Improve errors for non-existent labels

This patch fixes #17469, by improving matters when you use
non-existent field names in a record construction:
   data T = MkT { x :: Int }
   f v = MkT { y = 3 }

The check is now made in the renamer, in GHC.Rename.Env.lookupRecFieldOcc.

That in turn led to a spurious error in T9975a, which is fixed by
making GHC.Rename.Names.extendGlobalRdrEnvRn fail fast if it finds
duplicate bindings.  See Note [Fail fast on duplicate definitions]
in that module for more details.

This patch was originated and worked on by Alex D (@nineonine)

3 files changed, 3 insertions, 11 deletions

diff --git a/compiler/GHC/Tc/Gen/Expr.hs b/compiler/GHC/Tc/Gen/Expr.hs
index 230acdc3f5..46775235df 100644
--- a/compiler/GHC/Tc/Gen/Expr.hs
+++ b/compiler/GHC/Tc/Gen/Expr.hs
@@ -52,7 +52,6 @@ import GHC.Tc.Utils.Env
 import GHC.Tc.Gen.Arrow
 import GHC.Tc.Gen.Match
 import GHC.Tc.Gen.HsType
-import GHC.Tc.Gen.Pat
 import GHC.Tc.Utils.TcMType
 import GHC.Tc.Types.Origin
 import GHC.Tc.Utils.TcType as TcType
@@ -1399,7 +1398,7 @@ tcRecordField con_like flds_w_tys (L loc (FieldOcc sel_name lbl)) rhs
                 --          (so the desugarer knows the type of local binder to make)
            ; return (Just (L loc (FieldOcc field_id lbl), rhs')) }
       | otherwise
-      = do { addErrTc (badFieldCon con_like field_lbl)
+      = do { addErrTc (badFieldConErr (getName con_like) field_lbl)
            ; return Nothing }
   where
         field_lbl = occNameFS $ rdrNameOcc (unLoc lbl)
diff --git a/compiler/GHC/Tc/Gen/Pat.hs b/compiler/GHC/Tc/Gen/Pat.hs
index 6034d05720..132f58b7b4 100644
--- a/compiler/GHC/Tc/Gen/Pat.hs
+++ b/compiler/GHC/Tc/Gen/Pat.hs
@@ -21,7 +21,6 @@ module GHC.Tc.Gen.Pat
    , tcCheckPat, tcCheckPat_O, tcInferPat
    , tcPats
    , addDataConStupidTheta
-   , badFieldCon
    , polyPatSig
    )
 where
@@ -1282,7 +1281,7 @@ tcConArgs con_like arg_tys tenv penv con_args thing_inside = case con_args of
                 --      f (R { foo = (a,b) }) = a+b
                 -- If foo isn't one of R's fields, we don't want to crash when
                 -- typechecking the "a+b".
-           [] -> failWith (badFieldCon con_like lbl)
+           [] -> failWith (badFieldConErr (getName con_like) lbl)
 
                 -- The normal case, when the field comes from the right constructor
            (pat_ty : extras) -> do
@@ -1489,12 +1488,6 @@ checkGADT conlike ex_tvs arg_tys = \case
     has_existentials :: Bool
     has_existentials = any (`elemVarSet` tyCoVarsOfTypes arg_tys) ex_tvs
 
-badFieldCon :: ConLike -> FieldLabelString -> TcRnMessage
-badFieldCon con field
-  = TcRnUnknownMessage $ mkPlainError noHints $
-    hsep [text "Constructor" <+> quotes (ppr con),
-          text "does not have field", quotes (ppr field)]
-
 polyPatSig :: TcType -> SDoc
 polyPatSig sig_ty
   = hang (text "Illegal polymorphic type signature in pattern:")
diff --git a/compiler/GHC/Tc/Utils/Monad.hs b/compiler/GHC/Tc/Utils/Monad.hs
index ea3b50fa3c..ca2915e8fa 100644
--- a/compiler/GHC/Tc/Utils/Monad.hs
+++ b/compiler/GHC/Tc/Utils/Monad.hs
@@ -1142,7 +1142,7 @@ reportDiagnostic msg
 -----------------------
 checkNoErrs :: TcM r -> TcM r
 -- (checkNoErrs m) succeeds iff m succeeds and generates no errors
--- If m fails then (checkNoErrsTc m) fails.
+-- If m fails then (checkNoErrs m) fails.
 -- If m succeeds, it checks whether m generated any errors messages
 --      (it might have recovered internally)
 --      If so, it fails too.