From 4e25325613e5d8b2bd67a87d4bbb86d5acaa40bd Mon Sep 17 00:00:00 2001
From: Mikko Pesari <mikko@pesari.fi>
Date: Mon, 16 Feb 2026 18:19:31 +0200
Subject: [PATCH] Fix BcMath\Number increment/decrement

---
 .../Operators/InvalidIncDecOperationRule.php  |  4 ++++
 tests/PHPStan/Analyser/nsrt/bcmath-number.php |  8 +++++++
 .../InvalidIncDecOperationRuleTest.php        |  6 ++++++
 .../Operators/data/inc-dec-bcmath-number.php  | 21 +++++++++++++++++++
 4 files changed, 39 insertions(+)
 create mode 100644 tests/PHPStan/Rules/Operators/data/inc-dec-bcmath-number.php

diff --git a/src/Rules/Operators/InvalidIncDecOperationRule.php b/src/Rules/Operators/InvalidIncDecOperationRule.php
index 44ea25b7e0..8c50854e7f 100644
--- a/src/Rules/Operators/InvalidIncDecOperationRule.php
+++ b/src/Rules/Operators/InvalidIncDecOperationRule.php
@@ -132,6 +132,10 @@ public function processNode(Node $node, Scope $scope): array
 			$deprecatedBool = true;
 		}
 
+		if ($this->phpVersion->supportsBcMathNumberOperatorOverloading()) {
+			$allowedTypes[] = new ObjectType('BcMath\Number');
+		}
+
 		$allowedTypes = new UnionType($allowedTypes);
 
 		$varType = $this->ruleLevelHelper->findTypeToCheck(
diff --git a/tests/PHPStan/Analyser/nsrt/bcmath-number.php b/tests/PHPStan/Analyser/nsrt/bcmath-number.php
index 2ead45175f..d78887e4ef 100644
--- a/tests/PHPStan/Analyser/nsrt/bcmath-number.php
+++ b/tests/PHPStan/Analyser/nsrt/bcmath-number.php
@@ -405,4 +405,12 @@ public function bcVsNever(Number $a): void
 			assertType('bool', $a or $b);
 		}
 	}
+
+	public function bcIncDec(Number $a): void
+	{
+		assertType('BcMath\Number', ++$a);
+		assertType('BcMath\Number', $a++);
+		assertType('BcMath\Number', --$a);
+		assertType('BcMath\Number', $a--);
+	}
 }
diff --git a/tests/PHPStan/Rules/Operators/InvalidIncDecOperationRuleTest.php b/tests/PHPStan/Rules/Operators/InvalidIncDecOperationRuleTest.php
index 9243a766a3..52ae098afa 100644
--- a/tests/PHPStan/Rules/Operators/InvalidIncDecOperationRuleTest.php
+++ b/tests/PHPStan/Rules/Operators/InvalidIncDecOperationRuleTest.php
@@ -234,4 +234,10 @@ public function testIncNonNumericString(): void
 		$this->analyse([__DIR__ . '/data/inc-non-numeric-string.php'], $errors);
 	}
 
+	#[RequiresPhp('>= 8.4')]
+	public function testBcMathNumber(): void
+	{
+		$this->analyse([__DIR__ . '/data/inc-dec-bcmath-number.php'], []);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Operators/data/inc-dec-bcmath-number.php b/tests/PHPStan/Rules/Operators/data/inc-dec-bcmath-number.php
new file mode 100644
index 0000000000..ea88d7c359
--- /dev/null
+++ b/tests/PHPStan/Rules/Operators/data/inc-dec-bcmath-number.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace IncDecBcMathNumber;
+
+use BcMath\Number;
+
+function testPreInc(Number $x): void {
+	++$x;
+}
+
+function testPostInc(Number $x): void {
+	$x++;
+}
+
+function testPreDec(Number $x): void {
+	--$x;
+}
+
+function testPostDec(Number $x): void {
+	$x--;
+}