Remove decideKindGeneralisationPlan

TypeInType came with a new function: decideKindGeneralisationPlan.
This type-level counterpart to the term-level decideGeneralisationPlan
chose whether or not a kind should be generalized. The thinking was
that if `let` should not be generalized, then kinds shouldn't either
(under the same circumstances around -XMonoLocalBinds).

However, this is too conservative -- the situation described in the
motivation for "let should be be generalized" does not occur in types.

This commit thus removes decideKindGeneralisationPlan, always
generalizing.

One consequence is that tc_hs_sig_type_and_gen no longer calls
solveEqualities, which reports all unsolved constraints, instead
relying on the solveLocalEqualities in tcImplicitTKBndrs. An effect
of this is that reporing kind errors gets delayed more frequently.
This seems to be a net benefit in error reporting; often, alongside
a kind error, the type error is now reported (and users might find
type errors easier to understand).

Some of these errors ended up at the top level, where it was
discovered that the GlobalRdrEnv containing the definitions in the
local module was not in the TcGblEnv, and thus errors were reported
with qualified names unnecessarily. This commit rejiggers some of
the logic around captureTopConstraints accordingly.

One error message (typecheck/should_fail/T1633)
is a regression, mentioning the name of a default method. However,
that problem is already reported as #10087, its solution is far from
clear, and so I'm not addressing it here.

This commit fixes #15141. As it's an internal refactor, there is
no concrete test case for it.

Along the way, we no longer need the hsib_closed field of
HsImplicitBndrs (it was used only in decideKindGeneralisationPlan)
and so it's been removed, simplifying the datatype structure.

Along the way, I removed code in the validity checker that looks
at coercions. This isn't related to this patch, really (though
it was, at one point), but it's an improvement, so I kept it.

This updates the haddock submodule.

8 files changed, 58 insertions, 25 deletions

diff --git a/testsuite/tests/dependent/should_fail/T14066h.hs b/testsuite/tests/dependent/should_compile/T14066h.hs
index a20ae30958..df3db1c15d 100644
--- a/testsuite/tests/dependent/should_fail/T14066h.hs
+++ b/testsuite/tests/dependent/should_compile/T14066h.hs
@@ -7,5 +7,5 @@ import Data.Proxy
 f :: forall b. b -> (Proxy Int, Proxy Maybe)
 f x = (fst y :: Proxy Int, fst y :: Proxy Maybe)
   where
-    y :: (Proxy a, b)  -- MonoLocalBinds means this won't generalize over the kind of a
+    y :: (Proxy a, b)  -- this generalizes over the kind of a
     y = (Proxy, x)
diff --git a/testsuite/tests/dependent/should_compile/all.T b/testsuite/tests/dependent/should_compile/all.T
index 4e096c1f71..418fba2d85 100644
--- a/testsuite/tests/dependent/should_compile/all.T
+++ b/testsuite/tests/dependent/should_compile/all.T
@@ -53,3 +53,4 @@ test('T15264', normal, compile, [''])
 test('DkNameRes', normal, compile, [''])
 test('T15346', normal, compile, [''])
 test('T15419', normal, compile, [''])
+test('T14066h', normal, compile, [''])
diff --git a/testsuite/tests/dependent/should_fail/DepFail1.stderr b/testsuite/tests/dependent/should_fail/DepFail1.stderr
index 630f010fa3..a8e64d4e0c 100644
--- a/testsuite/tests/dependent/should_fail/DepFail1.stderr
+++ b/testsuite/tests/dependent/should_fail/DepFail1.stderr
@@ -2,11 +2,25 @@
 DepFail1.hs:7:6: error:
     • Expecting one more argument to ‘Proxy Bool’
       Expected a type, but ‘Proxy Bool’ has kind ‘Bool -> *’
-    • In the type signature:
-        z :: Proxy Bool
+    • In the type signature: z :: Proxy Bool
+
+DepFail1.hs:8:5: error:
+    • Couldn't match expected type ‘Proxy Bool’
+                  with actual type ‘Proxy k0 a1’
+    • In the expression: P
+      In an equation for ‘z’: z = P
 
 DepFail1.hs:10:16: error:
     • Expected kind ‘Int’, but ‘Bool’ has kind ‘*’
     • In the second argument of ‘Proxy’, namely ‘Bool’
-      In the type signature:
-        a :: Proxy Int Bool
+      In the type signature: a :: Proxy Int Bool
+
+DepFail1.hs:11:5: error:
+    • Couldn't match kind ‘*’ with ‘Int’
+      When matching types
+        a0 :: Int
+        Bool :: *
+      Expected type: Proxy Int Bool
+        Actual type: Proxy Int a0
+    • In the expression: P
+      In an equation for ‘a’: a = P
diff --git a/testsuite/tests/dependent/should_fail/T13895.stderr b/testsuite/tests/dependent/should_fail/T13895.stderr
index 0ae1710bf0..3e8bef6858 100644
--- a/testsuite/tests/dependent/should_fail/T13895.stderr
+++ b/testsuite/tests/dependent/should_fail/T13895.stderr
@@ -1,4 +1,28 @@
 
