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79e8804db9
This fixes github issue #85. A complication is that the compiler itself has code, in make.util.m, in which a disjunct has no solutions in only one mode of a two mode function, but in this case, the code works (though its programming style is pretty bad), so to get this change to bootstrap, we also need a way to disable the "this disjunct can't have solutions" warning in a scope. compiler/simplify_goal_disj.m: When we generate a "this disjunct can't succeed" warning, do not insist on all modes generating that warning. We used to insist on that because in a multi-mode predicate, such warnings can be inappropriate for other modes. Instead, achieve the same objective of minimizing programmer confusion by adding a codicil explicitly mentioninging this possibility. Make the generation of this warning conditional on a simplify task that can be disabled by "disable_warnings" scope. compiler/prog_data.m: Add "no_solution_disjunct" as a warning kind that may be disabled. compiler/parse_goal.m: Parse the new kind of warning. compiler/prog_out.m: Output the new kind of warning. Improve some adjacent though unrelated code. compiler/make.util.m: Add code disable this warning in the affected predicate. Comment out this code until installed compilers know how to parse it and understand it. compiler/Mercury.options: Don't turn warnings into errors for make.util.m until then. compiler/simplify_goal_scope.m: compiler/simplify_info.m: compiler/simplify_tasks.m: Provide the mechanism needed to make it possible to disable warnings about no solution disjuncts. doc/reference_manual.texi: Document the new disable-able warning. NEWS: Document both the changed behavior of the old warning and the new way to disable it. tests/warnings/gh85.{m,exp}: A regression test for the bug, based on the code in the github issue. It also tests the way to disable the warning. tests/warnings/Mmakefile: Enable the new test case.
80 lines
2.2 KiB
Mathematica
80 lines
2.2 KiB
Mathematica
%---------------------------------------------------------------------------%
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% vim: ft=mercury ts=4 sw=4 et
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%---------------------------------------------------------------------------%
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% Any copyright is dedicated to the Public Domain.
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% http://creativecommons.org/publicdomain/zero/1.0/
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%
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% Released by Transnat Games for testing purposes.
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%
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% This is a regression test for github issue #85.
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%
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% The bug was that the presence of the second mode on test1 used to silence
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% the "disjunct has no solutions" warning for the second disjunct.
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:- module gh85.
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:- interface.
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:- type x
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---> a
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; b
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; c.
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:- type y
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---> ok
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; error(string).
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:- pred test1(x, y).
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:- mode test1(out, in) is det.
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:- mode test1(in, out) is det.
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:- pred test2(x, y).
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:- mode test2(out, in) is det.
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:- mode test2(in, out) is det.
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%---------------------------------------------------------------------------%
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:- implementation.
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:- use_module exception.
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% In the first mode, which is the <out,in> mode, the second disjunct here
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% is not part of the switch on the second argument; it is just a disjunct
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% that can have no solution. Since --warn-simple-code is on by default,
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% the compiler should generate a warning about this fact.
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%
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% The bug was that although the compiler *did* generate this warning,
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% the warning was marked report_only_if_in_all_modes. In the second mode,
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% which is the <in,out> mode, the second clause turns into a switch arm
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% in the switch on the first argument. In this mode, we don't generate
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% the same message about a disjunct having no solutions, for two separate
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% and distinct reasons: first, it is ok (and common) for a switch arm
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% to have no solutions, and second, there is no disjunct left to complain
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% about anyway (switch arms are *made* from disjuncts, but *are not*
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% disjuncts anymore).
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test1(X, Y) :-
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(
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X = a,
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Y = ok
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;
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X = b,
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exception.throw(exception.software_error("ERROR"))
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;
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X = c,
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Y = error("c")
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).
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test2(X, Y) :-
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disable_warning [no_solution_disjunct]
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(
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X = a,
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Y = ok
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;
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X = b,
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exception.throw(exception.software_error("ERROR"))
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;
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X = c,
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Y = error("c")
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).
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