main-eisop: x(Foo<? super T>) cannot override identical signature

[cpovirk]

This is responsible for perhaps 90 errors in initial testing on Google's codebase, such as in AbstractHasher. That might make it the last significant source of errors in that testing. But of course I could be missing others among the noise, and we'll see whether new problems pop up as we fix the old :)

import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

@NullMarked
interface SuperWildcardParent {
  <T extends @Nullable Object> void x(Foo<? super T> foo);
}

@NullMarked
interface SuperWildcardOverride extends SuperWildcardParent {
  @Override
  <T extends @Nullable Object> void x(Foo<? super T> foo);
}

@NullMarked
interface Foo<T extends @Nullable Object> {}

$ ../checker-framework/checker/bin/javac -processorpath $HOME/.m2/repository/org/jspecify/jspecify/0.3.0/jspecify-0.3.0.jar:build/libs/jspecify-reference-checker-0.0.0-SNAPSHOT.jar -processor com.google.jspecify.nullness.NullSpecChecker -AcheckImpl -AassumePure -AsuppressWarnings=contracts.conditional.postcondition.false.methodref,contracts.conditional.postcondition.false.override,contracts.conditional.postcondition.true.methodref,contracts.conditional.postcondition.true.override,purity.methodref,purity.overriding,type.anno.before.decl.anno,type.anno.before.modifier -cp $HOME/.m2/repository/org/jspecify/jspecify/0.3.0/jspecify-0.3.0.jar:build/libs/jspecify-reference-checker-0.0.0-SNAPSHOT.jar SuperWildcardOverride.java
SuperWildcardOverride.java:12: error: [override.param.invalid] Incompatible parameter type for foo.
  <T extends @Nullable Object> void x(Foo<? super T> foo);
                                                     ^
  found   : Foo<? super T>
  required: Foo<? super T>
  Consequence: method in SuperWildcardOverride
    void x(Foo<? super T>)
  cannot override method in SuperWildcardParent
    void x(Foo<? super T>)
1 error

This error doesn't jump out to me as obviously related to any of the issues under https://github.com/jspecify/checker-framework/issues, but I'm also not ruling it out.

[wmdietl]

Fixed by #171.