flambda-backend: Clean up mode error printing (#2478)

* clean up mode error printing

* better phrasing

Author: riaqn

testsuite/tests/typing-local/crossing.ml

@@ -54,8 +54,9 @@ let f : local_ _ -> _ =
 Line 2, characters 14-15:
 2 |   fun x -> f' x
                   ^
-Error: This value escapes its region
-  Hint: This argument cannot be local, because it is an argument in a tail call
+Error: This value escapes its region.
+  Hint: This argument cannot be local,
+  because it is an argument in a tail call.
 |}]
 
 (* 2. constructor argument crosses mode at construction *)
@@ -71,7 +72,7 @@ let f : local_ _ -> bar =
 Line 2, characters 21-22:
 2 |   fun n -> Bar0 (42, n)
                          ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 (* 3. record field crosses mode at construction *)
@@ -87,7 +88,7 @@ let f : local_ _ -> foo =
 Line 2, characters 24-25:
 2 |   fun n -> {x = 42; y = n}
                             ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 (* 4. expression crosses mode when being constrained *)
@@ -103,7 +104,7 @@ let f : local_ _ -> _ =
 Line 2, characters 12-13:
 2 |   fun n -> (n : string)
                 ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 (* 5. polymorphic variant arguments crosses mode on construction*)
@@ -119,7 +120,7 @@ let f : local_ _ -> [> `Text of string] =
 Line 2, characters 17-18:
 2 |   fun n -> `Text n
                      ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 (* tuple elements crosses mode at construction *)
@@ -135,7 +136,7 @@ let f : local_ _ -> string * string =
 Line 2, characters 12-13:
 2 |   fun n -> (n, n)
                 ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 (* array elements crosses mode at construction *)
@@ -151,7 +152,7 @@ let f: local_ _ -> string array =
 Line 2, characters 13-14:
 2 |   fun n -> [|n; n|]
                  ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 (* after discussion with sdolan, we agree that
@@ -179,7 +180,7 @@ let f : local_ foo -> _ =
 Line 2, characters 11-14:
 2 |   fun r -> r.y
                ^^^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 (* the expected type is not considered when mode crossing the result of
@@ -215,8 +216,9 @@ val g : string -> string = <fun>
 Line 6, characters 6-22:
 6 |     g (local_ "world")
           ^^^^^^^^^^^^^^^^
-Error: This value escapes its region
-  Hint: This argument cannot be local, because it is an argument in a tail call
+Error: This value escapes its region.
+  Hint: This argument cannot be local,
+  because it is an argument in a tail call.
 |}]
 
 (* the result of function application crosses mode *)
@@ -244,7 +246,7 @@ let g : _ -> _ =
 Line 2, characters 28-29:
 2 |   fun () -> let x = f () in x
                                 ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 (* constructor argument crosses modes upon pattern matching *)
@@ -276,7 +278,7 @@ let f : local_ bar -> _ =
 Line 4, characters 21-22:
 4 |     | Bar0 (_, y) -> y
                          ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 (* record fields crosses modes upon pattern matching *)
@@ -306,7 +308,7 @@ let f : local_ foo -> _ =
 Line 4, characters 16-17:
 4 |     | {y; _} -> y
                     ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 (* constraint crosses modes upon pattern matching  *)
@@ -322,7 +324,7 @@ let f : local_ _ -> _ =
 Line 2, characters 22-23:
 2 |   fun (x : string) -> x
                           ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 

testsuite/tests/typing-local/exclave.ml

@@ -62,7 +62,7 @@ let foo x =
 Line 5, characters 8-9:
 5 |     ref y
             ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 (* following we check error detection *)
@@ -84,7 +84,7 @@ let foo x =
 Line 3, characters 10-25:
 3 |   let z = exclave_ Some y in
               ^^^^^^^^^^^^^^^
-Error: Exclave expression should only be in tail position of the current region
+Error: Exclave expression should only be in tail position of the current region.
 |}]
 
 (* following we test WHILE loop *)
@@ -108,7 +108,7 @@ let foo () =
 Line 3, characters 4-17:
 3 |     (exclave_ ());
         ^^^^^^^^^^^^^
-Error: Exclave expression should only be in tail position of the current region
+Error: Exclave expression should only be in tail position of the current region.
 |}]
 
 (* following we test FOR loop *)
@@ -129,7 +129,7 @@ let foo () =
 Line 3, characters 4-17:
 3 |     (exclave_ ());
         ^^^^^^^^^^^^^
-Error: Exclave expression should only be in tail position of the current region
+Error: Exclave expression should only be in tail position of the current region.
 |}]
 
 type t = { x : int option }
@@ -162,7 +162,7 @@ type data = { mutable a : string; }
 Line 6, characters 9-10:
 6 |   x.a <- z;
              ^
-Error: This value escapes its region
+Error: This value escapes its region.
 |}]
 
 let foo x =