Add config for reporting transitively dead things.

This is the normal behaviour: no change.
When turned off, only the top dead things, and not the transitive ones, are reported.

Author: cristianoc

analysis/reanalyze/src/Common.ml

@@ -197,7 +197,7 @@ type decl = {
   pos: Lexing.position;
   posEnd: Lexing.position;
   posStart: Lexing.position;
-  mutable resolved: bool;
+  mutable resolvedDead: bool option;
   mutable report: bool;
 }
 

analysis/reanalyze/src/DeadCommon.ml

@@ -13,6 +13,7 @@ module Config = struct
   let analyzeTypes = ref true
   let analyzeExternals = ref false
   let reportUnderscore = false
+  let reportTransitive = true
   let reportTypesDeadOnlyInInterface = false
   let recursiveDebug = false
   let warnOnCircularDependencies = false
@@ -375,7 +376,7 @@ let addDeclaration_ ?posEnd ?posStart ~declKind ~path ~(loc : Location.t)
         pos;
         posEnd;
         posStart;
-        resolved = false;
+        resolvedDead = None;
         report = true;
       }
     in
@@ -536,12 +537,21 @@ module Decl = struct
         | VariantCase ->
           (WarningDeadType, "is a variant case which is never constructed")
       in
+      let hasRefBelow () =
+        let refs = ValueReferences.find decl.pos in
+        let refIsBelow (pos : Lexing.position) =
+          decl.pos.pos_fname <> pos.pos_fname
+          || decl.pos.pos_cnum < pos.pos_cnum
+             && decl.posEnd.pos_cnum < pos.pos_cnum
+        in
+        refs |> PosSet.exists refIsBelow
+      in
       let shouldEmitWarning =
         (not insideReportedValue)
-        &&
-        match decl.path with
-        | name :: _ when name |> Name.isUnderscore -> Config.reportUnderscore
-        | _ -> true
+        && (match decl.path with
+           | name :: _ when name |> Name.isUnderscore -> Config.reportUnderscore
+           | _ -> true)
+        && (Config.reportTransitive || not (hasRefBelow ()))
       in
       if shouldEmitWarning then (
         decl.path
@@ -563,7 +573,7 @@ let doReportDead pos = not (ProcessDeadAnnotations.isAnnotatedGenTypeOrDead pos)
 let rec resolveRecursiveRefs ~checkOptionalArg ~deadDeclarations ~level
     ~orderedFiles ~refs ~refsBeingResolved decl : bool =
   match decl.pos with
-  | _ when decl.resolved ->
+  | _ when decl.resolvedDead <> None ->
     if Config.recursiveDebug then
       Log_.item "recursiveDebug %s [%d] already resolved@."
         (decl.path |> Path.toString)
@@ -609,13 +619,13 @@ let rec resolveRecursiveRefs ~checkOptionalArg ~deadDeclarations ~level
                         ~level:(level + 1) ~orderedFiles ~refs:xRefs
                         ~refsBeingResolved
                  in
-                 if not xDecl.resolved then allDepsResolved := false;
+                 if xDecl.resolvedDead = None then allDepsResolved := false;
                  not xDeclIsDead)
     in
     let isDead = decl |> declIsDead ~refs:newRefs in
     let isResolved = (not isDead) || !allDepsResolved || level = 0 in
     if isResolved then (
-      decl.resolved <- true;
+      decl.resolvedDead <- Some isDead;
       if isDead then (
         decl.path
         |> DeadModules.markDead
@@ -691,4 +701,5 @@ let reportDead ~checkOptionalArg =
   let sortedDeadDeclarations =
     !deadDeclarations |> List.fast_sort Decl.compareForReporting
   in
+  (* XXX *)
   sortedDeadDeclarations |> List.iter Decl.report