fixes #4856

compiler/seminst.nim

@@ -99,7 +99,8 @@ proc genericCacheGet(genericSym: PSym, entry: TInstantiation;
 
 proc freshGenSyms(n: PNode, owner, orig: PSym, symMap: var TIdTable) =
   # we need to create a fresh set of gensym'ed symbols:
-  if n.kind == nkSym and sfGenSym in n.sym.flags and n.sym.owner == orig:
+  if n.kind == nkSym and sfGenSym in n.sym.flags and
+      (n.sym.owner == orig or n.sym.owner.kind == skPackage):
     let s = n.sym
     var x = PSym(idTableGet(symMap, s))
     if x == nil:

compiler/vm.nim

@@ -1421,7 +1421,7 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
                  else: regs[rc].node.strVal
       if k < 0 or k > ord(high(TSymKind)):
         internalError(c.debug[pc], "request to create symbol of invalid kind")
-      var sym = newSym(k.TSymKind, name.getIdent, c.module, c.debug[pc])
+      var sym = newSym(k.TSymKind, name.getIdent, c.module.owner, c.debug[pc])
       incl(sym.flags, sfGenSym)
       regs[ra].node = newSymNode(sym)
     of opcTypeTrait:

tests/async/tgenericasync.nim

@@ -0,0 +1,14 @@
+discard """
+  output: '''123
+abc'''
+"""
+
+# bug #4856
+
+import asyncdispatch
+
+proc say[T](t: T): Future[void] {.async.} =
+  echo $t
+
+waitFor(say(123))
+waitFor(say("abc"))