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Fix missing detection of dead code in expressions #4090

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Fix missing detection of dead code in expressions #4090

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staabm
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@staabm staabm commented Jul 11, 2025 •
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staabm commented Jul 11, 2025 •
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hmm I wonder whether I should add this $isAlwaysTerminating = $isAlwaysTerminating || $result->isAlwaysTerminating(); handling everywhere, where we have

			$hasYield = $hasYield || $result->hasYield();
			$throwPoints = array_merge($throwPoints, $result->getThrowPoints());
			$impurePoints = array_merge($impurePoints, $result->getImpurePoints());

etc...?

edit: I added it in all places where I could think of a example which I was able to test

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staabm commented Jul 12, 2025

I think the new behaviour makes sense but the errors are unfortunate

https://github.com/laravel/framework/blob/43993ed92af54aa8620d8e779a7dcd658f44364c/types/Support/Helpers.php#L44-L60

------ ------------------------------------------------------- 
  Line   Support/Helpers.php                                    
 ------ ------------------------------------------------------- 
  47     Unreachable statement - code above always terminates.  
         🪪  deadCode.unreachable                               
  66     Unreachable statement - code above always terminates.  
         🪪  deadCode.unreachable                               
 ------ -------------------------------------------------------

@staabm staabm marked this pull request as ready for review July 12, 2025 06:26
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ondrejmirtes
ondrejmirtes requested changes Jul 17, 2025
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There is StatementResultTest that tests "is always terminating". Please add a similar test for ExpressionResult. Thank you.

ondrejmirtes
ondrejmirtes requested changes Jul 17, 2025
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src/Analyser/ExpressionResult.php Outdated
@@ -28,6 +28,7 @@ public function __construct(
private array $impurePoints,
?callable $truthyScopeCallback = null,
?callable $falseyScopeCallback = null,
private bool $isAlwaysTerminating = false,
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Doesn't have to be optional and doesn't have to be at the end. I'd prefer it to be after hasYield, for consistency with StatementResult.

ondrejmirtes
ondrejmirtes requested changes Jul 17, 2025
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src/Analyser/NodeScopeResolver.php Outdated
@@ -2408,6 +2413,7 @@ public function processExprNode(Node\Stmt $stmt, Expr $expr, MutatingScope $scop
return $this->processExprNode($stmt, $newExpr, $scope, $nodeCallback, $context);
}

$isAlwaysTerminating = false;
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Remove the variable assign from here. It should be set inside each if about each node type.

ondrejmirtes
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src/Analyser/NodeScopeResolver.php Outdated
} elseif ($expr instanceof PropertyFetch) {
$scopeBeforeVar = $scope;
$result = $this->processExprNode($stmt, $expr->var, $scope, $nodeCallback, $context->enterDeep());
$hasYield = $result->hasYield();
$throwPoints = $result->getThrowPoints();
$impurePoints = $result->getImpurePoints();
$isAlwaysTerminating = false;
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should be taken from $result and also updated in $expr->name instanceof Expr branch

src/Analyser/NodeScopeResolver.php
$scope = $result->getScope();
}
} elseif ($expr instanceof ArrayDimFetch) {
$hasYield = false;
$throwPoints = [];
$impurePoints = [];
$isAlwaysTerminating = false;
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Basically this should be updated every time $hasYield is updated. Please review all branches in processExprNode like that.

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@staabm staabm Jul 17, 2025 •
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I adjusted it in most cases.

I left out e.g. null-safe operations, as these would only terminate for always-non-nullables and similar stuff.

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staabm commented Jul 17, 2025

I think this should be ready to land.

thanks for the feedback

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never return not detected never return type should lead to error when used
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@staabm @phpstan-bot @ondrejmirtes