[caml] do not use `let _ =`

Summary:
Use `ignore` instead, as this will warn if the argument is an arrow type,
unlike `let _ = ...`. This makes the code more future-proof: if an argument is
added to a function called in `let _ = f x` then the compiler will complain
instead of silently turning a value into a partial evaluation.

Also got rid of particularly irksome `let _ = <stuff returning unit> in` where I could.

Reviewed By: mbouaziz

Differential Revision: D9217176

fbshipit-source-id: 3be463405

infer/src/backend/mergeCapture.ml

@@ -34,7 +34,7 @@ let empty_stats () = {files_linked= 0; targets_merged= 0}
 
 let link_exists s =
   try
-    let _ = Unix.lstat s in
+    ignore (Unix.lstat s) ;
     true
   with Unix.Unix_error _ -> false
 

infer/src/biabduction/Prop.ml

@@ -2568,7 +2568,7 @@ let prop_iter_gc_fields iter =
   prop_iter_map f iter
 
 
-let prop_case_split tenv prop =
+let prop_expand tenv prop =
   let pi_sigma_list = Sil.sigma_to_sigma_ne prop.sigma in
   let f props_acc (pi, sigma) =
     let sigma' = sigma_normalize_prop tenv prop sigma in
@@ -2578,13 +2578,6 @@ let prop_case_split tenv prop =
   List.fold ~f ~init:[] pi_sigma_list
 
 
-let prop_expand prop =
-  (*
-  let _ = check_prop_normalized prop in
-  *)
-  prop_case_split prop
-
-
 (*** START of module Metrics ***)
 module Metrics : sig
   val prop_size : 'a t -> int

infer/src/biabduction/Prover.ml

@@ -1932,16 +1932,14 @@ module Subtyping_check = struct
 end
 
 let cast_exception tenv texp1 texp2 e1 subs =
-  let _ =
+  ( match (texp1, texp2) with
-    match (texp1, texp2) with
   | Exp.Sizeof {typ= t1}, Exp.Sizeof {typ= t2; subtype= st2} ->
       if
         Config.developer_mode
         || (Subtype.is_cast st2 && not (Subtyping_check.check_subtype tenv t1 t2))
       then ProverState.checks := Class_cast_check (texp1, texp2, e1) :: !ProverState.checks
   | _ ->
-        ()
+      () ) ;
-  in
   raise (IMPL_EXC ("class cast exception", subs, EXC_FALSE))
 
