fixes #2167

compiler/semcall.nim

@@ -72,8 +72,9 @@ proc pickBestCandidate(c: PContext, headSymbol: PNode,
           if cmp < 0: best = z   # x is better than the best so far
           elif cmp == 0: alt = z # x is as good as the best so far
           else: discard
-        #if sym.name.s == "shl" and (n.info ?? "net.nim"):
+        #if sym.name.s == "*" and (n.info ?? "temp5.nim"):
         #  echo "Matches ", n.info, " ", typeToString(sym.typ)
+        #  debug sym
         #  writeMatches(z)
     sym = nextOverloadIter(o, c, headSymbol)
 

compiler/types.nim

@@ -796,7 +796,7 @@ template ifFastObjectTypeCheckFailed(a, b: PType, body: stmt) {.immediate.} =
   else:
     # expensive structural equality test; however due to the way generic and
     # objects work, if one of the types does **not** contain tfFromGeneric,
-    # they cannot be equal. The check ``a.sym.Id == b.sym.Id`` checks
+    # they cannot be equal. The check ``a.sym.id == b.sym.id`` checks
     # for the same origin and is essential because we don't want "pure" 
     # structural type equivalence:
     #

compiler/vm.nim

@@ -1087,14 +1087,20 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
     of opcNAdd:
       decodeBC(rkNode)
       var u = regs[rb].node
-      u.add(regs[rc].node)
+      if u.kind notin {nkEmpty..nkNilLit}:
+        u.add(regs[rc].node)
+      else:
+        stackTrace(c, tos, pc, errGenerated, "cannot add to node kind: " & $u.kind)
       regs[ra].node = u
     of opcNAddMultiple:
       decodeBC(rkNode)
       let x = regs[rc].node
       var u = regs[rb].node
-      # XXX can be optimized:
-      for i in 0.. <x.len: u.add(x.sons[i])
+      if u.kind notin {nkEmpty..nkNilLit}:
+        # XXX can be optimized:
+        for i in 0.. <x.len: u.add(x.sons[i])
+      else:
+        stackTrace(c, tos, pc, errGenerated, "cannot add to node kind: " & $u.kind)
       regs[ra].node = u
     of opcNKind:
       decodeB(rkInt)