tcLookupId, tcLookupTyVar, getScopedTyVarBinds,
lclEnvElts, getInLocalScope, findGlobals,
wrongThingErr, pprBinders,
- refineEnvironment,
tcExtendRecEnv, -- For knot-tying
import TcRnMonad
import TcMType
import TcType
-import TcGadt
-- import TcSuspension
import qualified Type
import Var
import SrcLoc
import Outputable
import Maybes
+import FastString
\end{code}
tcLookupField :: Name -> TcM Id -- Returns the selector Id
tcLookupField name = do
- thing <- tcLookupGlobal name
+ thing <- tcLookup name -- Note [Record field lookup]
case thing of
- AnId id -> return id
- other -> wrongThingErr "field name" (AGlobal thing) name
+ AGlobal (AnId id) -> return id
+ thing -> wrongThingErr "field name" thing name
+
+{- Note [Record field lookup]
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~
+You might think we should have tcLookupGlobal here, since record fields
+are always top level. But consider
+ f = e { f = True }
+Then the renamer (which does not keep track of what is a record selector
+and what is not) will rename the definition thus
+ f_7 = e { f_7 = True }
+Now the type checker will find f_7 in the *local* type environment, not
+the global one. It's wrong, of course, but we want to report a tidy
+error, not in TcEnv.notFound. -}
tcLookupDataCon :: Name -> TcM DataCon
tcLookupDataCon name = do
find_thing _ _ thing = pprPanic "find_thing" (ppr thing)
\end{code}
-\begin{code}
-refineEnvironment
- :: Refinement
- -> Bool -- whether type equations are involved
- -> TcM a
- -> TcM a
--- I don't think I have to refine the set of global type variables in scope
--- Reason: the refinement never increases that set
-refineEnvironment reft otherEquations thing_inside
- | isEmptyRefinement reft -- Common case
- , not otherEquations
- = thing_inside
- | otherwise
- = do { env <- getLclEnv
- ; let le' = mapNameEnv refine (tcl_env env)
- ; setLclEnv (env {tcl_env = le'}) thing_inside }
- where
- refine elt@(ATcId { tct_co = Rigid co, tct_type = ty })
- | Just (co', ty') <- refineType reft ty
- = elt { tct_co = Rigid (WpCo co' <.> co), tct_type = ty' }
- refine elt@(ATcId { tct_co = Wobbly})
--- Main new idea: make wobbly things invisible whenever there
--- is a refinement of any sort
--- | otherEquations
- = elt { tct_co = WobblyInvisible}
- refine (ATyVar tv ty)
- | Just (_, ty') <- refineType reft ty
- = ATyVar tv ty' -- Ignore the coercion that refineType returns
-
- refine elt = elt -- Common case
-\end{code}
-
%************************************************************************
%* *
\subsection{The global tyvars}