Yet more work on TcSimplify.simplifyInfer

The proximate cause for this patch is Trac #13482, which pointed out
further subtle interactions between
   - Inferring the most general type of a function
   - A partial type signature for that function

That led me into /further/ changes to the shiny new stuff in
TcSimplify.simplifyInfer, decideQuantification, decideMonoTyVars,
and related functions.

Happily, I was able to make some of it quite a bit simpler,
notably the bit about promoting free tyvars.  I'm happy with
the result.

Moreover I fixed Trac #13524 at the same time.  Happy days.

1 files changed, 31 insertions, 0 deletions

diff --git a/testsuite/tests/partial-sigs/should_compile/T13482.stderr b/testsuite/tests/partial-sigs/should_compile/T13482.stderr
new file mode 100644
index 0000000000..87eef5caa7
--- /dev/null
+++ b/testsuite/tests/partial-sigs/should_compile/T13482.stderr
@@ -0,0 +1,31 @@
+
+T13482.hs:8:32: warning: [-Wpartial-type-signatures (in -Wdefault)]
+    • Found type wildcard ‘_’ standing for ‘(Monoid m, Eq m)’
+      Where: ‘m’ is a rigid type variable bound by
+               the inferred type of
+               minimal1_noksig :: (Monoid m, Eq m) => Int -> Bool
+               at T13482.hs:9:1-50
+    • In the type signature:
+        minimal1_noksig :: forall m. _ => Int -> Bool
+
+T13482.hs:11:30: warning: [-Wpartial-type-signatures (in -Wdefault)]
+    • Found type wildcard ‘_’ standing for ‘(Monoid m, Eq m)’
+      Where: ‘m’ is a rigid type variable bound by
+               the inferred type of minimal1 :: (Monoid m, Eq m) => Bool
+               at T13482.hs:12:1-41
+    • In the type signature: minimal1 :: forall (m :: *). _ => Bool
+
+T13482.hs:14:30: warning: [-Wpartial-type-signatures (in -Wdefault)]
+    • Found type wildcard ‘_’ standing for ‘Monoid m’
+      Where: ‘m’ is a rigid type variable bound by
+               the inferred type of minimal2 :: (Eq m, Monoid m) => Bool
+               at T13482.hs:15:1-41
+    • In the type signature: minimal2 :: forall m. (Eq m, _) => Bool
+
+T13482.hs:17:34: warning: [-Wpartial-type-signatures (in -Wdefault)]
+    • Found type wildcard ‘_’ standing for ‘Eq m’
+      Where: ‘m’ is a rigid type variable bound by
+               the inferred type of minimal3 :: (Monoid m, Eq m) => Bool
+               at T13482.hs:18:1-41
+    • In the type signature:
+        minimal3 :: forall m. (Monoid m, _) => Bool