warn when using $l[$#l], advice $l[-1] instead

3 files changed, 21 insertions, 11 deletions

diff --git a/perl_checker.src/parser.mly b/perl_checker.src/parser.mly
index 080295c..e0c5fe6 100644
--- a/perl_checker.src/parser.mly
+++ b/perl_checker.src/parser.mly
@@ -339,21 +339,21 @@ diamond:
 
 subscripted: /* Some kind of subscripted expression */
 | variable PKG_SCOPE bracket_subscript {sp_0($2); sp_0($3); Call(Too_complex, [fst $3]), sp_pos_range $1 $3} /* $foo::{something} */
-| scalar bracket_subscript             {sp_0($2); to_Deref_with(I_hash , I_scalar, from_scalar $1, fst      $2), sp_pos_range $1 $2} /* $foo{bar} */
-| scalar arrayref                      {sp_0($2); to_Deref_with(I_array, I_scalar, from_scalar $1, only_one $2), sp_pos_range $1 $2} /* $array[$element] */
-| term ARROW bracket_subscript         {sp_0($2); sp_0($3); check_arrow_needed $1 $2; to_Deref_with(I_hash , I_scalar, sndfst $1, fst      $3), sp_pos_range $1 $3} /* somehref->{bar} */
-| term ARROW arrayref                  {sp_0($2); sp_0($3); check_arrow_needed $1 $2; to_Deref_with(I_array, I_scalar, sndfst $1, only_one $3), sp_pos_range $1 $3} /* somearef->[$element] */
+| scalar bracket_subscript             {sp_0($2); to_Deref_with(I_hash , I_scalar, from_scalar $1, fst                $2), sp_pos_range $1 $2} /* $foo{bar} */
+| scalar arrayref                      {sp_0($2); to_Deref_with(I_array, I_scalar, from_scalar $1, only_one_array_ref $2), sp_pos_range $1 $2} /* $array[$element] */
+| term ARROW bracket_subscript         {sp_0($2); sp_0($3); check_arrow_needed $1 $2; to_Deref_with(I_hash , I_scalar, sndfst $1, fst                $3), sp_pos_range $1 $3} /* somehref->{bar} */
+| term ARROW arrayref                  {sp_0($2); sp_0($3); check_arrow_needed $1 $2; to_Deref_with(I_array, I_scalar, sndfst $1, only_one_array_ref $3), sp_pos_range $1 $3} /* somearef->[$element] */
 | term ARROW parenthesized             {sp_0($2); sp_0($3); to_Deref_with(I_func , I_scalar, sndfst $1, List(sndfst $3)), sp_pos_range $1 $3} /* $subref->(@args) */
-| subscripted bracket_subscript        {sp_0($2); to_Deref_with(I_hash , I_scalar, fst $1, fst      $2), sp_pos_range $1 $2} /* $foo->[bar]{baz} */
-| subscripted arrayref                 {sp_0($2); to_Deref_with(I_array, I_scalar, fst $1, only_one $2), sp_pos_range $1 $2} /* $foo->[$bar][$baz] */
+| subscripted bracket_subscript        {sp_0($2); to_Deref_with(I_hash , I_scalar, fst $1, fst                $2), sp_pos_range $1 $2} /* $foo->[bar]{baz} */
+| subscripted arrayref                 {sp_0($2); to_Deref_with(I_array, I_scalar, fst $1, only_one_array_ref $2), sp_pos_range $1 $2} /* $foo->[$bar][$baz] */
 | subscripted parenthesized            {sp_0($2); to_Deref_with(I_func , I_scalar, fst $1, List(sndfst $2)), sp_pos_range $1 $2} /* $foo->{bar}(@args) */
 
