Fix suggestions for unbound variables (#11680)

When the typechecker generates the error message for an out-of-scope
variable, it now uses the GlobalRdrEnv with respect to which the
variable is unbound, not the GlobalRdrEnv which is available at the time
the error is reported.  Doing so ensures we do not provide suggestions
which themselves are out-of-scope (because they are bound in a later
inter-splice group).

Nonetheless, we do note in the error message if an unambiguous, exact
match to the out-of-scope variable is found in a later inter-splice
group, and we specify where that match is not in scope.

Test Plan: ./validate

Reviewers: goldfire, austin, bgamari

Reviewed By: goldfire

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2000

GHC Trac Issues: #11680

1 files changed, 2 insertions, 2 deletions

diff --git a/compiler/deSugar/DsMeta.hs b/compiler/deSugar/DsMeta.hs
index 84f1a9ca58..b14c0a4bf5 100644
--- a/compiler/deSugar/DsMeta.hs
+++ b/compiler/deSugar/DsMeta.hs
@@ -1179,8 +1179,8 @@ repE (ArithSeq _ _ aseq) =
 
 repE (HsSpliceE splice)    = repSplice splice
 repE (HsStatic e)          = repLE e >>= rep2 staticEName . (:[]) . unC
-repE (HsUnboundVar name)   = do
-                               occ   <- occNameLit name
+repE (HsUnboundVar uv)     = do
+                               occ   <- occNameLit (unboundVarOcc uv)
                                sname <- repNameS occ
                                repUnboundVar sname