First collector rule: NotAnalysedTraitRule

conf/bleedingEdge.neon

@@ -17,3 +17,4 @@ parameters:
 		readOnlyByPhpDoc: true
 		phpDocParserRequireWhitespaceBeforeDescription: true
 		runtimeReflectionRules: true
+		notAnalysedTrait: true

conf/config.level4.neon

@@ -22,6 +22,12 @@ rules:
 conditionalTags:
 	PHPStan\Rules\Comparison\ConstantLooseComparisonRule:
 		phpstan.rules.rule: %featureToggles.looseComparison%
+	PHPStan\Rules\Traits\TraitDeclarationCollector:
+		phpstan.collector: %featureToggles.notAnalysedTrait%
+	PHPStan\Rules\Traits\TraitUseCollector:
+		phpstan.collector: %featureToggles.notAnalysedTrait%
+	PHPStan\Rules\Traits\NotAnalysedTraitRule:
+		phpstan.rules.rule: %featureToggles.notAnalysedTrait%
 
 parameters:
 	checkAdvancedIsset: true
@@ -175,3 +181,12 @@ services:
 		class: PHPStan\Rules\Properties\NullsafePropertyFetchRule
 		tags:
 			- phpstan.rules.rule
+
+	-
+		class: PHPStan\Rules\Traits\TraitDeclarationCollector
+
+	-
+		class: PHPStan\Rules\Traits\TraitUseCollector
+
+	-
+		class: PHPStan\Rules\Traits\NotAnalysedTraitRule

conf/config.neon

@@ -47,6 +47,7 @@ parameters:
 		readOnlyByPhpDoc: false
 		phpDocParserRequireWhitespaceBeforeDescription: false
 		runtimeReflectionRules: false
+		notAnalysedTrait: false
 	fileExtensions:
 		- php
 	checkAdvancedIsset: false
@@ -251,6 +252,7 @@ parametersSchema:
 		readOnlyByPhpDoc: bool()
 		phpDocParserRequireWhitespaceBeforeDescription: bool()
 		runtimeReflectionRules: bool()
+		notAnalysedTrait: bool()
 	])
 	fileExtensions: listOf(string())
 	checkAdvancedIsset: bool()

src/Rules/Traits/NotAnalysedTraitRule.php

@@ -0,0 +1,55 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Traits;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Node\CollectedDataNode;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use function sprintf;
+use function strtolower;
+
+/**
+ * @implements Rule<CollectedDataNode>
+ */
+class NotAnalysedTraitRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return CollectedDataNode::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		$traitDeclarationData = $node->get(TraitDeclarationCollector::class);
+		$traitUseData = $node->get(TraitUseCollector::class);
+
+		$declaredTraits = [];
+		foreach ($traitDeclarationData as $file => $declaration) {
+			foreach ($declaration as [$name, $line]) {
+				$declaredTraits[strtolower($name)] = [$file, $name, $line];
+			}
+		}
+
+		foreach ($traitUseData as $usedNamesData) {
+			foreach ($usedNamesData as $usedNames) {
+				foreach ($usedNames as $usedName) {
+					unset($declaredTraits[strtolower($usedName)]);
+				}
+			}
+		}
+
+		$errors = [];
+		foreach ($declaredTraits as [$file, $name, $line]) {
+			$errors[] = RuleErrorBuilder::message(sprintf(
+				'Trait %s is used zero times and is not analysed.',
+				$name,
+			))->file($file)->line($line)->build();
+		}
+
+		return $errors;
+	}
+
+}

src/Rules/Traits/TraitDeclarationCollector.php

@@ -0,0 +1,29 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Traits;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Collectors\Collector;
+
+/**
+ * @implements Collector<Node\Stmt\Trait_, array{string, int}>
+ */
+class TraitDeclarationCollector implements Collector
+{
+
+	public function getNodeType(): string
+	{
+		return Node\Stmt\Trait_::class;
+	}
+
+	public function processNode(Node $node, Scope $scope)
+	{
+		if ($node->namespacedName === null) {
+			return null;
+		}
+
+		return [$node->namespacedName->toString(), $node->getLine()];
+	}
+
+}

src/Rules/Traits/TraitUseCollector.php

@@ -0,0 +1,26 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Traits;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Collectors\Collector;
+use function array_map;
+
+/**
+ * @implements Collector<Node\Stmt\TraitUse, list<int, string>>
+ */
+class TraitUseCollector implements Collector
+{
+
+	public function getNodeType(): string
+	{
+		return Node\Stmt\TraitUse::class;
+	}
+
+	public function processNode(Node $node, Scope $scope)
+	{
+		return array_map(static fn (Node\Name $traitName) => $traitName->toString(), $node->traits);
+	}
+
+}

tests/PHPStan/Rules/Traits/NotAnalysedTraitRuleTest.php

@@ -0,0 +1,37 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Traits;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<NotAnalysedTraitRule>
+ */
+class NotAnalysedTraitRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new NotAnalysedTraitRule();
+	}
+
+	protected function getCollectors(): array
+	{
+		return [
+			new TraitDeclarationCollector(),
+			new TraitUseCollector(),
+		];
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/not-analysed-trait.php'], [
+			[
+				'Trait NotAnalysedTrait\Bar is used zero times and is not analysed.',
+				10,
+			],
+		]);
+	}
+
+}

tests/PHPStan/Rules/Traits/data/not-analysed-trait.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace NotAnalysedTrait;
+
+trait Foo
+{
+
+}
+
+trait Bar
+{
+
+}
+
+class UsesFoo
+{
+
+	use Foo;
+
+}