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c5fc9a929d
compiler/det_report.m:
... when a "declared det, inferred multi" kind of determinism error
is caused by the (probably unexpected, possibly hard-to-see) presence
of a disjunction.
Change the wording to refer to "disjuncts" instead of "clauses";
while in Mercury, all clauses in multi-clause definitions are implicitly
also disjuncts, not all disjuncts are whole clauses.
tests/invalid/bug496.err_exp:
tests/invalid/det_errors.err_exp:
tests/invalid/not_a_switch.err_exp:
tests/invalid/require_scopes.err_exp:
tests/invalid/switch_arm_multi_not_det.err_exp:
Expect the updated form of the error message.
27 lines
1.7 KiB
Plaintext
27 lines
1.7 KiB
Plaintext
bug496.m:022: In `options_to_action'(in, in, out):
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bug496.m:022: error: determinism declaration not satisfied.
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bug496.m:022: Declared `det', inferred `nondet'.
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bug496.m:022: The reasons for the difference are the following.
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bug496.m:050: Inside the case [|]/2 of the switch on AllActions:
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bug496.m:050: disjunction has more than one disjunct with solutions.
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bug496.m:050: In argument 2 of functor `[|]/2':
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bug496.m:050: unification with `list.[]' can fail.
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bug496.m:053: In argument 2 of functor `[|]/2':
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bug496.m:053: unification with `list.[V_11 | V_12]' can fail.
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bug496.m:053: This later disjunct may have a solution.
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bug496.m:050: It is possible that the cause of the declared determinism not
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bug496.m:050: being satisfied is the inability of determinism analysis to
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bug496.m:050: recognize that a disjunction (usually created by the compiler
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bug496.m:050: for a switch arm) is a switch on a *subterm* of a variable when
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bug496.m:050: the instantiation state of that variable is at least partially
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bug496.m:050: unique. This is because converting such a disjunction to a
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bug496.m:050: switch requires replacing several unifications, one in each arm
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bug496.m:050: of the disjunction, that each unify the variable representing
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bug496.m:050: the subterm (e.g. the tail of a list) with the same function
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bug496.m:050: symbol, with just one unification before the disjunction, but
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bug496.m:050: due to limitations of the current modechecker, this
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bug496.m:050: transformation could destroy the uniqueness.
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bug496.m:050: In cases where this uniqueness is not needed, the programmer
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bug496.m:050: can fix the determinism error by performing this transformation
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bug496.m:050: manually.
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