| Age | Commit message (Collapse) | Author |
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Kernel should be mostly correct, higher levels do random stuff at
times.
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It does checking of evar instance and Evd.define, assuming an
occur-check has already been performed.
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This is a pre-requisite to use automated formatting tools such as
`ocamlformat`, also, there were quite a few places where the comments
had basically no effect, thus it was confusing for the developer.
p.s: Reading some comments was a lot of fun :)
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This emphasizes that it works only on inductive types.
Also, the name is_template_polymorphic will be reused for a more
general version.
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This avoids all the side effects associated with the manipulation of an
unresolvable flag. In the new design:
- The evar_map stores a set of evars that are candidates for typeclass
resolution, which can be retrieved and set.
We maintain the invariant that it always contains only undefined
evars.
- At the creation time of an evar (new_evar), we classify it as a
potential candidate of resolution.
- This uses a hook to test if the conclusion ends in a typeclass
application. (hook set in typeclasses.ml)
- This is an approximation if the conclusion is an existential (i.e.
not yet determined). In that case we register the evar as
potentially a typeclass instance, and later phases must consider
that case, dropping the evar if it is not a typeclass.
- One can pass the ~typeclass_candidate:false flag to new_evar to
prevent classification entirely. Typically this is for new goals
which should not ever be considered to be typeclass resolution
candidates.
- One can mark a subset of evars unresolvable later if
needed. Typically for clausenv, and marking future goals as
unresolvable even if they are typeclass goals. For clausenv for
example, after turing metas into evars we first (optionally) try a
typeclass resolution on the newly created evars and only then mark
the remaining newly created evars as subgoals. The intent of the
code looks clearer now.
This should prevent keeping testing if undefined evars are classes
all the time and crawling large sets when no typeclasses are present.
- Typeclass candidate evars stay candidates through
restriction/evar-evar solutions.
- Evd.add uses ~typeclass_candidate:false to avoid recomputing if the new
evar is a candidate. There's a deficiency in the API, in most use
cases of Evd.add we should rather use a:
`Evd.update_evar_info : evar_map -> Evar.t -> (evar_info -> evar_info)
-> evar_map`
Usually it is only about nf_evar'ing the evar_info's contents, which
doesn't change the evar candidate status.
- Typeclass resolution can now handle the set of candidates
functionally: it always starts from the set of candidates (and not the
whole undefined_map) and a filter on it, potentially splitting it in
connected components, does proof search for each component in an
evar_map with an empty set of typeclass evars (allowing clean
reentrancy), then reinstates the potential remaining unsolved
components and filtered out typeclass evars at the end of
resolution.
This means no more marking of resolvability/unresolvability
everywhere, and hopefully a more efficient implementation in general.
- This is on top of the cleanup of evar_info's currently but can
be made independent.
[typeclasses] Fix cases.ml: none of the new_evars should be typeclass candidates
Solve bug in inheritance of flags in evar-evar solutions.
Renaming unresolvable to typeclass_candidate (positive) and fix maybe_typeclass_hook
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They were allowed to stay in terms in some cases. We now ensure that if
an evar is defined as e.g. fun x => Type@{foo}, foo is properly
refreshed to be non-algebraic as it could otherwise appear in the term
and break the invariant.
Also cleanup the implementation of refresh_universes to avoid using a
mutable reference and simply rely on the Constr.map smartmap idiom
instead.
This might have compatibility issues, e.g. in HoTT where maybe more
non-algebraic proxy universes could be generated, we'll see.
For the bug report proper, there is a lack of bidirectional
type-checking that makes the initial definition fail (there's a
non-canonical choice of dependency if we don't consider the typing
constraint). With the Program bidir hint it passes.
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All the `evar_map` APIs were deprecated in 8.9, thus we deprecate the
combinators to discourage this style of programming.
Still a few places do use imperative style, but they are pretty
localized and should be cleaned up separately.
As these are the last bits of `e_` API remaining this PR closes #6342.
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A few of them will be of help for future cleanups. We have spared the
stuff in `Names` due to bad organization of this module following the
split from `Term`, which really difficult things removing the
constructors.
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This refines even further c24bcae8 (PR #924) and 6304c843:
- c24bcae8 fixed the order in the heuristic
- 6304c843 improved the order by preferring projections
There remained a dependency in the alphabetic order in selecting
unification candidates. The current commit fixes it.
We radically change the representation of the substitution to invert
by using a map indexed on the rank in the signature rather than on the
name of the variable.
More could be done to use numbers further, e.g. for representing
aliases.
Note that this has consequences on the test-suite (in
output/Notations.v) as some problems now infer a dependent return
clause.
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We bootstrap the circular evar_map <-> econstr dependency by moving
the internal EConstr.API module to Evd.MiniEConstr. Then we make the
Evd functions use econstr.
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This is more efficient in general, because Termops.dependent doesn't take
advantage of the knowledge of its pattern argument.
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We forbid calling `EConstr.to_constr` on terms that are not evar-free,
as to progress towards enforcing the invariant that `Constr.t` is
evar-free. [c.f. #6308]
Due to compatibility constraints we provide an optional parameter to
`to_constr`, `abort` which can be used to overcome this restriction
until we fix all parts of the code.
