Add support for PHP 8.5 #[\NoDiscard]

Makefile

@@ -110,6 +110,8 @@ lint:
 		--exclude tests/PHPStan/Rules/Classes/data/enum-cannot-be-attribute.php \
 		--exclude tests/PHPStan/Rules/Classes/data/class-attributes.php \
 		--exclude tests/PHPStan/Rules/Classes/data/enum-attributes.php \
+		--exclude tests/PHPStan/Rules/Cast/data/void-cast.php \
+		--exclude tests/PHPStan/Rules/Properties/data/property-hook-attributes-nodiscard.php \
 		src tests
 
 install-paratest:

build/collision-detector.json

@@ -15,6 +15,11 @@
 		"../tests/PHPStan/Rules/Functions/data/define-bug-3349.php",
 		"../tests/PHPStan/Levels/data/stubs/function.php",
 		"../tests/PHPStan/Rules/Properties/data/abstract-final-property-hook-parse-error.php",
-		"../tests/PHPStan/Rules/Properties/data/final-property-hooks.php"
+		"../tests/PHPStan/Rules/Properties/data/final-property-hooks.php",
+		"../tests/PHPStan/Rules/Functions/data/function-call-statement-result-discarded.php",
+		"../tests/PHPStan/Rules/Methods/data/method-call-statement-result-discarded.php",
+		"../tests/PHPStan/Rules/Methods/data/static-method-call-statement-result-discarded.php",
+		"../tests/PHPStan/Rules/Properties/data/property-hook-attributes-nodiscard.php",
+		"../tests/PHPStan/Rules/Cast/data/void-cast.php"
     ]
 }

src/Parser/VoidCastVisitor.php

@@ -0,0 +1,31 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Parser;
+
+use Override;
+use PhpParser\Node;
+use PhpParser\Node\Expr\Cast\Void_;
+use PhpParser\NodeVisitorAbstract;
+use PHPStan\DependencyInjection\AutowiredService;
+
+#[AutowiredService]
+final class VoidCastVisitor extends NodeVisitorAbstract
+{
+
+	private bool $pendingVoidCast = false;
+
+	public const ATTRIBUTE_NAME = 'voidCastExpr';
+
+	#[Override]
+	public function enterNode(Node $node): ?Node
+	{
+		if ($node instanceof Void_) {
+			$this->pendingVoidCast = true;
+		} elseif ($this->pendingVoidCast) {
+			$node->setAttribute(self::ATTRIBUTE_NAME, true);
+			$this->pendingVoidCast = false;
+		}
+		return null;
+	}
+
+}

src/Reflection/Annotations/AnnotationMethodReflection.php

@@ -183,4 +183,9 @@ public function getAttributes(): array
 		return [];
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 }

src/Reflection/Dummy/ChangedTypeMethodReflection.php

@@ -171,4 +171,9 @@ public function getAttributes(): array
 		return $this->reflection->getAttributes();
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		return $this->reflection->hasNoDiscardAttribute();
+	}
+
 }

src/Reflection/Dummy/DummyConstructorReflection.php

@@ -157,4 +157,10 @@ public function getAttributes(): array
 		return [];
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		// Align with the getAttributes() returning empty
+		return TrinaryLogic::createNo();
+	}
+
 }

src/Reflection/Dummy/DummyMethodReflection.php

@@ -149,4 +149,10 @@ public function getAttributes(): array
 		return [];
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		// Align with the getAttributes() returning empty
+		return TrinaryLogic::createNo();
+	}
+
 }

src/Reflection/ExtendedMethodReflection.php

@@ -65,4 +65,11 @@ public function isPure(): TrinaryLogic;
 	 */
 	public function getAttributes(): array;
 
+	/**
+	 * Has the #[\NoDiscard] attribute - on PHP 8.5+ if the function's return
+	 * value is unused at runtime a warning is emitted, phpstan will emit the
+	 * warning during analysis and on older PHP versions too
+	 */
+	public function hasNoDiscardAttribute(): TrinaryLogic;
+
 }

src/Reflection/FunctionReflection.php

@@ -62,4 +62,11 @@ public function isPure(): TrinaryLogic;
 	 */
 	public function getAttributes(): array;
 
+	/**
+	 * Has the #[\NoDiscard] attribute - on PHP 8.5+ if the function's return
+	 * value is unused at runtime a warning is emitted, phpstan will emit the
+	 * warning during analysis and on older PHP versions too
+	 */
+	public function hasNoDiscardAttribute(): TrinaryLogic;
+
 }

src/Reflection/Native/NativeFunctionReflection.php

@@ -150,4 +150,14 @@ public function getAttributes(): array
 		return $this->attributes;
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		foreach ($this->attributes as $attrib) {
+			if ($attrib->getName() === 'NoDiscard') {
+				return TrinaryLogic::createYes();
+			}
+		}
+		return TrinaryLogic::createNo();
+	}
+
 }

src/Reflection/Native/NativeMethodReflection.php

@@ -227,4 +227,14 @@ public function getAttributes(): array
 		return $this->attributes;
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		foreach ($this->attributes as $attrib) {
+			if ($attrib->getName() === 'NoDiscard') {
+				return TrinaryLogic::createYes();
+			}
+		}
+		return TrinaryLogic::createNo();
+	}
+
 }

src/Reflection/Php/ClosureCallMethodReflection.php

@@ -202,4 +202,9 @@ public function getAttributes(): array
 		return $this->nativeMethodReflection->getAttributes();
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		return $this->nativeMethodReflection->hasNoDiscardAttribute();
+	}
+
 }

src/Reflection/Php/EnumCasesMethodReflection.php

@@ -161,4 +161,9 @@ public function getAttributes(): array
 		return [];
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		return TrinaryLogic::createYes();
+	}
+
 }

