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dde8c1f396
This functor was intended to have the same semantics as free/0, while
containing the type of the value it was applied to. However, commit
87e7e3bafa, the commit in which Fergus
introduced this function symbol, also contained an "XXX temporary hack"
in which the code that was supposed to create a value using this function
symbol when propagating a type into a free/0 inst, just ignored the type,
and left the inst as free/0. THIS TEMPORARY HACK HAS REMAINED IN THE CODE
SINCE 1994.
In a few places, we did hand-create insts using free/1 for code created
by the compiler itself. However, as far as I can tell, no free/1 inst
ever described any code read in from source files. This meant that
any code in switch arms for free/1 in switches on insts was never tested
in any meaningful sense. And predicates such as inst_merge_4, which
processed several kinds of insts without doing a complete switch on insts,
simply lacked code handle free/1 at all.
This diff deletes the free/1 function symbol. It does so NOT because
the type stored as its argument is not useful, but because it is useful
NOT JUST for free insts, but for ALL insts. This means that any mechanism
for providing information about the type of the value that an inst applies to
should work for all insts. This can be done
- either by passing along the type with every inst, and stepping into
the argument types of each argument of a function symbol as we process
bound insts, in every operation that operates on insts that needs
type information.
- or by including a type in ALL the function symbols of the inst type.
(We could do this either by adding a maybe(mer_type) field to each
function symbol, which would be "no" before the propagate-types-
into-modes pass, or by adding just a mer_type field, which would
be a special dummy value before that pass. I (zs) prefer the latter,
and so would juliensf.)
The second option would involve reintroducing a free/1 function symbol
into the inst type, but this would replace the existing free/0
function symbol, and it would inherit all the code that currently
handles free/0, NOT the code being deleted by this diff for handling
the *current* free/1.
The first option would be easier to implement if only one or maybe two
operations needed type info, the second would be both easier to implement
and more efficient if more operations needed that info.
compiler/prog_data.m:
Delete free/1.
compiler/add_mode.m:
compiler/add_mutable_aux_preds.m:
compiler/comp_unit_interface.m:
compiler/dep_par_conj.m:
compiler/direct_arg_in_out.m:
compiler/equiv_type_hlds.m:
compiler/error_msg_inst.m:
compiler/float_regs.m:
compiler/hlds_code_util.m:
compiler/hlds_out_goal.m:
compiler/hlds_out_mode.m:
compiler/hlds_statistics.m:
compiler/inst_abstract_unify.m:
compiler/inst_check.m:
compiler/inst_match.m:
compiler/inst_merge.m:
compiler/inst_mode_type_prop.m:
compiler/inst_test.m:
compiler/inst_user.m:
compiler/inst_util.m:
compiler/mode_constraints.m:
compiler/mode_errors.m:
compiler/mode_top_functor.m:
compiler/modecheck_coerce.m:
compiler/modecheck_util.m:
compiler/modes.m:
compiler/module_qual.qualify_items.m:
compiler/parse_tree_out_inst.m:
compiler/parse_tree_to_term.m:
compiler/pd_util.m:
compiler/prog_mode.m:
compiler/prog_rep.m:
compiler/recompilation.usage.m:
compiler/types_into_modes.m:
compiler/unused_imports.m:
compiler/xml_documentation.m:
Conform to the change above.
192 lines
7.3 KiB
Mathematica
192 lines
7.3 KiB
Mathematica
%---------------------------------------------------------------------------%
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% vim: ft=mercury ts=4 sw=4 et
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%---------------------------------------------------------------------------%
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% Copyright (C) 1994-2012 The University of Melbourne.
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% Copyright (C) 2015 The Mercury team.
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% This file may only be copied under the terms of the GNU General
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% Public License - see the file COPYING in the Mercury distribution.
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%---------------------------------------------------------------------------%
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%
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% File: mode_top_functor.m.
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%
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% This module computes top_functor_modes.
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%
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%---------------------------------------------------------------------------%
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:- module check_hlds.mode_top_functor.
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:- interface.
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:- import_module hlds.
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:- import_module hlds.hlds_module.
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:- import_module hlds.hlds_pred.
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:- import_module parse_tree.
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:- import_module parse_tree.prog_data.
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:- import_module list.
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%---------------------------------------------------------------------------%
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%
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% Computing top_functor_modes.
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%
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% mode_to_top_functor_mode converts a mode (and corresponding type)
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% to a top_functor_mode.
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%
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% A mode is a high-level notion, the normal Mercury language mode.
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% A top_functor_mode is a low-level notion used for code generation,
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% which indicates the argument passing convention (top_in, top_out, or
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% top_unused) that corresponds to that mode. We need to know the type,
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% not just the mode, because the argument passing convention can depend
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% on the type's representation.
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%
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:- pred mode_to_top_functor_mode(module_info::in, mer_mode::in,
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mer_type::in, top_functor_mode::out) is det.
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:- pred init_final_insts_to_top_functor_mode(module_info::in,
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mer_inst::in, mer_inst::in, mer_type::in, top_functor_mode::out) is det.
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% Zip together the given lists of modes and types, and return
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% the top_functor_mode computed by mode_to_top_functor_mode
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% for each pair.
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%
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:- pred modes_to_top_functor_modes(module_info::in,
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list(mer_mode)::in, list(mer_type)::in, list(top_functor_mode)::out)
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is det.
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%---------------------------------------------------------------------------%
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%---------------------------------------------------------------------------%
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:- implementation.
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:- import_module check_hlds.inst_lookup.
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:- import_module check_hlds.inst_test.
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:- import_module check_hlds.mode_util.
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:- import_module check_hlds.type_util.
