Mise en place du visiteur et ébauche de pretty printer.

src/expr.rs

@@ -1,13 +1,13 @@
 use crate::token::Token;
 
 pub struct Binary {
-    left: Expr,
+    left: Box<Expr>,
     operator: Token,
-    right: Expr,
+    right: Box<Expr>,
 }
 
 pub struct Grouping {
-    expression: Expr,
+    expression: Box<Expr>,
 }
 
 pub enum Literal {
@@ -19,12 +19,58 @@ pub enum Literal {
 
 pub struct Unary {
     operator: Token,
-    right: Expr,
+    right: Box<Expr>,
 }
 
 pub enum Expr {
-    Binary ,
-    Grouping,
-    Literal,
-    Unary,
+    BinaryExpr(Binary),
+    GroupingExpr(Grouping),
+    LiteralExpr(Literal),
+    UnaryExpr(Unary),
+}
+
+pub trait Visitor {
+    fn visit(&self);
+}
+
+impl Visitor for Binary {
+    fn visit(&self) {
+        print!("( {}",&self.operator.literal);
+        &self.left.visit();
+        &self.right.visit();
+        print!(")");
+    }
+}
+
+impl Visitor for Grouping {
+    fn visit(&self) {
+        print!("( group ");
+        &self.expression.visit();
+        print!(")");
+    }
+}
+
+impl Visitor for Literal {
+    fn visit(&self) {
+        match &self {
+            Literal::LiteralNumber(i) => print!("{}", i),
+            Literal::LiteralString(s) => print!("{}", s),
+            Literal::LiteralBool(b) => print!("{}", b),
+            Literal::LiteralNil => print!("nil"),
+        }
+    }
+}
+
+impl Visitor for Unary {
+    fn visit(&self) {
+        print!("( {}",&self.operator.literal);
+        &self.right.visit();
+        print!(")");
+    }
+}
+
+impl Visitor for Expr {
+    fn visit(&self) {
+        &self.visit();
+    }
 }