From 193ea74aa24e59bd1eca7019dd817ab55b9ab9dd Mon Sep 17 00:00:00 2001
From: Garrit Franke <garritfranke@gmail.com>
Date: Sat, 5 Dec 2020 13:32:38 +0100
Subject: [PATCH] Allow empty returns

---
 examples/hello_world.sb |  2 +-
 src/parser/mod.rs       | 11 ++++++++++-
 src/parser/node_type.rs |  2 +-
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/examples/hello_world.sb b/examples/hello_world.sb
index 1221350..23e8dbd 100644
--- a/examples/hello_world.sb
+++ b/examples/hello_world.sb
@@ -1,6 +1,6 @@
 fn main() {
     let x = "Hello World";
-    return x;
+    return;
 }
 
 fn fib() {}
\ No newline at end of file
diff --git a/src/parser/mod.rs b/src/parser/mod.rs
index 7918d13..7940acf 100644
--- a/src/parser/mod.rs
+++ b/src/parser/mod.rs
@@ -169,7 +169,7 @@ impl Parser {
                 state
             }
             TokenKind::Keyword(Keyword::Return) => {
-                let state = Statement::Return(self.parse_expression()?);
+                let state = self.parse_return()?;
                 self.match_token(TokenKind::SemiColon)?;
 
                 Ok(state)
@@ -178,6 +178,15 @@ impl Parser {
         }
     }
 
+    fn parse_return(&mut self) -> Result<Statement, String> {
+        // TODO: Replace unwrap with make_error
+        let peeked = self.peek().unwrap();
+        match peeked.kind {
+            TokenKind::SemiColon => Ok(Statement::Return(None)),
+            _ => Ok(Statement::Return(Some(self.parse_expression()?))),
+        }
+    }
+
     fn parse_expression(&mut self) -> Result<Expression, String> {
         let token = self.next_token();
         match token.kind {
diff --git a/src/parser/node_type.rs b/src/parser/node_type.rs
index 2c544a9..008898d 100644
--- a/src/parser/node_type.rs
+++ b/src/parser/node_type.rs
@@ -19,7 +19,7 @@ pub struct Variable {
 #[derive(Debug, Eq, PartialEq)]
 pub enum Statement {
     Declare(Variable, Option<Expression>),
-    Return(Expression),
+    Return(Option<Expression>),
     If(Expression, Box<Statement>, Option<Box<Statement>>),
     While(Expression, Box<Statement>),
     Exp(Expression),