src/Reflection/Php/ExitFunctionReflection.php

@@ -143,4 +143,9 @@ public function getAttributes(): array
 		return [];
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		return TrinaryLogic::createNo();
+	}
+
 }

src/Reflection/Php/PhpFunctionFromParserNodeReflection.php

@@ -330,4 +330,14 @@ public function getAttributes(): array
 		return $this->attributes;
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		foreach ($this->attributes as $attrib) {
+			if ($attrib->getName() === 'NoDiscard') {
+				return TrinaryLogic::createYes();
+			}
+		}
+		return TrinaryLogic::createNo();
+	}
+
 }

src/Reflection/Php/PhpFunctionReflection.php

@@ -275,4 +275,14 @@ public function getAttributes(): array
 		return $this->attributes;
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		foreach ($this->attributes as $attrib) {
+			if ($attrib->getName() === 'NoDiscard') {
+				return TrinaryLogic::createYes();
+			}
+		}
+		return TrinaryLogic::createNo();
+	}
+
 }

src/Reflection/Php/PhpMethodReflection.php

@@ -520,4 +520,14 @@ public function getAttributes(): array
 		return $this->attributes;
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		foreach ($this->attributes as $attrib) {
+			if ($attrib->getName() === 'NoDiscard') {
+				return TrinaryLogic::createYes();
+			}
+		}
+		return TrinaryLogic::createNo();
+	}
+
 }

src/Reflection/ResolvedMethodReflection.php

@@ -229,4 +229,9 @@ public function getAttributes(): array
 		return $this->reflection->getAttributes();
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		return $this->reflection->hasNoDiscardAttribute();
+	}
+
 }

src/Reflection/Type/IntersectionTypeMethodReflection.php

@@ -228,4 +228,9 @@ public function getAttributes(): array
 		return $this->methods[0]->getAttributes();
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		return TrinaryLogic::lazyMaxMin($this->methods, static fn (ExtendedMethodReflection $method): TrinaryLogic => $method->hasNoDiscardAttribute());
+	}
+
 }

src/Reflection/Type/UnionTypeMethodReflection.php

@@ -205,4 +205,9 @@ public function getAttributes(): array
 		return $this->methods[0]->getAttributes();
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		return TrinaryLogic::lazyExtremeIdentity($this->methods, static fn (ExtendedMethodReflection $method): TrinaryLogic => $method->hasNoDiscardAttribute());
+	}
+
 }

src/Reflection/WrappedExtendedMethodReflection.php

@@ -173,4 +173,10 @@ public function getAttributes(): array
 		return [];
 	}
 
+	public function hasNoDiscardAttribute(): TrinaryLogic
+	{
+		// Align with the getAttributes() returning empty
+		return TrinaryLogic::createNo();
+	}
+
 }

src/Rules/AttributesCheck.php

@@ -40,6 +40,7 @@ public function check(
 		array $attrGroups,
 		int $requiredTarget,
 		string $targetName,
+		bool $isPropertyHook = false,
 	): array
 	{
 		$errors = [];
@@ -81,6 +82,12 @@ public function check(
 						->identifier('attribute.target')
 						->line($attribute->getStartLine())
 						->build();
+				} elseif ($isPropertyHook && strtolower($name) === 'nodiscard') {
+					// #[\NoDiscard] cannot be used on property hooks
+					$errors[] = RuleErrorBuilder::message(sprintf('Attribute class %s cannot be used on property hooks.', $name))
+						->identifier('attribute.target')
+						->line($attribute->getStartLine())
+						->build();
 				}
 
 				if (($flags & Attribute::IS_REPEATABLE) === 0) {

src/Rules/Cast/VoidCastRule.php

@@ -0,0 +1,41 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Cast;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\DependencyInjection\RegisteredRule;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+
+/**
+ * @implements Rule<Node\Expr\Cast\Void_>
+ */
+#[RegisteredRule(level: 0)]
+final class VoidCastRule implements Rule
+{
+
+	public function __construct()
+	{
+	}
+
+	public function getNodeType(): string
+	{
+		return Node\Expr\Cast\Void_::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if ($scope->isInFirstLevelStatement()) {
+			return [];
+		}
+
+		return [
+			RuleErrorBuilder::message('The (void) cast cannot be used within an expression.')
+				->identifier('cast.void')
+				->nonIgnorable()
+				->build(),
+		];
+	}
+
+}

src/Rules/Functions/CallToFunctionStatementWithNoDiscardRule.php

@@ -0,0 +1,58 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Functions;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\DependencyInjection\RegisteredRule;
+use PHPStan\Reflection\ReflectionProvider;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use function sprintf;
+
+/**
+ * @implements Rule<Node\Stmt\Expression>
+ */
+#[RegisteredRule(level: 4)]
+final class CallToFunctionStatementWithNoDiscardRule implements Rule
+{
+
+	public function __construct(private ReflectionProvider $reflectionProvider)
+	{
+	}
+
+	public function getNodeType(): string
+	{
+		return Node\Stmt\Expression::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if (!$node->expr instanceof Node\Expr\FuncCall) {
+			return [];
+		}
+
+		$funcCall = $node->expr;
+		if (!($funcCall->name instanceof Node\Name)) {
+			return [];
+		}
+
+		if (!$this->reflectionProvider->hasFunction($funcCall->name, $scope)) {
+			return [];
+		}
+
+		$function = $this->reflectionProvider->getFunction($funcCall->name, $scope);
+
+		if (!$function->hasNoDiscardAttribute()->yes()) {
+			return [];
+		}
+
+		return [
+			RuleErrorBuilder::message(sprintf(
+				'Call to function %s() on a separate line discards return value.',
+				$function->getName(),
+			))->identifier('function.resultDiscarded')->build(),
+		];
+	}
+
+}