Fix parsing bug in SelectorParser

[RobinMalfait]

While working on another feature, I noticed that a selector such as .foo::before was parsed as:

[
  {
    kind: 'compound',
    nodes: [
      { kind: 'selector', value: '.foo' },
      { kind: 'selector', value: ':' },
      { kind: 'selector', value: '::before' },
    ],
  },
]

Instead of:

[
  {
    kind: 'compound',
    nodes: [
      { kind: 'selector', value: '.foo' },
      { kind: 'selector', value: '::before' },
    ],
  },
]

So far this hasn't been a real issue in practice, but it is in a follow-up PR that I'm working on. To keep things separated, I wanted to fix this behavior in a dedicated PR instead.

Test plan

1. Added a test case for this situation
2. Other tests still pass

[greptile-apps]

Confidence Score: 5/5

Safe to merge — the change is a one-condition guard in a well-tested parser that corrects a silent mis-parse of double-colon pseudo-elements.

The fix is minimal and surgical: a single if inside one switch case, guarded by a precise equality check (buffer === ':') that can only match the exact scenario being corrected. The logic traces cleanly through all realistic CSS selectors (.foo::before, standalone ::before, :hover::before, and invalid inputs like :::). The added test directly covers the regression, and no existing test surfaces break.

No files require special attention.

_{Reviews (1): Last reviewed commit: "ensure `::before` gets parsed as a singl..." | Re-trigger Greptile}

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 2c4726d and 6349d5e.

📒 Files selected for processing (2)

• packages/tailwindcss/src/selector-parser.test.ts
• packages/tailwindcss/src/selector-parser.ts

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Walkthrough

This PR adds support for parsing CSS pseudo-element selectors using double-colon syntax (e.g., ::before, ::after). The parser's tokenization logic now detects when a colon character immediately follows an existing colon in the buffer and concatenates them into a single token instead of treating them as separate selector nodes. A test case validates that .foo::before is parsed as a compound selector containing the element selector and the pseudo-element selector node.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'Fix parsing bug in SelectorParser' clearly and concisely describes the main change: fixing a parsing bug in the SelectorParser component.
Description check	✅ Passed	The description is directly related to the changeset, explaining the bug (incorrect parsing of pseudo-element selectors), showing the before/after behavior, and outlining the test plan.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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