fix #5864

compiler/sigmatch.nim

@@ -2228,6 +2228,8 @@ proc matches*(c: PContext, n, nOrig: PNode, m: var TCandidate) =
         var def = copyTree(formal.ast)
         if def.kind == nkNilLit:
           def = implicitConv(nkHiddenStdConv, formal.typ, def, m, c)
+        if {tfImplicitTypeParam, tfGenericTypeParam} * formal.typ.flags != {}:
+          put(m, formal.typ, def.typ)
         setSon(m.call, formal.position + 1, def)
     inc(f)
   # forget all inferred types if the overload matching failed

tests/generics/tgenericsdefaultvalues.nim

@@ -0,0 +1,14 @@
+discard """
+output: "12"
+"""
+
+# https://github.com/nim-lang/Nim/issues/5864
+
+proc defaultStatic(s: openarray, N: static[int] = 1): int = N
+proc defaultGeneric[T](a: T = 2): int = a
+
+let a = [1, 2, 3, 4].defaultStatic()
+let b = defaultGeneric()
+
+echo a, b
+