Improve layout history error message: review new messages

ocaml/testsuite/tests/typing-immediate/immediate.ml

@@ -161,7 +161,7 @@ Line 2, characters 2-41:
 2 |   type t = Foo of int | Bar [@@immediate]
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Error: The layout of type t is value, because
-         it's a boxed variant.
+         it's a boxed variant type.
        But the layout of type t must be a sublayout of immediate, because
          of the annotation on the declaration of the type t.
 |}];;
@@ -175,7 +175,7 @@ Line 2, characters 2-38:
 2 |   type t = { foo : int } [@@immediate]
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Error: The layout of type t is value, because
-         it's a boxed record.
+         it's a boxed record type.
        But the layout of type t must be a sublayout of immediate, because
          of the annotation on the declaration of the type t/2.
 |}];;

ocaml/testsuite/tests/typing-layouts-err-msg/any_missing_cmi.ml

@@ -10,8 +10,6 @@ module = "any_missing_cmi_lib.ml"
 script = "rm -f any_missing_cmi_lib2.cmi"
 ***** expect
 *)
-(* CR layouts v2.9: all error messages below here are unreviewed *)
-
 
 #directory "ocamlc.byte";;
 #load "any_missing_cmi_lib.cmo";;
@@ -24,8 +22,8 @@ Line 1, characters 30-44:
 Error: Function arguments and returns must be representable.
        The layout of Any_missing_cmi_lib2.t is any, because
          the .cmi file for Any_missing_cmi_lib2.t is missing.
-       But the layout of Any_missing_cmi_lib2.t must be a sublayout of '_representable_layout_1, because
-         it's used as a function argument.
+       But the layout of Any_missing_cmi_lib2.t must be representable, because
+         it's the type of a function argument.
        No .cmi file found containing Any_missing_cmi_lib2.t.
        Hint: Adding "any_missing_cmi_lib2" to your dependencies might help.
 |}]

ocaml/testsuite/tests/typing-layouts-err-msg/concrete.ml

@@ -22,7 +22,7 @@ Error: This expression has type t_any but an expression was expected of type
          ('a : '_representable_layout_1)
        The layout of t_any is any, because
          of the definition of t_any at line 1, characters 0-16.
-       But the layout of t_any must be a sublayout of '_representable_layout_1, because
+       But the layout of t_any must be representable, because
          a value of this type is matched against a pattern.
 |}]
 
@@ -36,8 +36,8 @@ Line 1, characters 9-19:
 Error: Constructor argument types must have a representable layout.
        The layout of t_any is any, because
          of the definition of t_any at line 1, characters 0-16.
-       But the layout of t_any must be a sublayout of '_representable_layout_2, because
-         it's used as the type of a constructor field.
+       But the layout of t_any must be representable, because
+         it's the type of a constructor field.
 |}]
 
 (* Label_declaration *)
@@ -50,7 +50,7 @@ Line 1, characters 10-18:
 Error: Record element types must have a representable layout.
        The layout of t_any is any, because
          of the definition of t_any at line 1, characters 0-16.
-       But the layout of t_any must be a sublayout of '_representable_layout_3, because
+       But the layout of t_any must be representable, because
          it is the type of record field a.
 |}]
 
@@ -63,10 +63,10 @@ Line 2, characters 9-14:
 2 | and t2 = t_any t
              ^^^^^
 Error: This type t_any should be an instance of type
-         ('a : '_representable_layout_4)
+         ('a : '_representable_layout_2)
        The layout of t_any is any, because
          of the definition of t_any at line 1, characters 0-16.
-       But the layout of t_any must be a sublayout of '_representable_layout_4, because
+       But the layout of t_any must be representable, because
          it instantiates an unannotated type parameter of t.
 |}]
 
