Psalm crash on @return (

[someniatko]

https://psalm.dev/r/b566eeeb37

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/b566eeeb37

<?php

/**
 * @return (
 */
function foo () {}

Psalm encountered an internal error:

/vendor/vimeo/psalm/src/Psalm/Internal/Type/TypeParser.php: Argument 1 passed to Psalm\Internal\Type\TypeParser::getTypeFromTree() must be an instance of Psalm\Internal\Type\ParseTree, null given, called in /vendor/vimeo/psalm/src/Psalm/Internal/Type/TypeParser.php on line 187

[Jack97]

I've been looking into this issue. The cause is when an EncapsulationTree has an empty array of children during the TypeParser::getTypeFromTree phase.

Psalm will crash with any variation of the following input for @return: (, (), ((())) etc. This can be easily fixed by verifying that the parse tree has children before recursively evaluating the type of its first child.

On a slightly unrelated note, I've also found that (((((string and ((((string)))) are valid aliases for string according to the parser. This doesn't feel quite right to me. The former can be fixed by verifying that the EncapsulationTree has been terminated before continuing. However, I'm not sure what to do about the latter 🤔

[weirdan]

I don't think anything needs to be done about the latter, as long as parens are balanced. Parentheses are valid in a type, they are used to override union vs intersection precedence (e.g. (A|B) & C) and to enclose conditional types. So a single type wrapped into a parenthesis is valid as well.

[Jack97]

Ah okay, thank you for the information - I thought I might have been missing something. I'll raise a PR for this as soon as I can 😄