[nullsafe] Handle intermediate typecasts in assignment expressions

Summary:
When expressions use generics or typecasts, CFG contains intermediate `_fun_cast` nodes which break some nullsafe heuristics and lead to false positives.
This affects different types of checks (null-check on assignment expressions, `map.containsKey` checks in assignment expressions, regular typecasts, etc.
See added tests for examples.

Reviewed By: mityal

Differential Revision: D22815631

fbshipit-source-id: 80d444b1c

infer/src/nullsafe/IDEnv.ml

@@ -14,7 +14,17 @@ type t = Exp.t Ident.Hash.t Lazy.t
 
 let create_ proc_desc =
   let map = Ident.Hash.create 1 in
-  let do_instr _ = function Sil.Load {id; e} -> Ident.Hash.add map id e | _ -> () in
+  let do_instr _ = function
+    | Sil.Load {id; e} ->
+        Ident.Hash.add map id e
+    | Sil.Call ((res_ident, _), Exp.Const (Const.Cfun fname), [(Exp.Var src_ident, _); _], _, _)
+    (* [id] = __cast([ex]) when [ex] is a frontend temporary, try to unfold it further *)
+      when Procname.equal fname BuiltinDecl.__cast ->
+        Ident.Hash.find_opt map src_ident
+        |> Option.iter ~f:(fun ex -> Ident.Hash.add map res_ident ex)
+    | _ ->
+        ()
+  in
   Procdesc.iter_instrs do_instr proc_desc ;
   map
 

infer/src/nullsafe/typeCheck.ml

@@ -717,31 +717,43 @@ let handle_assignment_in_condition_for_sil_prune idenv node pvar =
           None )
 
 
+let pp_normalized_cond fmt (_, exp) = Exp.pp fmt exp
+
 let rec normalize_cond_for_sil_prune_rec idenv ~node ~original_node cond =
-  match cond with
-  | Exp.UnOp (Unop.LNot, c, top) ->
-      let node', c' = normalize_cond_for_sil_prune_rec idenv ~node ~original_node c in
-      (node', Exp.UnOp (Unop.LNot, c', top))
-  | Exp.BinOp (bop, c1, c2) ->
-      let node', c1' = normalize_cond_for_sil_prune_rec idenv ~node ~original_node c1 in
-      let node'', c2' = normalize_cond_for_sil_prune_rec idenv ~node:node' ~original_node c2 in
-      (node'', Exp.BinOp (bop, c1', c2'))
-  | Exp.Var _ ->
-      let c' = IDEnv.expand_expr idenv cond in
-      if not (Exp.equal c' cond) then normalize_cond_for_sil_prune_rec idenv ~node ~original_node c'
-      else (node, c')
-  | Exp.Lvar pvar when Pvar.is_frontend_tmp pvar -> (
-    match handle_assignment_in_condition_for_sil_prune idenv original_node pvar with
-    | None -> (
-      match Decompile.find_program_variable_assignment node pvar with
-      | Some (node', id) ->
-          (node', Exp.Var id)
-      | None ->
-          (node, cond) )
-    | Some e2 ->
-        (node, e2) )
-  | c ->
-      (node, c)
+  L.d_with_indent ~name:"normalize_cond_for_sil_prune_rec" ~pp_result:pp_normalized_cond (fun () ->
+      L.d_printfln "cond=%a" Exp.pp cond ;
+      match cond with
+      | Exp.UnOp (Unop.LNot, c, top) ->
+          L.d_printfln "UnOp" ;
+          let node', c' = normalize_cond_for_sil_prune_rec idenv ~node ~original_node c in
+          (node', Exp.UnOp (Unop.LNot, c', top))
+      | Exp.BinOp (bop, c1, c2) ->
+          L.d_printfln "BinOp" ;
+          let node', c1' = normalize_cond_for_sil_prune_rec idenv ~node ~original_node c1 in
+          let node'', c2' = normalize_cond_for_sil_prune_rec idenv ~node:node' ~original_node c2 in
+          L.d_printfln "c1=%a@\nc2=%a" Exp.pp c1 Exp.pp c2 ;
+          (node'', Exp.BinOp (bop, c1', c2'))
+      | Exp.Var _ ->
+          L.d_printfln "Var" ;
+          let c' = IDEnv.expand_expr idenv cond in
+          L.d_printfln "c'=%a" Exp.pp c' ;
+          if not (Exp.equal c' cond) then
+            normalize_cond_for_sil_prune_rec idenv ~node ~original_node c'
+          else (node, c')
+      | Exp.Lvar pvar when Pvar.is_frontend_tmp pvar -> (
+          L.d_printfln "Lvar" ;
+          match handle_assignment_in_condition_for_sil_prune idenv original_node pvar with
+          | None -> (
+            match Decompile.find_program_variable_assignment node pvar with
+            | Some (node', id) ->
+                (node', Exp.Var id)
+            | None ->
+                (node, cond) )
+          | Some e2 ->
+              (node, e2) )
+      | c ->
+          L.d_printfln "other" ;
+          (node, c) )
 