 
@@ -2073,8 +2071,7 @@ let rec hpred_imply tenv calc_index_frame calc_missing subs prop1 sigma2 hpred2
   | Sil.Hpointsto (e2_, se2, texp2)
     -> (
       let e2 = Sil.exp_sub (`Exp (snd subs)) e2_ in
-      let _ =
+      ( match e2 with
-        match e2 with
       | Exp.Lvar _ ->
           ()
       | Exp.Var v ->
@@ -2082,8 +2079,7 @@ let rec hpred_imply tenv calc_index_frame calc_missing subs prop1 sigma2 hpred2
             d_impl_err ("rhs |-> not implemented", subs, EXC_FALSE_HPRED hpred2) ;
             raise (Exceptions.Abduction_case_not_implemented __POS__) )
       | _ ->
-            ()
+          () ) ;
-      in
       match Prop.prop_iter_create prop1 with
       | None ->
           raise (IMPL_EXC ("lhs is empty", subs, EXC_FALSE))
@@ -2182,8 +2178,7 @@ let rec hpred_imply tenv calc_index_frame calc_missing subs prop1 sigma2 hpred2
     -> (
       (* for now ignore implications between PE and NE *)
       let e2, f2 = (Sil.exp_sub (`Exp (snd subs)) e2_, Sil.exp_sub (`Exp (snd subs)) f2_) in
-      let _ =
+      ( match e2 with
-        match e2 with
       | Exp.Lvar _ ->
           ()
       | Exp.Var v ->
@@ -2191,8 +2186,7 @@ let rec hpred_imply tenv calc_index_frame calc_missing subs prop1 sigma2 hpred2
             d_impl_err ("rhs |-> not implemented", subs, EXC_FALSE_HPRED hpred2) ;
             raise (Exceptions.Abduction_case_not_implemented __POS__) )
       | _ ->
-            ()
+          () ) ;
-      in
       if Exp.equal e2 f2 && Sil.equal_lseg_kind k Sil.Lseg_PE then (subs, prop1)
       else
         match Prop.prop_iter_create prop1 with
@@ -2253,8 +2247,7 @@ let rec hpred_imply tenv calc_index_frame calc_missing subs prop1 sigma2 hpred2
       (* for now ignore implications between PE and NE *)
       let iF2, oF2 = (Sil.exp_sub (`Exp (snd subs)) iF2, Sil.exp_sub (`Exp (snd subs)) oF2) in
       let iB2, oB2 = (Sil.exp_sub (`Exp (snd subs)) iB2, Sil.exp_sub (`Exp (snd subs)) oB2) in
-      let _ =
+      ( match oF2 with
-        match oF2 with
       | Exp.Lvar _ ->
           ()
       | Exp.Var v ->
@@ -2262,10 +2255,8 @@ let rec hpred_imply tenv calc_index_frame calc_missing subs prop1 sigma2 hpred2
             d_impl_err ("rhs dllseg not implemented", subs, EXC_FALSE_HPRED hpred2) ;
             raise (Exceptions.Abduction_case_not_implemented __POS__) )
       | _ ->
-            ()
+          () ) ;
-      in
+      ( match oB2 with
-      let _ =
-        match oB2 with
       | Exp.Lvar _ ->
           ()
       | Exp.Var v ->
@@ -2273,8 +2264,7 @@ let rec hpred_imply tenv calc_index_frame calc_missing subs prop1 sigma2 hpred2
             d_impl_err ("rhs dllseg not implemented", subs, EXC_FALSE_HPRED hpred2) ;
             raise (Exceptions.Abduction_case_not_implemented __POS__) )
       | _ ->
-            ()
+          () ) ;
-      in
       match Prop.prop_iter_create prop1 with
       | None ->
           raise (IMPL_EXC ("lhs is empty", subs, EXC_FALSE))

infer/src/checkers/printfArgs.ml

@@ -95,7 +95,7 @@ let rec format_string_type_names (fmt_string: string) (start: int) : string list
   try
     let fmt_re = Str.regexp "%[0-9]*\\.?[0-9]*[A-mo-z]" in
     (* matches '%2.1d' etc. *)
-    let _ = Str.search_forward fmt_re fmt_string start in
+    ignore (Str.search_forward fmt_re fmt_string start) ;
     let fmt_match = Str.matched_string fmt_string in
     let fmt_type = String.sub fmt_match ~pos:(String.length fmt_match - 1) ~len:1 in
     fmt_type :: format_string_type_names fmt_string (Str.match_end ())

infer/src/clang/cFrontend_errors.ml

@@ -141,7 +141,7 @@ let rec expand_message_string context message an =
   (* reg exp should match alphanumeric id with possibly somee _ *)
   let re = Str.regexp "%[a-zA-Z0-9_]+%" in
   try
-    let _ = Str.search_forward re message 0 in
+    ignore (Str.search_forward re message 0) ;
     let ms = Str.matched_string message in
     let res = evaluate_place_holder context ms an in
     L.(debug Linters Medium) "@\nMatched string '%s'@\n" ms ;

infer/src/clang/cTrans.ml

@@ -2079,7 +2079,7 @@ module CTrans_funct (F : CModule_type.CFrontend) : CModule_type.CTranslation = s
      }
   *)
   and objCForCollectionStmt_trans trans_state item items body stmt_info =
-    let _ = instruction trans_state item in
+    ignore (instruction trans_state item) ;
     (* Here we do ast transformation, so we don't need the value of the translation of the *)
     (* variable item but we still need to add the variable to the locals *)
     let assign_next_object, cond = Ast_expressions.make_next_object_exp stmt_info item items in