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:- import_module mdbcomp.
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:- import_module mdbcomp.sym_name.
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:- import_module parse_tree.prog_type.
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:- import_module require.
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:- import_module term.
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%---------------------------------------------------------------------------%
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mode_to_top_functor_mode(ModuleInfo, Mode, Type, TopFunctorMode) :-
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mode_get_insts(ModuleInfo, Mode, InitialInst, FinalInst),
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find_top_functor_mode_loop_over_notags(ModuleInfo, Type, [],
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InitialInst, FinalInst, TopFunctorMode).
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init_final_insts_to_top_functor_mode(ModuleInfo, InitialInst, FinalInst, Type,
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TopFunctorMode) :-
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find_top_functor_mode_loop_over_notags(ModuleInfo, Type, [],
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InitialInst, FinalInst, TopFunctorMode).
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:- pred find_top_functor_mode_loop_over_notags(module_info::in,
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mer_type::in, list(type_ctor)::in, mer_inst::in, mer_inst::in,
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top_functor_mode::out) is det.
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find_top_functor_mode_loop_over_notags(ModuleInfo, Type, ContainingTypes,
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InitialInst, FinalInst, TopFunctorMode) :-
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% We need to handle no_tag types (types which have exactly one constructor,
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% and whose one constructor has exactly one argument) specially here,
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% since for them an inst of bound(f(free)) is not really bound as far as
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% code generation is concerned, since the f/1 will get optimized away.
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( if
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% Is this a no_tag type?
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type_is_no_tag_type(ModuleInfo, Type, FunctorName, ArgType),
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% Avoid infinite recursion.
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type_to_ctor(Type, TypeCtor),
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not list.member(TypeCtor, ContainingTypes)
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then
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% The top_functor_mode will be determined by the mode and type of the
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% functor's argument, so we figure out the mode and type of the
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% argument, and then recurse.
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ConsId = cons(FunctorName, 1, TypeCtor),
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get_single_arg_inst(ModuleInfo, InitialInst, ConsId, InitialArgInst),
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get_single_arg_inst(ModuleInfo, FinalInst, ConsId, FinalArgInst),
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find_top_functor_mode_loop_over_notags(ModuleInfo,
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ArgType, [TypeCtor | ContainingTypes],
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InitialArgInst, FinalArgInst, TopFunctorMode)
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else
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( if inst_is_bound(ModuleInfo, InitialInst) then
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TopFunctorMode = top_in
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else if inst_is_bound(ModuleInfo, FinalInst) then
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TopFunctorMode = top_out
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else
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TopFunctorMode = top_unused
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)
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).
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% get_single_arg_inst(ModuleInfo, Inst, ConsId, ArgInsts):
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%
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% Given an inst `Inst', figure out what the inst of the argument would be,
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% assuming that the functor is the one given by the specified ConsId,
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% whose arity is 1.
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%
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:- pred get_single_arg_inst(module_info::in, mer_inst::in, cons_id::in,
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mer_inst::out) is det.
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get_single_arg_inst(ModuleInfo, Inst, ConsId, ArgInst) :-
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% XXX This is very similar to get_arg_insts in prog_mode.
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(
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Inst = defined_inst(InstName),
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inst_lookup(ModuleInfo, InstName, NamedInst),
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get_single_arg_inst(ModuleInfo, NamedInst, ConsId, ArgInst)
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;
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Inst = not_reached,
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ArgInst = not_reached
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;
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Inst = ground(Uniq, _PredInst),
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ArgInst = ground(Uniq, none_or_default_func)
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;
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Inst = bound(_Uniq, _InstResult, List),
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( if get_single_arg_inst_in_bound_insts(List, ConsId, ArgInst0) then
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ArgInst = ArgInst0
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else
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% The code is unreachable.
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ArgInst = not_reached
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)
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;
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Inst = free,
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ArgInst = free
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;
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Inst = any(Uniq, _),
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ArgInst = any(Uniq, none_or_default_func)
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;
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Inst = inst_var(_),
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unexpected($pred, "inst_var")
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;
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Inst = constrained_inst_vars(_, InsideInst),
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get_single_arg_inst(ModuleInfo, InsideInst, ConsId, ArgInst)
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).
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:- pred get_single_arg_inst_in_bound_insts(list(bound_inst)::in, cons_id::in,
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mer_inst::out) is semidet.
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get_single_arg_inst_in_bound_insts([BoundInst | BoundInsts], ConsId,
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ArgInst) :-
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( if
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BoundInst = bound_functor(InstConsId, [ArgInst0]),
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% The cons_ids for types and insts can differ in the type_ctor field
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% so we must ignore them.
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equivalent_cons_ids(ConsId, InstConsId)
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then
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ArgInst = ArgInst0
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else
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get_single_arg_inst_in_bound_insts(BoundInsts, ConsId, ArgInst)
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).
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modes_to_top_functor_modes(_ModuleInfo, [], [], []).
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modes_to_top_functor_modes(_ModuleInfo, [], [_ | _], _) :-
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unexpected($pred, "length mismatch").
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modes_to_top_functor_modes(_ModuleInfo, [_ | _], [], _) :-
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unexpected($pred, "length mismatch").
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modes_to_top_functor_modes(ModuleInfo, [Mode | Modes], [Type | Types],
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[TopFunctorMode | TopFunctorModes]) :-
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mode_to_top_functor_mode(ModuleInfo, Mode, Type, TopFunctorMode),
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modes_to_top_functor_modes(ModuleInfo, Modes, Types, TopFunctorModes).
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%---------------------------------------------------------------------------%
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:- end_module check_hlds.mode_top_functor.
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%---------------------------------------------------------------------------%
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