 
 (* Normalize the condition by resolving temp variables. *)

infer/tests/codetoanalyze/java/nullsafe/ReturnNotNullable.java

@@ -233,8 +233,7 @@ public class ReturnNotNullable {
     // 1. The argument is a generic,
     // 2. The type parameter is not {@code Object}.
     // Both are important to trigger the behaviour we're checking (indirection via typecast in CFG).
-    public List<String> nullCheckGenericAssignmentResultAsNonnullOk_FP(
-        BlockingQueue<Runnable> queue) {
+    public List<String> nullCheckGenericAssignmentResultAsNonnullOk(BlockingQueue<Runnable> queue) {
       final ArrayList<String> records = new ArrayList<>(queue.size());
       try {
         Runnable task;
@@ -258,7 +257,7 @@ public class ReturnNotNullable {
       }
     }
 
-    public void chainedCallsWithAssignmentChecksOk_FP(@Nullable NullableGetter<NullableGetter> c1) {
+    public void chainedCallsWithAssignmentChecksOk(@Nullable NullableGetter<NullableGetter> c1) {
       NullableGetter<NullableGetter> c2, c3;
 
       if (c1 != null && (c2 = c1.get()) != null && (c3 = c2.get()) != null) {

infer/tests/codetoanalyze/java/nullsafe/issues.exp

@@ -301,10 +301,7 @@ codetoanalyze/java/nullsafe/PropagatesNullable.java, codetoanalyze.java.nullsafe
 codetoanalyze/java/nullsafe/PropagatesNullable.java, codetoanalyze.java.nullsafe.TestPropagatesNullable$TestSecondParameter.test(java.lang.String,java.lang.String):void, 7, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [`nullable(...)` is nullable and is not locally checked for null when calling `length()`.]
 codetoanalyze/java/nullsafe/PropagatesNullable.java, codetoanalyze.java.nullsafe.TestPropagatesNullable$TestSecondParameter.test(java.lang.String,java.lang.String):void, 11, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [`nullable(...)` is nullable and is not locally checked for null when calling `length()`.]
 codetoanalyze/java/nullsafe/PropagatesNullable.java, codetoanalyze.java.nullsafe.TestPropagatesNullable$TestSecondParameter.test(java.lang.String,java.lang.String):void, 15, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [`nullable(...)` is nullable and is not locally checked for null when calling `length()`.]
-codetoanalyze/java/nullsafe/ReturnNotNullable.java, Linters_dummy_method, 23, ERADICATE_META_CLASS_NEEDS_IMPROVEMENT, no_bucket, INFO, [], ReturnNotNullable, codetoanalyze.java.nullsafe, issues: 12, curr_mode: "Default"
-codetoanalyze/java/nullsafe/ReturnNotNullable.java, codetoanalyze.java.nullsafe.ReturnNotNullable$AssignmentResultCheck.chainedCallsWithAssignmentChecksOk_FP(codetoanalyze.java.nullsafe.ReturnNotNullable$AssignmentResultCheck$NullableGetter):void, 3, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [`c2` is nullable and is not locally checked for null when calling `get()`: call to get() at line 264.]
-codetoanalyze/java/nullsafe/ReturnNotNullable.java, codetoanalyze.java.nullsafe.ReturnNotNullable$AssignmentResultCheck.chainedCallsWithAssignmentChecksOk_FP(codetoanalyze.java.nullsafe.ReturnNotNullable$AssignmentResultCheck$NullableGetter):void, 4, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [`c3` is nullable and is not locally checked for null when calling `get()`: call to get() at line 264.]
-codetoanalyze/java/nullsafe/ReturnNotNullable.java, codetoanalyze.java.nullsafe.ReturnNotNullable$AssignmentResultCheck.nullCheckGenericAssignmentResultAsNonnullOk_FP(java.util.concurrent.BlockingQueue):java.util.List, 7, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [`task` is nullable and is not locally checked for null when calling `toString()`: call to BlockingQueue.poll(...) at line 242 (declared nullable in nullsafe/third-party-signatures/java.sig at line 3).]
+codetoanalyze/java/nullsafe/ReturnNotNullable.java, Linters_dummy_method, 23, ERADICATE_META_CLASS_NEEDS_IMPROVEMENT, no_bucket, INFO, [], ReturnNotNullable, codetoanalyze.java.nullsafe, issues: 9, curr_mode: "Default"
 codetoanalyze/java/nullsafe/ReturnNotNullable.java, codetoanalyze.java.nullsafe.ReturnNotNullable$ConditionalAssignment.test(boolean):java.lang.Object, 0, ERADICATE_RETURN_NOT_NULLABLE, no_bucket, WARNING, [`test(...)`: return type is declared non-nullable but the method returns a nullable value: field f1 at line 203.]
 codetoanalyze/java/nullsafe/ReturnNotNullable.java, codetoanalyze.java.nullsafe.ReturnNotNullable.constantToNullableIsOverannotated():java.lang.String, 0, ERADICATE_RETURN_OVER_ANNOTATED, no_bucket, ADVICE, [Method `constantToNullableIsOverannotated()` is annotated with `@Nullable` but never returns null.]
 codetoanalyze/java/nullsafe/ReturnNotNullable.java, codetoanalyze.java.nullsafe.ReturnNotNullable.getResourceNullable(java.lang.Class,java.lang.String):java.net.URL, 0, ERADICATE_RETURN_NOT_NULLABLE, no_bucket, WARNING, [`getResourceNullable(...)`: return type is declared non-nullable but the method returns a nullable value: call to Class.getResource(...) at line 181 (nullable according to nullsafe internal models).]