[autofix] Add autofix for unnecessary copy on field init exp

Summary:
```
C(T f): f_(f) {}
=================
C(T f): f_(std::move(f)) {}
```

This is one of the frequent unnecessary copy patterns that is
straightforward to fix.  This diff generates autofix when

- the procedure is a constructor and
- a field is initialized by a parameter.

Reviewed By: ngorogiannis

Differential Revision: D63505474

fbshipit-source-id: da0b162d4bc6e75ec9a6509707bee91a8f8868b9

infer/src/pulse/PulseDiagnostic.ml

@@ -918,6 +918,27 @@ let get_message_and_suggestion diagnostic =
           , Some (get_suggestion_msg source_opt) ) )
 
 
+let get_autofix pdesc diagnostic =
+  match diagnostic with
+  | UnnecessaryCopy {copied_into; source_opt; copied_location= None} -> (
+      let is_formal pvar =
+        let pvar_name = Pvar.get_name pvar in
+        List.exists (Procdesc.get_formals pdesc) ~f:(fun (formal, _, _) ->
+            Mangled.equal pvar_name formal )
+      in
+      match (copied_into, source_opt) with
+      | IntoField {field}, Some (DecompilerExpr.PVar pvar, [Dereference])
+        when Procname.is_constructor (Procdesc.get_proc_name pdesc) && is_formal pvar ->
+          let param = Pvar.to_string pvar in
+          Some
+            { Jsonbug_t.original= F.asprintf "%a(%s)" Fieldname.pp field param
+            ; replacement= F.asprintf "%a(std::move(%s))" Fieldname.pp field param }
+      | _ ->
+          None )
+  | _ ->
+      None
+
+
 let add_errlog_header ~nesting ~title location errlog =
   let tags = [] in
   Errlog.make_trace_element nesting location title tags :: errlog

infer/src/pulse/PulseDiagnostic.mli

@@ -132,6 +132,8 @@ val aborts_execution : t -> bool
 
 val get_message_and_suggestion : t -> string * string option
 
+val get_autofix : Procdesc.t -> t -> Jsonbug_t.autofix option
+
 val get_location : t -> Location.t
 
 val get_location_instantiated : t -> Location.t option

infer/src/pulse/PulseReport.ml

@@ -137,10 +137,11 @@ let report {InterproceduralAnalysis.tenv; proc_desc; err_log} ~is_suppressed ~la
     in
     let issue_type = get_issue_type tenv ~latent diagnostic proc_desc in
     let message, suggestion = get_message_and_suggestion diagnostic in
+    let autofix = get_autofix proc_desc diagnostic in
     L.d_printfln ~color:Red "Reporting issue: %a: %s" IssueType.pp issue_type message ;
     Reporting.log_issue proc_desc err_log ~loc:(get_location diagnostic) ?loc_instantiated
       ~ltr:(extra_trace @ get_trace diagnostic)
-      ~extras ?suggestion Pulse issue_type message
+      ~extras ?autofix ?suggestion Pulse issue_type message
 
 
 let report_latent_issue analysis_data latent_issue ~is_suppressed =