) 'in' expr colcom stmt
+  #| forExpr = forStmt
+  result = newNodeP(nkForStmt, p)
+  getTokNoInd(p)
+  var a = identWithPragma(p)
+  addSon(result, a)
+  while p.tok.tokType == tkComma:
+    getTok(p)
+    optInd(p, a)
+    a = identWithPragma(p)
+    addSon(result, a)
+  eat(p, tkIn)
+  addSon(result, parseExpr(p))
+  colcom(p, result)
+  addSon(result, parseStmt(p))
+
 proc parseExpr(p: var TParser): PNode =
   #| expr = (blockExpr
   #|       | ifExpr
   #|       | whenExpr
   #|       | caseExpr
+  #|       | forExpr
   #|       | tryExpr)
   #|       / simpleExpr
   case p.tok.tokType:
   of tkBlock: result = parseBlock(p)
   of tkIf: result = parseIfExpr(p, nkIfExpr)
+  of tkFor: result = parseFor(p)
   of tkWhen: result = parseIfExpr(p, nkWhenExpr)
   of tkCase: result = parseCase(p)
   of tkTry: result = parseTry(p, isExpr=true)
@@ -1568,22 +1587,6 @@ proc parseExceptBlock(p: var TParser, kind: TNodeKind): PNode =
   colcom(p, result)
   addSon(result, parseStmt(p))
 
-proc parseFor(p: var TParser): PNode =
-  #| forStmt = 'for' (identWithPragma ^+ comma) 'in' expr colcom stmt
-  result = newNodeP(nkForStmt, p)
-  getTokNoInd(p)
-  var a = identWithPragma(p)
-  addSon(result, a)
-  while p.tok.tokType == tkComma:
-    getTok(p)
-    optInd(p, a)
-    a = identWithPragma(p)
-    addSon(result, a)
-  eat(p, tkIn)
-  addSon(result, parseExpr(p))
-  colcom(p, result)
-  addSon(result, parseStmt(p))
-
 proc parseBlock(p: var TParser): PNode =
   #| blockStmt = 'block' symbol? colcom stmt
   #| blockExpr = 'block' symbol? colcom stmt

compiler/sem.nim

@@ -37,7 +37,7 @@ proc changeType(c: PContext; n: PNode, newType: PType, check: bool)
 
 proc semLambda(c: PContext, n: PNode, flags: TExprFlags): PNode
 proc semTypeNode(c: PContext, n: PNode, prev: PType): PType
-proc semStmt(c: PContext, n: PNode): PNode
+proc semStmt(c: PContext, n: PNode; flags: TExprFlags): PNode
 proc semOpAux(c: PContext, n: PNode)
 proc semParamList(c: PContext, n, genericParams: PNode, s: PSym)
 proc addParams(c: PContext, n: PNode, kind: TSymKind)
@@ -399,7 +399,7 @@ proc semAfterMacroCall(c: PContext, call, macroResult: PNode,
   excl(result.flags, nfSem)
   #resetSemFlag n
   if s.typ.sons[0] == nil:
-    result = semStmt(c, result)
+    result = semStmt(c, result, flags)
   else:
     case s.typ.sons[0].kind
     of tyExpr:
@@ -408,7 +408,7 @@ proc semAfterMacroCall(c: PContext, call, macroResult: PNode,
       # semExprWithType(c, result)
       result = semExpr(c, result, flags)
     of tyStmt:
-      result = semStmt(c, result)
+      result = semStmt(c, result, flags)
     of tyTypeDesc:
       if result.kind == nkStmtList: result.kind = nkStmtListType
       var typ = semTypeNode(c, result, nil)
@@ -557,7 +557,7 @@ proc semStmtAndGenerateGenerics(c: PContext, n: PNode): PNode =
     result = semAllTypeSections(c, n)
   else:
     result = n
-  result = semStmt(c, result)
+  result = semStmt(c, result, {})
   when false:
     # Code generators are lazy now and can deal with undeclared procs, so these
     # steps are not required anymore and actually harmful for the upcoming

