reanalyze: remove global exception decl table (pure)

Stop using global mutable exception declaration state during AST processing.
Instead, derive a pure exception lookup from merged Declarations and use it
when processing CrossFileItems exception refs.

Signed-Off-By: Cristiano Calcagno <cristiano.calcagno@gmail.com>

Author: cristianoc

analysis/reanalyze/src/DeadException.ml

@@ -1,16 +1,37 @@
 open DeadCommon
 
-let declarations = Hashtbl.create 1
+module PathMap = Map.Make (struct
+  type t = DcePath.t
+
+  let compare = Stdlib.compare
+end)
+
+let find_exception_from_decls (decls : Declarations.t) :
+    DcePath.t -> Location.t option =
+  let index =
+    Declarations.fold
+      (fun _pos (decl : Decl.t) acc ->
+        match decl.Decl.declKind with
+        | Exception ->
+          (* Use raw decl positions: reference graph keys are raw positions. *)
+          let loc : Location.t =
+            {
+              Location.loc_start = decl.pos;
+              loc_end = decl.posEnd;
+              loc_ghost = false;
+            }
+          in
+          PathMap.add decl.path loc acc
+        | _ -> acc)
+      decls PathMap.empty
+  in
+  fun path -> PathMap.find_opt path index
 
 let add ~config ~decls ~file ~path ~loc ~(strLoc : Location.t)
     ~(moduleLoc : Location.t) name =
-  let exceptionPath = name :: path in
-  Hashtbl.add declarations exceptionPath loc;
+  addDeclaration_ ~config ~decls ~file ~posEnd:strLoc.loc_end
+    ~posStart:strLoc.loc_start ~declKind:Exception ~moduleLoc ~path ~loc name;
   name
-  |> addDeclaration_ ~config ~decls ~file ~posEnd:strLoc.loc_end
-       ~posStart:strLoc.loc_start ~declKind:Exception ~moduleLoc ~path ~loc
-
-let find_exception path = Hashtbl.find_opt declarations path
 
 let markAsUsed ~config ~refs ~file_deps ~cross_file ~(binding : Location.t)
     ~(locFrom : Location.t) ~(locTo : Location.t) path_ =

analysis/reanalyze/src/DeadException.mli

@@ -0,0 +1,25 @@
+open DeadCommon
+
+val find_exception_from_decls : Declarations.t -> DcePath.t -> Location.t option
+
+val add :
+  config:DceConfig.t ->
+  decls:Declarations.builder ->
+  file:FileContext.t ->
+  path:DcePath.t ->
+  loc:Location.t ->
+  strLoc:Location.t ->
+  moduleLoc:Location.t ->
+  Name.t ->
+  Name.t
+
+val markAsUsed :
+  config:DceConfig.t ->
+  refs:References.builder ->
+  file_deps:FileDeps.builder ->
+  cross_file:CrossFileItems.builder ->
+  binding:Location.t ->
+  locFrom:Location.t ->
+  locTo:Location.t ->
+  Path.t ->
+  unit

analysis/reanalyze/src/Reanalyze.ml

@@ -167,10 +167,10 @@ let runAnalysis ~dce_config ~cmtRoot =
     (* Compute type-label dependencies after merge (no global TypeLabels table during traversal) *)
     DeadType.process_type_label_dependencies ~config:dce_config ~decls
       ~refs:refs_builder;
+    let find_exception = DeadException.find_exception_from_decls decls in
     (* Process cross-file exception refs - they write to refs_builder and file_deps_builder *)
     CrossFileItems.process_exception_refs cross_file ~refs:refs_builder
-      ~file_deps:file_deps_builder ~find_exception:DeadException.find_exception
-      ~config:dce_config;
+      ~file_deps:file_deps_builder ~find_exception ~config:dce_config;
     (* Now freeze refs and file_deps for solver *)
     let refs = References.freeze_builder refs_builder in
     let file_deps = FileDeps.freeze_builder file_deps_builder in