Now, grepping for `~abort:false` should return the questionable
parts of the system.
Not a lot of places had to be fixed, some comments:
- problems with the interface due to `Evd/Constr` [`Evd.define` being
the prime example] do seem real!
- inductives also look bad with regards to `Constr/EConstr`.
- code in plugins needs work.
A notable user of this "feature" is `Obligations/Program` that seem to
like to generate kernel-level entries with free evars, then to scan
them and workaround this problem by generating constants.
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Previously [fun x : Ind@{i} => x : Ind@{j}] with Ind some cumulative
inductive would try to generate a constraint [i = j] and use
cumulativity only if this resulted in an inconsistency. This is
confusingly different from the behaviour with [Type] and means
cumulativity can only be used to lift between universes related by
strict inequalities. (This isn't a kernel restriction so there might
be some workaround to send the kernel the right constraints, but
not in a nice way.)
See modified test for more details of what is now possible.
Technical notes:
When universe constraints were inferred by comparing the shape of
terms without reduction, cumulativity was not used and so too-strict
equality constraints were generated. Then in order to use cumulativity
we had to make this comparison fail to fall back to full conversion.
When unifiying 2 instances of a cumulative inductive type, if there
are any Irrelevant universes we try to unify them if they are
flexible.
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We mirror the structure of EConstr and move the destructors from `Term`
to `Constr`.
This is a step towards having a single module for `Constr`.
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We do up to `Term` which is the main bulk of the changes.
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We refine the criterion for selecting a projection. Before PR#924 it
was alphabetic (i.e. morally "random" up to alpha-conversion). After
PR#924 it was chronological.
We refine a bit more by giving priority to simple projections when
they exist over projections which include an evar instantiation (and
which may actually be ill-typed).
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This is a first step towards some of the solutions proposed in #6008.
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alphabet
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The old algorithm was relying on list membership, which is O(n). This was
nefarious for terms with many binders. We use instead sets in O(log n).
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This surprising bug was caused by an Id.Set which was ordering
solutions to variable-projection problems in ascii order.
We fix it by re-considering the variables involved in the solutions
using the declaration order.
Note that in practice, this implies preferring a dependent solution
over a non-dependent one.
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The use of template polymorphism in constants was quite limited, as it
only applied to definitions that were exactly inductive types without any
parameter whatsoever. Furthermore, it seems that following the introduction
of polymorphic definitions, the code path enforced regular polymorphism as
soon as the type of a definition was given, which was in practice almost
always.
Removing this feature had no observable effect neither on the test-suite,
nor on any development that we monitor on Travis. I believe it is safe to
assume it was nowadays useless.
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Reminder of (some of) the reasons for removal:
- Despite the claim in sigma.mli, it does *not* prevent evar
leaks, something like:
fun env evd ->
let (evd',ev) = new_evar env evd in
(evd,ev)
will typecheck even with Sigma-like type annotations (with a proof of
reflexivity)
- The API stayed embryonic. Even typing functions were not ported to
Sigma.
- Some unsafe combinators (Unsafe.tclEVARS) were replaced with slightly
less unsafe ones (e.g. s_enter), but those ones were not marked unsafe
at all (despite still being so).
- There was no good story for higher order functions manipulating evar
maps. Without higher order, one can most of the time get away with
reusing the same name for the updated evar map.
- Most of the code doing complex things with evar maps was using unsafe
casts to sigma. This code should be fixed, but this is an orthogonal
issue.
Of course, this was showing a nice and elegant use of GADTs, but the
cost/benefit ratio in practice did not seem good.
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Use an explicit label ~algebraic for make_flexible_variable as well.
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As per https://github.com/coq/coq/pull/716#issuecomment-305140839
Partially using
```bash
git grep --name-only 'anomaly\s*\(~label:"[^"]*"\s*\)\?\(Pp.\)\?(\(\(Pp.\)\?str\)\?\s*".*[^\.!]")' | xargs sed s'/\(anomaly\s*\(~label:"[^"]*"\s*\)\?\(Pp.\)\?(\(\(Pp.\)\?str\)\?\s*".*\s*[^\.! ]\)\s*")/\1.")/g' -i
```
and
```bash
git grep --name-only ' !"' | xargs sed s'/ !"/!"/g' -i
```
The rest were manually edited by looking at the results of
```bash
git grep anomaly | grep '\.ml' | grep -v 'anomaly\s*\(~label:"[^"]*"\s*\)\?\(Pp\.\)\?(\(\(Pp.\)\?str\)\?\s*".*\(\.\|!\)")' | grep 'anomaly\($\|[^_]\)' | less
```
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This is the continuation of #244, we now deprecate `CErrors.error`,
the single entry point in Coq is `user_err`.
The rationale is to allow for easier grepping, and to ease a future
cleanup of error messages. In particular, we would like to
systematically classify all error messages raised by Coq and be sure
they are properly documented.
We restore the two functions removed in #244 to improve compatibility,
but mark them deprecated.
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