Cannot use lexical variable

[SignpostMarv]

using whichever version is on the PHPStan playground at the time of writing

Summary of a problem or a feature request

Under php 7.0, variable/param name collisions seem to be silently ignored, but under php 7.1 onwards it's identified as a fatal error.

Code snippet that reproduces the problem

"Cannot use lexical variable $foo as a parameter name"

• https://phpstan.org/r/b965308c-4d1b-43c3-ada1-20890ebd46b4
• https://3v4l.org/Kpsn4

<?php
declare(strict_types=1);

$foo = 'bar';
  
$a = function (string $foo) use ($foo) : string {
  return $foo;
};

echo $a('baz');

Expected output

An error similar to that which occurs with an "unused use", e.g. https://phpstan.org/r/cff41209-747e-414d-8ef3-60fa360f5bfd

[SignpostMarv]

also tracking in psalm on vimeo/psalm#1256

[ondrejmirtes]

Thanks. Adding this as another thing that should be detected:

• https://phpstan.org/r/64a933f7-2615-4c87-ba28-3fa120f00da7
• https://3v4l.org/4G9Jk

[phpstan-bot]

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

@@ @@
-No errors
+5: Redefinition of parameter $foo.

Full report

Line	Error
5	Redefinition of parameter $foo.

[ondrejmirtes]

Implemented: phpstan/phpstan-src#2755

[github-actions]

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