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Corrrect fragile matching 

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@7634 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
master
Luc Maranget 2006-09-21 14:54:54 +00:00
parent 366af60a74
commit 6c05350ca4
5 changed files with 188 additions and 157 deletions
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325
typing/parmatch.ml
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@ -29,6 +29,9 @@ let make_pat desc ty tenv =
let omega = make_pat Tpat_any Ctype.none Env.empty
let extra_pat =
make_pat (Tpat_var (Ident.create "+")) Ctype.none Env.empty
let rec omegas i =
if i <= 0 then [] else omega :: omegas (i-1)
@ -625,8 +628,7 @@ let full_match closing env = match env with
| _ -> fatal_error "Parmatch.full_match"
let extendable_match env = match env with
| ({pat_desc = Tpat_construct ({cstr_tag=Cstr_exception _},_)},_)::_ -> false
| ({pat_desc = Tpat_construct(c,_)} as p,_) :: _ ->
| ({pat_desc = Tpat_construct({cstr_tag=(Cstr_constant _|Cstr_block _)},_)} as p,_) :: _ ->
let path = get_type_path p.pat_type p.pat_env in
not
(Path.same path Predef.path_bool ||
@ -635,6 +637,16 @@ let extendable_match env = match env with
| _ -> false
let should_extend ext env = match ext with
| None -> false
| Some ext -> match env with
| ({pat_desc =
Tpat_construct({cstr_tag=(Cstr_constant _|Cstr_block _)},_)} as p,_)
:: _ ->
let path = get_type_path p.pat_type p.pat_env in
Path.same path ext
| _ -> false
(* complement constructor tags *)
let complete_tags nconsts nconstrs tags =
let seen_const = Array.create nconsts false
@ -705,7 +717,7 @@ let build_other_constant proj make first next p env =
in the first column of env
*)
let build_other env = match env with
let build_other ext env = match env with
| ({pat_desc = Tpat_construct ({cstr_tag=Cstr_exception _} as c,_)},_)
::_ ->
make_pat
@ -716,11 +728,16 @@ let build_other env = match env with
[]))
Ctype.none Env.empty
| ({pat_desc = Tpat_construct (_,_)} as p,_) :: _ ->
let get_tag = function
| {pat_desc = Tpat_construct (c,_)} -> c.cstr_tag
| _ -> fatal_error "Parmatch.get_tag" in
let all_tags = List.map (fun (p,_) -> get_tag p) env in
pat_of_constrs p (complete_constrs p all_tags)
begin match ext with
| Some ext when Path.same ext (get_type_path p.pat_type p.pat_env) ->
extra_pat
| _ ->
let get_tag = function
| {pat_desc = Tpat_construct (c,_)} -> c.cstr_tag
| _ -> fatal_error "Parmatch.get_tag" in
let all_tags = List.map (fun (p,_) -> get_tag p) env in
pat_of_constrs p (complete_constrs p all_tags)
end
| ({pat_desc = Tpat_variant(_,_,row)} as p,_) :: _ ->
let tags =
List.map
@ -879,62 +896,6 @@ let rec satisfiable pss qs = match pss with
let q0 = discr_pat q pss in
satisfiable (filter_one q0 pss) (simple_match_args q0 q @ qs)
(*
Like satisfiable, looking for a matching value with an extra constructor.
That is, look for the situation where adding one constructor
would NOT yield a non-exhaustive matching.
