Fix int overflow internal error

Author: ondrejmirtes

src/Analyser/MutatingScope.php

@@ -124,6 +124,7 @@
 use function get_class;
 use function in_array;
 use function is_float;
+use function is_int;
 use function is_string;
 use function ltrim;
 use function max;
@@ -1060,7 +1061,12 @@ private function resolveType(Expr $node): Type
 				$newTypes = [];
 				foreach ($scalarValues as $scalarValue) {
 					if ($scalarValue instanceof ConstantIntegerType) {
-						$newTypes[] = new ConstantIntegerType(-$scalarValue->getValue());
+						/** @var int|float $newValue */
+						$newValue = -$scalarValue->getValue();
+						if (!is_int($newValue)) {
+							return $type;
+						}
+						$newTypes[] = new ConstantIntegerType($newValue);
 					} elseif ($scalarValue instanceof ConstantFloatType) {
 						$newTypes[] = new ConstantFloatType(-$scalarValue->getValue());
 					}

tests/PHPStan/Analyser/AnalyserIntegrationTest.php

@@ -641,6 +641,12 @@ public function testBug4308(): void
 		$this->assertNoErrors($errors);
 	}
 
+	public function testBug6979(): void
+	{
+		$errors = $this->runAnalyse(__DIR__ . '/data/bug-6979.php');
+		$this->assertNoErrors($errors);
+	}
+
 	/**
 	 * @param string[]|null $allAnalysedFiles
 	 * @return Error[]

tests/PHPStan/Analyser/data/bug-6979.php

@@ -0,0 +1,9 @@
+<?php declare(strict_types=1);
+
+namespace Bug6979;
+
+foreach ([PHP_INT_MIN, 0, PHP_INT_MAX] as $v) {
+	if ($v !== PHP_INT_MIN) {
+		$invalidNumbers[] = -$v;
+	}
+}