Feature request

https://3v4l.org/b3Vem
As we can see here, there are two types of isOffsetAccessible->no. Whether it throws a fatal error in isset/coalesce/empty ($scope->isUndefinedExpressionAllowed) or not.
I think we can improve NonexistentOffsetInArrayDimFetchRule by separating these.

Also, a lot of people are not aware why StrictMixedType throws an error with the code below, maybe we can add some information in the document

/** @var mixed $mixed */
isset($mixed['foo']);

Goal

https://phpstan.org/r/1087a148-ae5b-477f-9003-215fefc3437f
No error in line 7, 21
Throw error in 12

Design

• Add method something like isOffsetAccessThrowsFatalError(): TernaryLogic (want a better naming...) to Types
• Return TernaryLogic::Yes for isOffsetAccessThrowsFatalError in MixedType/StrictMixedType if object type is subtracted

Related issues

These issues should be closed after documented

• recursive traversal of data: array|mixed (level=9) #7229
• Cannot access offset on mixed when using isset() #8388
• Null coalesce operator on nested array returns unexpected error #8069

The test should be reverted after this is implemented

• https://github.com/phpstan/phpstan-src/pull/1791/files#r1025871491

Array access with json_decode mixed problems

• Specifiy json_decode default return type phpstan-src#1283
• [Types] Add JsonDecodeDynamicReturnTypeExtension phpstan-nette#89

Did PHPStan help you today? Did it make you happy in any way?

PHPStan on PHPStan finds error while developing PHPStan 😄