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MissingPureAnnotation

Emitted when a potentially pure function or method does not have a @psalm-pure or @psalm-capabilities declaration: the issue suggests the capabilities it was inferred to need.

To automatically add pure annotations where needed, run Psalm with --alter --issues=MissingPureAnnotation.

This issue is emitted to aid security analysis, which works best when all explicitly pure functions and methods are marked as pure.

<?php

function couldBePure(int $a): int {
    return $a+1;
}

Purity is inferred as a fixpoint over the call graph after the whole codebase has been analysed: a function-like that only calls other pure (or as-yet-unannotated but inferred-pure) function-likes is itself reported, regardless of the order in which they are declared, and mutual recursion, recursive closures and closures assigned to a variable are handled.