Support for throw expression (PHP 8.0)

https://wiki.php.net/rfc/throw_expression

Author: ondrejmirtes

conf/config.level0.neon

@@ -26,6 +26,7 @@ rules:
 	- PHPStan\Rules\Classes\ExistingClassInTraitUseRule
 	- PHPStan\Rules\Classes\InstantiationRule
 	- PHPStan\Rules\Classes\NewStaticRule
+	- PHPStan\Rules\Exceptions\ThrowExpressionRule
 	- PHPStan\Rules\Functions\CallToFunctionParametersRule
 	- PHPStan\Rules\Functions\ExistingClassesInArrowFunctionTypehintsRule
 	- PHPStan\Rules\Functions\ExistingClassesInClosureTypehintsRule

src/Analyser/MutatingScope.php

@@ -494,7 +494,7 @@ private function getNodeKey(Expr $node): string
 
 	private function resolveType(Expr $node): Type
 	{
-		if ($node instanceof Expr\Exit_) {
+		if ($node instanceof Expr\Exit_ || $node instanceof Expr\Throw_) {
 			return new NeverType();
 		}
 

src/Php/PhpVersion.php

@@ -61,4 +61,9 @@ public function requiresParenthesesForNestedTernaries(): bool
 		return $this->versionId >= 80000;
 	}
 
+	public function supportsThrowExpression(): bool
+	{
+		return $this->versionId >= 80000;
+	}
+
 }

src/Rules/Exceptions/ThrowExpressionRule.php

@@ -0,0 +1,40 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Exceptions;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Php\PhpVersion;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+
+/**
+ * @implements Rule<Node\Expr\Throw_>
+ */
+class ThrowExpressionRule implements Rule
+{
+
+	private PhpVersion $phpVersion;
+
+	public function __construct(PhpVersion $phpVersion)
+	{
+		$this->phpVersion = $phpVersion;
+	}
+
+	public function getNodeType(): string
+	{
+		return Node\Expr\Throw_::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if ($this->phpVersion->supportsThrowExpression()) {
+			return [];
+		}
+
+		return [
+			RuleErrorBuilder::message('Throw expression is supported only on PHP 8.0 and later.')->nonIgnorable()->build(),
+		];
+	}
+
+}

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -10146,6 +10146,15 @@ public function dataPow(): array
 		return $this->gatherAssertTypes(__DIR__ . '/data/pow.php');
 	}
 
+	public function dataThrowExpression(): array
+	{
+		if (PHP_VERSION_ID < 80000 && !self::$useStaticReflectionProvider) {
+			return [];
+		}
+
+		return $this->gatherAssertTypes(__DIR__ . '/data/throw-expr.php');
+	}
+
 	/**
 	 * @dataProvider dataBug2574
 	 * @dataProvider dataBug2577
@@ -10223,6 +10232,7 @@ public function dataPow(): array
 	 * @dataProvider dataBug1014
 	 * @dataProvider dataBugFromPr339
 	 * @dataProvider dataPow
+	 * @dataProvider dataThrowExpression
 	 * @param string $assertType
 	 * @param string $file
 	 * @param mixed ...$args

tests/PHPStan/Analyser/data/throw-expr.php

@@ -0,0 +1,21 @@
+<?php // lint >= 8.0
+
+namespace ThrowExpr;
+
+use function PHPStan\Analyser\assertType;
+
+class Foo
+{
+
+	public function doFoo(bool $b): void
+	{
+		$result = $b ? true : throw new \Exception();
+		assertType('true', $result);
+	}
+
+	public function doBar(): void
+	{
+		assertType('*NEVER*', throw new \Exception());
+	}
+
+}

tests/PHPStan/Rules/Exceptions/ThrowExpressionRuleTest.php

@@ -0,0 +1,53 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Exceptions;
+
+use PHPStan\Php\PhpVersion;
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<ThrowExpressionRule>
+ */
+class ThrowExpressionRuleTest extends RuleTestCase
+{
+
+	/** @var PhpVersion */
+	private $phpVersion;
+
+	protected function getRule(): Rule
+	{
+		return new ThrowExpressionRule($this->phpVersion);
+	}
+
+	public function dataRule(): array
+	{
+		return [
+			[
+				70400,
+				[
+					[
+						'Throw expression is supported only on PHP 8.0 and later.',
+						10,
+					],
+				],
+			],
+			[
+				80000,
+				[],
+			],
+		];
+	}
+
+	/**
+	 * @dataProvider dataRule
+	 * @param int $phpVersion
+	 * @param mixed[] $expectedErrors
+	 */
+	public function testRule(int $phpVersion, array $expectedErrors): void
+	{
+		$this->phpVersion = new PhpVersion($phpVersion);
+		$this->analyse([__DIR__ . '/data/throw-expr.php'], $expectedErrors);
+	}
+
+}

tests/PHPStan/Rules/Exceptions/data/throw-expr.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace ThrowExpr;
+
+class Bar
+{
+
+	public function doFoo(bool $b): void
+	{
+		$b ? true : throw new \Exception();
+
+		throw new \Exception();
+	}
+
+}