fixes #2051

compiler/semexprs.nim

@@ -756,6 +756,9 @@ proc semOverloadedCallAnalyseEffects(c: PContext, n: PNode, nOrig: PNode,
     else:
       if callee.kind in skIterators and callee.id == c.p.owner.id:
         localError(n.info, errRecursiveDependencyX, callee.name.s)
+        # error correction, prevents endless for loop elimination in transf.
+        # See bug #2051:
+        result.sons[0] = newSymNode(errorSym(c, n))
       if sfNoSideEffect notin callee.flags: 
         if {sfImportc, sfSideEffect} * callee.flags != {}:
           incl(c.p.owner.flags, sfSideEffect)

compiler/transf.nim

@@ -492,7 +492,8 @@ proc transformFor(c: PTransf, n: PNode): PTransNode =
   var newC = newTransCon(getCurrOwner(c))
   newC.forStmt = n
   newC.forLoopBody = loopBody
-  internalAssert iter.kind == skIterator
+  # this can fail for 'nimsuggest' and 'check':
+  if iter.kind != skIterator: return result
   # generate access statements for the parameters (unless they are constant)
   pushTransCon(c, newC)
   for i in countup(1, sonsLen(call) - 1):