Description:
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Reflection normalises typehints on parameters with defaults of null to be Nullable typehints.

This is a change of behaviour and caused issues in Prophecy (Mocking library) and probably other tools that lean on reflection. It's not appropriate for a minor version number.

Test script:
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function foo(Bar $bar = null){}

echo ((new ReflectionFunction('foo'))->getParameters()[0]->getType());

Expected result:
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output 'Bar'

Actual result:
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output '?Bar'