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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2016-02-15 08:46:36 +0000 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2016-02-15 08:47:31 +0000 |
| commit | bb7f23084e2a886f5b48442458d33b43c4628b3c (patch) | |
| tree | 41311ad7b6045111e5cc8a9a736585a8db2c6ffa /compiler | |
| parent | 18cd712427182e76d38047860ee3e26799bc3fe2 (diff) | |
| download | haskell-bb7f23084e2a886f5b48442458d33b43c4628b3c.tar.gz | |
Comments only
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/typecheck/TcErrors.hs | 17 | ||||
| -rw-r--r-- | compiler/typecheck/TcSimplify.hs | 8 |
2 files changed, 19 insertions, 6 deletions
diff --git a/compiler/typecheck/TcErrors.hs b/compiler/typecheck/TcErrors.hs index 5f2c908849..e97e3c566e 100644 --- a/compiler/typecheck/TcErrors.hs +++ b/compiler/typecheck/TcErrors.hs @@ -134,7 +134,12 @@ reportUnsolved wanted ; getTcEvBinds binds_var } -- | Report *all* unsolved goals as errors, even if -fdefer-type-errors is on +-- However, do not make any evidence bindings, because we don't +-- have any convenient place to put them. -- See Note [Deferring coercion errors to runtime] +-- Used by solveEqualities for kind equalities +-- (see Note [Fail fast on kind errors] in TcSimplify] +-- and for simplifyDefault. reportAllUnsolved :: WantedConstraints -> TcM () reportAllUnsolved wanted = report_unsolved Nothing False TypeError HoleError HoleError wanted @@ -240,11 +245,15 @@ data ReportErrCtxt -- (innermost first) -- ic_skols and givens are tidied, rest are not , cec_tidy :: TidyEnv + , cec_binds :: Maybe EvBindsVar - -- Nothinng <=> Report all errors, including holes; no bindings - -- Just ev <=> make some errors (depending on cec_defer) - -- into warnings, and emit evidence bindings - -- into 'ev' for unsolved constraints + -- Nothing <=> Report all errors, including holes + -- Do not add any evidence bindings, because + -- we have no convenient place to put them + -- See TcErrors.reportAllUnsolved + -- Just ev <=> make some errors (depending on cec_defer) + -- into warnings, and emit evidence bindings + -- into 'ev' for unsolved constraints , cec_errors_as_warns :: Bool -- Turn all errors into warnings -- (except for Holes, which are diff --git a/compiler/typecheck/TcSimplify.hs b/compiler/typecheck/TcSimplify.hs index 8cc9b4939b..be0735816b 100644 --- a/compiler/typecheck/TcSimplify.hs +++ b/compiler/typecheck/TcSimplify.hs @@ -188,11 +188,15 @@ defaultCallStacks wanteds solveEqualities is used to solve kind equalities when kind-checking user-written types. If solving fails we should fail outright, rather than just accumulate an error message, for two reasons: + * A kind-bogus type signature may cause a cascade of knock-on errors if we let it pass - * More seriously, if we don't solve a constraint we'll be left - with a type that has a coercion hole in it, something like + * More seriously, we don't have a convenient term-level place to add + deferred bindings for unsolved kind-equality constraints, so we + don't build evidence bindings (by usine reportAllUnsolved). That + means that we'll be left with with a type that has coercion holes + in it, something like <type> |> co-hole where co-hole is not filled in. Eeek! That un-filled-in hole actually causes GHC to crash with "fvProv falls into a hole" |