Narrow division to int when modulo is known to be zero

src/Reflection/InitializerExprTypeResolver.php

@@ -1240,6 +1240,20 @@ public function getDivType(Expr $left, Expr $right, callable $getTypeCallback):
 		$leftType = $getTypeCallback($left);
 		$rightType = $getTypeCallback($right);
 
+		$result = $this->getDivTypeFromTypes($left, $right, $leftType, $rightType);
+
+		if ($leftType->isInteger()->yes() && $rightType->isInteger()->yes()) {
+			$modType = $getTypeCallback(new BinaryOp\Mod($left, $right));
+			if ($modType->isInteger()->yes() && (new ConstantIntegerType(0))->isSuperTypeOf($modType)->yes()) {
+				return TypeCombinator::remove($result, new FloatType());
+			}
+		}
+
+		return $result;
+	}
+
+	private function getDivTypeFromTypes(Expr $left, Expr $right, Type $leftType, Type $rightType): Type
+	{
 		$leftTypes = $leftType->getConstantScalarTypes();
 		$rightTypes = $rightType->getConstantScalarTypes();
 		$leftTypesCount = count($leftTypes);

tests/PHPStan/Analyser/nsrt/bug-9724.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Bug9724;
+
+use function PHPStan\Testing\assertType;
+
+class HelloWorld
+{
+	public function thisWorks(?int $limit, int $offset = 0): void
+	{
+		if ($limit && 0 === ($offset % $limit)) {
+			assertType('int', $offset / $limit);
+			assertType('int', ($offset / $limit) + 1);
+		}
+	}
+
+	public function thisDoesntWork(?int $limit, int $offset = 0): void
+	{
+		if ($limit && $offset && (0 === ($offset % $limit))) {
+			assertType('int<min, -1>|int<1, max>', $offset / $limit);
+			assertType('int<min, 0>|int<2, max>', ($offset / $limit) + 1);
+		}
+	}
+
+	/** @param int<-2, 2> $offsetRange */
+	public function withRange(int $limit, int $offset, int $offsetRange): void
+	{
+		if ($limit) {
+			assertType('(float|int)', $offset / $limit);
+			assertType('float|int<-2, 2>', $offsetRange / $limit);
+		}
+	}
+}

tests/PHPStan/Rules/Methods/CallMethodsRuleTest.php

@@ -4106,4 +4106,12 @@ public function testBug14596(): void
 		]);
 	}
 
+	public function testBug9724(): void
+	{
+		$this->checkThisOnly = false;
+		$this->checkNullables = true;
+		$this->checkUnionTypes = true;
+		$this->analyse([__DIR__ . '/data/bug-9724.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Methods/data/bug-9724.php

@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Bug9724Rule;
+
+class HelloWorld
+{
+	private function expectInt(int $page): void
+	{
+	}
+
+	public function originalIssue(?int $limit, int $offset = 0): void
+	{
+		if ($limit && $offset && (0 === ($offset % $limit))) {
+			$this->expectInt(($offset / $limit) + 1);
+		}
+	}
+}