From dd0ac6e5fdc8e4d2cdc52267bfa829ff27ec4bd7 Mon Sep 17 00:00:00 2001
From: Simon Peyton Jones <simonpj@microsoft.com>
Date: Thu, 24 Jun 2021 11:30:53 +0100
Subject: [PATCH] Extend the in-scope set to silence substExpr warnings
substExpr warns if it finds a LocalId that isn't in the in-scope set.
This patch extends the in-scope set to silence the warnings. (It has
no effect on behaviour.)
(cherry picked from commit 25ca0b5aef54281d161288d9d951a6325d0ab53f)
---
compiler/GHC/Core/SimpleOpt.hs | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/compiler/GHC/Core/SimpleOpt.hs b/compiler/GHC/Core/SimpleOpt.hs
index 16c485d8dfe8..a79323a88a42 100644
--- a/compiler/GHC/Core/SimpleOpt.hs
+++ b/compiler/GHC/Core/SimpleOpt.hs
@@ -1175,7 +1175,12 @@ exprIsConApp_maybe (in_scope, id_unf) expr
-- Look through dictionary functions; see Note [Unfolding DFuns]
| DFunUnfolding { df_bndrs = bndrs, df_con = con, df_args = dfun_args } <- unfolding
, bndrs `equalLength` args -- See Note [DFun arity check]
- , let subst = mkOpenSubst in_scope (bndrs `zip` args)
+ , let in_scope' = extend_in_scope (exprsFreeVars dfun_args)
+ subst = mkOpenSubst in_scope' (bndrs `zip` args)
+ -- We extend the in-scope set here to silence warnings from
+ -- substExpr when it finds not-in-scope Ids in dfun_args.
+ -- simplOptExpr initialises the in-scope set with exprFreeVars,
+ -- but that doesn't account for DFun unfoldings
= succeedWith in_scope floats $
pushCoDataCon con (map (substExpr subst) dfun_args) co
@@ -1186,7 +1191,7 @@ exprIsConApp_maybe (in_scope, id_unf) expr
-- CPR'd workers getting inlined back into their wrappers,
| idArity fun == 0
, Just rhs <- expandUnfolding_maybe unfolding
- , let in_scope' = extendInScopeSetSet in_scope (exprFreeVars rhs)
+ , let in_scope' = extend_in_scope (exprFreeVars rhs)
= go (Left in_scope') floats rhs cont
-- See Note [exprIsConApp_maybe on literal strings]
@@ -1198,6 +1203,11 @@ exprIsConApp_maybe (in_scope, id_unf) expr
dealWithStringLiteral fun str co
where
unfolding = id_unf fun
+ extend_in_scope unf_fvs
+ | isLocalId fun = in_scope `extendInScopeSetSet` unf_fvs
+ | otherwise = in_scope
+ -- A GlobalId has no (LocalId) free variables; and the
+ -- in-scope set tracks only LocalIds
go _ _ _ _ = Nothing
--
GitLab