fixes #25796; fixes procParamTypeRel to ensure backend type consistency

compiler/sigmatch.nim

@@ -791,8 +791,12 @@ proc procParamTypeRel(c: var TCandidate; f, a: PType): TTypeRelation =
     # different C types (size_t vs unsigned long long).
     let fCheck = concreteType(c, f)
     let aCheck = concreteType(c, a)
+    # Notes that `result` is requal, now
+    # we checks whether they have the same backend type
     if fCheck != nil and aCheck != nil and
-        not sameBackendTypePickyAliases(fCheck, aCheck):
+        not sameBackendTypePickyAliases(
+          fCheck.skipTypes({tyVar, tyLent, tySink, tyOwned}),
+          aCheck.skipTypes({tyVar, tyLent, tySink, tyOwned})):
       result = isNone
 
   if result <= isSubrange or inconsistentVarTypes(f, a):

tests/proc/tproc.nim

@@ -29,3 +29,30 @@ block tnestprc:
       result = x + y
     result = add(x, 3)
   doAssert Add3(7) == 10
+
+block:
+  type A = object
+    c: int
+  type H = proc(): lent A {.nimcall.}
+  const u = A(c: 0)
+  proc e(T: typedesc): lent A = u
+  proc y(T: typedesc): H =
+    proc(): lent A {.nimcall.} = T.e
+  discard y(int)
+
+block:
+  type A = object
+    c: int
+  type H = proc(): lent A {.nimcall.}
+  let u = A(c: 0)
+  proc y(_: int | int): H =
+    proc(): lent A {.nimcall.} = u
+  discard y(0)
+
+block:
+  type A = object
+    c: int
+  type H = proc(): lent A {.nimcall.}
+  let u = A()
+  let _: H = proc(): lent A {.nimcall.} = u
+