Improve pseudo-constant support in the typechecker

Summary:
These pseudo-constants are always considered to be global (even in namespaces), because they compile to literals or special bytecodes.

This enforces that the pseudo-constant names are reserved and that we do not elaborate them, regardless of whether they're in a namespace.

Reviewed By: Wilfred

Differential Revision: D10204718

fbshipit-source-id: 73641478ef74ea0a6d5dd8da6d74a1aa9b397751

hphp/hack/src/naming/naming.ml

@@ -493,44 +493,6 @@ end = struct
   let get_name genv get_pos x =
     lookup genv get_pos x; x
 
-  (* For dealing with namespace fallback on constants *)
-  let elaborate_and_get_name_with_fallback
-    mk_dep
-    genv
-    (get_pos : string -> FileInfo.pos option) x =
-    let get_name x = get_name genv get_pos x in
-    let fq_x = NS.elaborate_id genv.namespace NS.ElaborateConst x in
-    let need_fallback =
-      genv.namespace.Namespace_env.ns_name <> None &&
-      not (String.contains (snd x) '\\') in
-    let use_fallback =
-      need_fallback &&
-      (* __FILE__, __LINE__ etc *)
-      (string_starts_with (snd x) "__") && (string_ends_with (snd x) "__") in
-    if use_fallback then begin
-      let global_x = (fst x, "\\" ^ (snd x)) in
-      (* Explicitly add dependencies on both of the consts we could be
-       * referring to here. Normally naming doesn't have to deal with
-       * deps at all -- they are added during typechecking just by the
-       * nature of looking up a class or function name. However, we're
-       * flattening namespaces here, and the fallback behavior of
-       * consts means that we might suddenly be referring to a
-       * different const without any change to the callsite at
-       * all. Adding both dependencies explicitly captures this
-       * action-at-a-distance. *)
-      Typing_deps.add_idep genv.droot (mk_dep (snd fq_x));
-      Typing_deps.add_idep genv.droot (mk_dep (snd global_x));
-      let mem (_, s) = get_pos s in
-      match mem fq_x, mem global_x with
-      (* Found in the current namespace *)
-      | Some _, _ -> get_name fq_x
-      (* Found in the global namespace *)
-      | _, Some _ -> get_name global_x
-      (* Not found. Pick the more specific one to error on. *)
-      | None, None -> get_name fq_x
-    end else
-      get_name fq_x
-
   (* For dealing with namespace resolution on functions *)
   let elaborate_and_get_name_with_canonicalized_fallback
       genv
@@ -543,13 +505,9 @@ end = struct
     let fq_x = canonicalize fq_x `func in
     get_name fq_x
 
-  let global_const (genv, _env) x  =
-    elaborate_and_get_name_with_fallback
-      (* Same idea as Dep.FunName, see below. *)
-      (fun x -> Typing_deps.Dep.GConstName x)
-      genv
-      (Naming_heap.ConstPosHeap.get)
-      x
+  let global_const (genv, _env) x =
+    let fq_x = NS.elaborate_id genv.namespace NS.ElaborateConst x in
+    get_name genv (Naming_heap.ConstPosHeap.get) fq_x
 
   let type_name (genv, _) x ~allow_typedef =
     (* Generic names are not allowed to shadow class names *)
@@ -2916,11 +2874,19 @@ module Make (GetLocals : GetLocals) = struct
     | None
     | Some _ -> ()
 
+  let check_constant_name genv cst =
+    if genv.namespace.Namespace_env.ns_name <> None then
+      let pos, name = cst.cst_name in
+      let name = Utils.strip_all_ns name in
+      if SN.PseudoConsts.is_pseudo_const (Utils.add_ns name) then
+        Errors.name_is_reserved name pos
+
   let global_const genv cst =
     let env = Env.make_const_env genv cst in
     let hint = Option.map cst.cst_type (hint env) in
     let e = match cst.cst_kind with
     | Ast.Cst_const ->
+      check_constant_name (fst env) cst;
       check_constant_hint cst;
       Some (constant_expr env cst.cst_value)
     (* Define allows any expression, so don't call check_constant.

hphp/hack/src/parser/namespaces.ml

@@ -11,6 +11,8 @@ open Core_kernel
 open Ast
 open Namespace_env
 
+module SN = Naming_special_names
+
 (* When dealing with an <?hh file, HHVM automatically imports a few
  * "core" classes into every namespace, mostly collections. Their
  * unqualified names always refer to this global version.
@@ -117,10 +119,10 @@ let autoimport_set =
  * Return false as first value if it is not auto imported
  *)
 let get_autoimport_name_namespace id =
-  if Naming_special_names.Typehints.is_reserved_global_name id
+  if SN.Typehints.is_reserved_global_name id
   then (true, None)
   else
-  if Naming_special_names.Typehints.is_reserved_hh_name id ||
+  if SN.Typehints.is_reserved_hh_name id ||
      SSet.mem id autoimport_set
   then (true, Some "HH")
   else (false, None)
@@ -204,6 +206,10 @@ let elaborate_id_impl ~autoimport nsenv kind (p, id) =
   else
   let was_renamed, fully_qualified =
     begin
+      let global_id = Utils.add_ns id in
+      if kind = ElaborateConst && SN.PseudoConsts.is_pseudo_const global_id
+      then false, global_id
+      else
       (* Expand "use" imports. *)
       let (bslash_loc, has_bslash) =
         match String.index id '\\' with

hphp/hack/src/utils/utils.ml

@@ -148,6 +148,12 @@ let strip_ns s =
   if String.length s == 0 || s.[0] <> '\\' then s
   else String.sub s 1 ((String.length s) - 1)
 
+(* A\B\C -> \A\B\C *)
+let add_ns s =
+  if String.length s = 0 || s.[0] <> '\\'
+  then "\\" ^ s
+  else s
+
 (* \A\B\C -> C *)
 let strip_all_ns s =
   try

hphp/hack/test/typecheck/reserved_name4.php

@@ -0,0 +1,5 @@
+<?hh
+
+namespace X {
+  const __FILE__ = 1;
+}

hphp/hack/test/typecheck/reserved_name4.php.exp

@@ -0,0 +1,2 @@
+File "reserved_name4.php", line 4, characters 9-16:
+__FILE__ cannot be used as it is reserved. (Naming[2068])