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diff --git a/compiler/GHC/Core/Lint/Interactive.hs b/compiler/GHC/Core/Lint/Interactive.hs
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+{-# LANGUAGE ScopedTypeVariables #-}
+
+{-
+(c) The University of Glasgow 2006
+(c) The GRASP/AQUA Project, Glasgow University, 1993-1998
+
+
+A ``lint'' pass to check for Core correctness.
+See Note [Core Lint guarantee].
+-}
+
+module GHC.Core.Lint.Interactive (
+    interactiveInScope,
+ ) where
+
+import GHC.Prelude
+
+import GHC.Runtime.Context
+
+import GHC.Core.Coercion
+import GHC.Core.TyCo.FVs
+import GHC.Core.InstEnv      ( instanceDFunId, instEnvElts )
+
+import GHC.Types.Id
+import GHC.Types.TypeEnv
+
+
+interactiveInScope :: InteractiveContext -> [Var]
+-- In GHCi we may lint expressions, or bindings arising from 'deriving'
+-- clauses, that mention variables bound in the interactive context.
+-- These are Local things (see Note [Interactively-bound Ids in GHCi] in GHC.Runtime.Context).
+-- So we have to tell Lint about them, lest it reports them as out of scope.
+--
+-- We do this by find local-named things that may appear free in interactive
+-- context.  This function is pretty revolting and quite possibly not quite right.
+-- When we are not in GHCi, the interactive context (hsc_IC hsc_env) is empty
+-- so this is a (cheap) no-op.
+--
+-- See #8215 for an example
+interactiveInScope ictxt
+  = tyvars ++ ids
+  where
+    -- C.f. GHC.Tc.Module.setInteractiveContext, Desugar.deSugarExpr
+    (cls_insts, _fam_insts) = ic_instances ictxt
+    te1    = mkTypeEnvWithImplicits (ic_tythings ictxt)
+    te     = extendTypeEnvWithIds te1 (map instanceDFunId $ instEnvElts cls_insts)
+    ids    = typeEnvIds te
+    tyvars = tyCoVarsOfTypesList $ map idType ids
+              -- Why the type variables?  How can the top level envt have free tyvars?
+              -- I think it's because of the GHCi debugger, which can bind variables
+              --   f :: [t] -> [t]
+              -- where t is a RuntimeUnk (see TcType)