infer/src/clang/objcCategory_decl.ml

@@ -91,12 +91,12 @@ let category_decl qual_type_to_sil_type procname_from_decl tenv decl =
       let name = CAst_utils.get_qualified_name name_info in
       let class_name = get_classname_from_category_decl cdi in
       L.(debug Capture Verbose) "ADDING: ObjCCategoryDecl for '%a'@\n" QualifiedCppName.pp name ;
-      let _ = add_class_decl qual_type_to_sil_type tenv cdi in
+      add_class_decl qual_type_to_sil_type tenv cdi ;
       let typ =
         process_category qual_type_to_sil_type procname_from_decl tenv class_name decl_info
           decl_list
       in
-      let _ = add_category_implementation qual_type_to_sil_type tenv cdi in
+      add_category_implementation qual_type_to_sil_type tenv cdi ;
       typ
   | _ ->
       assert false
@@ -109,7 +109,7 @@ let category_impl_decl qual_type_to_sil_type procname_from_decl tenv decl =
       let name = CAst_utils.get_qualified_name name_info in
       let class_name = get_classname_from_category_impl cii in
       L.(debug Capture Verbose) "ADDING: ObjCCategoryImplDecl for '%a'@\n" QualifiedCppName.pp name ;
-      let _ = add_category_decl qual_type_to_sil_type tenv cii in
+      add_category_decl qual_type_to_sil_type tenv cii ;
       let typ =
         process_category qual_type_to_sil_type procname_from_decl tenv class_name decl_info
           decl_list

infer/src/clang/objcInterface_decl.ml

@@ -133,11 +133,11 @@ let interface_declaration qual_type_to_sil_type procname_from_decl tenv decl =
         add_class_to_tenv qual_type_to_sil_type procname_from_decl tenv decl_info name_info
           decl_list ocidi
       in
-      let _ = add_class_implementation qual_type_to_sil_type tenv ocidi in
+      add_class_implementation qual_type_to_sil_type tenv ocidi ;
-      let _ = add_super_class_decl qual_type_to_sil_type tenv ocidi in
+      add_super_class_decl qual_type_to_sil_type tenv ocidi ;
-      let _ = add_protocols_decl qual_type_to_sil_type tenv ocidi.Clang_ast_t.otdi_protocols in
+      add_protocols_decl qual_type_to_sil_type tenv ocidi.Clang_ast_t.otdi_protocols ;
       let known_categories = ocidi.Clang_ast_t.otdi_known_categories in
-      let _ = add_categories_decl qual_type_to_sil_type tenv known_categories in
+      add_categories_decl qual_type_to_sil_type tenv known_categories ;
       typ
   | _ ->
       assert false
@@ -151,7 +151,7 @@ let interface_impl_declaration qual_type_to_sil_type procname_from_decl tenv dec
       let class_name = CAst_utils.get_qualified_name name_info in
       L.(debug Capture Verbose)
         "ADDING: ObjCImplementationDecl for class '%a'@\n" QualifiedCppName.pp class_name ;
-      let _ = add_class_decl qual_type_to_sil_type tenv idi in
+      add_class_decl qual_type_to_sil_type tenv idi ;
       let class_tn_name = Typ.Name.Objc.from_qual_name class_name in
       let fields = CField_decl.get_fields qual_type_to_sil_type tenv class_tn_name decl_list in
       CField_decl.add_missing_fields tenv class_name fields ;

infer/src/scripts/checkCopyright.ml

@@ -170,7 +170,7 @@ let get_copyright_year cstart cend lines =
   let do_line line =
     try
       let fmt_re = Str.regexp "[0-9]+" in
-      let _ = Str.search_forward fmt_re line 0 in
+      ignore (Str.search_forward fmt_re line 0) ;
       let fmt_match = Str.matched_string line in
       if String.length fmt_match = 4 then
         try found := Some (int_of_string fmt_match) with _ -> ()

infer/tests/repl/infer_batch_script.mltop

@@ -5,14 +5,14 @@
  * LICENSE file in the root directory of this source tree.
  *)
 
-(* Example of ocaml script starting with infer code. To execute a scipt run:
+(** Example of ocaml script starting with infer code. To execute a scipt run:
     ./scripts/infer_repl <path/to/this/script.ml>
    It's used as a basic integration test *)
 
 (* "import" infer code *)
 #use "toplevel_init";;
 
-let _ = Ident.create_fresh Ident.knormal in
+ignore (Ident.create_fresh Ident.knormal) ;
 let ident = Ident.create_fresh Ident.knormal in
 let e = Exp.Var ident in
 print_endline (Exp.to_string e) ;