+T13895.hs:8:14: error:
+    • Could not deduce (Typeable (t dict0))
+      from the context: (Data a, Typeable (t dict))
+        bound by the type signature for:
+                   dataCast1 :: forall k (dict :: Typeable k) (dict1 :: Typeable
+                                                                          *) a (c :: *
+                                                                                     -> *) (t :: forall k1.
+                                                                                                 Typeable
+                                                                                                   k1 =>
+                                                                                                 k1
+                                                                                                 -> *).
+                                (Data a, Typeable (t dict)) =>
+                                (forall d. Data d => c (t dict1 d)) -> Maybe (c a)
+        at T13895.hs:(8,14)-(14,24)
+      The type variable ‘dict0’ is ambiguous
+    • In the ambiguity check for ‘dataCast1’
+      To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
+      In the type signature:
+        dataCast1 :: forall (a :: Type).
+                     Data a =>
+                     forall (c :: Type -> Type)
+                            (t :: forall (k :: Type). Typeable k => k -> Type).
+                     Typeable t => (forall d. Data d => c (t d)) -> Maybe (c a)
+
 T13895.hs:12:23: error:
     • Illegal constraint in a kind: Typeable k0
     • In the first argument of ‘Typeable’, namely ‘t’
diff --git a/testsuite/tests/dependent/should_fail/T14066.stderr b/testsuite/tests/dependent/should_fail/T14066.stderr
index cd0142f5c1..e5179e510b 100644
--- a/testsuite/tests/dependent/should_fail/T14066.stderr
+++ b/testsuite/tests/dependent/should_fail/T14066.stderr
@@ -1,6 +1,6 @@
 
 T14066.hs:15:59: error:
-    • Expected kind ‘k0’, but ‘b’ has kind ‘k’
+    • Expected kind ‘k’, but ‘b’ has kind ‘k1’
     • In the second argument of ‘SameKind’, namely ‘b’
       In the type signature: g :: forall k (b :: k). SameKind a b
       In the expression:
@@ -8,4 +8,6 @@ T14066.hs:15:59: error:
           g :: forall k (b :: k). SameKind a b
           g = undefined
         in ()
-    • Relevant bindings include x :: Proxy a (bound at T14066.hs:15:4)
+    • Relevant bindings include
+        x :: Proxy a (bound at T14066.hs:15:4)
+        f :: Proxy a -> () (bound at T14066.hs:15:1)
diff --git a/testsuite/tests/dependent/should_fail/T14066e.stderr b/testsuite/tests/dependent/should_fail/T14066e.stderr
index 504ca5a80e..193c74d193 100644
--- a/testsuite/tests/dependent/should_fail/T14066e.stderr
+++ b/testsuite/tests/dependent/should_fail/T14066e.stderr
@@ -1,6 +1,15 @@
 
 T14066e.hs:13:59: error:
-    • Expected kind ‘c’, but ‘b'’ has kind ‘k0’
+    • Couldn't match kind ‘k1’ with ‘*’
+      ‘k1’ is a rigid type variable bound by
+        the type signature for:
+          j :: forall k k1 (c :: k1) (b :: k).
+               Proxy a -> Proxy b -> Proxy c -> Proxy b
+        at T14066e.hs:12:5-61
+      When matching kinds
+        k :: *
+        c :: k1
+      Expected kind ‘c’, but ‘b'’ has kind ‘k’
     • In the first argument of ‘Proxy’, namely ‘(b' :: c')’
       In an expression type signature: Proxy (b' :: c')
       In the expression: (p1 :: Proxy (b' :: c'))
diff --git a/testsuite/tests/dependent/should_fail/T14066h.stderr b/testsuite/tests/dependent/should_fail/T14066h.stderr
deleted file mode 100644
index bfd33693b6..0000000000
--- a/testsuite/tests/dependent/should_fail/T14066h.stderr
+++ /dev/null
@@ -1,16 +0,0 @@
-
-T14066h.hs:8:28: error:
-    • Couldn't match kind ‘* -> *’ with ‘*’
-      When matching types
-        a0 :: *
-        Maybe :: * -> *
-      Expected type: Proxy Maybe
-        Actual type: Proxy a0
-    • In the expression: fst y :: Proxy Maybe
-      In the expression: (fst y :: Proxy Int, fst y :: Proxy Maybe)
-      In an equation for ‘f’:
-          f x
-            = (fst y :: Proxy Int, fst y :: Proxy Maybe)
-            where
-                y :: (Proxy a, b)
-                y = (Proxy, x)
diff --git a/testsuite/tests/dependent/should_fail/all.T b/testsuite/tests/dependent/should_fail/all.T
index 593b7787a1..0f7129020e 100644
--- a/testsuite/tests/dependent/should_fail/all.T
+++ b/testsuite/tests/dependent/should_fail/all.T
@@ -26,7 +26,6 @@ test('T14066d', normal, compile_fail, [''])
 test('T14066e', normal, compile_fail, [''])
 test('T14066f', normal, compile_fail, [''])
 test('T14066g', normal, compile_fail, [''])
-test('T14066h', normal, compile_fail, [''])
 test('T14845_fail1', normal, compile_fail, [''])
 test('T14845_fail2', normal, compile_fail, [''])
 test('InferDependency', normal, compile_fail, [''])