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| author | Richard Eisenberg <eir@cis.upenn.edu> | 2013-06-21 13:54:49 +0100 |
|---|---|---|
| committer | Richard Eisenberg <eir@cis.upenn.edu> | 2013-06-21 13:54:49 +0100 |
| commit | 569b26526403df4d88fe2a6d64c7dade09d003ad (patch) | |
| tree | f216a5ceaf5d655248564abefab6765aaa9da37d /compiler/coreSyn | |
| parent | 11db9cf82e014de43d8ab04947ef2a2b7fa30f37 (diff) | |
| download | haskell-569b26526403df4d88fe2a6d64c7dade09d003ad.tar.gz | |
Revise implementation of overlapping type family instances.
This commit changes the syntax and story around overlapping type
family instances. Before, we had "unbranched" instances and
"branched" instances. Now, we have closed type families and
open ones.
The behavior of open families is completely unchanged. In particular,
coincident overlap of open type family instances still works, despite
emails to the contrary.
A closed type family is declared like this:
> type family F a where
> F Int = Bool
> F a = Char
The equations are tried in order, from top to bottom, subject to
certain constraints, as described in the user manual. It is not
allowed to declare an instance of a closed family.
Diffstat (limited to 'compiler/coreSyn')
| -rw-r--r-- | compiler/coreSyn/CoreLint.lhs | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/compiler/coreSyn/CoreLint.lhs b/compiler/coreSyn/CoreLint.lhs index b00b452502..f9256e18ad 100644 --- a/compiler/coreSyn/CoreLint.lhs +++ b/compiler/coreSyn/CoreLint.lhs @@ -939,7 +939,7 @@ lintCoercion co@(AxiomInstCo con ind cos) ; let lhs' = Type.substTys subst_l lhs rhs' = Type.substTy subst_r rhs ; case checkAxInstCo co of - Just bad_index -> bad_ax $ ptext (sLit "inconsistent with") <+> (ppr bad_index) + Just bad_branch -> bad_ax $ ptext (sLit "inconsistent with") <+> (pprCoAxBranch (coAxiomTyCon con) bad_branch) Nothing -> return () ; return (typeKind rhs', mkTyConApp (coAxiomTyCon con) lhs', rhs') } where |