test cases for the new handling of iterators by the is operator

compiler/semexprs.nim

@@ -323,11 +323,6 @@ proc isOpImpl(c: PContext, n: PNode): PNode =
       result = newIntNode(nkIntLit, ord(t.kind == tyProc and
                                         t.callConv == ccClosure and 
                                         tfIterator notin t.flags))
-    of "iterator":
-      let t = skipTypes(t1, abstractRange)
-      result = newIntNode(nkIntLit, ord(t.kind == tyProc and
-                                        t.callConv == ccClosure and 
-                                        tfIterator in t.flags))
   else:
     var t2 = n[2].typ.skipTypes({tyTypeDesc})
     let lifted = liftParamType(c, skType, newNodeI(nkArgList, n.info),

compiler/sigmatch.nim

@@ -410,7 +410,10 @@ proc procTypeRel(c: var TCandidate, f, a: PType): TTypeRelation =
         return isNone
     when useEffectSystem:
       if not compatibleEffects(f, a): return isNone
-  of tyNil: result = f.allowsNil
+  of tyNil:
+    result = f.allowsNil
+  of tyIter:
+    if tfIterator in f.flags: result = typeRel(c, f.base, a.base)
   else: discard
 
 proc typeRangeRel(f, a: PType): TTypeRelation {.noinline.} =
@@ -923,8 +926,11 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation =
         result = isNone
  
   of tyIter:
-    if a.kind == f.kind: result = typeRel(c, f.base, a.base)
+    if a.kind == tyIter or 
-    else: result = isNone
+      (a.kind == tyProc and tfIterator in a.flags):
+      result = typeRel(c, f.base, a.base)
+    else:
+      result = isNone
 
   of tyStmt:
     result = isGeneric

tests/types/tisopr.nim

@@ -1,5 +1,8 @@
 discard """
-  output: "true true false yes"
+  output: '''true
+true
+false
+yes'''
 """
 
 proc IsVoid[T](): string = 
@@ -11,3 +14,26 @@ proc IsVoid[T](): string =
 const x = int is int
 echo x, " ", float is float, " ", float is string, " ", IsVoid[void]()
 
+template yes(e: expr): stmt =
+  static: assert e
+
+template no(e: expr): stmt =
+  static: assert(not e)
+
+var s = @[1, 2, 3]
+
+yes s.items is iterator
+no  s.items is proc
+
+yes s.items is iterator: int
+no  s.items is iterator: float
+
+yes s.items is iterator: TNumber
+no  s.items is iterator: object
+
+type 
+  Iter[T] = iterator: T
+
+yes s.items is Iter[TNumber]
+no  s.items is Iter[float]
+