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Fix a name shadowing warning (#1406) #1407

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merged 3 commits into from
Jun 10, 2022
Merged

Fix a name shadowing warning (#1406) #1407

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b9807d6
Fix a name shadowing warning
parsonsmatt Jun 10, 2022
398382f
stylish
parsonsmatt Jun 10, 2022
d2cee53
changelog
parsonsmatt Jun 10, 2022
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5 changes: 5 additions & 0 deletions persistent/ChangeLog.md
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Original file line number Diff line number Diff line change
@@ -1,5 +1,10 @@
# Changelog for persistent

## 2.14.0.2

* [#1407](https://github.com/yesodweb/persistent/pull/1407)
* Fix a name shadowing warning.

## 2.14.0.1

* [#1392](https://github.com/yesodweb/persistent/pull/1392)
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44 changes: 27 additions & 17 deletions persistent/Database/Persist/TH.hs
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Expand Up @@ -119,8 +119,8 @@ import Language.Haskell.TH.Syntax
import Web.HttpApiData (FromHttpApiData(..), ToHttpApiData(..))
import Web.PathPieces (PathPiece(..))

import Database.Persist.Class.PersistEntity
import Database.Persist
import Database.Persist.Class.PersistEntity
import Database.Persist.Quasi
import Database.Persist.Quasi.Internal
import Database.Persist.Sql
Expand Down Expand Up @@ -1462,9 +1462,15 @@ fieldUpd :: Name -- ^ constructor name
-> Exp -- ^ record value
-> Name -- ^ field name to update
-> Exp -- ^ new value
-> Exp
fieldUpd con names record name new = CaseE record
[ Match (RecP con pats) (NormalB body) []]
-> Q Exp
fieldUpd con names record name new = do
pats <-
fmap mconcat $ forM names $ \k -> do
varName <- VarP <$> newName (nameBase k)
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And, this line is the real fix. By creating a newName, we're guaranteeing that the variable is fresh and uncapturable and isn't shadowing anything.

@fumieval This is one of those tricky things about TemplateHaskell - it's so easy to use and make names that can cause warnings and bugs! I do it all the time and I really ought to write up a lil' how to on the matter.

pure [(k, varName) | k /= name]

pure $ CaseE record
[ Match (RecP con pats) (NormalB body) []]
Comment on lines +1466 to +1473
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This is the function that was introducing the problem.

where
body = RecConE con
[ if k == name then (name, new) else (k, VarE k)
Expand All @@ -1486,23 +1492,26 @@ mkLensClauses mps entDef genDataType = do
let idClause = normalClause
[conp (keyIdName entDef) []]
(lens' `AppE` getId `AppE` setId)
return $ idClause : if unboundEntitySum entDef
then fmap (toSumClause lens' keyVar valName xName) (getUnboundFieldDefs entDef)
else zipWith (toClause lens' getVal dot keyVar valName xName) (getUnboundFieldDefs entDef) fieldNames
(idClause :) <$> if unboundEntitySum entDef
then pure $ fmap (toSumClause lens' keyVar valName xName) (getUnboundFieldDefs entDef)
else zipWithM (toClause lens' getVal dot keyVar valName xName) (getUnboundFieldDefs entDef) fieldNames
where
fieldNames = fieldDefToRecordName mps entDef <$> getUnboundFieldDefs entDef
toClause lens' getVal dot keyVar valName xName fieldDef fieldName = normalClause
[conp (filterConName mps entDef fieldDef) []]
(lens' `AppE` getter `AppE` setter)
toClause lens' getVal dot keyVar valName xName fieldDef fieldName = do
setter <- mkSetter
pure $ normalClause
[conp (filterConName mps entDef fieldDef) []]
(lens' `AppE` getter `AppE` setter)
where
defName = mkEntityDefName entDef
getter = InfixE (Just $ fieldSel defName fieldName) dot (Just getVal)
setter = LamE
[ conp 'Entity [VarP keyVar, VarP valName]
, VarP xName
]
$ ConE 'Entity `AppE` VarE keyVar
`AppE` fieldUpd defName fieldNames (VarE valName) fieldName (VarE xName)
mkSetter = do
updExpr <- fieldUpd defName fieldNames (VarE valName) fieldName (VarE xName)
pure $ LamE
[ conp 'Entity [VarP keyVar, VarP valName]
, VarP xName
]
$ ConE 'Entity `AppE` VarE keyVar `AppE` updExpr

toSumClause lens' keyVar valName xName fieldDef = normalClause
[conp (filterConName mps entDef fieldDef) []]
Expand Down Expand Up @@ -2167,6 +2176,7 @@ mkLenses mps entityMap ent = fmap mconcat $ forM (getUnboundFieldDefs ent `zip`
t1 `arrow` t2 = ArrowT `AppT` t1 `AppT` t2
vars = mkForallTV fT
: (if mpsGeneric mps then [mkForallTV backend1{-, PlainTV backend2-}] else [])
fieldUpdClause <- fieldUpd (mkEntityDefName ent) fieldNames a fieldName y
return
[ SigD lensName $ ForallT vars [mkClassP ''Functor [VarT fT]] $
(aT `arrow` (VarT fT `AppT` bT)) `arrow`
Expand All @@ -2179,7 +2189,7 @@ mkLenses mps entityMap ent = fmap mconcat $ forM (getUnboundFieldDefs ent `zip`
[ FunD needleN [normalClause [] (fieldSel (mkEntityDefName ent) fieldName `AppE` a)]
, FunD setterN $ return $ normalClause
[VarP yN]
(fieldUpd (mkEntityDefName ent) fieldNames a fieldName y)
fieldUpdClause
]
]
where
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2 changes: 1 addition & 1 deletion persistent/persistent.cabal
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@@ -1,5 +1,5 @@
name: persistent
version: 2.14.0.1
version: 2.14.0.2
license: MIT
license-file: LICENSE
author: Michael Snoyman <michael@snoyman.com>
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6 changes: 3 additions & 3 deletions persistent/test/Database/Persist/TH/NoFieldSelectorsSpec.hs
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Expand Up @@ -32,9 +32,9 @@ spec = it "compiles" True

#else

spec :: Spec
spec :: Spec
spec = do
it "only works with GHC 9.2 or greater" $ do
pendingWith "only works with GHC 9.2 or greater"
pendingWith "only works with GHC 9.2 or greater"

#endif
#endif
2 changes: 2 additions & 0 deletions persistent/test/Database/Persist/TH/OverloadedLabelSpec.hs
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Expand Up @@ -13,6 +13,8 @@
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}

{-# OPTIONS_GHC -Wname-shadowing -Werror=name-shadowing #-}
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This warning is the 'test' for the feature.


module Database.Persist.TH.OverloadedLabelSpec where

import TemplateTestImports
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6 changes: 3 additions & 3 deletions stack.yaml
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@@ -1,4 +1,4 @@
resolver: nightly-2022-01-14
resolver: nightly-2022-06-10

packages:
- ./persistent
Expand All @@ -14,7 +14,7 @@ extra-deps:
- lift-type-0.1.0.0
- mysql-0.2.1
- mysql-simple-0.4.7
- aeson-2.0.2.0
# - aeson-2.0.2.0
# https://github.com/yesodweb/shakespeare/pull/260
# https://github.com/commercialhaskell/stackage/issues/6294
- happy-1.20.0
# - happy-1.20.0