Implement basic variance support #4185
Conversation
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I've included #4184 in here as well now, because it requires some additional handling (some things work by accident without it). |
Fixes bug #76451, and more importantly lays necessary groundwork for covariant/contravariant types. Bug #76451 is just an edge case, but once covariance is introduced this will become a common problem instead.
The autoload case is supposed to work, but doesn't actually :(
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Rebased over #4184. |
| // Illegal: A::parent is ill-defined | ||
| class A { | ||
| public function method(parent $x) {} | ||
| } |
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I had originally added a compile-time check for this in 7.4, but reverted it again in deb44d4 because it broke Mockery, which is used by Laravel. Maybe we can do this for PHP 8.
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might be a good idea to add this into deprecations for PHP-7.4
Which should make it more obvious if an inheritance check fails due to a cycle.
| @@ -6392,6 +6394,7 @@ zend_op *zend_compile_class_decl(zend_ast *ast, zend_bool toplevel) /* {{{ */ | |||
| && !(CG(compiler_options) & ZEND_COMPILE_PRELOAD) /* delay inheritance till preloading */ | |||
| && ((parent_ce->type != ZEND_INTERNAL_CLASS) || !(CG(compiler_options) & ZEND_COMPILE_IGNORE_INTERNAL_CLASSES)) | |||
| && ((parent_ce->type != ZEND_USER_CLASS) || !(CG(compiler_options) & ZEND_COMPILE_IGNORE_OTHER_FILES) || (parent_ce->info.user.filename == ce->info.user.filename)) | |||
| && zend_can_early_bind(ce, parent_ce) | |||
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We should try to reduce overhead of zend_can_early_bind(), but we can do it later.
| @@ -3491,6 +3529,10 @@ static void preload_link(void) | |||
| if (!found) continue; | |||
| } | |||
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| if (!preload_all_types_known(ce)) { | |||
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This check is seriously more restricted than necessary, but we try to improve it later. Please add TODO comments.
| zend_class_entry *fe_ce = lookup_class(fe, fe_class_name); | ||
| if (!fe_ce) { | ||
| *unresolved_class = fe_class_name; | ||
| return INHERITANCE_UNRESOLVED; | ||
| } |
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This check is not necessary. Any class should work, so we may avoid class loading.
<?php
interface A {
function m(): object;
}
interface B extends A {
function m(): unknown;
}
@dstogov My proposal for "minimal" variance support, with only enough to make the non-circular cases work.