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Fix nested patterns in rustboot

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The code for taking pattern-bound variables was being interspersed
with pattern code, so that if a nested pattern failed partway through,
a variable would be taken but never dropped (because the drop code
is inside the block representing the action for the pattern). For
example, in the pattern foo(?i, bar(some[t](_)), _), if the scrutinee
was foo(x, bar(none[t]), y), the variable i would be taken but never
dropped. The patch fixes this bug.
This commit is contained in:
Tim Chevalier 2011-04-27 14:40:07 -07:00 committed by Graydon Hoare
parent 25694582d9
commit 93845d0bae
1 changed files with 34 additions and 16 deletions
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50
src/boot/me/trans.ml
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@ -4793,18 +4793,28 @@ let trans_visitor
let trans_arm arm : quad_idx =
let (pat, block) = arm.node in
(* Translates the pattern and returns the addresses of the branch
* instructions that are taken if the match fails.
(* Translates the pattern and returns a pair where the first
component is a list of the addresses of the branch
instructions that are taken if the match fails,
and the second component is a thunk that, when invoked,
emits initialization code for the variables bound in this pattern.
trans_pat can't just emit the initialization code itself, because
then, pattern-bound variables could be taken without ever being
dropped if a nested pattern fails partway through (because the
drop code is part of the action for the pattern).
*)
let rec trans_pat
(pat:Ast.pat)
(src_cell:Il.cell)
(src_ty:Ast.ty)
: quad_idx list =
: (quad_idx list *
(unit -> unit)) =
match pat with
Ast.PAT_lit lit ->
trans_compare_simple Il.JNE (trans_lit lit) (Il.Cell src_cell)
(trans_compare_simple Il.JNE (trans_lit lit) (Il.Cell src_cell),
fun _ -> ())
| Ast.PAT_tag (lval, pats) ->
let tag_ident =
@ -4815,7 +4825,7 @@ let trans_visitor
| Ast.LVAL_base { node = Ast.BASE_app (id, _); id = _ } ->
id
| _ -> bug cx "expected lval ending in ident"
in
in
let ttag =
match strip_mutable_or_constrained_ty src_ty with
Ast.TY_tag ttag -> ttag
@ -4843,7 +4853,8 @@ let trans_visitor
let tup_cell:Il.cell = get_variant_ptr union_cell i in
let trans_elem_pat i elem_pat : quad_idx list =
let trans_elem_pat i elem_pat :
(quad_idx list * (unit -> unit)) =
let elem_cell =
get_element_ptr_dyn_in_current_frame tup_cell i
in
@ -4852,24 +4863,31 @@ let trans_visitor
in
let elem_jumps =
List.concat (Array.to_list (Array.mapi trans_elem_pat pats))
(Array.to_list (Array.mapi trans_elem_pat pats)) in
let (elem_jump_addrs, ks) = List.split elem_jumps
in
next_jumps @ elem_jumps
(next_jumps @ (List.concat elem_jump_addrs),
(* Compose all the var-initialization thunks together
to make one thunk that initializes all the vars *)
List.fold_left (fun g f -> (fun x -> f (g x)))
(fun _ -> ()) ks)
| Ast.PAT_slot (dst, _) ->
let dst_slot = get_slot cx dst.id in
let dst_cell = cell_of_block_slot dst.id in
trans_init_slot_from_cell
(get_ty_params_of_current_frame())
CLONE_none dst_cell dst_slot
src_cell src_ty;
[] (* irrefutable *)
| Ast.PAT_wild -> [] (* irrefutable *)
(* irrefutable *)
([], (fun () -> (* init the slot later, inside the block,
once we know we had a match *)
trans_init_slot_from_cell
(get_ty_params_of_current_frame())
CLONE_none dst_cell dst_slot
src_cell src_ty))
| Ast.PAT_wild -> ([], fun _ -> ()) (* irrefutable *)
in
let (lval_cell, lval_ty) = trans_lval at.Ast.alt_tag_lval in
let next_jumps = trans_pat pat lval_cell lval_ty in
let (next_jumps, prologue) = trans_pat pat lval_cell lval_ty in
prologue (); (* binds any pattern-bound variables *)
trans_block block;
let last_jump = mark() in
emit (Il.jmp Il.JMP Il.CodeNone);