add some tests

tests/spec/tobjectconstr_unamed.nim

@@ -0,0 +1,78 @@
+type
+  Vector = object
+    a: int = 999
+    b, c: int
+
+block: # positional construction
+  ## It specifies all the unnamed parameters
+  var x = Vector(1, 2, 3)
+  doAssert x.b == 2
+
+block:
+  ## unnamed parameters can be mixed with named parameters
+  block:
+    var x = Vector(a: 1, 2, 3)
+    doAssert x.c == 3
+
+  block:
+    var x = Vector(1, b: 2, 3)
+    doAssert x.c == 3
+
+  block:
+    var x = Vector(1, 2, c: 3)
+    doAssert x.c == 3
+
+  block:
+    ## Parameters can be omitted before a named parameter
+    var x = Vector(b: 2, 3)
+    doAssert x.c == 3
+
+
+block:
+  ## Object variants support unnamed parameters for tags, which should be known at the compile time.
+  type
+    Color = enum
+      Red, Blue, Yellow
+    Factor = object
+      id: int
+      case flag: Color
+      of Red:
+        num: int
+      of Blue, Yellow:
+        done: bool
+      name: string
+
+  block:
+    var x = Factor(1, Red, 2, "1314")
+    doAssert x.num == 2
+
+  block:
+    var x = Factor(1, Blue, true, "1314")
+    doAssert x.done == true
+
+  block:
+    var x = Factor(1, Yellow, false, "1314")
+    doAssert x.done == false
+
+
+  type
+    Ciao = object
+      id: int
+      case flag: bool = false
+      of true:
+        num: int
+      of false:
+        done: bool
+      name: string
+
+  block:
+    var x = Ciao(12, false, false, "123")
+    doAssert x.num == false
+
+  block:
+    var x = Ciao(12, flag: true, 1, "123")
+    doAssert x.num == 1
+
+  block:
+    var x = Ciao(flag: true, 1, "123")
+    doAssert x.num == 1