The compiler compiles $value == true to ZEND_BOOL, which always returns true for
objects (with the default cast_object handler). However, when compared to a
statically unknown rhs $value == $true, the resulting opcode ZEND_IS_EQUAL would
call the objects compare handler.
The zend_objects_not_comparable() handler, which is installed for enums and
other internal classes, blanketly returns false. This does not match the
ZEND_BOOL semantics.
Object to boolean comparison is now handled directly in zend_compare(),
analogous to object to null comparison. It continuous to call the cast_object
handler, but guarantees consistent behavior across ZEND_BOOL and ZEND_IS_EQUAL.
Fixes GH-16954
Closes GH-17031
5a482a139c