Why are arrays covariant but generics are invariant?

Why are arrays covariant but generics are invariant?

java arrays generics language-design covariance

arrays

Is there a better PHP way for getting default value by key from array (dictionary)?

php arrays key default-value language-design

arrays

When auto is used against array, why it's converted to pointer and not reference?

c++ arrays c++11 language-design

arrays

What is the motivation of retrieving the length of an array using a public instance variable, instead of calling a method? [duplicate]

java arrays language-design

arrays

Javascript: why Object.keys(someobject), rather than someobject.keys?

javascript arrays oop language-design javascript-objects

arrays