*)
let relevant_location loc r = match r with
| None -> None
| Some rloc ->
if rloc = Location.none then
Some loc
else
r
let rec satisfiable_extra some pss qs = match qs with
| [] -> if pss = [] then some else None
| {pat_desc = Tpat_or(q1,q2,_)}::qs ->
let r1 = satisfiable_extra some pss (q1::qs) in
begin match r1 with
| Some _ -> r1
| None -> satisfiable_extra some pss (q2::qs)
end
| {pat_desc = Tpat_alias(q,_)}::qs ->
satisfiable_extra some pss (q::qs)
| {pat_desc = (Tpat_any | Tpat_var(_))} as q::qs ->
let q0 = discr_pat omega pss in
let r =
match filter_all q0 pss with
(* first column of pss is made of variables only *)
| [] -> satisfiable_extra some (filter_extra pss) qs
| constrs ->
if extendable_match constrs then
let rloc =
satisfiable_extra (Some q.pat_loc) (filter_extra pss) qs in
match rloc with
| Some loc -> rloc
| None -> try_many_extra some qs constrs
else
try_many_extra some qs constrs in
relevant_location q.pat_loc r
| q::qs ->
let q0 = discr_pat q pss in
relevant_location
q.pat_loc
(satisfiable_extra
some (filter_one q0 pss) (simple_match_args q0 q @ qs))
and try_many_extra some qs = function
| [] -> None
| (p,pss)::rem ->
let rloc = satisfiable_extra some pss (simple_match_args p omega @ qs) in
match rloc with
| Some _ -> rloc
| None -> try_many_extra some qs rem
(*
Now another satisfiable function that additionally
supplies an example of a matching value.
@ -954,7 +915,7 @@ let rec try_many f = function
| r -> r
end
let rec exhaust pss n = match pss with
let rec exhaust ext pss n = match pss with
| [] -> Rsome (omegas n)
| []::_ -> Rnone
| pss ->
@ -962,7 +923,7 @@ let rec exhaust pss n = match pss with
begin match filter_all q0 pss with
(* first column of pss is made of variables only *)
| [] ->
begin match exhaust (filter_extra pss) (n-1) with
begin match exhaust ext (filter_extra pss) (n-1) with
| Rsome r -> Rsome (q0::r)
| r -> r
end
@ -972,11 +933,13 @@ let rec exhaust pss n = match pss with
Rnone
else
match
exhaust pss (List.length (simple_match_args p omega) + n - 1)
exhaust
ext pss (List.length (simple_match_args p omega) + n - 1)
with
| Rsome r -> Rsome (set_args p r)
| r -> r in
if full_match false constrs
if
full_match false constrs && not (should_extend ext constrs)
then
try_many try_non_omega constrs
else
@ -988,12 +951,12 @@ let rec exhaust pss n = match pss with
* D exhaustive => pss exhaustive
* D non-exhaustive => we have a non-filtered value
*)
let r = exhaust (filter_extra pss) (n-1) in
let r = exhaust ext (filter_extra pss) (n-1) in
match r with
| Rnone -> Rnone
| Rsome r ->
try
Rsome (build_other constrs::r)
Rsome (build_other ext constrs::r)
with
(* cannot occur, since constructors don't make a full signature *)
| Empty -> fatal_error "Parmatch.exhaust"
@ -1419,10 +1382,7 @@ and lubs ps qs = match ps,qs with
(******************************)
(* Entry points *)
(* - Variant closing *)
(* - Partial match *)
(* - Unused match case *)
(* Exported variant closing *)
(******************************)
(* Apply pressure to variants *)
@ -1431,9 +1391,13 @@ let pressure_variants tdefs patl =
let pss = List.map (fun p -> [p;omega]) patl in
ignore (pressure_variants (Some tdefs) pss)
(*****************************)
(* Utilities for diagnostics *)
(*****************************)
(*
Build up a working pattern matrix.
- Forget about guarded patterns
Build up a working pattern matrix by forgetting
about guarded patterns
*)
let has_guard act = match act.exp_desc with
@ -1450,13 +1414,17 @@ let rec initial_matrix = function
else
[pat] :: initial_matrix rem
(******************************************)
(* Look for a row that matches some value *)
(******************************************)
(*
All the following ``*_all'' functions
check whether a given value [v] is matched by some row in pss.
