Fix phpstan errors

[BenMorel]

Q	A
Type	improvement
BC Break	no
Fixed issues	none

Summary

A method declared with a string return type attempts to return null. This is not caught by tests as this method is never called because SqlitePlatform does not support exceptions.

This now throws a LogicException instead, as this is not expected to be executed.

Update

Following the discussion below, this now fixes many more phpstan errors.

[BenMorel]

All phpstan errors fixed now! @morozov, waiting for your feedback on assertions, in particular.

[morozov]

@BenMorel I reviewed this partially. Please see my recommendations on using assertions and see if the rest of the assertions follow them.

[morozov]

Here we could use the same approach as with private methods above, however, this one is protected. We should see what prevents this class from being finalized (#3590).

[BenMorel]

What should we do here then? There are only 4 assert() left in this PR; do you want to find a solution to get rid of each of them individually, or is it OK if they stay?

[morozov]

Let's leave those assertions for now. Please rebase and squash.

[BenMorel]

Rebased & squashed!

[morozov]

@BenMorel once this is done, could you please also take a look at

dbal/phpstan.neon.dist

Lines 35 to 36 in f9b3e79

	- '~^Parameter #2 \$registeredAliases of static method Doctrine\\DBAL\\Query\\QueryException::unknownAlias\(\) expects array<string>, array<int, int|string> given\.\z~'
	- '~^Parameter #2 \$registeredAliases of static method Doctrine\\DBAL\\Query\\QueryException::nonUniqueAlias\(\) expects array<string>, array<int, int|string> given\.\z~'

If the | is properly escaped, PHPStan produces 14 more errors that need to be fixed or properly suppressed.

[BenMorel]

@BenMorel once this is done, could you please also take a look at (...)

I'll try to have a look tomorrow!

[morozov]

Thanks @BenMorel. Great work 👍