Fix arithmetic operations with BenevolentUnionType

src/Type/UnionType.php

@@ -735,12 +735,12 @@ public function isConstantScalarValue(): TrinaryLogic
 
 	public function getConstantScalarTypes(): array
 	{
-		return $this->pickFromTypes(static fn (Type $type) => $type->getConstantScalarTypes());
+		return $this->notBenevolentPickFromTypes(static fn (Type $type) => $type->getConstantScalarTypes());
 	}
 
 	public function getConstantScalarValues(): array
 	{
-		return $this->pickFromTypes(static fn (Type $type) => $type->getConstantScalarValues());
+		return $this->notBenevolentPickFromTypes(static fn (Type $type) => $type->getConstantScalarValues());
 	}
 
 	public function isTrue(): TrinaryLogic
@@ -1008,4 +1008,26 @@ protected function pickFromTypes(callable $getValues): array
 		return $values;
 	}
 
+	/**
+	 * @template T
+	 * @param callable(Type $type): list<T> $getValues
+	 * @return list<T>
+	 */
+	private function notBenevolentPickFromTypes(callable $getValues): array
+	{
+		$values = [];
+		foreach ($this->types as $type) {
+			$innerValues = $getValues($type);
+			if ($innerValues === []) {
+				return [];
+			}
+
+			foreach ($innerValues as $innerType) {
+				$values[] = $innerType;
+			}
+		}
+
+		return $values;
+	}
+
 }

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -1201,6 +1201,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/list-shapes.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-7607.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/ibm_db2.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/benevolent-union-math.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/benevolent-union-math.php

@@ -0,0 +1,44 @@
+<?php
+
+namespace BenevolentUnionMath;
+
+use function PHPStan\Testing\assertType;
+use function strtotime;
+
+class Foo
+{
+
+	public function doFoo($s, $r)
+	{
+		$timeS = strtotime($s);
+		assertType('(int|false)', $timeS);
+
+		$timeR = strtotime($r);
+		assertType('(int|false)', $timeR);
+
+		assertType('int', $timeS - $timeR);
+	}
+
+}
+
+class HelloWorld
+{
+	public function sayHello(int $x): void
+	{
+		$dbresponse = $this->getBenevolent();
+		assertType('array<string, (float|int|string|null)>|null', $dbresponse);
+
+		if ($dbresponse === null) {return;}
+
+		assertType('array<string, (float|int|string|null)>', $dbresponse);
+		assertType('(float|int|string|null)', $dbresponse['Value']);
+		assertType('int<0, max>', strlen($dbresponse['Value']));
+	}
+
+	/**
+	 * @return array<string, __benevolent<float|int|string|null>>|null
+	 */
+	private function getBenevolent(): ?array{
+		return rand(10) > 1 ? null : [];
+	}
+}