They are used to whether the exhaustiveness exemple is
matched by a guarded clause
Useful for seeing if the example of
non-matched value can indeed be matched
(by a guarded clause)
*)
exception NoGuard
@ -1513,12 +1481,12 @@ let check_partial_all v casel =
with
| NoGuard -> None
let check_partial loc casel =
if Warnings.is_active (Warnings.Partial_match "") then begin
let pss = initial_matrix casel in
let pss = get_mins le_pats pss in
match pss with
| [] ->
(************************)
(* Exhaustiveness check *)
(************************)
let do_check_partial loc casel pss = match pss with
| [] ->
(*
This can occur
- For empty matches generated by ocamlp4 (no warning)
@ -1527,66 +1495,134 @@ let check_partial loc casel =
Then match MUST be considered non-exhaustive,
otherwise compilation of PM is broken.
*)
begin match casel with
| [] -> ()
| _ -> Location.prerr_warning loc Warnings.All_clauses_guarded
end ;
Partial
| ps::_ ->
begin match exhaust pss (List.length ps) with
| Rnone -> Total
| Rsome [v] ->
let errmsg =
try
let buf = Buffer.create 16 in
let fmt = formatter_of_buffer buf in
top_pretty fmt v;
begin match check_partial_all v casel with
| None -> ()
| Some _ ->
(* This is ``Some l'', where l is the location of
begin match casel with
| [] -> ()
| _ -> Location.prerr_warning loc Warnings.All_clauses_guarded
end ;
Partial
| ps::_ ->
begin match exhaust None pss (List.length ps) with
| Rnone -> Total
| Rsome [v] ->
let errmsg =
try
let buf = Buffer.create 16 in
let fmt = formatter_of_buffer buf in
top_pretty fmt v;
begin match check_partial_all v casel with
| None -> ()
| Some _ ->
(* This is 'Some loc', where loc is the location of
a possibly matching clause.
I forget about l, because printing two locations
Forget about loc, because printing two locations
is a pain in the top-level *)
Buffer.add_string buf
"\n(However, some guarded clause may match this value.)"
end ;
Buffer.contents buf
with _ ->
"" in
Location.prerr_warning loc (Warnings.Partial_match errmsg) ;
Partial
| _ ->
fatal_error "Parmatch.check_partial"
end
Buffer.add_string buf
"\n(However, some guarded clause may match this value.)"
end ;
Buffer.contents buf
with _ ->
"" in
Location.prerr_warning loc (Warnings.Partial_match errmsg) ;
Partial
| _ ->
fatal_error "Parmatch.check_partial"
end
(*****************)
(* Fragile check *)
(*****************)
(* Collect all data types in a pattern *)
let rec add_path path = function
| [] -> [path]
| x::rem as paths ->
if Path.same path x then paths
else x::add_path path rem
let extendable_path path =
not
(Path.same path Predef.path_bool ||
Path.same path Predef.path_list ||
Path.same path Predef.path_option)
let rec collect_paths_from_pat r p = match p.pat_desc with
| Tpat_construct({cstr_tag=(Cstr_constant _|Cstr_block _)},ps) ->
let path = get_type_path p.pat_type p.pat_env in
List.fold_left
collect_paths_from_pat
(if extendable_path path then add_path path r else r)
ps
| Tpat_any|Tpat_var _|Tpat_constant _| Tpat_variant (_,None,_) -> r
| Tpat_tuple ps | Tpat_array ps
| Tpat_construct ({cstr_tag=Cstr_exception _}, ps)->
List.fold_left collect_paths_from_pat r ps
| Tpat_record lps ->
List.fold_left
(fun r (_,p) -> collect_paths_from_pat r p)
r lps
| Tpat_variant (_, Some p, _) | Tpat_alias (p,_) -> collect_paths_from_pat r p
| Tpat_or (p1,p2,_) ->
collect_paths_from_pat (collect_paths_from_pat r p1) p2
(*
Actual fragile check
1. Collect data types in the patterns of the match.
2. One exhautivity check per datatype, considering that
the type is extended.
