[commit: ghc] ghc-8.0: Not-in-scope variables are always errors (6071ecf)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : ghc-8.0
Link       : http://ghc.haskell.org/trac/ghc/changeset/6071ecf4ff7501c70456c1448fa2f78e91bc8078/ghc

>---------------------------------------------------------------

commit 6071ecf4ff7501c70456c1448fa2f78e91bc8078
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Wed Aug 17 12:04:30 2016 +0100

    Not-in-scope variables are always errors
    
    This fixes Trac #12406.  A not-in-scope error shoudl be an error
    even if you have -fdefer-typed-holes.
    
    (cherry picked from commit efc0372a157eadeee58bbada77c64d53590e04af)


>---------------------------------------------------------------

6071ecf4ff7501c70456c1448fa2f78e91bc8078
 compiler/typecheck/TcErrors.hs                       | 10 ++++++++--
 .../tests/partial-sigs/should_compile/T12156.stderr  |  3 +--
 testsuite/tests/partial-sigs/should_compile/all.T    |  2 +-
 testsuite/tests/typecheck/should_fail/T12406.hs      | 20 ++++++++++++++++++++
 testsuite/tests/typecheck/should_fail/T12406.stderr  | 12 ++++++++++++
 testsuite/tests/typecheck/should_fail/all.T          |  1 +
 6 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/compiler/typecheck/TcErrors.hs b/compiler/typecheck/TcErrors.hs
index 406f13d..d638892 100644
--- a/compiler/typecheck/TcErrors.hs
+++ b/compiler/typecheck/TcErrors.hs
@@ -613,9 +613,15 @@ maybeReportHoleError ctxt ct err
        HoleWarn  -> reportWarning (Reason Opt_WarnPartialTypeSignatures) err
        HoleDefer -> return ()
 
-  -- Otherwise this is a typed hole in an expression
+  | isOutOfScopeCt ct
+  = -- Always report an error for out-of-scope variables
+    -- See Trac #12170, #12406
+    reportError err
+
+  -- Otherwise this is a typed hole in an expression,
+  -- but not for an out-of-scope variable
   | otherwise
-  = -- If deferring, report a warning only if -Wtyped-holds is on
+  = -- If deferring, report a warning only if -Wtyped-holes is on
     case cec_expr_holes ctxt of
        HoleError -> reportError err
        HoleWarn  -> reportWarning (Reason Opt_WarnTypedHoles) err
diff --git a/testsuite/tests/partial-sigs/should_compile/T12156.stderr b/testsuite/tests/partial-sigs/should_compile/T12156.stderr
index 6508d8a..f1a5b9d 100644
--- a/testsuite/tests/partial-sigs/should_compile/T12156.stderr
+++ b/testsuite/tests/partial-sigs/should_compile/T12156.stderr
@@ -1,3 +1,2 @@
 
-T12156.hs:3:14: warning: [-Wtyped-holes (in -Wdefault)]
-    Variable not in scope: v
+T12156.hs:3:14: error: Variable not in scope: v
diff --git a/testsuite/tests/partial-sigs/should_compile/all.T b/testsuite/tests/partial-sigs/should_compile/all.T
index bc3531a..63a6efc 100644
--- a/testsuite/tests/partial-sigs/should_compile/all.T
+++ b/testsuite/tests/partial-sigs/should_compile/all.T
@@ -62,4 +62,4 @@ test('T10463', normal, compile, [''])
 test('ExprSigLocal', normal, compile, [''])
 test('T11016', normal, compile, [''])
 test('T11192', normal, compile, [''])
-test('T12156', normal, compile, ['-fdefer-typed-holes'])
+test('T12156', normal, compile_fail, ['-fdefer-typed-holes'])
diff --git a/testsuite/tests/typecheck/should_fail/T12406.hs b/testsuite/tests/typecheck/should_fail/T12406.hs
new file mode 100644
index 0000000..20264cc
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/T12406.hs
@@ -0,0 +1,20 @@
+{-# LANGUAGE TypeFamilies #-}
+{-# OPTIONS_GHC -fdefer-typed-holes #-}
+
+module T12406 where
+
+-- import Control.Monad  -- comment this out to cause error
+import Data.IORef
+
+class MonadRef m where
+    type Ref m :: * -> *
+    newRef :: a -> m (Ref m a)
+    readRef :: Ref m a -> m a
+
+instance MonadRef IO where
+    type Ref IO = IORef
+    newRef = newIORef
+    readRef = readIORef
+
+foo :: IO ()
+foo = newRef (pure ()) >>= join . readRef
diff --git a/testsuite/tests/typecheck/should_fail/T12406.stderr b/testsuite/tests/typecheck/should_fail/T12406.stderr
new file mode 100644
index 0000000..85096e6
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/T12406.stderr
@@ -0,0 +1,12 @@
+
+T12406.hs:20:7: error:
+    • Couldn't match type ‘Ref m0’ with ‘IORef’
+      Expected type: IO (Ref m0 (f0 ()))
+        Actual type: IO (Ref IO (f0 ()))
+      The type variable ‘m0’ is ambiguous
+    • In the first argument of ‘(>>=)’, namely ‘newRef (pure ())’
+      In the expression: newRef (pure ()) >>= join . readRef
+      In an equation for ‘foo’: foo = newRef (pure ()) >>= join . readRef
+
+T12406.hs:20:28: error:
+    Variable not in scope: join :: m0 (f0 ()) -> IO ()
diff --git a/testsuite/tests/typecheck/should_fail/all.T b/testsuite/tests/typecheck/should_fail/all.T
index e6aa020..3880287 100644
--- a/testsuite/tests/typecheck/should_fail/all.T
+++ b/testsuite/tests/typecheck/should_fail/all.T
@@ -419,3 +419,4 @@ test('T12151', normal, compile_fail, [''])
 test('T7437', normal, compile_fail, [''])
 test('T11947a', normal, compile_fail, [''])
 test('T11974b', normal, compile_fail, [''])
+test('T12406', normal, compile_fail, [''])