1381724 - stylo: panic "pseudos can't generate sibling invalidations, since using them in other position that isn't the rightmost part of the selector is invalid (for now at least)" loading a MozReview page

Status: RESOLVED DUPLICATE of bug 1381682

(Core :: CSS Parsing and Computation, defect)

Description

[Cameron McCormack (:heycam)]

I encountered this panic while loading a MozReview page:

thread '<unnamed>' panicked at 'pseudos can't generate sibling invalidations, since using them in other position that isn't the rightmost part of the selector is invalid (for now at least)', /z/moz/d/servo/components/style/invalidation/element/invalidator.rs:269

Comment 1

[Cameron McCormack (:heycam)]

Here is some trace output just before the assertion:

DEBUG:style::invalidation::element::invalidator: TreeStyleInvalidator::process_invalidation(<_moz_generated_content_after> (0x7f46eeff53a0), Invalidation(:first-child.diff-container))
DEBUG:style::invalidation::element::invalidator: TreeStyleInvalidator::process_invalidation(<_moz_generated_content_after> (0x7f46eeff53a0), Invalidation(:not(.diff-container)))
DEBUG:style::invalidation::element::invalidator:  > Invalidation matched, next: Invalidation(.diff-container), (NextSibling)
DEBUG:style::invalidation::element::invalidator: TreeStyleInvalidator::process_invalidation(<_moz_generated_content_after> (0x7f46eeff53a0), Invalidation(:first-child.diff-container))
DEBUG:style::invalidation::element::invalidator: TreeStyleInvalidator::process_invalidation(<_moz_generated_content_after> (0x7f46eeff53a0), Invalidation(:not(.diff-container)))
DEBUG:style::invalidation::element::invalidator:  > Invalidation matched, next: Invalidation(.diff-container), (NextSibling)
DEBUG:style::invalidation::element::invalidator: StyleTreeInvalidator::invalidate_descendants(<_moz_generated_content_after> (0x7f46eeff53a0))
DEBUG:style::invalidation::element::invalidator:  > [Invalidation(:first-child.diff-container), Invalidation(:not(.diff-container)), Invalidation(:first-child.diff-container), Invalidation(:not(.diff-container))
]

This makes me think that we shouldn't be matching the invalidation (:not(.diff-container)) here against the element-backed pseudo.  Should we be taking into account that the <_moz_generated_content_before> element is NAC, and so invalidations that came from document style sheet rules can be ignored?

Comment 2

[Cameron McCormack (:heycam)]

Oh, this is already being discussed in bug 1381682.