CSS syntax highlighting never terminates in HTML document when using multiple nested @ rules

[alexr00]

From @aahancoc in microsoft/vscode#91107

Issue Type: Bug

When using multiple nested @ rules in an inline <style> tag in an HTML document, the CSS syntax highlighting doesn't stop when the </style> tag is encountered.

Here's a minimal test document that exhibits the buggy behaviour. (Strangely, this seems to break in GitHub's syntax highlighter as well.)

<style>
	@page {
		@bottom-center { }
		@bottom-right { font-weight: bold; }
	}
</style>

<div class="example">
	Some page div
	span {font-size: 14pt;}
</div>

The span rule in the div tag is hilighted as if it was in the style tag, and the class attribute on the div tag is not higlighted.

Removing the font-weight rule fixes the issue, as does removing @bottom-center. This also works fine, for some reason:

<style>
	@page {
		@bottom-center { }
		@bottom-right { font-weight: bold;
		}
	}
</style>

<div class="example">
	Some page div
	span {font-size: 14pt;}
</div>
...

VS Code version: Code 1.42.1 (c47d83b293181d9be64f27ff093689e8e7aed054, 2020-02-11T14:45:59.656Z)
OS version: Windows_NT x64 10.0.16299

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz (8 x 3408)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: disabled_off protected_video_decode: unavailable_off rasterization: enabled skia_renderer: disabled_off surface_control: disabled_off surface_synchronization: enabled_on video_decode: enabled viz_display_compositor: enabled_on viz_hit_test_surface_layer: disabled_off webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	15.88GB (6.02GB free)
Process Argv
Screen Reader	no
VM	0%

Extensions: none

[darangi]

This issue cannot be reproduced. I will go ahead to close this and feel free to re-open it if you think otherwise