Yield type check

conf/config.level3.neon

@@ -23,6 +23,8 @@ conditionalTags:
 		phpstan.rules.rule: %featureToggles.yieldRules%
 	PHPStan\Rules\Generators\YieldInGeneratorRule:
 		phpstan.rules.rule: %featureToggles.yieldRules%
+	PHPStan\Rules\Generators\YieldTypeRule:
+		phpstan.rules.rule: %featureToggles.yieldRules%
 
 services:
 	-
@@ -63,6 +65,9 @@ services:
 		arguments:
 			reportMaybes: %reportMaybes%
 
+	-
+		class: PHPStan\Rules\Generators\YieldTypeRule
+
 	-
 		class: PHPStan\Rules\Methods\MethodSignatureRule
 		arguments:

src/Rules/Generators/YieldFromTypeRule.php

@@ -88,8 +88,6 @@ public function processNode(Node $node, Scope $scope): array
 			);
 		}
 
-		// TODO test
-
 		return $messages;
 	}
 

src/Rules/Generators/YieldTypeRule.php

@@ -0,0 +1,85 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Generators;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleLevelHelper;
+use PHPStan\Type\IntegerType;
+use PHPStan\Type\MixedType;
+use PHPStan\Type\NullType;
+use PHPStan\Type\VerbosityLevel;
+
+class YieldTypeRule implements Rule
+{
+
+	/** @var RuleLevelHelper */
+	private $ruleLevelHelper;
+
+	public function __construct(
+		RuleLevelHelper $ruleLevelHelper
+	)
+	{
+		$this->ruleLevelHelper = $ruleLevelHelper;
+	}
+
+	public function getNodeType(): string
+	{
+		return Node\Expr\Yield_::class;
+	}
+
+	/**
+	 * @param Node\Expr\Yield_ $node
+	 * @param Scope $scope
+	 * @return string[]
+	 */
+	public function processNode(Node $node, Scope $scope): array
+	{
+		$anonymousFunctionReturnType = $scope->getAnonymousFunctionReturnType();
+		$scopeFunction = $scope->getFunction();
+		if ($anonymousFunctionReturnType !== null) {
+			$returnType = $anonymousFunctionReturnType;
+		} elseif ($scopeFunction !== null) {
+			$returnType = ParametersAcceptorSelector::selectSingle($scopeFunction->getVariants())->getReturnType();
+		} else {
+			return []; // already reported by YieldInGeneratorRule
+		}
+
+		if ($returnType instanceof MixedType) {
+			return [];
+		}
+
+		if ($node->key === null) {
+			$keyType = new IntegerType();
+		} else {
+			$keyType = $scope->getType($node->key);
+		}
+
+		if ($node->value === null) {
+			$valueType = new NullType();
+		} else {
+			$valueType = $scope->getType($node->value);
+		}
+
+		$messages = [];
+		if (!$this->ruleLevelHelper->accepts($returnType->getIterableKeyType(), $keyType, $scope->isDeclareStrictTypes())) {
+			$messages[] = sprintf(
+				'Generator expects key type %s, %s given.',
+				$returnType->getIterableKeyType()->describe(VerbosityLevel::typeOnly()),
+				$keyType->describe(VerbosityLevel::typeOnly())
+			);
+		}
+		if (!$this->ruleLevelHelper->accepts($returnType->getIterableValueType(), $valueType, $scope->isDeclareStrictTypes())) {
+			$messages[] = sprintf(
+				'Generator expects value type %s, %s given.',
+				$returnType->getIterableValueType()->describe(VerbosityLevel::typeOnly()),
+				$valueType->describe(VerbosityLevel::typeOnly())
+			);
+		}
+
+		return $messages;
+	}
+
+}

tests/PHPStan/Rules/Generators/YieldTypeRuleTest.php

@@ -0,0 +1,47 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Generators;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleLevelHelper;
+use PHPStan\Testing\RuleTestCase;
+
+class YieldTypeRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new YieldTypeRule(new RuleLevelHelper($this->createBroker(), true, false, true));
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/yield.php'], [
+			[
+				'Generator expects value type int, string given.',
+				14,
+			],
+			[
+				'Generator expects key type string, int given.',
+				15,
+			],
+			[
+				'Generator expects value type int, null given.',
+				15,
+			],
+			[
+				'Generator expects key type string, int given.',
+				16,
+			],
+			[
+				'Generator expects key type string, int given.',
+				17,
+			],
+			[
+				'Generator expects value type int, string given.',
+				17,
+			],
+		]);
+	}
+
+}

tests/PHPStan/Rules/Generators/data/yield.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace YieldTypeRuleTest;
+
+class Foo
+{
+
+	/**
+	 * @return \Generator<string, int>
+	 */
+	public function doFoo(): \Generator
+	{
+		yield 'foo' => 1;
+		yield 'foo' => 'bar';
+		yield;
+		yield 1;
+		yield 'foo';
+	}
+
+}