TFs: Proper error message for GADT12

testsuite/tests/ghc-regress/indexed-types/should_compile/GADT12.hs

-{-# LANGUAGE TypeFamilies, GADTs, PatternSignatures, KindSignatures, EmptyDataDecls #-}
+{-# LANGUAGE TypeFamilies, GADTs, ScopedTypeVariables, KindSignatures #-}
+{-# LANGUAGE EmptyDataDecls #-}
 
 module ShouldCompile where
 

testsuite/tests/ghc-regress/indexed-types/should_compile/GADT12.stderr

+
+GADT12.hs:28:17:
+    Pattern signature must exactly match: TU Typed (Type a)
+    In the pattern: TypeBool :: Type Bool
+    In the pattern: Var2 "x" (TypeBool :: Type Bool)
+    In the definition of `bug2a':
+        bug2a (Var2 "x" (TypeBool :: Type Bool)) = ()

testsuite/tests/ghc-regress/indexed-types/should_compile/all.T

@@ -67,7 +67,7 @@ test('GADT8', normal, compile, [''])
 test('GADT9', normal, compile, [''])
 test('GADT10', expect_fail, compile, [''])
 test('GADT11', normal, compile, [''])
-test('GADT12', expect_fail, compile, [''])
+test('GADT12', normal, compile_fail, [''])
 test('GADT13', expect_fail, compile, [''])
 test('GADT14', normal, compile, [''])