Post Content: adding pseudo states + typography breaks block margin

[jffng]

Description

Adding a pseudo state + typography config to post content in theme.json breaks the block margin — this specifically happens when styles.blocks.core/post-content.elements.link.:hover.typography and any of the following properties are configured:

fontWeight, fontSize, fontStyle

I found that property is applied correctly, but the block margin breaks. There may be more combinations but that's what I discovered in my testing.

Step-by-step reproduction instructions

Add this CSS to your theme.json.

	"styles": {
		"blocks": {
			"core/post-content": {
				"elements": {
					"link": {
						":hover": {
							"typography": {
								"fontStyle": "italic"
							}
						}
					}
				}
			}
		}
	}

Or checkout this PR for emptytheme: WordPress/theme-experiments#309

Verify the margin-block-start breaks (is not parsed correctly?).

Screenshots, screen recording, code snippet

Before	After

Environment info

• Gutenberg trunk
• MacOS 12.2
• Chrome, Safari

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[jffng]

Fixed by #43925