compiler/semexprs.nim

@@ -918,7 +918,7 @@ proc semExprNoType(c: PContext, n: PNode): PNode =
   let isPush = hintExtendedContext in c.config.notes
   if isPush: pushInfoContext(c.config, n.info)
   result = semExpr(c, n, {efWantStmt})
-  discardCheck(c, result)
+  discardCheck(c, result, {})
   if isPush: popInfoContext(c.config)
 
 proc isTypeExpr(n: PNode): bool =
@@ -1530,7 +1530,7 @@ proc semAsgn(c: PContext, n: PNode; mode=asgnNormal): PNode =
       # unfortunately we need to rewrite ``(x, y) = foo()`` already here so
       # that overloading of the assignment operator still works. Usually we
       # prefer to do these rewritings in transf.nim:
-      return semStmt(c, lowerTupleUnpackingForAsgn(c.graph, n, c.p.owner))
+      return semStmt(c, lowerTupleUnpackingForAsgn(c.graph, n, c.p.owner), {})
     else:
       a = semExprWithType(c, a, {efLValue})
   else:
@@ -1614,7 +1614,7 @@ proc semProcBody(c: PContext, n: PNode): PNode =
       a.sons[1] = result
       result = semAsgn(c, a)
   else:
-    discardCheck(c, result)
+    discardCheck(c, result, {})
 
   if c.p.owner.kind notin {skMacro, skTemplate} and
      c.p.resultSym != nil and c.p.resultSym.typ.isMetaType:
@@ -1990,7 +1990,7 @@ proc semMagic(c: PContext, n: PNode, s: PSym, flags: TExprFlags): PNode =
     var x = n.lastSon
     if x.kind == nkDo: x = x.sons[bodyPos]
     inc c.inParallelStmt
-    result.sons[1] = semStmt(c, x)
+    result.sons[1] = semStmt(c, x, {})
     dec c.inParallelStmt
   of mSpawn:
     result = setMs(n, s)
@@ -2241,7 +2241,7 @@ proc isTupleType(n: PNode): bool =
 
 include semobjconstr
 
-proc semBlock(c: PContext, n: PNode): PNode =
+proc semBlock(c: PContext, n: PNode; flags: TExprFlags): PNode =
   result = n
   inc(c.p.nestedBlockCounter)
   checkSonsLen(n, 2, c.config)
@@ -2253,7 +2253,7 @@ proc semBlock(c: PContext, n: PNode): PNode =
     n.sons[0] = newSymNode(labl, n.sons[0].info)
     suggestSym(c.config, n.sons[0].info, labl, c.graph.usageSym)
     styleCheckDef(c.config, labl)
-  n.sons[1] = semExpr(c, n.sons[1])
+  n.sons[1] = semExpr(c, n.sons[1], flags)
   n.typ = n.sons[1].typ
   if isEmptyType(n.typ): n.kind = nkBlockStmt
   else: n.kind = nkBlockExpr
@@ -2498,7 +2498,7 @@ proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
     checkSonsLen(n, 1, c.config)
     n.sons[0] = semExpr(c, n.sons[0], flags)
   of nkCast: result = semCast(c, n)
-  of nkIfExpr, nkIfStmt: result = semIf(c, n)
+  of nkIfExpr, nkIfStmt: result = semIf(c, n, flags)
   of nkHiddenStdConv, nkHiddenSubConv, nkConv, nkHiddenCallConv:
     checkSonsLen(n, 2, c.config)
     considerGenSyms(c, n)
@@ -2519,7 +2519,7 @@ proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
     discard
   of nkStaticExpr: result = semStaticExpr(c, n[0])
   of nkAsgn: result = semAsgn(c, n)
-  of nkBlockStmt, nkBlockExpr: result = semBlock(c, n)
+  of nkBlockStmt, nkBlockExpr: result = semBlock(c, n, flags)
   of nkStmtList, nkStmtListExpr: result = semStmtList(c, n, flags)
   of nkRaiseStmt: result = semRaise(c, n)
   of nkVarSection: result = semVarOrLet(c, n, skVar)
@@ -2527,11 +2527,11 @@ proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
   of nkConstSection: result = semConst(c, n)
   of nkTypeSection: result = semTypeSection(c, n)
   of nkDiscardStmt: result = semDiscard(c, n)
-  of nkWhileStmt: result = semWhile(c, n)
-  of nkTryStmt: result = semTry(c, n)
+  of nkWhileStmt: result = semWhile(c, n, flags)
+  of nkTryStmt: result = semTry(c, n, flags)
   of nkBreakStmt, nkContinueStmt: result = semBreakOrContinue(c, n)
-  of nkForStmt, nkParForStmt: result = semFor(c, n)
-  of nkCaseStmt: result = semCase(c, n)
+  of nkForStmt, nkParForStmt: result = semFor(c, n, flags)
+  of nkCaseStmt: result = semCase(c, n, flags)
   of nkReturnStmt: result = semReturn(c, n)
   of nkUsingStmt: result = semUsing(c, n)
   of nkAsmStmt: result = semAsm(c, n)