*)
let do_check_fragile loc casel pss =
let exts =
List.fold_left
(fun r (p,_) -> collect_paths_from_pat r p)
[] casel in
match exts with
| [] -> ()
| _ -> match pss with
| [] -> ()
| ps::_ ->
List.iter
(fun ext ->
match exhaust (Some ext) pss (List.length ps) with
| Rnone ->
Location.prerr_warning
loc
(Warnings.Fragile_match (Path.name ext))
| Rsome _ -> ())
exts
(********************************)
(* Exported exhustiveness check *)
(********************************)
(*
Fragile check is performed when required and
on exhaustive matches only.
*)
let check_partial loc casel =
if Warnings.is_active (Warnings.Partial_match "") then begin
let pss = initial_matrix casel in
let pss = get_mins le_pats pss in
let total = do_check_partial loc casel pss in
if
total = Total && Warnings.is_active (Warnings.Fragile_match "")
then begin
do_check_fragile loc casel pss
end ;
total
end else
Partial
let location_of_clause = function
pat :: _ -> pat.pat_loc
| _ -> fatal_error "Parmatch.location_of_clause"
(********************************)
(* Exported unused clause check *)
(********************************)
let seen_pat q pss = [q]::pss
(* Extra check
Will this clause match if someone adds a constructor somewhere
*)
let warn_fragile () = Warnings.is_active (Warnings.Fragile_pat "")
let check_used_extra pss qs =
if warn_fragile () then begin
match satisfiable_extra None pss qs with
| Some location ->
Location.prerr_warning
location
(Warnings.Fragile_pat "")
| None -> ()
end
let check_unused tdefs casel =
if Warnings.is_active Warnings.Unused_match then
let rec do_rec pref = function
@ -1600,23 +1636,20 @@ let check_unused tdefs casel =
match r with
| Unused ->
Location.prerr_warning
(location_of_clause qs) Warnings.Unused_match
q.pat_loc Warnings.Unused_match
| Upartial ps ->
List.iter
(fun p ->
Location.prerr_warning
p.pat_loc Warnings.Unused_pat)
ps
| Used ->
check_used_extra pss qs
| Used -> ()
with e -> assert false
end ;
if has_guard act then
do_rec pref rem
else
do_rec (seen_pat q pref) rem in
do_rec ([q]::pref) rem in
do_rec [] casel

18
utils/warnings.ml
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@ -18,7 +18,7 @@ type t = (* A is all *)
| Comment_start (* C *)
| Comment_not_end
| Deprecated (* D *)
| Fragile_pat of string (* E *)
| Fragile_match of string (* E *)
| Partial_application (* F *)
| Labels_omitted (* L *)
| Method_override of string list (* M *)
@ -46,7 +46,7 @@ let letter = function (* 'a' is all *)
| Comment_start
| Comment_not_end -> 'c'
| Deprecated -> 'd'
| Fragile_pat _ -> 'e'
| Fragile_match _ -> 'e'
| Partial_application -> 'f'
| Labels_omitted -> 'l'
| Method_override _ -> 'm'
@ -112,14 +112,12 @@ let message = function
"this pattern-matching is not exhaustive.\n\
Here is an example of a value that is not matched:\n" ^ s
| Unused_match -> "this match case is unused."
| Unused_pat -> "this pattern is unused."
| Fragile_pat "" ->
"this pattern is fragile. It would hide\n\
the addition of new constructors to the data types it matches."
| Fragile_pat s ->
"this pattern is fragile. It would hide\n\
the addition of new constructors to the data types it matches.\n\
Here is an example of a more robust pattern:\n" ^ s
| Unused_pat -> "this sub-pattern is unused."
| Fragile_match "" ->
"this pattern-matching is fragile."
| Fragile_match s ->
"this pattern-matching is fragile.\n\
It will remain exhaustive when constructors are added to type " ^ s ^ "."
| Labels_omitted ->
"labels were omitted in the application of this function."
| Method_override [lab] ->

2
utils/warnings.mli
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@ -18,7 +18,7 @@ type t = (* A is all *)
| Comment_start (* C *)
| Comment_not_end
| Deprecated (* D *)
| Fragile_pat of string (* E *)
| Fragile_match of string (* E *)
| Partial_application (* F *)
| Labels_omitted (* L *)
| Method_override of string list (* M *)