Psalm emits UnusedProperty and PossiblyUnusedProperty issues when properties are declared but never referenced. Previously Psalm would count a property assignment as a reference to a property, but this has now been fixed so a property is treated as unused unless it is explicitly read from (#5810). As before, UnusedProperty is emitted for private properties, while PossiblyUnusedProperty is emitted for public and protected properties.
More ParamNameMismatch strictness
When I originally implemented ParamNameMismatch I ignored methods with only one param, thinking that people would not call methods with a single param using named arguments, but in retrospect this was a little too liberal. @VincentLanglet has restricted this appropriately (#5732)
Other bugfixes
Improved negation of complex conditionals containing assignments (#5685)
combining scalar and empty-scalar should result in scalar (#5696)
