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Fix Signature Help inside do Notation in GHC >= 9.10 #4904

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Fix Signature Help inside do Notation in GHC >= 9.10 #4904

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85b02d3
Traverse Generated Nodes
vidit-od Apr 19, 2026
e108151
Add regression tests
vidit-od Apr 21, 2026
9344a71
Add one more regression test
vidit-od May 1, 2026
20e9d05
Handle identifier info
vidit-od May 1, 2026
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18 changes: 16 additions & 2 deletions plugins/hls-signature-help-plugin/src/Ide/Plugin/SignatureHelp.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@

module Ide.Plugin.SignatureHelp (descriptor) where

import Control.Applicative
import Control.Arrow ((>>>))
import Control.Monad.Trans.Except (ExceptT (ExceptT))
import Data.Bifunctor (bimap)
Expand All @@ -29,6 +30,7 @@ import Development.IDE.Core.PluginUtils (runIdeActionE,
import Development.IDE.Core.PositionMapping (fromCurrentPosition)
import Development.IDE.GHC.Compat (FastStringCompat, Name,
RealSrcSpan,
generatedNodeInfo,
getSourceNodeIds,
isAnnotationInNodeInfo,
mkRealSrcLoc,
Expand All @@ -48,6 +50,7 @@ import GHC.Iface.Ext.Types (ContextInfo (Use),
HieAST (nodeChildren, nodeSpan),
HieASTs (getAsts),
IdentifierDetails (identInfo, identType),
NodeInfo (nodeIdentifiers),
nodeType)
import GHC.Iface.Ext.Utils (smallestContainingSatisfying)
import GHC.Types.Name.Env (lookupNameEnv)
Expand Down Expand Up @@ -294,12 +297,23 @@ getNodeNameAndTypes hieKind hieAst =
case extractName identifier of
Nothing -> Nothing
Just name ->
let mTypeOfName = identType identifierDetails
let mTypeOfName = identType identifierDetails <|> do
nodeInfo <- generatedNodeInfo hieAst
details <- M.lookup identifier (nodeIdentifiers nodeInfo)
identType details
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@vidit-od vidit-od May 1, 2026

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@jian-lin This should take care of lookup to generated nodes on fallback for identifier details.

-- types from the source NodeInfo
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typesOfNode = case sourceNodeInfo hieAst of
Nothing -> []
Just nodeInfo -> nodeType nodeInfo
-- fall back to generated NodeInfo when source has no types
typesOfGeneratedNode = case generatedNodeInfo hieAst of
Nothing -> []
Just nodeInfo -> nodeType nodeInfo
allTypes = case mTypeOfName of
Nothing -> typesOfNode
Nothing ->
case typesOfNode of
[] -> typesOfGeneratedNode
ts -> ts
-- (the last?) one type of 'typesOfNode' may (always?) be the same as 'typeOfName'
-- To avoid generating two identical signature helps, we do a filtering here
-- This is similar to 'dropEnd1' in Development.IDE.Spans.AtPoint.atPoint
Expand Down
17 changes: 17 additions & 0 deletions plugins/hls-signature-help-plugin/test/Main.hs
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Expand Up @@ -381,6 +381,23 @@ main =
Nothing,
Nothing,
Just $ SimilarSignatureHelp $ SignatureHelp [SignatureInformation "f :: forall a b c. a -> b -> c" Nothing (Just [ParameterInformation (InR (19, 20)) Nothing, ParameterInformation (InR (24, 25)) Nothing]) (Just (InL 0))] (Just 0) (Just (InL 0))
],
-- Prevents https://github.com/haskell/haskell-language-server/issues/4769
mkTest
"inside do block"
[__i|
f :: Int -> Int -> Int
f = _
test :: IO ()
test = do
x <- pure 1
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^
print (f x 2)
^ ^
|]
[ Just $ SimilarSignatureHelp $ SignatureHelp [SignatureInformation "pure :: forall (f :: Type -> Type) a. Applicative f => a -> f a" (Just $ InR $ MarkupContent MarkupKind_Markdown "Lift a value") (Just [ParameterInformation (InR (55,56)) Nothing]) (Just (InL 0)), SignatureInformation "pure :: Int -> IO Int" (Just $ InR $ MarkupContent MarkupKind_Markdown "Lift a value") (Just [ParameterInformation (InR (8,11)) Nothing]) (Just (InL 0)), SignatureInformation "pure :: forall a. a -> IO a" (Just $ InR $ MarkupContent MarkupKind_Markdown "Lift a value") (Just [ParameterInformation (InR (18,19)) Nothing]) (Just (InL 0))] (Just 0) (Just (InL 0)),
Just $ SimilarSignatureHelp $ SignatureHelp [SignatureInformation "f :: Int -> Int -> Int" Nothing (Just [ParameterInformation (InR (5, 8)) Nothing, ParameterInformation (InR (12, 15)) Nothing]) (Just (InL 0))] (Just 0) (Just (InL 0)),
Just $ SimilarSignatureHelp $ SignatureHelp [SignatureInformation "f :: Int -> Int -> Int" Nothing (Just [ParameterInformation (InR (5, 8)) Nothing, ParameterInformation (InR (12, 15)) Nothing]) (Just (InL 1))] (Just 0) (Just (InL 1))
]
]

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