Support constructor promotion (sirbrillig#266)

* Add test for constructor promotion

* Support constructor promotion in parameters

* Fix linting errors

* Add counterexample test of constructor promotion

* Turn off allowUnusedParametersBeforeUsed in ClassWithMembers test

* Fix token checks in isConstructorPromotion

Author: sirbrillig

Tests/VariableAnalysisSniff/VariableAnalysisTest.php

@@ -187,6 +187,11 @@ public function testClassWithMembersWarnings()
 	{
 		$fixtureFile = $this->getFixture('ClassWithMembersFixture.php');
 		$phpcsFile = $this->prepareLocalFileForSniffs($fixtureFile);
+		$phpcsFile->ruleset->setSniffProperty(
+			'VariableAnalysis\Sniffs\CodeAnalysis\VariableAnalysisSniff',
+			'allowUnusedParametersBeforeUsed',
+			'false'
+		);
 		$phpcsFile->process();
 		$lines = $this->getWarningLineNumbersFromFile($phpcsFile);
 		$expectedWarnings = [
@@ -202,6 +207,8 @@ public function testClassWithMembersWarnings()
 			18,
 			19,
 			66,
+			115,
+			116,
 		];
 		$this->assertSame($expectedWarnings, $lines);
 	}

Tests/VariableAnalysisSniff/fixtures/ClassWithMembersFixture.php

@@ -108,3 +108,18 @@ function method_with_static_assigned_var_inside_block() {
         }
     }
 }
+
+class ClassWithConstructorPromotion {
+  public function __construct(
+        public string $name = 'Brent',
+        $unused, // Unused variable $unused
+        string $unused2, // Unused variable $unused2
+        public string $role,
+        private string $role2,
+        protected string $role3,
+        public $nickname,
+        private $nickname2,
+        protected $nickname3
+  ) {
+  }
+}

VariableAnalysis/Lib/Helpers.php

@@ -1278,4 +1278,49 @@ public static function getForLoopForIncrementVariable($stackPtr, $forLoops)
 		}
 		return null;
 	}
+
+	/**
+	 * Return true if the token looks like constructor promotion.
+	 *
+	 * Call on a parameter variable token only.
+	 *
+	 * @param File $phpcsFile
+	 * @param int  $stackPtr
+	 *
+	 * @return bool
+	 */
+	public static function isConstructorPromotion(File $phpcsFile, $stackPtr)
+	{
+		$functionIndex = self::getFunctionIndexForFunctionParameter($phpcsFile, $stackPtr);
+		if (! $functionIndex) {
+			return false;
+		}
+
+		$tokens = $phpcsFile->getTokens();
+
+		// If the previous token is a visibility keyword, this is constructor
+		// promotion. eg: `public $foobar`.
+		$prev = $phpcsFile->findPrevious(Tokens::$emptyTokens, ($stackPtr - 1), $functionIndex, true);
+		if (! is_int($prev)) {
+			return false;
+		}
+		$prevToken = $tokens[$prev];
+		if (in_array($prevToken['code'], Tokens::$scopeModifiers, true)) {
+			return true;
+		}
+
+		// If the previous token is not a visibility keyword, but the one before it
+		// is, the previous token was probably a typehint and this is constructor
+		// promotion. eg: `public boolean $foobar`.
+		$prev = $phpcsFile->findPrevious(Tokens::$emptyTokens, ($prev - 1), $functionIndex, true);
+		if (! is_int($prev)) {
+			return false;
+		}
+		$prevToken = $tokens[$prev];
+		if (in_array($prevToken['code'], Tokens::$scopeModifiers, true)) {
+			return true;
+		}
+
+		return false;
+	}
 }

VariableAnalysis/Sniffs/CodeAnalysis/VariableAnalysisSniff.php

@@ -761,6 +761,12 @@ protected function processVariableAsFunctionParameter(File $phpcsFile, $stackPtr
 			Helpers::debug('processVariableAsFunctionParameter optional with default');
 			$this->markVariableAssignment($varName, $stackPtr, $functionPtr);
 		}
+
+		// Are we using constructor promotion? If so, that counts as both definition and use.
+		if (Helpers::isConstructorPromotion($phpcsFile, $stackPtr)) {
+			Helpers::debug('processVariableAsFunctionParameter constructor promotion');
+			$this->markVariableRead($varName, $stackPtr, $outerScope);
+		}
 	}
 
 	/**