Calling non-nullable by-ref param with unset should result in error

[muglug]

Snippet:

<?php
function foo(string &$s) : void {}
function bar() : void {
  foo($byref);
}

Expected: complain about mismatching non-nullable param with null argument
Actual: no issue - https://phpstan.org/r/18f1ffe1-738c-46e2-8c57-f10e2e078867

[adaamz]

ref https://3v4l.org/RCajG

[ondrejmirtes]

This is more complicated. We have different types of by-ref parameters:

1. Built-in functions with read-write parameter. Types are checked.
2. Built-in functions with write parameter. Types are not checked.
3. Userland functions with by-ref parameters - we don't know whether they are write or read-write so we assume they can always create new variable. (they are write) Types are not checked.

Currently, read-write parameter is represented as PassedByReference::createReadsArgument() and write as PassedByReference::createsNewVariable().

For this feature request to be fulfilled, we would need to have a third state - "this userland function might create a variable, but check the type anyway".

[muglug]

3. Userland functions with by-ref parameters - we don't know whether they are write or read-write so we assume they can always create new variable. (they are write) Types are not checked.

But that's erroneous - all userland functions with a declared non-nullable type are read-write - types are always checked e.g.

function foo(string &$s) : void {}

$bar = [];
foo($bar);

[muglug]

When only a @param type is included I still treat it as a limitation on the read portion of the variable, and I'm working on improving support for @param-out to allow changing types in the write phase (currently it just allows type narrowing).

[phpstan-bot]

@muglug After the latest push in 1.11.x, PHPStan now reports different result with your code snippet:

@@ @@
-No errors
+5: Variable $bar might not be defined.

Full report

Line	Error
5	Variable $bar might not be defined.