Preserve variable flow through declare blocks

Author: drewmt

src/Analyser/StmtHandler/DeclareHandler.php

@@ -44,6 +44,7 @@ public function processStmt(
 		$impurePoints = [];
 		$alwaysTerminating = false;
 		$exitPoints = [];
+		$variableFlow = null;
 		foreach ($stmt->declares as $declare) {
 			$nodeScopeResolver->callNodeCallback($nodeCallback, $declare, $scope, $storage);
 			// the value is a constant scalar - process it so its result is stored
@@ -69,9 +70,10 @@ public function processStmt(
 			$impurePoints = $result->getImpurePoints();
 			$alwaysTerminating = $result->isAlwaysTerminating();
 			$exitPoints = $result->getExitPoints();
+			$variableFlow = $result->getVariableFlow();
 		}
 
-		return new InternalStatementResult($scope, hasYield: $hasYield, isAlwaysTerminating: $alwaysTerminating, exitPoints: $exitPoints, throwPoints: $throwPoints, impurePoints: $impurePoints, dependencies: Dependencies::merge(...$dependencies));
+		return new InternalStatementResult($scope, hasYield: $hasYield, isAlwaysTerminating: $alwaysTerminating, exitPoints: $exitPoints, throwPoints: $throwPoints, impurePoints: $impurePoints, variableFlow: $variableFlow, dependencies: Dependencies::merge(...$dependencies));
 	}
 
 }

tests/PHPStan/Rules/DeadCode/UnusedVariableRuleTest.php

@@ -23,6 +23,14 @@ public function testBug15411(): void
 		$this->analyse([__DIR__ . '/data/bug-15411.php'], []);
 	}
 
+	public function testBug15394(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-15394.php'], [
+			['Variable $unused is never read.', 34],
+			['Value assigned to variable $value is never read before being overwritten.', 40],
+		]);
+	}
+
 	public function testThrowableCatchAfterDocumentedException(): void
 	{
 		$this->analyse([__DIR__ . '/data/unused-variable-throwable-catch.php'], []);

tests/PHPStan/Rules/DeadCode/data/bug-15394.php

@@ -0,0 +1,60 @@
+<?php declare(strict_types = 1);
+
+namespace Bug15394;
+
+function readInBlock(): void
+{
+	$value = 1;
+	declare(ticks=1) {
+		echo $value;
+	}
+}
+
+function writeInBlock(): void
+{
+	declare(ticks=1) {
+		$value = 1;
+	}
+	echo $value;
+}
+
+function readInNestedBlock(): void
+{
+	$value = 1;
+	declare(ticks=1) {
+		declare(ticks=2) {
+			echo $value;
+		}
+	}
+}
+
+function unusedInBlock(): void
+{
+	declare(ticks=1) {
+		$unused = 1;
+	}
+}
+
+function overwrittenInBlock(): void
+{
+	$value = 1;
+	declare(ticks=1) {
+		$value = 2;
+	}
+	echo $value;
+}
+
+function readAfterDeclareStatement(): void
+{
+	$value = 1;
+	declare(ticks=1);
+	echo $value;
+}
+
+function readInAlternativeBlock(): void
+{
+	$value = 1;
+	declare(ticks=1):
+		echo $value;
+	enddeclare;
+}

turbo-ext/src/DeclareHandler.cpp

@@ -122,6 +122,9 @@ class DeclareHandler
 		zv::Val exitPointsHold;
 		zval *exitPoints = pt_internal_statement_result_exit_points(result.raw(), exitPointsHold);
 		if (UNEXPECTED(exitPoints == NULL)) return zv::Val();
+		zv::Val variableFlowHold;
+		zval *variableFlow = pt_internal_statement_result_variable_flow(result.raw(), variableFlowHold);
+		if (UNEXPECTED(variableFlow == NULL)) return zv::Val();
 		{
 			zv::Val hold;
 			zval *resultDependencies = pt_internal_statement_result_dependencies(result.raw(), hold);
@@ -130,7 +133,7 @@ class DeclareHandler
 		}
 		zv::Val mergedDependencies = pt_dependencies_merge_list(dependencies.table());
 		if (UNEXPECTED(mergedDependencies.isUndef())) return zv::Val();
-		return pt_internal_statement_result_new(resultScope, hasYield, alwaysTerminating, exitPoints, throwPoints, impurePoints, NULL, NULL, -1, mergedDependencies.raw());
+		return pt_internal_statement_result_new(resultScope, hasYield, alwaysTerminating, exitPoints, throwPoints, impurePoints, NULL, variableFlow, -1, mergedDependencies.raw());
 	}
 
 	/* the statement-handler entry (Engine.h) */