impl interpret block return

src/ast/types.rs

@@ -33,7 +33,6 @@ pub enum Expr {
     },
     Continue,
     Break,
-    Return(Box<Expr>),
     */
 }
 
@@ -203,6 +202,8 @@ impl Record {
     }
 }
 
+pub const UNIT: Expr = Expr::Value(Value::Record(Record(BTreeMap::new())));
+
 #[derive(PartialEq, Debug, thiserror::Error)]
 pub enum Error {
     #[error("Label not found: {0:?}")]

src/interpret/interpret.rs

@@ -27,19 +27,27 @@ pub fn run(
     Ok(result)
 }
 
+enum StatementResult {
+    Result(ast::Value),
+    Return(ast::Value),
+}
+
 fn eval_statement(
     expr_env: &mut Env,
     state: &mut State,
     statement: &ast::Statement,
-) -> Result<ast::Value, Error> {
+) -> Result<StatementResult, Error> {
     match statement {
-        ast::Statement::Expr(expr) => eval_expr(expr_env, state, expr),
+        ast::Statement::Expr(expr) => eval_expr(expr_env, state, expr).map(StatementResult::Result),
         ast::Statement::Let(ast::Definition { name, expr }) => {
             let result = eval_expr(expr_env, state, expr)?;
             expr_env.insert(name.clone(), result.clone());
-            Ok(result)
+            Ok(StatementResult::Result(result))
         }
-        ast::Statement::Return(_) => todo!(),
+        ast::Statement::Return(expr) => match expr {
+            Some(expr) => eval_expr(expr_env, state, expr).map(StatementResult::Return),
+            None => eval_expr(expr_env, state, &ast::UNIT).map(StatementResult::Return),
+        },
     }
 }
 
@@ -70,7 +78,14 @@ fn eval_expr(expr_env: &Env, state: &mut State, expr: &ast::Expr) -> Result<ast:
             let mut block_env = expr_env.clone();
             if let Some(last) = statements.iter().try_fold(None, |_, statement| {
                 let result = eval_statement(&mut block_env, state, statement)?;
-                Ok::<Option<ast::Value>, Error>(Some(result))
+                match result {
+                    StatementResult::Result(result) => {
+                        Ok::<Option<ast::Value>, Error>(Some(result))
+                    }
+                    StatementResult::Return(result) => {
+                        return Ok::<Option<ast::Value>, Error>(Some(result));
+                    }
+                }
             })? {
                 Ok(last)
             } else {