the is operator now uses exactly the same algorithm as proc signature matching

compiler/semexprs.nim

@@ -322,24 +322,13 @@ proc isOpImpl(c: PContext, n: PNode): PNode =
                                         t.callConv == ccClosure and 
                                         tfIterator in t.flags))
   else:
-    var match: bool
-    let t2 = n[2].typ.skipTypes({tyTypeDesc})
-    case t2.kind
-    of tyTypeClasses:
-      var m: TCandidate
-      initCandidate(c, m, t2)
-      match = typeRel(m, t2, t1) != isNone
-    of tyOrdinal:
-      var m: TCandidate
-      initCandidate(c, m, t2)
-      match = isOrdinalType(t1)
-    of tySequence, tyArray, tySet:
-      var m: TCandidate
-      initCandidate(c, m, t2)
-      match = typeRel(m, t2, t1) != isNone
-    else:
-      match = sameType(t1, t2)
- 
+    var t2 = n[2].typ.skipTypes({tyTypeDesc})
+    let lifted = liftParamType(c, skType, newNodeI(nkArgList, n.info),
+                               t2, ":anon", n.info)
+    if lifted != nil: t2 = lifted
+    var m: TCandidate
+    initCandidate(c, m, t2)
+    let match = typeRel(m, t2, t1) != isNone
     result = newIntNode(nkIntLit, ord(match))
 
   result.typ = n.typ

compiler/sigmatch.nim

@@ -820,7 +820,7 @@ proc typeRel(c: var TCandidate, f, aOrig: PType, doBind = true): TTypeRelation =
       else:
         return isNone
 
-  of tyUserTypeClassInst:
+  of tyUserTypeClass, tyUserTypeClassInst:
     considerPreviousT:
       result = matchUserTypeClass(c.c, c, f, a)
       if result == isGeneric:

lib/pure/sockets.nim

@@ -192,7 +192,7 @@ when defined(Posix):
     of AF_UNIX:        result = posix.AF_UNIX
     of AF_INET:        result = posix.AF_INET
     of AF_INET6:       result = posix.AF_INET6
-    else: nil
+    else: discard
 
   proc toInt(typ: TType): cint =
     case typ
@@ -200,7 +200,7 @@ when defined(Posix):
     of SOCK_DGRAM:     result = posix.SOCK_DGRAM
     of SOCK_SEQPACKET: result = posix.SOCK_SEQPACKET
     of SOCK_RAW:       result = posix.SOCK_RAW
-    else: nil
+    else: discard
 
   proc toInt(p: TProtocol): cint =
     case p
@@ -210,7 +210,7 @@ when defined(Posix):
     of IPPROTO_IPV6:   result = posix.IPPROTO_IPV6
     of IPPROTO_RAW:    result = posix.IPPROTO_RAW
     of IPPROTO_ICMP:   result = posix.IPPROTO_ICMP
-    else: nil
+    else: discard
 
 else:
   proc toInt(domain: TDomain): cint =