return type hint

example/hello_world.hyc

@@ -1,10 +1,10 @@
 // user defined function
-func foo :: (a, b) = {
-    return a;
+func foo :: (a, b) -> Bool = {
+    return a == b;
 };
 
 // entry point
-func main :: () = {
+func main :: () -> Int = {
     // if else in variable definition
     let cond_str :: String = if true { return "t" } else { return "f" };
 

src/front/lex.rs

@@ -32,6 +32,7 @@ syntax! { not_operator      , "!", Token::Not }
 
 // Punctuations
 syntax! { typehint_punctuation   , "::", Token::Typehint }
+syntax! { returnhint_punctuation , "->", Token::Return }
 syntax! { lparen_punctuation     , "(",  Token::LParen }
 syntax! { rparen_punctuation     , ")",  Token::RParen }
 syntax! { lbrace_punctuation     , "{",  Token::LBrace }
@@ -43,6 +44,11 @@ syntax! { comma_punctuation     , ",",  Token::Comma }
 // Operator & Punctuation
 fn lex_operator_punctuation(input: &Bytes) -> IResult<&Bytes, Token> {
     alt((
+        typehint_punctuation, returnhint_punctuation,
+        lparen_punctuation, rparen_punctuation,
+        lbrace_punctuation, rbrace_punctuation,
+        semicolon_punctuation, colon_punctuation, comma_punctuation,
+        
         equal_operator, not_equal_operator,
         less_than_operator, greater_than_operator,
         less_than_equal_operator, greater_than_equal_operator,
@@ -51,10 +57,6 @@ fn lex_operator_punctuation(input: &Bytes) -> IResult<&Bytes, Token> {
         add_operator, subtract_operator, multiply_operator, divide_operator,
         not_operator,
 
-        typehint_punctuation,
-        lparen_punctuation, rparen_punctuation,
-        lbrace_punctuation, rbrace_punctuation,
-        semicolon_punctuation, colon_punctuation, comma_punctuation,
     ))(input)
 }
 

src/front/model.rs

@@ -9,7 +9,7 @@ pub enum Token {
     Identifier(String), String(String),
     Int(i64), Bool(bool),
 
-    Assign, Typehint,
+    Assign, Typehint, Returnhint,
 
     Plus, Minus, Mul, Div, Not,
     Eq, NEq, Lt, Gt, Lte, Gte,
@@ -101,7 +101,7 @@ pub type Program = Vec<Stmt>;
 #[derive(Clone, Debug, PartialEq)]
 pub enum Stmt {
     Let(Ident, Ident, Expr),
-    Func(Ident, Vec<Ident>, Vec<Stmt>),
+    Func(Ident, Vec<Ident>, Ident, Vec<Stmt>),
     Call(Ident, Vec<Expr>),
     Return(Expr),
 }

src/front/parser.rs

@@ -31,6 +31,7 @@ tag_token!(tag_not, Token::Not);
 
 tag_token!(tag_assign, Token::Assign);
 tag_token!(tag_typehint, Token::Typehint);
+tag_token!(tag_returnhint, Token::Return);
 tag_token!(tag_semicolon, Token::Semicolon);
 tag_token!(tag_lparen, Token::LParen);
 tag_token!(tag_rparen, Token::RParen);
@@ -245,11 +246,13 @@ fn parse_func_stmt(input: Tokens) -> IResult<Tokens, Stmt> {
             tag_lparen,
             alt((parse_params, empty_params)),
             tag_rparen,
+            tag_returnhint,
+            parse_ident,
             tag_assign,
             parse_block_stmt,
             opt(tag_semicolon),
         )),
-        |(_, ident, _, _, params, _, _, block, _)| Stmt::Func(ident, params, block),
+        |(_, ident, _, _, params, _, _, returntype, _, block, _)| Stmt::Func(ident, params, returntype, block),
     )(input)
 }