Pretty up this testcase, NFC.

Author: lattner

validation-test/compiler_crashers/28238-swift-typechecker-validatedecl.swift

@@ -5,4 +5,7 @@
 // Test case submitted to project by https://github.com/practicalswift (practicalswift)
 // Test case found by fuzzing
 
-class B<T:B{class B<class b{}func b(T.B
+class B<T : B> {
+  class C {}
+  func b(xx : T.C) {}
+}