compiler/semfields.nim

@@ -70,7 +70,7 @@ proc semForObjectFields(c: TFieldsCtx, typ, forLoop, father: PNode) =
     openScope(c.c)
     inc c.c.inUnrolledContext
     let body = instFieldLoopBody(fc, lastSon(forLoop), forLoop)
-    father.add(semStmt(c.c, body))
+    father.add(semStmt(c.c, body, {}))
     dec c.c.inUnrolledContext
     closeScope(c.c)
   of nkNilLit: discard
@@ -145,7 +145,7 @@ proc semForFields(c: PContext, n: PNode, m: TMagic): PNode =
       fc.replaceByFieldName = m == mFieldPairs
       var body = instFieldLoopBody(fc, loopBody, n)
       inc c.inUnrolledContext
-      stmts.add(semStmt(c, body))
+      stmts.add(semStmt(c, body, {}))
       dec c.inUnrolledContext
       closeScope(c)
   else:

compiler/semstmts.nim

@@ -76,17 +76,19 @@ proc semAsm(c: PContext, n: PNode): PNode =
   if marker == '\0': marker = '`' # default marker
   result = semAsmOrEmit(c, n, marker)
 
-proc semWhile(c: PContext, n: PNode): PNode =
+proc semWhile(c: PContext, n: PNode; flags: TExprFlags): 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])
+  n.sons[1] = semStmt(c, n.sons[1], flags)
   dec(c.p.nestedLoopCounter)
   closeScope(c)
   if n.sons[1].typ == c.enforceVoidContext:
     result.typ = c.enforceVoidContext
+  elif efInTypeof in flags:
+    result.typ = n[1].typ
 
 proc toCover(c: PContext, t: PType): BiggestInt =
   let t2 = skipTypes(t, abstractVarRange-{tyTypeDesc})
@@ -97,8 +99,8 @@ proc toCover(c: PContext, t: PType): BiggestInt =
 
 proc semProc(c: PContext, n: PNode): PNode
 
-proc semExprBranch(c: PContext, n: PNode): PNode =
-  result = semExpr(c, n)
+proc semExprBranch(c: PContext, n: PNode; flags: TExprFlags = {}): PNode =
+  result = semExpr(c, n, flags)
   if result.typ != nil:
     # XXX tyGenericInst here?
     if result.typ.kind in {tyVar, tyLent}: result = newDeref(result)
@@ -130,8 +132,9 @@ proc fixNilType(c: PContext; n: PNode) =
     for it in n: fixNilType(c, it)
   n.typ = nil
 
-proc discardCheck(c: PContext, result: PNode) =
-  if c.matchedConcept != nil: return
+proc discardCheck(c: PContext, result: PNode, flags: TExprFlags) =
+  if c.matchedConcept != nil or efInTypeof in flags: return
+
   if result.typ != nil and result.typ.kind notin {tyStmt, tyVoid}:
     if implicitlyDiscardable(result):
       var n = newNodeI(nkDiscardStmt, result.info, 1)
@@ -148,7 +151,7 @@ proc discardCheck(c: PContext, result: PNode) =
         s.add "; for a function call use ()"
       localError(c.config, n.info, s)
 