@@ -85,10 +85,10 @@ Line 1, characters 4-12:
         ^^^^^^^^
 Error: This pattern matches values of type t_any
        but a pattern was expected which matches values of type
-         ('a : '_representable_layout_5)
+         ('a : '_representable_layout_3)
        The layout of t_any is any, because
          of the definition of t_any at line 1, characters 0-16.
-       But the layout of t_any must be a sublayout of '_representable_layout_5, because
+       But the layout of t_any must be representable, because
          it's the type of a variable bound by a `let`.
 |}]
 
@@ -101,11 +101,11 @@ Line 1, characters 6-16:
           ^^^^^^^^^^
 Error: This pattern matches values of type t_any
        but a pattern was expected which matches values of type
-         ('a : '_representable_layout_6)
+         ('a : '_representable_layout_4)
        The layout of t_any is any, because
          of the definition of t_any at line 1, characters 0-16.
-       But the layout of t_any must be a sublayout of '_representable_layout_6, because
-         it's used as a function argument.
+       But the layout of t_any must be representable, because
+         it's the type of a function argument.
 |}]
 
 (* Function_result *)
@@ -116,11 +116,11 @@ Line 1, characters 18-30:
 1 | let f (): t_any = assert false
                       ^^^^^^^^^^^^
 Error: This expression has type t_any but an expression was expected of type
-         ('a : '_representable_layout_7)
+         ('a : '_representable_layout_5)
        The layout of t_any is any, because
          of the definition of t_any at line 1, characters 0-16.
-       But the layout of t_any must be a sublayout of '_representable_layout_7, because
-         it's used as a function result.
+       But the layout of t_any must be representable, because
+         it's the type of a function result.
 |}]
 
 (* Structure_item_expression *)
@@ -138,8 +138,8 @@ Line 1, characters 14-19:
 Error: Function argument types must have a representable layout.
        The layout of t_any is any, because
          of the definition of t_any at line 1, characters 0-16.
-       But the layout of t_any must be a sublayout of '_representable_layout_8, because
-         it's used as a function argument.
+       But the layout of t_any must be representable, because
+         it's the type of a function argument.
 |}]
 (* Shadowed by Function_argument *)
 
@@ -152,8 +152,8 @@ Line 1, characters 26-31:
 Error: Function return types must have a representable layout.
        The layout of t_any is any, because
          of the definition of t_any at line 1, characters 0-16.
-       But the layout of t_any must be a sublayout of '_representable_layout_9, because
-         it's used as a function result.
+       But the layout of t_any must be representable, because
+         it's the type of a function result.
 |}]
 (* Shadowed by Function_result *)
 

ocaml/testsuite/tests/typing-layouts-err-msg/concrete_struct_item_expr.compilers.reference

@@ -6,6 +6,6 @@ Error: This expression has type t_any but an expression was expected of type
          ('a : '_representable_layout_1)
        The layout of t_any is any, because
          of the definition of t_any at line 6, characters 0-16.
-       But the layout of t_any must be a sublayout of '_representable_layout_1, because
-         it's used as the type of an expression in a structure.
+       But the layout of t_any must be representable, because
+         it's the type of an expression in a structure.
 

ocaml/testsuite/tests/typing-layouts-err-msg/immediate.ml

@@ -29,7 +29,7 @@ Line 3, characters 21-22:
 Error: This expression has type v = unit
        but an expression was expected of type 'a t = ('a : void)
        The layout of unit is immediate, because
-         it's an enumeration variant (all constructors are constant).
+         it's an enumeration variant type (all constructors are constant).
        But the layout of unit must be a sublayout of void, because
          of the definition of t at line 1, characters 0-22.
 |}]
@@ -61,7 +61,7 @@ Line 2, characters 29-30:
 Error: This expression has type [ `A | `B ]
        but an expression was expected of type 'a t = ('a : void)
        The layout of [ `A | `B ] is immediate, because
-         it's an enumeration variant (all constructors are constant).
+         it's an enumeration variant type (all constructors are constant).
        But the layout of [ `A | `B ] must be a sublayout of void, because
          of the definition of t at line 1, characters 0-22.
 |}]

ocaml/testsuite/tests/typing-layouts-err-msg/value.ml

@@ -2,7 +2,6 @@
    flags = "-extension layouts_alpha"
    * expect
 *)
-(* CR layouts v2.9: all error messages below here are not reviewed for quality *)
 
