diff --git a/lib/Less/Parser.php b/lib/Less/Parser.php
index 904af615..ef8a8164 100644
--- a/lib/Less/Parser.php
+++ b/lib/Less/Parser.php
@@ -1615,7 +1615,7 @@ private function parseUnicodeDescriptor() {
 	 *	 `window.location.href`
 	 *
 	 * @return Less_Tree_JavaScript|null
-	 * @see less-2.5.3.js#parsers.entities.javascript
+	 * @see less-3.13.1.js#parsers.entities.javascript
 	 */
 	private function parseEntitiesJavascript() {
 		// Optimization: Hardcode first char, to avoid save()/restore() overhead
@@ -1642,7 +1642,7 @@ private function parseEntitiesJavascript() {
 		$js = $this->matchReg( '/\\G[^`]*`/' );
 		if ( $js ) {
 			$this->forget();
-			return new Less_Tree_JavaScript( substr( $js, 0, -1 ), $index, $isEscaped );
+			return new Less_Tree_JavaScript( substr( $js, 0, -1 ), $isEscaped, $index );
 		}
 		$this->restore();
 	}
@@ -1764,7 +1764,9 @@ private function parseExtend( $isRule = false ) {
 	// namespaced, but we only support the child and descendant
 	// selector for now.
 	//
-	private function parseMixinCall( $inValue = false, $getLookup = false ) {
+	// @see less-3.13.1.js#parsers.mixin.call
+	//
+	private function parseMixinCall( $inValue, $getLookup = null ) {
 		$s = $this->input[$this->pos] ?? null;
 		$important = false;
 		$lookups = null;
@@ -2470,7 +2472,7 @@ private function parseDeclaration() {
 				if ( is_array( $name ) && array_key_exists( 0, $name ) // to satisfy phan
 					&& $name[0] instanceof Less_Tree_Keyword
 					&& $name[0]->value && strpos( $name[0]->value, '--' ) === 0 ) {
-					$value = $this->parsePermissiveValue( ';' );
+					$value = $this->parsePermissiveValue();
 				} else {
 					// Try to store values as anonymous
 					// If we need the value later we'll re-parse it in ruleset.parseValue
@@ -2489,7 +2491,7 @@ private function parseDeclaration() {
 				if ( $value ) {
 					$important = $this->parseImportant();
 				} elseif ( $isVariable ) {
-					$value = $this->parsePermissiveValue( ';' );
+					$value = $this->parsePermissiveValue();
 				}
 			}
 			if ( $value && ( $this->parseEnd() || $hasDR ) ) {
@@ -2527,7 +2529,6 @@ private function parseAnonymousValue() {
 	 * @param null|string|array $untilTokens
 	 */
 	private function parsePermissiveValue( $untilTokens = null ) {
-		$value = [];
 		$tok = $untilTokens ?? ';';
 		$index = $this->pos;
 		$result = [];
@@ -2545,6 +2546,8 @@ private function parsePermissiveValue( $untilTokens = null ) {
 		if ( $testCurrentChar( $this->input[$this->pos] ) ) {
 			return;
 		}
+
+		$value = [];
 		do {
 			$e = $this->parseComment();
 			if ( $e ) {
@@ -2574,7 +2577,7 @@ private function parsePermissiveValue( $untilTokens = null ) {
 
 		if ( $value ) {
 			if ( is_string( $value ) ) {
-				$this->error( "expected '" . $value . "'" );
+				$this->Error( "expected '" . $value . "'" );
 			}
 			if ( count( $value ) === 1 && $value[0] === ' ' ) {
 				$this->forget();
@@ -2849,19 +2852,19 @@ private function parseAtRule() {
 		if ( $hasIdentifier ) {
 			$value = $this->parseEntity();
 			if ( !$value ) {
-				$this->error( "expected " . $name . " identifier" );
+				$this->Error( "expected " . $name . " identifier" );
 			}
 		} elseif ( $hasExpression ) {
 			$value = $this->parseExpression();
 			if ( !$value ) {
-				$this->error( "expected " . $name . " expression" );
+				$this->Error( "expected " . $name . " expression" );
 			}
 		} elseif ( $hasUnknown ) {
 			$value = $this->parsePermissiveValue( [ '{', ';' ] );
 			$hasBlock = $this->input[$this->pos] === '{';
 			if ( !$value ) {
 				if ( !$hasBlock && $this->input[$this->pos] !== ';' ) {
-					$this->error( $name . " rule is missing block or ending semi-colon" );
+					$this->Error( $name . " rule is missing block or ending semi-colon" );
 				}
 			} elseif ( !$value->value ) {
 				$value = null;
diff --git a/lib/Less/Tree/Anonymous.php b/lib/Less/Tree/Anonymous.php
index f7235824..dc48cac2 100644
--- a/lib/Less/Tree/Anonymous.php
+++ b/lib/Less/Tree/Anonymous.php
@@ -39,18 +39,23 @@ public function compile( $env ) {
 	/**
 	 * @param Less_Tree|mixed $x
 	 * @return int|null
-	 * @see less-2.5.3.js#Anonymous.prototype.compare
+	 * @see less-3.13.1.js#Anonymous.prototype.compare
 	 */
 	public function compare( $x ) {
-		return ( is_object( $x ) && $this->toCSS() === $x->toCSS() ) ? 0 : null;
+		return ( $x instanceof Less_Tree && $this->toCSS() === $x->toCSS() ) ? 0 : null;
 	}
 
 	public function isRulesetLike() {
 		return $this->rulesetLike;
 	}
 
+	/**
+	 * @see less-3.13.1.js#Anonymous.prototype.genCSS
+	 */
 	public function genCSS( $output ) {
-		if ( $this->value !== "" && $this->value !== 0 ) {
+		// TODO: When we implement $visibilityInfo, store this result in-class
+		$nodeVisible = $this->value !== "" && $this->value !== 0;
+		if ( $nodeVisible ) {
 			$output->add( $this->value, $this->currentFileInfo, $this->index, $this->mapLines );
 		}
 	}
diff --git a/lib/Less/Tree/JavaScript.php b/lib/Less/Tree/JavaScript.php
index ff432c19..1bb1e8b4 100644
--- a/lib/Less/Tree/JavaScript.php
+++ b/lib/Less/Tree/JavaScript.php
@@ -1,6 +1,7 @@
 <?php
 /**
  * @private
+ * @see less-3.13.1.js#JavaScript.prototype
  */
 class Less_Tree_JavaScript extends Less_Tree {
 
@@ -10,10 +11,10 @@ class Less_Tree_JavaScript extends Less_Tree {
 
 	/**
 	 * @param string $string
-	 * @param int $index
 	 * @param bool $escaped
+	 * @param int $index
 	 */
-	public function __construct( $string, $index, $escaped ) {
+	public function __construct( $string, $escaped, $index ) {
 		$this->escaped = $escaped;
 		$this->expression = $string;
 		$this->index = $index;
diff --git a/lib/Less/Tree/NamespaceValue.php b/lib/Less/Tree/NamespaceValue.php
index 0559860a..1a7fc858 100644
--- a/lib/Less/Tree/NamespaceValue.php
+++ b/lib/Less/Tree/NamespaceValue.php
@@ -1,10 +1,11 @@
 <?php
 /**
  * @private
- * @see less-3.13.1.js#NamespaceValue
+ * @see less-3.13.1.js#NamespaceValue.prototype
  */
 class Less_Tree_NamespaceValue extends Less_Tree {
 
+	/** @var Less_Tree_Mixin_Call|Less_Tree_VariableCall */
 	public $value;
 	public $index;
 	public $lookups;