Commit 95841216 authored by POTTIER Francois's avatar POTTIER Francois

SelectiveExpansion: add a protection against name capture.

(Makes no difference in practice, because formal parameters are already renamed elsewhere (PartialGrammar) and can never conflict with toplevel symbols.)
parent 7803b134
......@@ -339,6 +339,15 @@ let subst_branches env branches =
(* -------------------------------------------------------------------------- *)
(* A quick and dirty way of mapping a name to a fresh name. *)
let freshen : string -> string =
let c = ref 0 in
fun x ->
Printf.sprintf "%s__menhir__%d" x (Misc.postincrement c)
(* -------------------------------------------------------------------------- *)
(* [instantiation_env] expects the formal parameters of a rule, [formals], and
an instantiation [inst] that dictates how this rule must be specialized. It
returns an environment [env] that can be used to perform specialization and
......@@ -355,8 +364,13 @@ let instantiation_env formals inst : env * symbol list =
param, residuals
| None ->
(* This formal parameter is not instantiated. *)
(* We map it to itself. TEMPORARY avoid capture by freshening;
required if [formal] occurs free in [inst] *)
(* We would like to map it to itself. *)
(* However, we must in principle be a bit careful: if a toplevel
symbol by the same name as [formal] appears free in the codomain
of the environment that we are building, then we will run intro
trouble. We avoid this problem by systematically renaming every
formal parameter to a fresh unlikely name. *)
let formal = freshen formal in
ParameterVar (unknown formal),
formal :: residuals
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