 (***********************)
 (* Value layout errors *)
@@ -39,7 +38,7 @@ Error: Variables bound in a class must have layout value.
        The layout of v is float64, because
          it's the type of a variable bound by a `let`, defaulted to layout float64.
        But the layout of v must be a sublayout of value, because
-         it's let-bound in a class expression.
+         it's the type of a let-bound variable in a class expression.
 |}];;
 (* CR layouts v2.9: The part about defaulting here is incorrect.
    It's due to the logic in Pcl_let using sorts directly instead of
@@ -55,7 +54,7 @@ Error: Tuple element types must have layout value.
        The layout of t_any is any, because
          of the definition of t_any at line 1, characters 0-18.
        But the layout of t_any must be a sublayout of value, because
-         it's a tuple element.
+         it's the type of a tuple element.
 |}];;
 
 (* Probe *)
@@ -81,7 +80,7 @@ Error: In this `with' constraint, the new definition of t
        is not included in
          type t : immediate
        The layout of the first is value, because
-         it's used as an element in a first-class module.
+         it's a type declaration in a first-class module.
        But the layout of the first must be a sublayout of immediate, because
          of the definition of t at line 2, characters 2-20.
 |}];;
@@ -92,11 +91,11 @@ let f: ('a : void) -> 'b = fun x -> x # baz
 Line 1, characters 36-37:
 1 | let f: ('a : void) -> 'b = fun x -> x # baz
                                         ^
-Error: Methods must have layout value.
-       The layout of this expression is void, because
+Error: The object type must have layout value.
+       The layout of the type of this expression is void, because
          of the annotation on the type variable 'a.
-       But the layout of this expression must overlap with value, because
-         it's an object.
+       But the layout of the type of this expression must overlap with value, because
+         it's the type of an object.
 |}];;
 
 (* Instance_variable *)
@@ -114,7 +113,7 @@ Error: Variables bound in a class must have layout value.
        The layout of baz is void, because
          of the definition of t_void at line 6, characters 0-19.
        But the layout of baz must be a sublayout of value, because
-         it's an instance variable.
+         it's the type of an instance variable.
 |}];;
 
 (* Object_field *)
@@ -128,7 +127,7 @@ Error: This expression has type ('a : value)
        The layout of t_void is void, because
          of the definition of t_void at line 6, characters 0-19.
        But the layout of t_void must be a sublayout of value, because
-         it's an object field.
+         it's the type of an object field.
 |}];;
 
 (* Class_field *)
@@ -144,7 +143,7 @@ Error: Variables bound in a class must have layout value.
        The layout of bar is void, because
          of the definition of t_void at line 6, characters 0-19.
        But the layout of bar must be a sublayout of value, because
-         it's an class field.
+         it's the type of a class field.
 |}];;
 
 (* Boxed_record *)
@@ -154,7 +153,7 @@ Line 1, characters 0-26:
 1 | type r : void = {a:string}
     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 Error: The layout of type r is value, because
-         it's a boxed record.
+         it's a boxed record type.
        But the layout of type r must be a sublayout of void, because
          of the annotation on the declaration of the type r.
 |}];;
@@ -166,7 +165,7 @@ Line 1, characters 0-28:
 1 | type v : void = A of t_value
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Error: The layout of type v is value, because
-         it's a boxed variant.
+         it's a boxed variant type.
        But the layout of type v must be a sublayout of void, because
          of the annotation on the declaration of the type v.
 |}];;
@@ -178,7 +177,7 @@ Line 1, characters 0-21:
 1 | type attr : void = ..
     ^^^^^^^^^^^^^^^^^^^^^
 Error: The layout of type attr is value, because
-         it's an extensible variant.
+         it's an extensible variant type.
        But the layout of type attr must be a sublayout of void, because
          of the annotation on the declaration of the type attr.
 |}]
@@ -239,7 +238,7 @@ Line 2, characters 36-37:
 Error: This expression has type [ `A of int | `B ]
        but an expression was expected of type 'a t = ('a : void)
        The layout of [ `A of int | `B ] is value, because
-         it's a polymorphic variant.
+         it's a polymorphic variant type.
        But the layout of [ `A of int | `B ] must be a sublayout of void, because
          of the definition of t at line 1, characters 0-22.
 |}]
@@ -300,7 +299,7 @@ Error: This expression has type ('a : value)
        The layout of 'b is void, because
          of the annotation on the type variable 'b.
        But the layout of 'b must overlap with value, because
-         it's an unannotated universal variable.
+         it is or unifies with an unannotated universal variable.
 |}];;
 
