github/semantic
1
1
Fork 0
mirror of https://github.com/github/semantic.git synced 2024-12-20 21:31:48 +03:00
Code Issues Projects Releases Wiki Activity

📝 why OVERLAPPABLE.

Browse Source
This commit is contained in:
Rob Rix 2016-06-16 11:58:17 -04:00
parent cff9ac00ab
commit 63ed038654
1 changed files with 2 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/Data/Record.hs
View File

@ -33,6 +33,8 @@ class HasField (fields :: [*]) (field :: *) where
-- Instances -- Instances
-- OVERLAPPABLE is required for the HasField instances so that we can handle the two cases: either the head of the non-empty h-list is the requested field, or it isn’t. The third possible case (the h-list is empty) is rejected at compile-time.
instance {-# OVERLAPPABLE #-} HasField fields field => HasField (notIt ': fields) field where instance {-# OVERLAPPABLE #-} HasField fields field => HasField (notIt ': fields) field where
getField (RCons _ t) = getField t getField (RCons _ t) = getField t