Fix usage of parameters types in templates #6756 (#6768)

tests/ccgbugs/t6756.nim

@@ -0,0 +1,18 @@
+import typetraits
+type
+  A[T] = ref object
+    v: T
+
+template templ(o: A, op: untyped): untyped =
+  type T = type(o.v)
+
+  var res: A[T]
+
+  block:
+    var it {.inject.}: T
+    it = o.v
+    res = A[T](v: op)
+  res
+
+let a = A[int](v: 1)
+echo templ(a, it + 2)[]