two small concept patches (#25076)

- slightly better typeclass logic (eg for bare `range`)
- reverse matching now substitutes potential implementation for `Self`

---------

Co-authored-by: ringabout <43030857+ringabout@users.noreply.github.com>

tests/concepts/tconceptsv2.nim

@@ -497,6 +497,28 @@ block:
 
   spring({One,Two})
 
+block: # bare `range`
+  type
+    MyRange = 0..64
+    MyConcept = concept
+      proc a(x: typedesc[Self])
+
+  proc a(x: typedesc[range]) = discard
+  proc spring(x: typedesc[MyConcept]) = discard
+  spring(MyRange)
+
+block:
+  type
+    A = object
+    TestConcept =
+      concept
+          proc x(x: Self)
+
+  proc x(x: not object) =
+    discard
+
+  assert A isnot TestConcept
+
 # this code fails inside a block for some reason
 type Indexable[T] = concept
   proc `[]`(t: Self, i: int): T