Fixed comparison of empty array with a scalar type

Author: staabm

Diff for: src/Reflection/InitializerExprTypeResolver.php

@@ -1253,6 +1253,15 @@ public function resolveEqualType(Type $leftType, Type $rightType): BooleanType
 			return $this->resolveIdenticalType($leftType, $rightType);
 		}
 
+		if ($leftType instanceof ConstantArrayType && $leftType->isEmpty() && $rightType instanceof ConstantScalarType) {
+			// @phpstan-ignore-next-line
+			return new ConstantBooleanType($rightType->getValue() == []); // phpcs:ignore
+		}
+		if ($rightType instanceof ConstantArrayType && $rightType->isEmpty() && $leftType instanceof ConstantScalarType) {
+			// @phpstan-ignore-next-line
+			return new ConstantBooleanType($leftType->getValue() == []); // phpcs:ignore
+		}
+
 		if ($leftType instanceof ConstantScalarType && $rightType instanceof ConstantScalarType) {
 			// @phpstan-ignore-next-line
 			return new ConstantBooleanType($leftType->getValue() == $rightType->getValue()); // phpcs:ignore

Diff for: tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -983,6 +983,14 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/composer-non-empty-array-after-unset.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/../Rules/Arrays/data/bug-6000.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/prestashop-breakdowns-empty-array.php');
+
+		if (PHP_VERSION_ID < 80000) {
+			yield from $this->gatherAssertTypes(__DIR__ . '/data/loose-comparisons-php7.php');
+		}
+		if (PHP_VERSION_ID >= 80000) {
+			yield from $this->gatherAssertTypes(__DIR__ . '/data/loose-comparisons-php8.php');
+		}
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/loose-comparisons.php');
 	}
 
 	/**

Diff for: tests/PHPStan/Analyser/data/loose-comparisons-php7.php

@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LooseSemanticsPhp7;
+
+use function PHPStan\Testing\assertType;
+
+class HelloWorld
+{
+	/**
+	 * @param 0 $zero
+	 * @param 'php' $phpStr
+	 * @param '' $emptyStr
+	 */
+	public function sayZero(
+		$zero,
+		$phpStr,
+		$emptyStr
+	): void
+	{
+		assertType('true', $zero == $phpStr);
+		assertType('true', $zero == $emptyStr);
+	}
+
+	/**
+	 * @param 0 $zero
+	 * @param 'php' $phpStr
+	 */
+	public function sayPhpStr(
+		$zero,
+		$phpStr,
+	): void
+	{
+		assertType('true', $phpStr == $zero);
+	}
+
+	/**
+	 * @param 0 $zero
+	 * @param '' $emptyStr
+	 */
+	public function sayEmptyStr(
+		$zero,
+		$emptyStr
+	): void
+	{
+		assertType('true', $emptyStr == $zero);
+	}
+}

Diff for: tests/PHPStan/Analyser/data/loose-comparisons-php8.php

@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LooseSemanticsPhp8;
+
+use function PHPStan\Testing\assertType;
+
+class HelloWorld
+{
+	/**
+	 * @param 0 $zero
+	 * @param 'php' $phpStr
+	 * @param '' $emptyStr
+	 */
+	public function sayZero(
+		$zero,
+		$phpStr,
+		$emptyStr
+	): void
+	{
+		assertType('false', $zero == $phpStr); // PHP8+ only
+		assertType('false', $zero == $emptyStr); // PHP8+ only
+	}
+
+	/**
+	 * @param 0 $zero
+	 * @param 'php' $phpStr
+	 */
+	public function sayPhpStr(
+		$zero,
+		$phpStr,
+	): void
+	{
+		assertType('false', $phpStr == $zero); // PHP8+ only
+	}
+
+	/**
+	 * @param 0 $zero
+	 * @param '' $emptyStr
+	 */
+	public function sayEmptyStr(
+		$zero,
+		$emptyStr
+	): void
+	{
+		assertType('false', $emptyStr == $zero); // PHP8+ only
+	}
+}