remove java implementation, was merely a book copy

src/expression.rs

@@ -0,0 +1,54 @@
+use crate::token::{self, Token};
+
+/// Enumeration of all types of expressions.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum Expression {
+    Assign {
+        name: Token,
+        value: Box<Expression>,
+    },
+    Binary {
+        left: Box<Expression>,
+        operator: Token,
+        right: Box<Expression>,
+    },
+    Call {
+        callee: Box<Expression>,
+        paren: Token,
+        args: Vec<Expression>,
+    },
+    Get {
+        object: Box<Expression>,
+        name: Token,
+    },
+    Set {
+        object: Box<Expression>,
+        name: Token,
+        value: Box<Expression>,
+    },
+    This {
+        keyword: Token,
+    },
+    Grouping {
+        expression: Box<Expression>,
+    },
+    Literal {
+        value: token::Literal,
+    },
+    Logical {
+        left: Box<Expression>,
+        operator: Token,
+        right: Box<Expression>,
+    },
+    Unary {
+        operator: Token,
+        right: Box<Expression>,
+    },
+    Variable {
+        name: Token,
+    },
+    Super {
+        keyword: Token,
+        method: Token,
+    },
+}