Fix #10963 and #11975 by adding new cmds to GHCi.

See the user's guide entry or the Note [TcRnExprMode] in TcRnDriver.

Test cases: ghci/scripts/T{10963,11975}

6 files changed, 49 insertions, 0 deletions

diff --git a/testsuite/tests/ghci/scripts/T10963.script b/testsuite/tests/ghci/scripts/T10963.script
new file mode 100644
index 0000000000..357d1256ba
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T10963.script
@@ -0,0 +1,7 @@
+:type mapM
+:type +d mapM
+:t +d length
+let foo :: (Num a, Monoid a) => a -> a; foo = undefined
+:t +d foo
+instance Monoid Double where mempty = 0; mappend = (+)
+:t +d foo
diff --git a/testsuite/tests/ghci/scripts/T10963.stderr b/testsuite/tests/ghci/scripts/T10963.stderr
new file mode 100644
index 0000000000..e20f792773
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T10963.stderr
@@ -0,0 +1,12 @@
+
+<interactive>:1:1: error:
+    Ambiguous type variable ‘a0’ arising from a use of ‘foo’
+    prevents the constraint ‘(Num a0)’ from being solved.
+    Probable fix: use a type annotation to specify what ‘a0’ should be.
+    These potential instances exist:
+      instance Num Integer -- Defined in ‘GHC.Num’
+      instance Num Double -- Defined in ‘GHC.Float’
+      instance Num Float -- Defined in ‘GHC.Float’
+      ...plus two others
+      ...plus five instances involving out-of-scope types
+      (use -fprint-potential-instances to see them all)
diff --git a/testsuite/tests/ghci/scripts/T10963.stdout b/testsuite/tests/ghci/scripts/T10963.stdout
new file mode 100644
index 0000000000..bf639a8aa5
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T10963.stdout
@@ -0,0 +1,4 @@
+mapM :: (Monad m, Traversable t) => (a -> m b) -> t a -> m (t b)
+mapM :: Monad m => (a -> m b) -> [a] -> m [b]
+length :: [a] -> Int
+foo :: Double -> Double
diff --git a/testsuite/tests/ghci/scripts/T11975.script b/testsuite/tests/ghci/scripts/T11975.script
new file mode 100644
index 0000000000..80061ef97b
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T11975.script
@@ -0,0 +1,9 @@
+:set -fprint-explicit-foralls
+:type mapM
+:type +v mapM
+:t +v mapM
+let foo :: (Show a, Num b) => a -> b; foo = undefined
+:set -XTypeApplications
+:type foo @Int
+:type +v foo @Int
+:t +v foo @Int
diff --git a/testsuite/tests/ghci/scripts/T11975.stdout b/testsuite/tests/ghci/scripts/T11975.stdout
new file mode 100644
index 0000000000..23adaf02db
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T11975.stdout
@@ -0,0 +1,15 @@
+mapM
+  :: forall {t :: * -> *} {b} {m :: * -> *} {a}.
+     (Monad m, Traversable t) =>
+     (a -> m b) -> t a -> m (t b)
+mapM
+  :: forall (t :: * -> *).
+     Traversable t =>
+     forall (m :: * -> *) a b. Monad m => (a -> m b) -> t a -> m (t b)
+mapM
+  :: forall (t :: * -> *).
+     Traversable t =>
+     forall (m :: * -> *) a b. Monad m => (a -> m b) -> t a -> m (t b)
+foo @Int :: forall {b}. Num b => Int -> b
+foo @Int :: forall b. (Show Int, Num b) => Int -> b
+foo @Int :: forall b. (Show Int, Num b) => Int -> b
diff --git a/testsuite/tests/ghci/scripts/all.T b/testsuite/tests/ghci/scripts/all.T
index dfedb39ea7..b2ea302f42 100755
--- a/testsuite/tests/ghci/scripts/all.T
+++ b/testsuite/tests/ghci/scripts/all.T
@@ -254,3 +254,5 @@ test('TypeAppData', normal, ghci_script, ['TypeAppData.script'])
 test('T11728', normal, ghci_script, ['T11728.script'])
 test('T11376', normal, ghci_script, ['T11376.script'])
 test('T12007', normal, ghci_script, ['T12007.script'])
+test('T11975', normal, ghci_script, ['T11975.script'])
+test('T10963', normal, ghci_script, ['T10963.script'])