 restricted_subscripted: /* Some kind of subscripted expression */
 | variable PKG_SCOPE bracket_subscript {sp_0($2); sp_0($3); Call(Too_complex, [fst $3]), sp_pos_range $1 $3} /* $foo::{something} */
-| scalar bracket_subscript             {sp_0($2); to_Deref_with(I_hash , I_scalar, from_scalar $1, fst      $2), sp_pos_range $1 $2} /* $foo{bar} */
-| scalar arrayref                      {sp_0($2); to_Deref_with(I_array, I_scalar, from_scalar $1, only_one $2), sp_pos_range $1 $2} /* $array[$element] */
-| restricted_subscripted bracket_subscript        {sp_0($2); to_Deref_with(I_hash , I_scalar, fst $1, fst      $2), sp_pos_range $1 $2} /* $foo->[bar]{baz} */
-| restricted_subscripted arrayref                 {sp_0($2); to_Deref_with(I_array, I_scalar, fst $1, only_one $2), sp_pos_range $1 $2} /* $foo->[$bar][$baz] */
+| scalar bracket_subscript             {sp_0($2); to_Deref_with(I_hash , I_scalar, from_scalar $1, fst                $2), sp_pos_range $1 $2} /* $foo{bar} */
+| scalar arrayref                      {sp_0($2); to_Deref_with(I_array, I_scalar, from_scalar $1, only_one_array_ref $2), sp_pos_range $1 $2} /* $array[$element] */
+| restricted_subscripted bracket_subscript        {sp_0($2); to_Deref_with(I_hash , I_scalar, fst $1, fst                $2), sp_pos_range $1 $2} /* $foo->[bar]{baz} */
+| restricted_subscripted arrayref                 {sp_0($2); to_Deref_with(I_array, I_scalar, fst $1, only_one_array_ref $2), sp_pos_range $1 $2} /* $foo->[$bar][$baz] */
 | restricted_subscripted parenthesized            {sp_0($2); to_Deref_with(I_func , I_scalar, fst $1, List(sndfst $2)), sp_pos_range $1 $2} /* $foo->{bar}(@args) */
 
 arrayref:
diff --git a/perl_checker.src/parser_helper.ml b/perl_checker.src/parser_helper.ml
index 9230074..680b571 100644
--- a/perl_checker.src/parser_helper.ml
+++ b/perl_checker.src/parser_helper.ml
@@ -372,6 +372,14 @@ let rec only_one (l, (spaces, pos)) =
   | [] -> die_with_rawpos pos "you must give one argument"
   | _  -> die_with_rawpos pos "you must give only one argument"
 
+let only_one_array_ref (l, (spaces, pos)) =
+  let e = only_one (l, (spaces, pos)) in
+  (match e with
+  | Call_op("last_array_index", [Deref(I_array, e)], _) ->
+      warn pos (sprintf "you can replace $#%s with -1" (string_of_Ident e))
+  | _ -> ());
+  e
+
 let only_one_in_List ((_, e), both) =
   match e with
   | List l -> only_one(l, both)
@@ -396,7 +404,7 @@ let to_List = function
   | [e] -> e
   | l -> List l
 
-let deref_arraylen e = Call(Deref(I_func, Ident(None, "int", raw_pos2pos bpos)), [Deref(I_array, e)])
+let deref_arraylen e = Call_op("last_array_index", [Deref(I_array, e)], raw_pos2pos bpos)
 let to_Ident ((fq, name), (_, pos)) = Ident(fq, name, raw_pos2pos pos)
 let to_Raw_string (s, (_, pos)) = Raw_string(s, raw_pos2pos pos)
 let to_Method_call (object_, method_, para) = 
diff --git a/perl_checker.src/parser_helper.mli b/perl_checker.src/parser_helper.mli
index faf5c45..3b776ea 100644
--- a/perl_checker.src/parser_helper.mli
+++ b/perl_checker.src/parser_helper.mli
@@ -87,6 +87,8 @@ val check_block_ref :
   'a * (Types.spaces * (int * 'b)) -> unit
 val check_my_our_paren : ((bool * 'a) * 'b) * 'c -> unit
 val only_one : Types.fromparser list * ('a * (int * int)) -> Types.fromparser
+val only_one_array_ref :
+  Types.fromparser list * ('a * (int * int)) -> Types.fromparser
 val only_one_in_List :
   ('a * Types.fromparser) * ('b * (int * int)) -> Types.fromparser
 val is_only_one_in_List : Types.fromparser list -> bool