Tokenizer/PHP: fix ? tokenization in property hook parameters

[lazerg]

Description

The ? of a nullable type on a property hook parameter, like set(?int $value), was tokenized as T_INLINE_THEN instead of T_NULLABLE, so Squiz.WhiteSpace.OperatorSpacing treated it as a ternary and phpcbf "fixed" the accessor to set( ? int $value).

When the backward walk in the ? disambiguation reaches the parameter list opener, it currently keeps walking and hits the { of the hook block, which is in the list of tokens that mean "ternary". A ? directly preceded by ( is always the start of a nullable type though, never a ternary, since a ternary needs an expression before its ?. This adds ( to the tokens that make the previous non-empty token check conclude T_NULLABLE, which also stops the walk before it can reach the hook block.

Regular methods and closures were never affected: their backward walk finds function/fn first.

Suggested changelog entry

• Fixed a bug where the ? of a nullable type on a property hook parameter would be tokenized as T_INLINE_THEN instead of T_NULLABLE, which made Squiz.WhiteSpace.OperatorSpacing report false positives and phpcbf break the code.

Related issues/external references

Fixes #1494

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
  • This change is only breaking for integrators, not for external standards or end-users.
• Documentation improvement

PR checklist

• I have checked there is no other PR open for the same change.
• I have read the Contribution Guidelines.
• I grant the project the right to include and distribute the code under the BSD-3-Clause license (and I have the right to grant these rights).
• I have added tests to cover my changes.
• I have verified that the code complies with the projects coding standards.
• [Required for new sniffs] I have added XML documentation for the sniff.
• I have opened a sister-PR in the documentation repository to update the Wiki.