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fix: ensure interface values aren't discarded (#1308)

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A call to sequence in our handling of polymorphics would result in
discarding legitimate interface implementation results in rare cases.
Calling rights instead fixes the issue. We also need to take the union
of the results to ensure we account for cases such as polymorphically
realized interfaces (e.g. the `prn` function for a (Maybe String), other
wise, we don't resolve to concrete polymorphics for types that have
ad hoc polymorphic members.

Fixes #1307
This commit is contained in:
Scott Olsen 2021-09-04 07:27:07 -05:00 committed by GitHub
parent d2dd875935
commit 03b453cb36
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1 changed files with 10 additions and 7 deletions
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17
src/Polymorphism.hs
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@ -7,7 +7,8 @@ module Polymorphism
)
where
import Data.Either (fromRight)
import Data.Either (fromRight, rights)
import Data.List (unionBy)
import Env
import Managed
import Obj
@ -54,14 +55,16 @@ allImplementations typeEnv env functionName functionType =
foundBindings = case getTypeBinder typeEnv functionName of
-- this function is an interface; lookup implementations
Right (Binder _ (XObj (Lst (XObj (Interface _ paths) _ _ : _)) _ _)) ->
case sequence $ map (\p -> searchValue env p) (paths ++ [(SymPath [] functionName)]) of
Right found -> found
Left _ ->
case findPoly env functionName functionType of
Right r -> [r]
Left _ -> (lookupEverywhere env functionName)
case rights $ map (\p -> searchValue env p) (paths ++ [(SymPath [] functionName)]) of
[] -> getPoly
-- getPoly might return some functions we already found. Use set ops
-- to remove duplicates.
found -> (unionBy (\x y -> (snd x) == (snd y)) found getPoly)
-- just a regular function; look for it
_ -> fromRight [] ((fmap (: []) (Env.getValue env functionName)) <> pure (lookupEverywhere env functionName))
getPoly = case findPoly env functionName functionType of
Right r -> [r]
Left _ -> (lookupEverywhere env functionName)
-- | The various results when trying to find a function using 'findFunctionForMember'.
data FunctionFinderResult