-proc semIf(c: PContext, n: PNode): PNode =
+proc semIf(c: PContext, n: PNode; flags: TExprFlags): PNode =
   result = n
   var typ = commonTypeBegin
   var hasElse = false
@@ -165,8 +168,9 @@ proc semIf(c: PContext, n: PNode): PNode =
       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)
+  if isEmptyType(typ) or typ.kind in {tyNil, tyExpr} or
+      (not hasElse and efInTypeof notin flags):
+    for it in n: discardCheck(c, it.lastSon, flags)
     result.kind = nkIfStmt
     # propagate any enforced VoidContext:
     if typ == c.enforceVoidContext: result.typ = c.enforceVoidContext
@@ -178,8 +182,7 @@ proc semIf(c: PContext, n: PNode): PNode =
     result.kind = nkIfExpr
     result.typ = typ
 
-proc semTry(c: PContext, n: PNode): PNode =
-
+proc semTry(c: PContext, n: PNode; flags: TExprFlags): PNode =
   var check = initIntSet()
   template semExceptBranchType(typeNode: PNode): bool =
     # returns true if exception type is imported type
@@ -246,12 +249,12 @@ proc semTry(c: PContext, n: PNode): PNode =
 
   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)
+    discardCheck(c, n.sons[0], flags)
+    for i in 1..n.len-1: discardCheck(c, n.sons[i].lastSon, flags)
     if typ == c.enforceVoidContext:
       result.typ = c.enforceVoidContext
   else:
-    if n.lastSon.kind == nkFinally: discardCheck(c, n.lastSon.lastSon)
+    if n.lastSon.kind == nkFinally: discardCheck(c, n.lastSon.lastSon, flags)
     n.sons[0] = fitNode(c, typ, n.sons[0], n.sons[0].info)
     for i in 1..last:
       var it = n.sons[i]
@@ -570,7 +573,7 @@ proc symForVar(c: PContext, n: PNode): PSym =
   if n.kind == nkPragmaExpr:
     pragma(c, result, n.sons[1], forVarPragmas)
 
-proc semForVars(c: PContext, n: PNode): PNode =
+proc semForVars(c: PContext, n: PNode; flags: TExprFlags): PNode =
   result = n
   var length = sonsLen(n)
   let iterBase = n.sons[length-2].typ
@@ -601,7 +604,7 @@ proc semForVars(c: PContext, n: PNode): PNode =
         addForVarDecl(c, v)
   inc(c.p.nestedLoopCounter)
   openScope(c)
-  n.sons[length-1] = semStmt(c, n.sons[length-1])
+  n.sons[length-1] = semExprBranch(c, n.sons[length-1], flags)
   closeScope(c)
   dec(c.p.nestedLoopCounter)
 
@@ -685,7 +688,7 @@ proc handleCaseStmtMacro(c: PContext; n: PNode): PNode =
   when false:
     result = handleStmtMacro(c, n, n[0], "CaseStmt")
 
-proc semFor(c: PContext, n: PNode): PNode =
+proc semFor(c: PContext, n: PNode; flags: TExprFlags): PNode =
   checkMinSonsLen(n, 3, c.config)
   var length = sonsLen(n)
   if forLoopMacros in c.features:
@@ -702,14 +705,14 @@ proc semFor(c: PContext, n: PNode): PNode =
   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 = semForVars(c, n, flags)
       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)
+    result = semForVars(c, n, flags)
   elif not isCallExpr or call.sons[0].kind != nkSym or
       call.sons[0].sym.kind != skIterator:
     if length == 3:
@@ -718,15 +721,17 @@ proc semFor(c: PContext, n: PNode): PNode =
       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)
+    result = semForVars(c, n, flags)
   else:
-    result = semForVars(c, n)
+    result = semForVars(c, n, flags)
   # propagate any enforced VoidContext:
   if n.sons[length-1].typ == c.enforceVoidContext:
     result.typ = c.enforceVoidContext
+  elif efInTypeof in flags:
+    result.typ = result.lastSon.typ
   closeScope(c)
 