 (* Polymorphic_variant_field *)
@@ -314,7 +313,7 @@ Error: This expression has type t_float64
        The layout of t_float64 is float64, because
          of the definition of t_float64 at line 5, characters 0-24.
        But the layout of t_float64 must be a sublayout of value, because
-         it's a field of a polymorphic variant.
+         it's the type of the field of a polymorphic variant.
 |}];;
 
 (* Default_type_layout *)
@@ -348,7 +347,7 @@ Error: This expression has type t_float64
        The layout of t_float64 is float64, because
          of the definition of t_float64 at line 5, characters 0-24.
        But the layout of t_float64 must be a sublayout of value, because
-         it's an array element.
+         it's the type of an array element.
 |}];;
 
 (* Lazy_expression *)
@@ -362,10 +361,30 @@ Error: This expression has type t_float64
        The layout of t_float64 is float64, because
          of the definition of t_float64 at line 5, characters 0-24.
        But the layout of t_float64 must be a sublayout of value, because
-         it's a lazy expression.
+         it's the type of a lazy expression.
 |}];;
 
-(* Class_argument *)
+(* Class_type_argument *)
+module M = struct
+  type ('a : void) t
+
+  class virtual ['a] foo =
+    object
+      val virtual baz : 'a t
+    end
+end
+[%%expect{|
+Line 6, characters 24-26:
+6 |       val virtual baz : 'a t
+                            ^^
+Error: This type ('a : void) should be an instance of type ('a0 : value)
+       The layout of 'a is value, because
+         it's a type argument to a class constructor.
+       But the layout of 'a must overlap with void, because
+         of the definition of t at line 2, characters 2-20.
+|}];;
+
+(* Class_term_argument *)
 class foo (x : t_float64) =
   object end;;
 [%%expect{|
@@ -377,7 +396,7 @@ Error: This pattern matches values of type t_float64
        The layout of t_float64 is float64, because
          of the definition of t_float64 at line 5, characters 0-24.
        But the layout of t_float64 must be a sublayout of value, because
-         it's a term-level argument to a class constructor.
+         it's the type of a term-level argument to a class constructor.
 |}];;
 
 (* Structure_element *)
@@ -386,11 +405,11 @@ module type S = sig val x : t_void end
 Line 1, characters 28-34:
 1 | module type S = sig val x : t_void end
                                 ^^^^^^
-Error: This type signature for x is not a value type.
-       The layout of x is void, because
+Error: This type for x is not a value type.
+       The layout of type t_void is void, because
          of the definition of t_void at line 6, characters 0-19.
-       But the layout of x must be a sublayout of value, because
-         it's stored in a module structure.
+       But the layout of type t_void must be a sublayout of value, because
+         it's the type of something stored in a module structure.
 |}];;
 
 (* Debug_printer_argument *)
@@ -424,7 +443,7 @@ Error: m1 must have a type of layout value because it is captured by an object.
        The layout of t_float64 is float64, because
          of the definition of t_float64 at line 5, characters 0-24.
        But the layout of t_float64 must be a sublayout of value, because
-         it's captured in an object.
+         it's the type of a variable captured in an object.
 |}];;
 
 (* Unknown *)