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matching: comments in matcher_constr

master
Gabriel Scherer 2019-06-11 11:41:05 +02:00 committed by Thomas Refis
parent 75133d93b2
commit aedc0cf89a
1 changed files with 9 additions and 1 deletions
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10
lambda/matching.ml
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@ -1313,6 +1313,9 @@ let matcher_constr cstr = match cstr.cstr_arity with
| 1 ->
let rec matcher_rec q rem = match q.pat_desc with
| Tpat_or (p1,p2,_) ->
(* if both sides of the or-pattern match the head constructor,
(K p1 | K p2) :: rem
return (p1 | p2) :: rem *)
let r1 = try Some (matcher_rec p1 rem) with NoMatch -> None
and r2 = try Some (matcher_rec p2 rem) with NoMatch -> None in
begin match r1,r2 with
@ -1333,7 +1336,12 @@ let matcher_constr cstr = match cstr.cstr_arity with
matcher_rec
| _ ->
fun q rem -> match q.pat_desc with
| Tpat_or (_,_,_) -> raise OrPat
| Tpat_or (_,_,_) ->
(* we cannot preserve the or-pattern as in the arity-1 case,
because we cannot express
(K (p1, .., pn) | K (q1, .. qn))
as (p1 .. pn | q1 .. qn) *)
raise OrPat
| Tpat_construct (_,cstr',args)
when Types.may_equal_constr cstr cstr' -> args @ rem
| Tpat_any -> Parmatch.omegas cstr.cstr_arity @ rem