assignment

src/parser.rs

@@ -21,6 +21,10 @@ pub enum Expr {
         right: Box<Expr>,
     },
     Variable(Token),
+    Assign {
+        name: Token,
+        value: Box<Expr>,
+    },
 }
 
 pub struct Parser {
@@ -66,7 +70,26 @@ impl Parser {
     }
 
     fn expression(&mut self) -> Result<Expr, MotError> {
-        self.equality()
+        self.assignment()
+    }
+
+    fn assignment(&mut self) -> Result<Expr, MotError> {
+        let expr = self.equality()?;
+
+        if self.match_token(&[TokenType::Equal]) {
+            let equals = self.previous().clone();
+            let value = self.assignment()?;
+
+            return match expr {
+                Expr::Variable(name) => Ok(Expr::Assign {
+                    name,
+                    value: Box::new(value),
+                }),
+                _ => return error!(equals.loc, "invalid assignment target"),
+            };
+        }
+
+        Ok(expr)
     }
 
     fn equality(&mut self) -> Result<Expr, MotError> {