Throw on invalid UnionType with AccessoryTypes

[staabm]

as discussed in phpstan/phpstan#11535 (comment)

[phpstan-bot]

You've opened the pull request against the latest branch 2.0.x. PHPStan 2.0 is not going to be released for months. If your code is relevant on 1.12.x and you want it to be released sooner, please rebase your pull request and change its target to 1.12.x.

[staabm]

ha, this change brings up super interessting exception cases :-)

Uncaught PHPStan\ShouldNotHappenException: Cannot create PHPStan\Type\UnionType with: non-empty-array, array{} in C:\dvl\Workspace\phpstan-src-staabm\src\Type\UnionType.php:61
#0 C:\dvl\Workspace\phpstan-src-staabm\src\Type\UnionType.php(73): PHPStan\Type\UnionType::PHPStan\Type\{closure}()
#1 C:\dvl\Workspace\phpstan-src-staabm\src\Type\TypeCombinator.php(369): PHPStan\Type\UnionType->__construct()
#2 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\ExpressionTypeHolder.php(41): PHPStan\Type\TypeCombinator::union()
#3 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\MutatingScope.php(4691): PHPStan\Analyser\ExpressionTypeHolder->and()
#4 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\MutatingScope.php(4565): PHPStan\Analyser\MutatingScope->mergeVariableHolders()
#5 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\NodeScopeResolver.php(1444): PHPStan\Analyser\MutatingScope->mergeWith()
#6 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\NodeScopeResolver.php(346): PHPStan\Analyser\NodeScopeResolver->processStmtNode()
#7 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\NodeScopeResolver.php(682): PHPStan\Analyser\NodeScopeResolver->processStmtNodes()
#8 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\NodeScopeResolver.php(346): PHPStan\Analyser\NodeScopeResolver->processStmtNode()
#9 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\NodeScopeResolver.php(871): PHPStan\Analyser\NodeScopeResolver->processStmtNodes()
#10 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\NodeScopeResolver.php(346): PHPStan\Analyser\NodeScopeResolver->processStmtNode()
#11 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\NodeScopeResolver.php(839): PHPStan\Analyser\NodeScopeResolver->processStmtNodes()
#12 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\NodeScopeResolver.php(302): PHPStan\Analyser\NodeScopeResolver->processStmtNode()
#13 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\FileAnalyser.php(212): PHPStan\Analyser\NodeScopeResolver->processNodes()
#14 C:\dvl\Workspace\phpstan-src-staabm\src\Analyser\Analyser.php(75): PHPStan\Analyser\FileAnalyser->analyseFile()
#15 C:\dvl\Workspace\phpstan-src-staabm\src\Command\AnalyserRunner.php(79): PHPStan\Analyser\Analyser->analyse()
#16 C:\dvl\Workspace\phpstan-src-staabm\src\Command\AnalyseApplication.php(215): PHPStan\Command\AnalyserRunner->runAnalyser()
#17 C:\dvl\Workspace\phpstan-src-staabm\src\Command\AnalyseApplication.php(69): PHPStan\Command\AnalyseApplication->runAnalyser()
#18 C:\dvl\Workspace\phpstan-src-staabm\src\Command\AnalyseCommand.php(283): PHPStan\Command\AnalyseApplication->analyse()
#19 C:\dvl\Workspace\phpstan-src-staabm\vendor\symfony\console\Command\Command.php(298): PHPStan\Command\AnalyseCommand->execute()
#20 C:\dvl\Workspace\phpstan-src-staabm\vendor\symfony\console\Application.php(1040): Symfony\Component\Console\Command\Command->run()
#21 C:\dvl\Workspace\phpstan-src-staabm\vendor\symfony\console\Application.php(301): Symfony\Component\Console\Application->doRunCommand()
#22 C:\dvl\Workspace\phpstan-src-staabm\vendor\symfony\console\Application.php(171): Symfony\Component\Console\Application->doRun()
#23 C:\dvl\Workspace\phpstan-src-staabm\bin\phpstan(165): Symfony\Component\Console\Application->run()
#24 C:\dvl\Workspace\phpstan-src-staabm\bin\phpstan(166): {closure}()
#25 {main}

I think we cannot do it like this