fixes #3054

compiler/ast.nim

@@ -1006,7 +1006,8 @@ proc newSym*(symKind: TSymKind, name: PIdent, owner: PSym,
   result.id = getID()
   when debugIds:
     registerId(result)
-  #if result.id < 2000:
+  #if result.id == 93289:
+  #  writeStacktrace()
   #  MessageOut(name.s & " has id: " & toString(result.id))
 
 var emptyNode* = newNode(nkEmpty)

compiler/lambdalifting.nim

@@ -1016,7 +1016,9 @@ proc liftForLoop*(body: PNode): PNode =
         ...
     """
   var L = body.len
-  internalAssert body.kind == nkForStmt and body[L-2].kind in nkCallKinds
+  if not (body.kind == nkForStmt and body[L-2].kind in nkCallKinds):
+    localError(body.info, "ignored invalid for loop")
+    return body
   var call = body[L-2]
 
   result = newNodeI(nkStmtList, body.info)

compiler/transf.nim

@@ -465,14 +465,13 @@ proc transformFor(c: PTransf, n: PNode): PTransNode =
   var call = n.sons[length - 2]
 
   let labl = newLabel(c, n)
-  c.breakSyms.add(labl)
   result = newTransNode(nkBlockStmt, n.info, 2)
   result[0] = newSymNode(labl).PTransNode
   if call.typ.isNil:
     # see bug #3051
     result[1] = newNode(nkEmpty).PTransNode
-    discard c.breakSyms.pop
     return result
+  c.breakSyms.add(labl)
   if call.typ.kind != tyIter and
     (call.kind notin nkCallKinds or call.sons[0].kind != nkSym or
       call.sons[0].sym.kind != skIterator):
@@ -483,10 +482,10 @@ proc transformFor(c: PTransf, n: PNode): PTransNode =
 
   #echo "transforming: ", renderTree(n)
   var stmtList = newTransNode(nkStmtList, n.info, 0)
+  result[1] = stmtList
 
   var loopBody = transformLoopBody(c, n.sons[length-1])
 
-  result[1] = stmtList
   discard c.breakSyms.pop
 
   var v = newNodeI(nkVarSection, n.info)