-proc semCase(c: PContext, n: PNode): PNode =
+proc semCase(c: PContext, n: PNode; flags: TExprFlags): PNode =
   result = n
   checkMinSonsLen(n, 2, c.config)
   openScope(c)
@@ -782,8 +787,9 @@ proc semCase(c: PContext, n: PNode): PNode =
     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)
+  if isEmptyType(typ) or typ.kind in {tyNil, tyExpr} or
+      (not hasElse and efInTypeof notin flags):
+    for i in 1..n.len-1: discardCheck(c, n.sons[i].lastSon, flags)
     # propagate any enforced VoidContext:
     if typ == c.enforceVoidContext:
       result.typ = c.enforceVoidContext
@@ -1795,7 +1801,7 @@ proc evalInclude(c: PContext, n: PNode): PNode =
       if containsOrIncl(c.includedFiles, f.int):
         localError(c.config, n.info, errRecursiveDependencyX % toFilename(c.config, f))
       else:
-        addSon(result, semStmt(c, c.graph.includeFileCallback(c.graph, c.module, f)))
+        addSon(result, semStmt(c, c.graph.includeFileCallback(c.graph, c.module, f), {}))
         excl(c.includedFiles, f.int)
 
 proc setLine(n: PNode, info: TLineInfo) =
@@ -1822,7 +1828,7 @@ proc semStaticStmt(c: PContext, n: PNode): PNode =
   #writeStackTrace()
   inc c.inStaticContext
   openScope(c)
-  let a = semStmt(c, n.sons[0])
+  let a = semStmt(c, n.sons[0], {})
   closeScope(c)
   dec c.inStaticContext
   n.sons[0] = a
@@ -1898,11 +1904,11 @@ proc semStmtList(c: PContext, n: PNode, flags: TExprFlags): PNode =
     if n.sons[i].typ == c.enforceVoidContext: #or usesResult(n.sons[i]):
       voidContext = true
       n.typ = c.enforceVoidContext
-    if i == last and (length == 1 or efWantValue in flags):
+    if i == last and (length == 1 or ({efWantValue, efInTypeof} * 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])
+      discardCheck(c, n.sons[i], flags)
     else:
       n.typ = n.sons[i].typ
       if not isEmptyType(n.typ): n.kind = nkStmtListExpr
@@ -1931,6 +1937,8 @@ proc semStmtList(c: PContext, n: PNode, flags: TExprFlags): PNode =
       # 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)
+proc semStmt(c: PContext, n: PNode; flags: TExprFlags): PNode =
+  if efInTypeof notin flags:
+    result = semExprNoType(c, n)
+  else:
+    result = semExpr(c, n, flags)

compiler/semtypes.nim

@@ -1161,7 +1161,7 @@ proc semStmtListType(c: PContext, n: PNode, prev: PType): PType =
   checkMinSonsLen(n, 1, c.config)
   var length = sonsLen(n)
   for i in countup(0, length - 2):
-    n.sons[i] = semStmt(c, n.sons[i])
+    n.sons[i] = semStmt(c, n.sons[i], {})
   if length > 0:
     result = semTypeNode(c, n.sons[length - 1], prev)
     n.typ = result
@@ -1406,6 +1406,13 @@ proc semStaticType(c: PContext, childNode: PNode, prev: PType): PType =
   result.rawAddSon(base)
   result.flags.incl tfHasStatic
 
