fixes #25252; Unexpected ambiguous call with fields over object with default fields (#25256)

fixes #25252

(cherry picked from commit d54b5f3ae1)

tests/objects/tobject_default_value.nim

@@ -375,7 +375,7 @@ template main {.dirty.} =
     type
       Color = enum
         Red, Blue, Yellow
-  
+
     type
       ObjectVarint3 = object
         case kind: Color = Blue
@@ -663,7 +663,7 @@ template main {.dirty.} =
 
       when not(T is void):
         v.vResultPrivate
-        
+
     type R = Result[int, string]
 
     proc testAssignResult() =
@@ -811,3 +811,17 @@ template main {.dirty.} =
 
 static: main()
 main()
+
+type
+  Thing = object
+    a: int = 100 # this is fine
+    b = 100 # this is not
+
+proc overloaded[T: SomeSignedInt](x: T) = discard
+proc overloaded[T: SomeUnsignedInt](x: T) = discard
+proc overloaded[T: object](x: T) =
+  for val in fields(x):
+    var v: typeof(val)
+    overloaded(v)
+
+overloaded(Thing())