[commit: ghc] master: A collection of type-inference refactorings. (3f5673f)
git at git.haskell.org
git at git.haskell.org
Fri Oct 21 16:16:35 UTC 2016
Repository : ssh://git@git.haskell.org/ghc
On branch : master
Link : http://ghc.haskell.org/trac/ghc/changeset/3f5673f34a2f761423027bf46f64f7499708725f/ghc
>---------------------------------------------------------------
commit 3f5673f34a2f761423027bf46f64f7499708725f
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date: Tue Sep 20 23:31:07 2016 +0100
A collection of type-inference refactorings.
This patch does a raft of useful tidy-ups in the type checker.
I've been meaning to do this for some time, and finally made
time to do it en route to ICFP.
1. Modify TcType.ExpType to make a distinct data type,
InferResult for the Infer case, and consequential
refactoring.
2. Define a new function TcUnify.fillInferResult, to fill in
an InferResult. It uses TcMType.promoteTcType to promote
the type to the level of the InferResult.
See TcMType Note [Promoting a type]
This refactoring is in preparation for an improvement
to typechecking pattern bindings, coming next.
I flirted with an elaborate scheme to give better
higher rank inference, but it was just too complicated.
See TcMType Note [Promotion and higher rank types]
3. Add to InferResult a new field ir_inst :: Bool to say
whether or not the type used to fill in the
InferResult should be deeply instantiated. See
TcUnify Note [Deep instantiation of InferResult].
4. Add a TcLevel to SkolemTvs. This will be useful generally
- it's a fast way to see if the type
variable escapes when floating (not used yet)
- it provides a good consistency check when updating a
unification variable (TcMType.writeMetaTyVarRef, the
level_check_ok check)
I originally had another reason (related to the flirting
in (2), but I left it in because it seems like a step in
the right direction.
5. Reduce and simplify the plethora of uExpType,
tcSubType and related functions in TcUnify. It was
such an opaque mess and it's still not great, but it's
better.
6. Simplify the uo_expected field of TypeEqOrigin. Richard
had generatlised it to a ExpType, but it was almost always
a Check type. Now it's back to being a plain TcType which
is much, much easier.
7. Improve error messages by refraining from skolemisation when
it's clear that there's an error: see
TcUnify Note [Don't skolemise unnecessarily]
8. Type.isPiTy and isForAllTy seem to be missing a coreView check,
so I added it
9. Kill off tcs_used_tcvs. Its purpose is to track the
givens used by wanted constraints. For dictionaries etc
we do that via the free vars of the /bindings/ in the
implication constraint ic_binds. But for coercions we
just do update-in-place in the type, rather than
generating a binding. So we need something analogous to
bindings, to track what coercions we have added.
That was the purpose of tcs_used_tcvs. But it only
worked for a /single/ iteration, whereas we may have
multiple iterations of solving an implication. Look
at (the old) 'setImplicationStatus'. If the constraint
is unsolved, it just drops the used_tvs on the floor.
If it becomes solved next time round, we'll pick up
coercions used in that round, but ignore ones used in
the first round.
There was an outright bug. Result = (potentialy) bogus
unused-constraint errors. Constructing a case where this
actually happens seems quite trick so I did not do so.
Solution: expand EvBindsVar to include the (free vars of
the) coercions, so that the coercions are tracked in
essentially the same way as the bindings.
This turned out to be much simpler. Less code, more
correct.
10. Make the ic_binds field in an implication have type
ic_binds :: EvBindsVar
instead of (as previously)
ic_binds :: Maybe EvBindsVar
This is notably simpler, and faster to use -- less
testing of the Maybe. But in the occaional situation
where we don't have anywhere to put the bindings, the
belt-and-braces error check is lost. So I put it back
as an ASSERT in 'setImplicationStatus' (see the use of
'termEvidenceAllowed')
All these changes led to quite bit of error message wibbling
>---------------------------------------------------------------
3f5673f34a2f761423027bf46f64f7499708725f