+proc semTypeof(c: PContext; n: PNode; prev: PType): PType =
+  openScope(c)
+  let t = semExprWithType(c, n, {efInTypeof})
+  closeScope(c)
+  fixupTypeOf(c, prev, t)
+  result = t.typ
+
 proc semTypeNode(c: PContext, n: PNode, prev: PType): PType =
   result = nil
   inc c.inTypeContext
@@ -1416,9 +1423,7 @@ proc semTypeNode(c: PContext, n: PNode, prev: PType): PType =
   of nkTypeOfExpr:
     # for ``type(countup(1,3))``, see ``tests/ttoseq``.
     checkSonsLen(n, 1, c.config)
-    let typExpr = semExprWithType(c, n.sons[0], {efInTypeof})
-    fixupTypeOf(c, prev, typExpr)
-    result = typExpr.typ
+    result = semTypeof(c, n.sons[0], prev)
     if result.kind == tyTypeDesc: result.flags.incl tfExplicit
   of nkPar:
     if sonsLen(n) == 1: result = semTypeNode(c, n.sons[0], prev)
@@ -1487,9 +1492,7 @@ proc semTypeNode(c: PContext, n: PNode, prev: PType): PType =
         result = semAnyRef(c, n, tyRef, prev)
       elif op.id == ord(wType):
         checkSonsLen(n, 2, c.config)
-        let typExpr = semExprWithType(c, n.sons[1], {efInTypeof})
-        fixupTypeOf(c, prev, typExpr)
-        result = typExpr.typ
+        result = semTypeof(c, n[1], prev)
       else:
         if c.inGenericContext > 0 and n.kind == nkCall:
           result = makeTypeFromExpr(c, n.copyTree)

lib/core/macros.nim

@@ -240,7 +240,7 @@ else: # bootstrapping substitute
 when defined(nimHasSymOwnerInMacro):
   proc owner*(sym: NimNode): NimNode {.magic: "SymOwner", noSideEffect.}
     ## accepts node of kind nnkSym and returns its owner's symbol.
-    ## result is also mnde of kind nnkSym if owner exists otherwise 
+    ## result is also mnde of kind nnkSym if owner exists otherwise
     ## nnkNilLit is returned
 
 proc getType*(n: NimNode): NimNode {.magic: "NGetType", noSideEffect.}
@@ -977,7 +977,7 @@ proc newIfStmt*(branches: varargs[tuple[cond, body: NimNode]]):
   ##
   result = newNimNode(nnkIfStmt)
   for i in branches:
-    result.add(newNimNode(nnkElifBranch).add(i.cond, i.body))
+    result.add(newTree(nnkElifBranch, i.cond, i.body))
 
 proc newEnum*(name: NimNode, fields: openArray[NimNode],
               public, pure: bool): NimNode {.compileTime.} =

tests/macros/tcollect.nim

@@ -0,0 +1,63 @@
+discard """
+  output: '''@[2, 3, 4, 2, 3, 4, 2, 3, 4, 2, 3, 4, 2, 3, 4]
+@[0, 1, 2, 3]'''
+"""
+
+const data = [1,2,3,4,5,6]
+
+import macros
+
+macro collect(body): untyped =
+  # analyse the body, find the deepest expression 'it' and replace it via
+  # 'result.add it'
+  let res = genSym(nskVar, "collectResult")
+
+  when false:
+    proc detectForLoopVar(n: NimNode): NimNode =
+      if n.kind == nnkForStmt:
+        result = n[0]
+      else:
+        for x in n:
+          result = detectForLoopVar(x)
+          if result != nil: return result
+        return nil
+
+  proc t(n, res: NimNode): NimNode =
+    case n.kind
+    of nnkStmtList, nnkStmtListExpr, nnkBlockStmt, nnkBlockExpr,
+       nnkWhileStmt,
+       nnkForStmt, nnkIfExpr, nnkIfStmt, nnkTryStmt, nnkCaseStmt,
+       nnkElifBranch, nnkElse, nnkElifExpr:
+      result = copyNimTree(n)
+      if n.len >= 1:
+        result[^1] = t(n[^1], res)
+    else:
+      if true: #n == it:
+        template adder(res, it) =
+          res.add it
+        result = getAst adder(res, n)
+      else:
+        result = n
+
+  when false:
+    let it = detectForLoopVar(body)
+    if it == nil: error("no for loop in body", body)
+
+  let v = newTree(nnkVarSection,
+     newTree(nnkIdentDefs, res, newTree(nnkBracketExpr, bindSym"seq",
+     newCall(bindSym"type", body)), newEmptyNode()))
+
+  result = newTree(nnkStmtListExpr, v, t(body, res), res)
+  #echo repr result
+
+let stuff = collect:
+  var i = -1
+  while i < 4:
+    inc i
+    for it in data:
+      if it < 5 and it > 1:
+        it
+
+echo stuff
+
+echo collect(for i in 0..3: i)