Package: ghc / 8.0.1-17

find-tycon-panic Patch series | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
From: Adam Gundry <adam@well-typed.com>
Subject: Avoid find_tycon panic if datacon is not in scope

When using TH to splice expressions involving record field construction,
the parent datacon may not be in scope.  We shouldn't panic about this,
because we will be renaming Exact RdrNames which don't require any
disambiguation.

Reviewers: austin, bgamari
Reviewed By: bgamari
Differential Revision: https://phabricator.haskell.org/D2321
GHC Trac Issues: #12130

Origin: upstream, https://git.haskell.org/ghc.git/commitdiff/694e0f3a08030

Index: b/compiler/rename/RnPat.hs
===================================================================
--- a/compiler/rename/RnPat.hs
+++ b/compiler/rename/RnPat.hs
@@ -636,7 +636,7 @@ rnHsRecFields ctxt mk_arg (HsRecFields {
     find_tycon :: GlobalRdrEnv -> Name {- DataCon -} -> Maybe Name {- TyCon -}
     -- Return the parent *type constructor* of the data constructor
     -- (that is, the parent of the data constructor),
-    -- or 'Nothing' if it is a pattern synonym.
+    -- or 'Nothing' if it is a pattern synonym or not in scope.
     -- That's the parent to use for looking up record fields.
     find_tycon env con
       | Just (AConLike (RealDataCon dc)) <- wiredInNameTyThing_maybe con
@@ -648,8 +648,9 @@ rnHsRecFields ctxt mk_arg (HsRecFields {
           ParentIs p -> Just p
           _          -> Nothing
 
-      | otherwise
-      = pprPanic "find_tycon" (ppr con $$ ppr (lookupGRE_Name env con))
+      | otherwise = Nothing
+        -- This can happen if the datacon is not in scope
+        -- and we are in a TH splice (Trac #12130)
 
     dup_flds :: [[RdrName]]
         -- Each list represents a RdrName that occurred more than once