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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2021-07-27 18:07:11 +0100 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2022-02-04 20:36:20 -0500 |
| commit | 6af8e71ed7e749ba94e7a7eaf8b2229341bf35da (patch) | |
| tree | aabf6c233d2067ca9f62b5c5ff4ec83576e58bd9 /compiler/GHC/Rename/Names.hs | |
| parent | bf495f7206741c81135c04ce6bb943c4a6729e80 (diff) | |
| download | haskell-6af8e71ed7e749ba94e7a7eaf8b2229341bf35da.tar.gz | |
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)
Diffstat (limited to 'compiler/GHC/Rename/Names.hs')
| -rw-r--r-- | compiler/GHC/Rename/Names.hs | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/compiler/GHC/Rename/Names.hs b/compiler/GHC/Rename/Names.hs index dbf1f88cba..b3360ad73b 100644 --- a/compiler/GHC/Rename/Names.hs +++ b/compiler/GHC/Rename/Names.hs @@ -690,7 +690,8 @@ extendGlobalRdrEnvRn :: [AvailInfo] -- see Note [Top-level Names in Template Haskell decl quotes] extendGlobalRdrEnvRn avails new_fixities - = do { (gbl_env, lcl_env) <- getEnvs + = checkNoErrs $ -- See Note [Fail fast on duplicate definitions] + do { (gbl_env, lcl_env) <- getEnvs ; stage <- getStage ; isGHCi <- getIsGHCi ; let rdr_env = tcg_rdr_env gbl_env @@ -767,7 +768,19 @@ extendGlobalRdrEnvRn avails new_fixities (False, True) -> isNoFieldSelectorGRE gre' (False, False) -> False -{- +{- Note [Fail fast on duplicate definitions] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +If there are duplicate bindings for the same thing, we want to fail +fast. Having two bindings for the same thing can cause follow-on errors. +Example (test T9975a): + data Test = Test { x :: Int } + pattern Test wat = Test { x = wat } +This defines 'Test' twice. The second defn has no field-names; and then +we get an error from Test { x=wat }, saying "Test has no field 'x'". + +Easiest thing is to bale out fast on duplicate definitions, which +we do via `checkNoErrs` on `extendGlobalRdrEnvRn`. + Note [Reporting duplicate local declarations] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In general, a single module may not define the same OccName multiple times. This |