fix #12864 static params were mutating arg types during sigmatch; fix #12713 ; refs #13529 (#13976)

* fix #12864 static params were mutating arg types during sigmatch

* fix test

* fix StaticParam

* also fixes #12713; added test case

tests/metatype/tstaticparams.nim

@@ -171,3 +171,27 @@ echo inSize([
   [1, 2, 3],
   [4, 5, 6]
 ])
+
+block: # #12864
+  template fun() =
+    type Object = object
+    proc fun(f: Object): int = 1
+    proc fun(f: static[int]): int = 2
+    doAssert fun(Object()) == 1
+
+    var a: Object
+    doAssert fun(a) == 1
+
+    proc fun2(f: Object): int = 1
+    proc fun2(f: static[Object]): int = 2
+    doAssert fun2(Object()) == 2
+    doAssert fun2(a) == 1
+    const a2 = Object()
+    doAssert fun2(a2) == 2
+
+  fun()
+  static: fun()
+
+when true: #12864 original snippet
+  import times
+  discard times.format(initDateTime(30, mMar, 2017, 0, 0, 0, 0, utc()), TimeFormat())

tests/metatype/ttypetraits.nim

@@ -145,6 +145,7 @@ block genericParams:
   doAssert genericParams(Bar3).get(0) is StaticParam
   doAssert genericParams(Bar3).get(0).value == 3
   doAssert genericParams(Bar[3, float]).get(0).value == 3
+  static: doAssert genericParams(Bar[3, float]).get(0).value == 3
 
   type
     VectorElementType = SomeNumber | bool