parser: support variable variables

trunk_parser/src/parser/mod.rs

@@ -1933,7 +1933,7 @@ impl Parser {
             TokenKind::Dollar => {
                 self.next();
 
-                match self.current.kind {
+                match &self.current.kind {
                     TokenKind::LeftBrace => {
                         self.next();
 
@@ -1945,6 +1945,15 @@ impl Parser {
                             name: Box::new(name),
                         }
                     }
+                    TokenKind::Variable(variable) => {
+                        let variable = variable.clone();
+
+                        self.next();
+
+                        Expression::DynamicVariable {
+                            name: Box::new(Expression::Variable { name: variable }),
+                        }
+                    }
                     _ => todo!(),
                 }
             }
@@ -4240,6 +4249,16 @@ mod tests {
         );
     }
 
+    #[test]
+    fn variable_variables() {
+        assert_ast(
+            "<?php $$a;",
+            &[expr!(Expression::DynamicVariable {
+                name: Box::new(Expression::Variable { name: "a".into() })
+            })],
+        );
+    }
+
     fn assert_ast(source: &str, expected: &[Statement]) {
         let mut lexer = Lexer::new(None);
         let tokens = lexer.tokenize(source).unwrap();