unikernel/duniverse/ppx_sexp_conv/expander/renaming.mli

@@ -0,0 +1,52 @@
+(* A renaming is a mapping from type variable name to type variable name.
+   In definitions such as:
+
+   type 'a t =
+   | A : <type> -> 'b t
+   | B of 'a
+
+   we generate a function that takes an sexp_of parameter named after 'a, but 'a is not in
+   scope in <type> when handling the constructor A (because A is a gadt constructor).
+   Instead the type variables in scope are the ones defined in the return type of A,
+   namely 'b. There could be less or more type variable in cases such as:
+
+   type _ less = Less : int less
+   type _ more = More : ('a * 'a) more
+
+   If for instance, <type> is ['b * 'c], when we find 'b, we will look for ['b] in the
+   renaming and find ['a] (only in that gadt branch, it could be something else in other
+   branches), at which point we can call the previously bound sexp_of parameter named
+   after 'a.
+   If we can't find a resulting name, like when looking up ['c] in the renaming, then we
+   assume the variable is existentially quantified and treat it as [_] (which is ok,
+   assuming there are no constraints). *)
+open! Base
+open! Ppxlib
+
+type t
+
+(** Renaming for contexts outside a type declaration, such as expression extensions. *)
+val without_type : unit -> t
+
+(** Renaming for a type declaration. Adds [prefix] to bindings for type parameters. *)
+val of_type_declaration : type_declaration -> prefix:string -> t
+
+(** Adds a new name with the given [prefix] for a universally bound type variable. *)
+val add_universally_bound : t -> string loc -> prefix:string -> t
+
+module Binding_kind : sig
+  type t =
+    | Universally_bound of Fresh_name.t
+    | Existentially_bound
+end
+
+(** Looks up the binding for a type variable. *)
+val binding_kind : t -> string -> loc:location -> Binding_kind.t
+
+(** Extends the renaming of a type declaration with GADT context for a constructor
+    declaration, if any. *)
+val with_constructor_declaration
+  :  t
+  -> constructor_declaration
+  -> type_parameters:string list
+  -> t