From 2c18f1218eb1ec8ee0ed47ef74170e625fd901f5 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Fri, 27 Feb 2026 17:22:01 +0000
Subject: [PATCH] Fix match(true) exhaustiveness for complementary integer
 comparisons

- Added resolveComplementaryComparison() method to MutatingScope that checks
  if the complement of a comparison expression has a stored type in the scope
- When resolving $a >= $b, if $a < $b is already stored as false (or true),
  the complement is returned, allowing match(true) to detect exhaustive arms
- Handles all four comparison pairs: < / >=, <= / >, > / <=, >= / <
- New regression test in tests/PHPStan/Rules/Comparison/data/bug-5610.php

Closes https://github.com/phpstan/phpstan/issues/5610
---
 src/Analyser/MutatingScope.php                | 30 ++++++++++++++---
 .../Comparison/MatchExpressionRuleTest.php    |  6 ++++
 .../Rules/Comparison/data/bug-5610.php        | 33 +++++++++++++++++++
 3 files changed, 65 insertions(+), 4 deletions(-)
 create mode 100644 tests/PHPStan/Rules/Comparison/data/bug-5610.php

diff --git a/src/Analyser/MutatingScope.php b/src/Analyser/MutatingScope.php
index a26a86a066..6378816e2b 100644
--- a/src/Analyser/MutatingScope.php
+++ b/src/Analyser/MutatingScope.php
@@ -987,19 +987,23 @@ private function resolveType(string $exprString, Expr $node): Type
 		}
 
 		if ($node instanceof Expr\BinaryOp\Smaller) {
-			return $this->getType($node->left)->isSmallerThan($this->getType($node->right), $this->phpVersion)->toBooleanType();
+			return $this->resolveComplementaryComparison($node, new Expr\BinaryOp\GreaterOrEqual($node->left, $node->right))
+				?? $this->getType($node->left)->isSmallerThan($this->getType($node->right), $this->phpVersion)->toBooleanType();
 		}
 
 		if ($node instanceof Expr\BinaryOp\SmallerOrEqual) {
-			return $this->getType($node->left)->isSmallerThanOrEqual($this->getType($node->right), $this->phpVersion)->toBooleanType();
+			return $this->resolveComplementaryComparison($node, new Expr\BinaryOp\Greater($node->left, $node->right))
+				?? $this->getType($node->left)->isSmallerThanOrEqual($this->getType($node->right), $this->phpVersion)->toBooleanType();
 		}
 
 		if ($node instanceof Expr\BinaryOp\Greater) {
-			return $this->getType($node->right)->isSmallerThan($this->getType($node->left), $this->phpVersion)->toBooleanType();
+			return $this->resolveComplementaryComparison($node, new Expr\BinaryOp\SmallerOrEqual($node->left, $node->right))
+				?? $this->getType($node->right)->isSmallerThan($this->getType($node->left), $this->phpVersion)->toBooleanType();
 		}
 
 		if ($node instanceof Expr\BinaryOp\GreaterOrEqual) {
-			return $this->getType($node->right)->isSmallerThanOrEqual($this->getType($node->left), $this->phpVersion)->toBooleanType();
+			return $this->resolveComplementaryComparison($node, new Expr\BinaryOp\Smaller($node->left, $node->right))
+				?? $this->getType($node->right)->isSmallerThanOrEqual($this->getType($node->left), $this->phpVersion)->toBooleanType();
 		}
 
 		if ($node instanceof Expr\BinaryOp\Equal) {
@@ -1609,6 +1613,24 @@ private function getNullsafeShortCircuitingType(Expr $expr, Type $type): Type
 		return $type;
 	}
 
+	private function resolveComplementaryComparison(Expr\BinaryOp $node, Expr\BinaryOp $complement): ?Type
+	{
+		$complementKey = $this->getNodeKey($complement);
+		if (!array_key_exists($complementKey, $this->expressionTypes)) {
+			return null;
+		}
+
+		$complementType = $this->expressionTypes[$complementKey]->getType();
+		if ($complementType->isTrue()->yes()) {
+			return new ConstantBooleanType(false);
+		}
+		if ($complementType->isFalse()->yes()) {
+			return new ConstantBooleanType(true);
+		}
+
+		return null;
+	}
+
 	private function transformVoidToNull(Type $type, Node $node): Type
 	{
 		if ($node->getAttribute(self::KEEP_VOID_ATTRIBUTE_NAME) === true) {
diff --git a/tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php b/tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php
index e92bd57639..ee3808a90f 100644
--- a/tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php
+++ b/tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php
@@ -446,6 +446,12 @@ public function testBug9534(): void
 		]);
 	}
 
+	#[RequiresPhp('>= 8.0')]
+	public function testBug5610(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-5610.php'], []);
+	}
+
 	#[RequiresPhp('>= 8.0')]
 	public function testBug11310(): void
 	{
diff --git a/tests/PHPStan/Rules/Comparison/data/bug-5610.php b/tests/PHPStan/Rules/Comparison/data/bug-5610.php
new file mode 100644
index 0000000000..2bc4a427a6
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/bug-5610.php
@@ -0,0 +1,33 @@
+<?php // lint >= 8.0
+
+declare(strict_types = 1);
+
+namespace Bug5610;
+
+function foo(int $bar, int $baz): int {
+	return match (true) {
+		$bar < $baz => 1,
+		$bar >= $baz => 2,
+	};
+}
+
+function foo3(int $bar, int $baz): int {
+	return match (true) {
+		$bar > $baz => 1,
+		$bar <= $baz => 2,
+	};
+}
+
+function foo4(int $bar, int $baz): int {
+	return match (true) {
+		$bar <= $baz => 1,
+		$bar > $baz => 2,
+	};
+}
+
+function foo5(int $bar, int $baz): int {
+	return match (true) {
+		$bar >= $baz => 1,
+		$bar < $baz => 2,
+	};
+}