fix iterators, revert sequtils changes, temp enable globally

compiler/semcall.nim

@@ -96,6 +96,7 @@ proc pickBestCandidate(c: PContext, headSymbol: PNode,
   # current overload being considered
   var sym = syms[0].s
   let name = sym.name
+  let wantIterator = flags*{efInTypeof, efWantIterator, efWantIterable} != {}
   template addTypeBoundOpsFor(arg: PNode) =
     # add type bound ops for `name` based on the type of the arg `arg`
     if arg.typ != nil:
@@ -108,7 +109,8 @@ proc pickBestCandidate(c: PContext, headSymbol: PNode,
           var iter = default(TIdentIter)
           var s = initIdentIter(iter, c.graph.typeBoundOps[tid], name)
           while s != nil:
-            if not containsOrIncl(symMarker, s.id):
+            if (s.kind != skIterator or wantIterator) and
+                not containsOrIncl(symMarker, s.id):
               # least priority scope, less than explicit imports:
               syms.add((s, -2))
             s = nextIdentIter(iter, c.graph.typeBoundOps[tid])

config/nim.cfg

@@ -18,6 +18,10 @@ cc = gcc
   hint[LineTooLong]=off
 @end
 
+@if nimHasTypeBoundOps:
+  experimental:typeBoundOps
+@end
+
 #hint[XDeclaredButNotUsed]=off
 
 threads:on

lib/pure/collections/sequtils.nim

@@ -803,12 +803,6 @@ template anyIt*(s, pred: untyped): bool =
       break
   result
 
-template toSeqIterable[T](s: iterable[T]): seq[T] =
-  var result: seq[T] = @[]
-  for it in s:
-    result.add(it)
-  result
-
 template toSeq1(s: not iterator): untyped =
   # overload for typed but not iterator
   type OutType = typeof(items(s))
@@ -868,9 +862,7 @@ template toSeq*(iter: untyped): untyped =
     assert mySeq1 == @[1, 2, 3, 4, 5]
     assert mySeq2 == @[1'i8, 3, 5]
 
-  when compiles(toSeqIterable(iter)):
-    toSeqIterable(iter)
-  elif compiles(toSeq1(iter)):
+  when compiles(toSeq1(iter)):
     toSeq1(iter)
   elif compiles(toSeq2(iter)):
     toSeq2(iter)

tests/stdlib/tsequtils.nim

@@ -342,14 +342,9 @@ block: # toSeq test
 block:
   # tests https://github.com/nim-lang/Nim/issues/7187
   counter = 0
-  var s: seq[int]
-  for x in @[1, 2, 3].identity().filter(proc (x: int): bool = x < 3):
-    s.add(x)
-  let intendedCounter = counter
-  counter = 0
   let ret = toSeq(@[1, 2, 3].identity().filter(proc (x: int): bool = x < 3))
   doAssert ret == @[1, 2]
-  doAssert counter == intendedCounter
+  doAssert counter == 1
 block: # foldl tests
   let
     numbers = @[5, 9, 11]