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f32a26b4b3
library/enum.m:
As above.
NEWS.md:
Announce this breaking change.
library/bool.m:
library/char.m:
library/int.m:
library/term.m:
library/uint.m:
tests/hard_coded/deep_copy_exist.m:
tests/typeclasses/extract_typeinfo2.m:
Conform to the change in enum.m.
compiler/pred_table.m:
When typechecking leaves am ambiguity unresolved, a predicate
in this module used to pick one of the candidate matches effectively
at random to "resolve" it.
After the change to enum.m, this led to a compiler abort when compiling
uint.m. The ambiguity was between uint.from_int/2 and the new
enum.from_int/2. The old algorithm picked enum.from_int/2, and tried
to look up its class constraints in the current class context; this failed
with an abort, because the current class context was empty.
Fix this by choosing the match (or *a* match) with the fewest typeclass
constraints to "resolve" any ambiguities.
tests/invalid/overload_resolution_preference.{m,err_exp}:
A test case for the change to pred_table.m.
tests/invalid/Mmakefile:
Enable the new test case.
tests/invalid_submodules/unresolved_overloading.err_exp:
Update this expected output after the change to pred_table.m.
33 lines
963 B
Mathematica
33 lines
963 B
Mathematica
%---------------------------------------------------------------------------%
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% vim: ts=4 sw=4 et ft=mercury
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%---------------------------------------------------------------------------%
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%
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% This is a regression test. It tests whether overload resolution will pick
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% a match *with* typeclass constraints over a match *without* such constraints.
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%
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:- module overload_resolution_preference.
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:- interface.
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:- import_module io.
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:- pred main(io::di, io::uo) is det.
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:- implementation.
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:- import_module enum.
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:- import_module list.
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:- import_module string.
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:- import_module uint.
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main(!IO) :-
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% This call to from_int matches both enum.from_int/2 and uint.from_int/2.
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% Having overload resolution pick enum.from_int/2 leads to a compiler
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% abort, due to the class constraints on that predicate not being found.
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( if from_int(42, U) then
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io.format("U = %u\n", [u(U)], !IO)
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else
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io.write_string("from_int failed.\n", !IO)
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).
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