Fix #13569: Catching undefined constant causes dead catch false positive

[phpstan-bot]

Summary

Dynamic class constant fetches like ReactionType::{$name} can throw \Error at runtime when the constant name doesn't exist. PHPStan was incorrectly reporting "Dead catch - Error is never thrown in the try block" for catch blocks around such expressions.

Changes

• Added an implicit throw point in src/Analyser/NodeScopeResolver.php when processing ClassConstFetch nodes with dynamic names ($expr->name instanceof Expr)
• Added regression test tests/PHPStan/Rules/Exceptions/data/bug-13569.php with a test method in CatchWithUnthrownExceptionRuleTest

Root cause

In NodeScopeResolver::processExprNode(), when handling Expr\ClassConstFetch, the code correctly processed the dynamic name expression but did not register an implicit throw point for the constant fetch itself. Since accessing a non-existent class constant with a dynamic name throws \Error at runtime, PHPStan needs to recognize this possibility. The fix adds InternalThrowPoint::createImplicit($scope, $expr) when the constant name is dynamic, matching the pattern used elsewhere (e.g., property fetches with hooks, dynamic method calls).

Test

Added a regression test using a backed enum with a tryFromName method that uses dynamic class constant fetch (ReactionType::{$name}) inside a try/catch block. The test expects no errors, confirming the catch block is correctly recognized as reachable.

Fixes phpstan/phpstan#13569

[VincentLanglet]

I don't think this is the right way to fix this since

• other catch won't be reported
• Something like

public static function tryFromName2(): ?self
	{
		$name = 'EMOJI_HEART';
		try {
			return ReactionType::{$name};
		} catch (\Error) {
			return null;
		}
	}

won't be reported