Added some syntax

rustfmt.toml

@@ -1,2 +1,3 @@
 enum_discrim_align_threshold = 16
 struct_field_align_threshold = 16
+imports_granularity          = "one"

src/main.rs

@@ -3,15 +3,23 @@
 mod syntax;
 mod utils;
 
-use bumpalo::Bump;
-use std::io::{stdin, Read};
-use utils::default;
+use {
+    bumpalo::Bump,
+    std::io::{stdin, Read},
+    utils::default,
+};
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
     let mut buf = default();
     stdin().read_to_string(&mut buf)?;
 
     let arena = Bump::new();
-    println!("{:?}", syntax::parser::parse(&buf, &arena));
+    match syntax::parser::parse(&buf, &arena) {
+        Ok(ast) => println!("{ast:?}"),
+        Err(e) => {
+            eprintln!("[ERROR] {e:?}");
+            eprintln!("        Caused at: `{}`", &buf[e.span.start..e.span.end])
+        }
+    }
     Ok(())
 }

src/syntax/ast.rs

@@ -59,6 +59,7 @@ pub enum Expr<'a> {
     },
     Break(Option<ExprRef<'a>>),
     Return(Option<ExprRef<'a>>),
+    Uninit,
     Continue,
 }
 
@@ -68,10 +69,10 @@ pub enum Definition<'a> {
         kind:  DefKind,
         ident: Spanned<Ident>,
         ty:    Option<Spanned<Type>>,
-        init:  Option<ExprRef<'a>>,
+        init:  ExprRef<'a>,
     },
     Func {
-        ident:  Spanned<Ident>,
+        name:  Spanned<Ident>,
         params: &'a [(Spanned<Ident>, Spanned<Type>)],
         ret:    Spanned<Type>,
         body:   ExprList<'a>,

src/syntax/parser.rs

@@ -1,19 +1,43 @@
-use bumpalo::Bump;
-use logos::Logos;
-
-use super::{
-    ast::{Definition, Spanned},
+use {
+    super::{
+        ast::{DefKind, Definition, Expr, ExprList, Ident, Spanned, Type},
         token::Token,
+    },
+    crate::syntax::token::T,
+    bumpalo::{vec, Bump},
+    logos::Logos,
 };
 
 type Lexer<'a> = logos::Lexer<'a, Token>;
 
 macro_rules! extract {
+    ($self:expr, $pat:pat) => {
+        let $pat = $self.next()? else {
+            return Err($self.error(ErrorKind::UnexpectedToken));
+        };
+    };
+}
+
+macro_rules! let_until {
     (
         $self:expr,
-        $(pat:pat),* $(,)?
+        let $bind:pat,
+        until |$next:pat_param| $cond:expr,
+        $expr:expr
+        $(,)?
     ) => {
+        loop {
+            let $next = $self.next()?;
+            if $cond {
+                break;
+            }
 
+            let $bind = $self.next()? else {
+                return Err($self.error(ErrorKind::UnexpectedToken));
+            };
+
+            $expr;
+        }
     };
 }
 
@@ -39,16 +63,133 @@ impl<'a, 'l> Parser<'a, 'l> {
         Spanned::new(kind, self.lexer.span())
     }
 
+    /// Mark with current span
+    #[inline]
+    fn spanned<T>(&self, item: T) -> Spanned<T> {
+        Spanned::new(item, self.lexer.span())
+    }
+
+    /// Require a token to be
+    fn require(&mut self, token: Token) -> Result<()> {
+        if self.next()? != token {
+            Err(self.error(ErrorKind::UnexpectedToken))
+        } else {
+            Ok(())
+        }
+    }
+
     /// Parse everything or DIE!
-    fn run(self) -> Result<&'a [Definition<'a>]> {
+    fn run(mut self) -> Result<&'a [Definition<'a>]> {
+        let mut defs = vec![in self.arena];
+        loop {
+            match self.lexer.next() {
+                Some(Ok(Token::Func)) => {
+                    defs.push(self.func()?);
+                }
+                Some(Ok(Token::Const)) => defs.push(self.var_def(DefKind::Const)?),
+                Some(Ok(Token::Var)) => defs.push(self.var_def(DefKind::Var)?),
+                Some(Ok(_)) => return Err(self.error(ErrorKind::UnexpectedToken)),
+                Some(Err(())) => return Err(self.error(ErrorKind::InvalidToken)),
+                None => return Ok(defs.into_bump_slice()),
+            }
+        }
+    }
+
+    fn ident(&mut self) -> Result<Spanned<Ident>> {
+        extract!(self, Token::Ident(id));
+        Ok(self.spanned(id))
+    }
+
+    fn ty(&mut self) -> Result<Spanned<Type>> {
+        extract!(self, Token::Ident(id));
+        Ok(self.spanned(Type::Ident(id)))
+    }
+
+    fn block(&mut self) -> Result<ExprList<'a>> {
+        self.require(T!["{"])?;
+        // TODO
+        self.require(T!["}"])?;
+
         Ok(self.arena.alloc_slice_copy(&[]))
     }
+
+    fn var_def(&mut self, kind: DefKind) -> Result<Definition<'a>> {
+        // <kind> <ident> [: <ty>] = <expr>;
+        // ^^^^^^
+
+        extract!(self, Token::Ident(id));
+        let ident = self.spanned(id);
+
+        let ty = match self.next()? {
+            Token::Colon => {
+                let r = Some(self.ty()?);
+                self.require(T!["="])?;
+                r
+            }
+            Token::Equ => None,
+            _ => return Err(self.error(ErrorKind::UnexpectedToken)),
+        };
+
+        self.require(T!["uninit"])?;
+        self.require(T![";"])?;
+
+        Ok(Definition::Binding {
+            kind,
+            ident,
+            ty,
+            init: self.arena.alloc(self.spanned(Expr::Uninit)),
+        })
+    }
+
+    fn func(&mut self) -> Result<Definition<'a>> {
+        // func <ident> ($(<ident>: <ty>),*) → <ty> { … }
+        // ^^^^
+
+        let name = self.ident()?;
+
+        // Parameter list
+        let mut params = vec![in self.arena];
+
+        self.require(T!["("])?;
+        let mut next = self.next()?;
+        if next != T![")"] {
+            loop {
+                let Token::Ident(id) = next else {
+                    return Err(self.error(ErrorKind::UnexpectedToken));
+                };
+
+                let id = self.spanned(id);
+                self.require(T![":"])?;
+                params.push((id, self.ty()?));
+
+                match self.next()? {
+                    Token::RightParen => break,
+                    Token::Comma => (),
+                    _ => return Err(self.error(ErrorKind::UnexpectedToken)),
+                }
+
+                next = self.next()?;
+            }
+        }
+
+        self.require(T!["→"])?;
+        let ret = self.ty()?;
+        let body = self.block()?;
+
+        Ok(Definition::Func {
+            name,
+            params: params.into_bump_slice(),
+            ret,
+            body,
+        })
+    }
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum ErrorKind {
     InvalidToken,
     UnexpectedEnd,
+    UnexpectedToken,
 }
 
 pub type Error = Spanned<ErrorKind>;

src/syntax/token.rs

@@ -35,6 +35,8 @@ macro_rules! token_def {
                 $($(
                     ($u_tok) => { $crate::syntax::token::Token::$u_name };
                 )*)*
+
+                $((~($kw)) => { $crate::syntax::token::Token::[<$kw:camel>] };)*
             }
         });
     };