compiler/ghci/RtClosureInspect.hs | 2 +-
compiler/typecheck/Inst.hs | 4 +-
compiler/typecheck/TcBinds.hs | 90 +--
compiler/typecheck/TcErrors.hs | 44 +-
compiler/typecheck/TcEvidence.hs | 33 +-
compiler/typecheck/TcExpr.hs | 24 +-
compiler/typecheck/TcHsSyn.hs | 7 +-
compiler/typecheck/TcHsType.hs | 21 +-
compiler/typecheck/TcInstDcls.hs | 7 +-
compiler/typecheck/TcMType.hs | 324 ++++++---
compiler/typecheck/TcMatches.hs | 19 +-
compiler/typecheck/TcPat.hs | 22 +-
compiler/typecheck/TcPatSyn.hs | 16 +-
compiler/typecheck/TcPluginM.hs | 16 +-
compiler/typecheck/TcRnDriver.hs | 9 +-
compiler/typecheck/TcRnMonad.hs | 28 +-
compiler/typecheck/TcRnTypes.hs | 29 +-
compiler/typecheck/TcSMonad.hs | 124 ++--
compiler/typecheck/TcSimplify.hs | 58 +-
compiler/typecheck/TcType.hs | 78 ++-
compiler/typecheck/TcUnify.hs | 731 +++++++++++++++------
compiler/typecheck/TcValidity.hs | 2 +-
compiler/types/Type.hs | 2 +
compiler/vectorise/Vectorise/Generic/PData.hs | 2 +-
testsuite/tests/ado/ado004.stderr | 4 +-
.../tests/annotations/should_fail/annfail10.stderr | 12 +-
testsuite/tests/driver/T2182.stderr | 32 +-
testsuite/tests/gadt/gadt-escape1.stderr | 16 +-
testsuite/tests/gadt/gadt13.stderr | 10 +-
testsuite/tests/gadt/gadt7.stderr | 18 +-
.../tests/ghci.debugger/scripts/break012.stdout | 8 +-
.../tests/ghci.debugger/scripts/print022.stdout | 4 +-
testsuite/tests/ghci/scripts/T11524a.stdout | 4 +-
testsuite/tests/ghci/scripts/T2182ghci.stderr | 10 +-
.../tests/indexed-types/should_fail/T12386.hs | 9 +
.../tests/indexed-types/should_fail/T12386.stderr | 7 +
.../tests/indexed-types/should_fail/T5439.stderr | 16 +-
.../tests/indexed-types/should_fail/T7354.stderr | 8 +-
.../tests/parser/should_compile/read014.stderr | 2 +-
testsuite/tests/parser/should_fail/T7848.stderr | 5 +-
.../tests/parser/should_fail/readFail003.stderr | 4 +-
.../partial-sigs/should_compile/T10438.stderr | 14 +-
.../partial-sigs/should_compile/T11192.stderr | 16 +-
.../tests/patsyn/should_compile/T11213.stderr | 2 +-
testsuite/tests/patsyn/should_fail/mono.stderr | 4 +-
testsuite/tests/polykinds/T7438.stderr | 16 +-
testsuite/tests/rebindable/rebindable6.stderr | 12 +-
.../tests/rename/should_compile/T12597.stderr | 2 +-
testsuite/tests/roles/should_compile/T8958.stderr | 5 +-
.../simplCore/should_compile/noinline01.stderr | 4 +-
testsuite/tests/th/T11452.stderr | 2 +-
testsuite/tests/th/T2222.stderr | 2 +-
.../typecheck/should_compile/ExPatFail.stderr | 4 +-
.../should_compile/T12427.stderr} | 0
.../tests/typecheck/should_compile/T12427a.stderr | 33 +
.../tests/typecheck/should_compile/tc141.stderr | 6 +-
.../tests/typecheck/should_fail/T10495.stderr | 10 +-
.../tests/typecheck/should_fail/T10619.stderr | 4 +-
.../tests/typecheck/should_fail/T12177.stderr | 19 +-
testsuite/tests/typecheck/should_fail/T3102.hs | 6 +-
testsuite/tests/typecheck/should_fail/T3102.stderr | 12 -
testsuite/tests/typecheck/should_fail/T7453.stderr | 50 +-
testsuite/tests/typecheck/should_fail/T7734.stderr | 12 +-
testsuite/tests/typecheck/should_fail/T9109.stderr | 10 +-
testsuite/tests/typecheck/should_fail/T9318.stderr | 12 +-
.../tests/typecheck/should_fail/VtaFail.stderr | 2 +-
testsuite/tests/typecheck/should_fail/all.T | 2 +-
.../tests/typecheck/should_fail/tcfail002.stderr | 6 +-
.../tests/typecheck/should_fail/tcfail004.stderr | 6 +-
.../tests/typecheck/should_fail/tcfail005.stderr | 6 +-
.../tests/typecheck/should_fail/tcfail013.stderr | 2 +-
.../tests/typecheck/should_fail/tcfail014.stderr | 6 +-
.../tests/typecheck/should_fail/tcfail018.stderr | 2 +-
.../tests/typecheck/should_fail/tcfail032.stderr | 6 +-
.../tests/typecheck/should_fail/tcfail099.stderr | 6 +-
.../tests/typecheck/should_fail/tcfail104.stderr | 10 +-
.../tests/typecheck/should_fail/tcfail140.stderr | 4 +-
.../tests/typecheck/should_fail/tcfail181.stderr | 2 +-
.../tests/warnings/should_compile/T12574.stderr | 2 +-
79 files changed, 1321 insertions(+), 859 deletions(-)
Diff suppressed because of size. To see it, use:
git diff-tree --root --patch-with-stat --no-color --find-copies-harder --ignore-space-at-eol --cc 3f5673f34a2f761423027bf46f64f7499708725f
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