[Git][ghc/ghc][wip/fabu/T24452-confusing-error] wip

[Fabricio Nascimento (@fabu)]

Fabricio Nascimento pushed to branch wip/fabu/T24452-confusing-error at Glasgow Haskell Compiler / GHC


Commits:
3850605a by Fabricio de Sousa Nascimento at 2024-06-19T20:46:51+09:00
wip

- - - - -


9 changed files:

- compiler/GHC/Rename/Env.hs
- + testsuite/tests/rename/T24452/T24452a.hs
- + testsuite/tests/rename/T24452/T24452b.hs
- + testsuite/tests/rename/T24452/T24452b.stderr
- + testsuite/tests/rename/T24452/T24452c.hs
- + testsuite/tests/rename/T24452/T24452c.stderr
- + testsuite/tests/rename/T24452/T24452d.hs
- + testsuite/tests/rename/T24452/T24452d.stderr
- + testsuite/tests/rename/T24452/all.T


Changes:

=====================================
compiler/GHC/Rename/Env.hs
=====================================
@@ -1,4 +1,5 @@
 {-# LANGUAGE FlexibleContexts #-}
+
 {-# LANGUAGE GADTs            #-}
 {-# LANGUAGE MultiWayIf       #-}
 {-# LANGUAGE TypeApplications #-}
@@ -709,7 +710,9 @@ lookupSubBndrOcc_helper must_have_parent warn_if_deprec parent rdr_name how_lkup
     DisambiguatedOccurrence g ->
       checkFld g
     AmbiguousOccurrence gres ->
-      mkNameClashErr gres
+      if must_have_parent
+      then noMatchingParentErr original_gres
+      else mkNameClashErr gres
     where
         checkFld :: GlobalRdrElt -> RnM ChildLookupResult
         checkFld g = do
@@ -721,21 +724,25 @@ lookupSubBndrOcc_helper must_have_parent warn_if_deprec parent rdr_name how_lkup
         -- 1. There were none to begin with.
         -- 2. None of the matching ones were the parent but
         --  a. They were from an overloaded record field so we can report
-        --     a better error
+        --     a better error, or we were looking for references that must
+        --     have the correct parent. For example instance member names
+        --     that need to match the class they come from. Reporting those
+        --     as clashing errors, gives the user a confusing message
+        --     as in (#24452).
         --  b. The original lookup was actually ambiguous.
         --     For example, the case where overloading is off and two
         --     record fields are in scope from different record
         --     constructors, neither of which is the parent.
         noMatchingParentErr :: [GlobalRdrElt] -> RnM ChildLookupResult
         noMatchingParentErr original_gres = do
-          traceRn "npe" (ppr original_gres)
+          traceRn "noMatchingParentErr" (ppr original_gres)
           dup_fields_ok <- xoptM LangExt.DuplicateRecordFields
           case original_gres of
             []  -> return NameNotFound
             [g] -> return $ IncorrectParent parent g
                               [p | ParentIs p <- [greParent g]]
             gss@(g:gss'@(_:_)) ->
-              if all isRecFldGRE gss && dup_fields_ok
+              if must_have_parent || all isRecFldGRE gss && dup_fields_ok
               then return $
                     IncorrectParent parent g
                       [p | x <- gss, ParentIs p <- [greParent x]]
@@ -838,6 +845,7 @@ lookupSubBndrOcc warn_if_deprec the_parent doc rdr_name =
   lookupExactOrOrig rdr_name (Right . greName) $
     -- This happens for built-in classes, see mod052 for example
     do { child <- lookupSubBndrOcc_helper True warn_if_deprec the_parent rdr_name what_lkup
+       ; traceTc "Here we go" (vcat [ppr child])
        ; return $ case child of
            FoundChild g       -> Right (greName g)
            NameNotFound       -> Left (UnknownSubordinate doc)


=====================================
testsuite/tests/rename/T24452/T24452a.hs
=====================================
@@ -0,0 +1,11 @@
+-- Note
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+module BugReproduce where
+
+import Control.Applicative (Alternative (empty, (<|>)))
+
+newtype Foo a = MkFoo [a] deriving (Functor, Applicative)
+
+instance Alternative Foo where
+  empty = undefined
+  p <|> q = undefined


=====================================
testsuite/tests/rename/T24452/T24452b.hs
=====================================
@@ -0,0 +1,10 @@
+-- Note
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+module BugReproduce where
+
+import Control.Applicative (Alternative)
+
+newtype Foo a = MkFoo [a] deriving (Functor, Applicative)
+
+instance Alternative Foo where
+  empty = undefined


=====================================
testsuite/tests/rename/T24452/T24452b.stderr
=====================================
@@ -0,0 +1,2 @@
+T24452b.hs:10:3: error: [GHC-54721]
+    ‘empty’ is not a (visible) method of class ‘Alternative’
\ No newline at end of file


=====================================
testsuite/tests/rename/T24452/T24452c.hs
=====================================
@@ -0,0 +1,11 @@
+-- Note
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+module BugReproduce where
+
+import Control.Applicative (Alternative)
+import qualified Data.Map as Map
+
+newtype Foo a = MkFoo [a] deriving (Functor, Applicative)
+
+instance Alternative Foo where
+  empty = undefined


=====================================
testsuite/tests/rename/T24452/T24452c.stderr
=====================================
@@ -0,0 +1,2 @@
+T24452c.hs:11:3: error: [GHC-54721]
+    ‘empty’ is not a (visible) method of class ‘Alternative’
\ No newline at end of file


=====================================
testsuite/tests/rename/T24452/T24452d.hs
=====================================
@@ -0,0 +1,12 @@
+-- Note
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+module BugReproduce where
+
+import Control.Applicative (Alternative)
+import qualified Data.Map as Map
+import qualified Data.Set as Set
+
+newtype Foo a = MkFoo [a] deriving (Functor, Applicative)
+
+instance Alternative Foo where
+  empty = undefined


=====================================
testsuite/tests/rename/T24452/T24452d.stderr
=====================================
@@ -0,0 +1,2 @@
+T24452d.hs:12:3: error: [GHC-54721]
+    ‘empty’ is not a (visible) method of class ‘Alternative’
\ No newline at end of file


=====================================
testsuite/tests/rename/T24452/all.T
=====================================
@@ -0,0 +1,4 @@
+test('T24452a', normal, compile, [''])
+test('T24452b', normal, compile_fail, [''])
+test('T24452c', normal, compile_fail, [''])
+test('T24452d', normal, compile_fail, [''])



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/3850605a1151a999aa0ad37ef7e72031b15ecbb1

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/3850605a1151a999aa0ad37ef7e72031b15ecbb1
You're receiving this email because of your account on gitlab.haskell.org.


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/ghc-commits/attachments/20240619/1e936600/attachment-0001.html>