Keep iterating a for loop when a nested loop hides its back edge

src/Analyser/StmtHandler/ForHandler.php

@@ -221,8 +221,14 @@ public function processStmt(
 					$passFlows[] = $bodyScopeResult->getVariableFlow();
 					$backEdgeScope = $bodyScopeResult->getLoopBackEdgeScope();
 					if ($backEdgeScope === null) {
-						$bodyScope = $prevScope;
-						break;
+						if ($nodeScopeResolver->isReplayableConvergenceBody($stmt, $stmt->stmts)) {
+							$bodyScope = $prevScope;
+							break;
+						}
+						// a nested loop is walked only once in deep context, so the
+						// back edge it would reach on a later iteration can look dead -
+						// continue from the end of the body instead of stopping here
+						$backEdgeScope = $bodyScopeResult->getScope();
 					}
 					$bodyScope = $backEdgeScope;
 

src/Turbo/TurboExtensionEnabler.php

@@ -33,7 +33,7 @@
 final class TurboExtensionEnabler
 {
 
-	public const EXPECTED_EXTENSION_VERSION = 'a0f7086';
+	public const EXPECTED_EXTENSION_VERSION = '6f46059';
 
 	private static bool $active = false;
 

tests/PHPStan/Rules/Comparison/NumberComparisonOperatorsConstantConditionRuleTest.php

@@ -327,6 +327,11 @@ public function testBug15243(): void
 		$this->analyse([__DIR__ . '/../../Analyser/nsrt/bug-15243.php'], []);
 	}
 
+	public function testBug15420(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-15420.php'], []);
+	}
+
 	public function testShiftLeftUnboundedRange(): void
 	{
 		$this->analyse([__DIR__ . '/../../Analyser/nsrt/shift-left-unbounded-range.php'], []);

tests/PHPStan/Rules/Comparison/data/bug-15420.php

@@ -0,0 +1,26 @@
+<?php declare(strict_types = 1);
+
+namespace Bug15420;
+
+class Test {
+	/** @param string[] $cards */
+	public function f(array $cards): void
+	{
+	    for ($i = 0; $i < 10; $i++) {
+	        $seen = [];
+	        $later = [];
+	        foreach ($cards as $card) {
+	            if (array_key_exists($card, $seen)) {
+	                $later[] = $card;
+	                continue;
+	            }
+	            $seen[$card] = true;
+	        }
+	        if ($later !== []) {
+	            $cards = $later;
+	        } else {
+	            break;
+	        }
+	    }
+	}
+}

turbo-ext/src/ForHandler.cpp

@@ -271,9 +271,20 @@ class ForHandler
 					zv::Val backEdgeScope = pt_internal_statement_result_loop_back_edge_scope(bodyScopeResult.raw());
 					if (UNEXPECTED(backEdgeScope.isUndef())) return;
 					if (backEdgeScope.isNull()) {
-						bodyScope = std::move(prevScope);
-						brokeOut = true;
-						return;
+						bool bodyIsReplayable;
+						if (UNEXPECTED(!pt_node_scope_resolver_is_replayable_convergence_body(nodeScopeResolver, stmt, stmtsHold.raw(), bodyIsReplayable))) return;
+						if (bodyIsReplayable) {
+							bodyScope = std::move(prevScope);
+							brokeOut = true;
+							return;
+						}
+						// a nested loop is walked only once in deep context, so the
+						// back edge it would reach on a later iteration can look dead -
+						// continue from the end of the body instead of stopping here
+						zv::Val hold;
+						zval *resultScope = pt_internal_statement_result_scope(bodyScopeResult.raw(), hold);
+						if (UNEXPECTED(resultScope == NULL)) return;
+						backEdgeScope = zv::Val::copyOf(zv::Ref(resultScope));
 					}
 					bodyScope = std::move(backEdgeScope);