flambda-backend: Expose Pprintast.tyvar (#1848)

Author: ccasin

boot/ocamlc

@@ -52,3 +52,8 @@ val payload: Format.formatter -> Parsetree.payload -> unit
 
 val class_signature: Format.formatter -> Parsetree.class_signature -> unit
 val type_declaration: Format.formatter -> Parsetree.type_declaration -> unit
+
+val tyvar: Format.formatter -> string -> unit
+  (** Print a type variable name as a valid identifier, taking care of the
+      special treatment required for the single quote character in second
+      position, or for keywords by escaping them with \#. No-op on "_". *)

parsing/pprintast.mli

@@ -74,6 +74,7 @@ module Example = struct
                          ; ptype_attributes = []
                          ; ptype_loc = loc
                          }
+  let tyvar            = "no_tyvars_require_extensions"
 end
 
 let print_test_header name =
@@ -144,6 +145,8 @@ end = struct
 
   let string_of_expression = test_string_of "string_of_expression" string_of_expression Example.expression
   let string_of_structure = test_string_of "string_of_structure" string_of_structure Example.structure
+
+  let tyvar = test "tyvar" tyvar Example.tyvar
 end
 
 

testsuite/tests/language-extensions/pprintast_unconditional.ml

@@ -51,6 +51,8 @@ string_of_expression: [x for x = 1 to 10]
 
 string_of_structure: include functor F
 
+tyvar: 'no_tyvars_require_extensions
+
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 
 ##### Extensions disallowed
@@ -106,6 +108,8 @@ string_of_expression: [x for x = 1 to 10]
 
 string_of_structure: include functor F
 
+tyvar: 'no_tyvars_require_extensions
+
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 
 ##### Calling [Language_extension.For_pprintast.make_printer_exporter ()]