support for generic params on alias types

[shmax]

Add Generic Type Parameters to Type Aliases

This PR adds support for generic type parameters on @phpstan-type aliases, including multiline syntax support.

See: phpstan/phpstan-src#5378

Features

Generic Type Parameters on Type Aliases

Type aliases can now declare template parameters directly on the alias definition:

/**
 * @phpstan-type Wrapper<T> T
 * @phpstan-type Pair<TFirst, TSecond> array{first: TFirst, second: TSecond}
 * @phpstan-type Collection<T of object> list<T>
 * @phpstan-type WithDefault<T = string> T
 */

Multiline Syntax Support

Complex generic type aliases can be formatted across multiple lines for improved readability:

/**
 * @phpstan-type Response<
 *     TData,
 *     TError extends \Throwable
 * > array{
 *     success: bool,
 *     data: TData|null,
 *     error: TError|null
 * }
 */

/**
 * @phpstan-type Repository<
 *     TEntity of object,
 *     TKey of int|string
 * > interface {
 *     find(TKey): ?TEntity,
 *     save(TEntity): void
 * }
 */

Use Cases

This enables more flexible and reusable type definitions:

/**
 * @phpstan-type Result<T, E = \Exception> array{ok: bool, value: T|null, error: E|null}
 */
class ResultHandler
{
    /**
     * @param Result<User, AuthException> $result
     */
    public function handle(array $result): void
    {
        // ...
    }
}

Technical Details

AST Changes

• TypeAliasTagValueNode now includes a $templateTypes property containing an array of TemplateTagValueNode[]
• The parser recognizes <...> syntax immediately after the alias name
• Supports all template features: bounds (of), defaults (=), and multiple parameters

Parser Behavior

The parser now:

• Skips horizontal whitespace and PHPDoc line continuations inside <...>
• Parses each template parameter using the existing parseTemplateTagValue() method
• Maintains backward compatibility with non-generic type aliases

Printer Support

The Printer class correctly outputs generic type aliases with template parameters in both regular and format-preserving modes.

Testing

Added comprehensive test coverage:

• Single template parameter
• Multiple template parameters
• Bounded template parameters (T of object)
• Default template parameters (T = string)
• Multiline formatting with whitespace
• Integration with existing type alias features

All existing tests pass, ensuring backward compatibility.

Examples

Before (workaround)

/**
 * @template T
 * @phpstan-type Container array{value: T}
 */

After (direct declaration)

/**
 * @phpstan-type Container<T> array{value: T}
 */

This aligns PHPDoc type alias syntax more closely with TypeScript, Java, and other languages that support generic type declarations.