To reproduce, build GHC HEAD with slow validate settings, then run the tests. Outputs:

=====> T7224(normal) 9 of 15 [0, 2, 0]
cd "polykinds/T7224.run" &&  "/home/omer/haskell/ghc/inplace/test   spaces/ghc-stage2" -c T7224.hs -dcore-lint -dcmm-lint -no-user-package-db -rtsopts -fno-warn-missed-specialisations -fshow-warning-groups -fdiagnostics-color=never -fno-diagnostics-show-caret -dno-debug-output
Actual stderr output differs from expected:
diff -uw "polykinds/T7224.run/T7224.stderr.normalised" "polykinds/T7224.run/T7224.comp.stderr.normalised"
--- polykinds/T7224.run/T7224.stderr.normalised 2018-08-11 13:33:16.874459507 +0300
+++ polykinds/T7224.run/T7224.comp.stderr.normalised    2018-08-11 13:33:16.874459507 +0300
@@ -1,13 +1,11 @@
+ghc: panic! (the 'impossible' happened)
+  (GHC version 8.7.20180809 for x86_64-unknown-linux):
+       ASSERT failed!
+  Type-correct unfilled coercion hole {co_asw}
+  Call stack:
+      CallStack (from HasCallStack):
+        callStackDoc, called at compiler/utils/Outputable.hs:<line>:<column> in <package-id>:Outputable
+        pprPanic, called at compiler/utils/Outputable.hs:<line>:<column> in <package-id>:Outputable
+        assertPprPanic, called at compiler/typecheck/TcHsSyn.hs:<line>:<column> in <package-id>:TcHsSyn

-T7224.hs:6:19:
-     Expected kind ‘i’, but ‘i’ has kind ‘*’
-     In the first argument of ‘m’, namely ‘i’
-      In the type signature: ret' :: a -> m i i a
-      In the class declaration for ‘PMonad'’
-
-T7224.hs:7:14:
-     Expected kind ‘i’, but ‘i’ has kind ‘*’
-     In the first argument of ‘m’, namely ‘i’
-      In the type signature:
-        bind' :: m i j a -> (a -> m j k b) -> m i k b
-      In the class declaration for ‘PMonad'’
+Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
*** unexpected failure for T7224(normal)

=====> T9201(normal) 11 of 15 [0, 3, 0]
cd "typecheck/should_fail/T9201.run" &&  "/home/omer/haskell/ghc/inplace/test   spaces/ghc-stage2" -c T9201.hs -dcore-lint -dcmm-lint -no-user-package-db -rtsopts -fno-warn-missed-specialisations -fshow-warning-groups -fdiagnostics-color=never -fno-diagnostics-show-caret -dno-debug-output
Actual stderr output differs from expected:
diff -uw "typecheck/should_fail/T9201.run/T9201.stderr.normalised" "typecheck/should_fail/T9201.run/T9201.comp.stderr.normalised"
--- typecheck/should_fail/T9201.run/T9201.stderr.normalised     2018-08-11 13:33:21.058404868 +0300
+++ typecheck/should_fail/T9201.run/T9201.comp.stderr.normalised        2018-08-11 13:33:21.058404868 +0300
@@ -1,7 +1,11 @@
+ghc: panic! (the 'impossible' happened)
+  (GHC version 8.7.20180809 for x86_64-unknown-linux):
+       ASSERT failed!
+  Type-correct unfilled coercion hole {co_asr}
+  Call stack:
+      CallStack (from HasCallStack):
+        callStackDoc, called at compiler/utils/Outputable.hs:<line>:<column> in <package-id>:Outputable
+        pprPanic, called at compiler/utils/Outputable.hs:<line>:<column> in <package-id>:Outputable
+        assertPprPanic, called at compiler/typecheck/TcHsSyn.hs:<line>:<column> in <package-id>:TcHsSyn

-T9201.hs:6:17:
-     Expected kind ‘x’, but ‘a’ has kind ‘y’
-     In the first argument of ‘f’, namely ‘a’
-      In the second argument of ‘d’, namely ‘(f a)’
-      In the type signature:
-        ret :: d a (f a)
+Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
*** unexpected failure for T9201(normal)

=====> LevPolyBounded(normal) 12 of 15 [0, 4, 0]
cd "typecheck/should_fail/LevPolyBounded.run" &&  "/home/omer/haskell/ghc/inplace/test   spaces/ghc-stage2" -c LevPolyBounded.hs -dcore-lint -dcmm-lint -no-user-package-db -rtsopts -fno-warn-missed-specialisations -fshow-warning-groups -fdiagnostics-color=never -fno-diagnostics-show-caret -dno-debug-output
Actual stderr output differs from expected:
diff -uw "typecheck/should_fail/LevPolyBounded.run/LevPolyBounded.stderr.normalised" "typecheck/should_fail/LevPolyBounded.run/LevPolyBounded.comp.stderr.normalised"
--- typecheck/should_fail/LevPolyBounded.run/LevPolyBounded.stderr.normalised   2018-08-11 13:33:21.150403667 +0300
+++ typecheck/should_fail/LevPolyBounded.run/LevPolyBounded.comp.stderr.normalised      2018-08-11 13:33:21.150403667 +0300
@@ -1,5 +1,11 @@
+ghc: panic! (the 'impossible' happened)
+  (GHC version 8.7.20180809 for x86_64-unknown-linux):
+       ASSERT failed!
+  Type-correct unfilled coercion hole {co_avm}
+  Call stack:
+      CallStack (from HasCallStack):
+        callStackDoc, called at compiler/utils/Outputable.hs:<line>:<column> in <package-id>:Outputable
+        pprPanic, called at compiler/utils/Outputable.hs:<line>:<column> in <package-id>:Outputable
+        assertPprPanic, called at compiler/typecheck/TcHsSyn.hs:<line>:<column> in <package-id>:TcHsSyn

-LevPolyBounded.hs:10:15:
-     Expected a type, but ‘a’ has kind ‘TYPE r’
-     In the type signature: LevPolyBounded.minBound :: a
-      In the class declaration for ‘XBounded’
+Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
*** unexpected failure for LevPolyBounded(normal)