generic multi-methods should work now

compiler/semtypinst.nim

@@ -289,7 +289,8 @@ proc handleGenericInvocation(cl: var TReplTypeVars, t: PType): PType =
     # but we already raised an error!
     rawAddSon(result, header.sons[i])
 
-  var newbody = replaceTypeVarsT(cl, lastSon(body))
+  let bbody = lastSon body
+  var newbody = replaceTypeVarsT(cl, bbody)
   cl.skipTypedesc = oldSkipTypedesc
   newbody.flags = newbody.flags + (t.flags + body.flags - tfInstClearedFlags)
   result.flags = result.flags + newbody.flags - tfInstClearedFlags
@@ -306,12 +307,18 @@ proc handleGenericInvocation(cl: var TReplTypeVars, t: PType): PType =
     # 'deepCopy' needs to be instantiated for
     # generics *when the type is constructed*:
     newbody.deepCopy = cl.c.instTypeBoundOp(cl.c, dc, result, cl.info,
-                                            attachedDeepCopy)
+                                            attachedDeepCopy, 1)
   let asgn = newbody.assignment
   if asgn != nil and sfFromGeneric notin asgn.flags:
     # '=' needs to be instantiated for generics when the type is constructed:
     newbody.assignment = cl.c.instTypeBoundOp(cl.c, asgn, result, cl.info,
-                                              attachedAsgn)
+                                              attachedAsgn, 1)
+  let methods = skipTypes(bbody, abstractPtrs).methods
+  for col, meth in items(methods):
+    # we instantiate the known methods belonging to that type, this causes
+    # them to be registered and that's enough, so we 'discard' the result.
+    discard cl.c.instTypeBoundOp(cl.c, meth, result, cl.info,
+      attachedAsgn, col)
 
 proc eraseVoidParams*(t: PType) =
   # transform '(): void' into '()' because old parts of the compiler really