Add tests for unused labels

testsuite/tests/typing-warnings/unused_types.ml

@@ -345,3 +345,75 @@ Line 3, characters 2-30:
 Warning 34 [unused-type-declaration]: unused type t.
 module Unused_constructor_disable_warning : sig end
 |}]
+
+
+module Unused_record : sig end = struct
+  type t = { a : int; b : int }
+  let foo (x : t) = x
+  let _ = foo
+end;;
+[%%expect {|
+module Unused_record : sig end
+|}]
+
+module Unused_field : sig end = struct
+  type t = { a : int }
+  let foo () = { a = 0 }
+  let _ = foo
+end;;
+[%%expect {|
+module Unused_field : sig end
+|}]
+
+module Unused_field : sig end = struct
+  type t = { a : int; b : int; c : int }
+  let foo () = { a = 0; b = 0; c = 0 }
+  let bar x = x.a
+  let baz { c; _ } = c
+  let _ = foo, bar, baz
+end;;
+[%%expect {|
+module Unused_field : sig end
+|}]
+
+module Unused_mutable_field : sig end = struct
+  type t = { a : int; mutable b : int }
+  let foo () = { a = 0; b = 0 }
+  let bar x = x.a, x.b
+  let _ = foo, bar
+end;;
+[%%expect {|
+module Unused_mutable_field : sig end
+|}]
+
+module Unused_field_exported_private : sig
+  type t = private { a : int }
+end = struct
+  type t = { a : int }
+end;;
+[%%expect {|
+module Unused_field_exported_private : sig type t = private { a : int; } end
+|}]
+
+module Unused_field_exported_private : sig
+  type t = private { a : int }
+end = struct
+  type t = { a : int }
+  let foo x = x.a
+  let _ = foo
+end;;
+[%%expect {|
+module Unused_field_exported_private : sig type t = private { a : int; } end
+|}]
+
+module Unused_mutable_field_exported_private : sig
+  type t = private { a : int; mutable b : int }
+end = struct
+  type t = { a : int; mutable b : int }
+  let foo () = { a = 0; b = 0 }
+  let _ = foo
+end;;
+[%%expect {|
+module Unused_mutable_field_exported_private :
+  sig type t = private { a : int; mutable b : int; } end
+|}]