NullComparisonWarnings.dfy(27,9): Warning: the type of the other operand is a non-null type, so this comparison with 'null' will always return 'false' (to make it possible for variable 'x' to have the value 'null', declare its type to be 'MyClass?')
NullComparisonWarnings.dfy(28,9): Warning: the type of the other operand is a non-null type, so this comparison with 'null' will always return 'false' (to make it possible for variable 'y' to have the value 'null', declare its type to be 'MyClass?')
NullComparisonWarnings.dfy(29,14): Warning: the type of the other operand is a non-null type, so this comparison with 'null' will always return 'false' (to make it possible for field 'next' to have the value 'null', declare its type to be 'MyClass?')
NullComparisonWarnings.dfy(30,9): Warning: the type of the other operand is a non-null type, so this comparison with 'null' will always return 'true' (to make it possible for variable 'x' to have the value 'null', declare its type to be 'MyClass?')
NullComparisonWarnings.dfy(31,9): Warning: the type of the other operand is a non-null type, so this comparison with 'null' will always return 'true' (to make it possible for variable 'y' to have the value 'null', declare its type to be 'MyClass?')
NullComparisonWarnings.dfy(32,14): Warning: the type of the other operand is a non-null type, so this comparison with 'null' will always return 'true' (to make it possible for field 'next' to have the value 'null', declare its type to be 'MyClass?')
NullComparisonWarnings.dfy(34,12): Warning: the type of the other operand is a non-null type, so this comparison with 'null' will always return 'false' (to make it possible for variable 'x' to have the value 'null', declare its type to be 'MyClass?')
NullComparisonWarnings.dfy(37,12): Warning: the type of the other operand is a set of non-null elements, so the inclusion test of 'null' will always return 'false'
NullComparisonWarnings.dfy(38,12): Warning: the type of the other operand is a set of non-null elements, so the non-inclusion test of 'null' will always return 'true'
NullComparisonWarnings.dfy(40,41): Warning: the type of the other operand is a non-null type, so this comparison with 'null' will always return 'true' (to make it possible for variable 'u' to have the value 'null', declare its type to be 'MyClass?')
NullComparisonWarnings.dfy(45,12): Warning: the type of the other operand is a non-null type, so this comparison with 'null' will always return 'true'

Dafny program verifier finished with 4 verified, 0 errors
despite the warnings, the program still compiles
