Check for type recursion without boxing

testsuite/tests/letrec-check/unboxed.ml

@@ -23,14 +23,17 @@ Line 2, characters 12-19:
 Error: This kind of expression is not allowed as right-hand side of "let rec"
 |}];;
 
+(* This test was made to error by disallowing singleton recursive unboxed types.
+   We keep it in case these are re-allowed, in which case it should error with:
+   [This kind of expression is not allowed as right-hand side of "let rec"] *)
 type r = A of r [@@unboxed]
 let rec y = A y;;
 [%%expect{|
-type r = A of r [@@unboxed]
-Line 2, characters 12-15:
-2 | let rec y = A y;;
-                ^^^
-Error: This kind of expression is not allowed as right-hand side of "let rec"
+Line 1, characters 0-27:
+1 | type r = A of r [@@unboxed]
+    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Error: The definition of "r" is recursive without boxing:
+         "r" contains "r"
 |}];;
 
 (* This test is not allowed if 'a' is unboxed, but should be accepted

testsuite/tests/typing-layouts-unboxed-records/basics_alpha.ml

@@ -25,19 +25,20 @@ type t = { x : t_void; } [@@unboxed]
 
 type bad : void = #{ bad : bad }
 [%%expect{|
-type bad = #{ bad : bad; }
+Line 1, characters 0-32:
+1 | type bad : void = #{ bad : bad }
+    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Error: The definition of "bad" is recursive without boxing:
+         "bad" contains "bad"
 |}]
 
 type ('a : void) bad  = #{ bad : 'a bad ; u : 'a}
 [%%expect{|
 Line 1, characters 0-49:
 1 | type ('a : void) bad  = #{ bad : 'a bad ; u : 'a}
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Error:
-       The layout of 'a bad is any & any
-         because it is an unboxed record.
-       But the layout of 'a bad must be representable
-         because it is the type of record field bad.
+Error: The definition of "bad" is recursive without boxing:
+         "'a bad" contains "'a bad"
 |}]
 
 (******************************************************************************)

testsuite/tests/typing-layouts-unboxed-records/basics_from_typing_atat_unboxed.ml

@@ -80,14 +80,24 @@ in assert (f x = #{ f = 3.14});;
 - : unit = ()
 |}];;
 
-(* Check for a potential infinite loop in the typing algorithm. *)
+(* Check for a potential infinite loop in the typing algorithm.
+   (This test was made to error upon disallowing singleton recursive unboxed
+   types. We keep it around in case these are re-allowed.) *)
 type 'a t12 : value = #{ a : 'a t12 };;
 [%%expect{|
-type 'a t12 = #{ a : 'a t12; }
+Line 1, characters 0-37:
+1 | type 'a t12 : value = #{ a : 'a t12 };;
+    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Error: The definition of "t12" is recursive without boxing:
+         "'a t12" contains "'a t12"
 |}];;
 let f (a : int t12 array) = a.(0);;
 [%%expect{|
-val f : int t12 array -> int t12 = <fun>
+Line 1, characters 15-18:
+1 | let f (a : int t12 array) = a.(0);;
+                   ^^^
+Error: Unbound type constructor "t12"
+Hint: Did you mean "t11" or "t2"?
 |}];;
 
 (* should work *)

testsuite/tests/typing-layouts-unboxed-records/letrec.ml

@@ -7,14 +7,17 @@
  }
 *)
 
+(* This test was made to error by disallowing singleton recursive unboxed types.
+   We keep it in case these are re-allowed, in which case it should error with:
+   [This kind of expression is not allowed as right-hand side of "let rec"] *)
 type t : value = #{ t : t }
 let rec t = #{ t = t }
 [%%expect{|
-type t = #{ t : t; }
-Line 2, characters 12-22:
-2 | let rec t = #{ t = t }
-                ^^^^^^^^^^
-Error: This kind of expression is not allowed as right-hand side of "let rec"
+Line 1, characters 0-27:
+1 | type t : value = #{ t : t }
+    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Error: The definition of "t" is recursive without boxing:
+         "t" contains "t"
 |}]
 
 type bx = { bx : ubx }