Prepare for proper type inference

src/main.rs

@@ -1,6 +1,6 @@
 use ariadne::{sources, Color, Label, Report, ReportKind};
 use chumsky::{Parser, prelude::Input};
-use self::{parse::parser::{lexer, exprs_parser}, typing::check::check};
+use self::{parse::parser::{lexer, exprs_parser}};
 
 pub mod parse;
 pub mod typing;
@@ -8,11 +8,10 @@ pub mod typing;
 fn main() {
     let src = "
             {
-                let foo : num =
+                let foo =
-                    let a : num = true,
+                    let a = true in
-                        b : num = 3
+                        let b = false in
-                    in
+                            a + b;
-                        a + b;
                 foo * 2
             }
         ".to_string();
@@ -27,34 +26,7 @@ fn main() {
             .into_output_errors();
 
         if let Some(ast) = ast.filter(|_| errs.len() + parse_errs.len() == 0) {
-            match check(ast.0) {
+            println!("{:?}", ast);
-                Ok(tast) => println!("{:?}", tast),
-                Err(ty_err) => {
-                    let mut r = Report::build(ReportKind::Error, filename.clone(), ty_err.loc.start)
-                        .with_message(ty_err.msg)
-                        .with_label(Label::new((filename.clone(), ty_err.loc.into_range()))
-                        .with_message(match ty_err.note {
-                            Some(note) => note,
-                            None => "While type checking this expression".to_string(),
-                        })
-                        .with_color(Color::Red)
-                    );
-
-                    if let Some((hint, loc)) = ty_err.hint {
-                        r = r.with_label(Label::new((filename.clone(), loc.into_range()))
-                            .with_message(hint)
-                            .with_color(Color::Yellow),
-                        );
-                    }
-
-                    r.finish()
-                        .print(sources([(
-                            filename.clone(),
-                            src.clone(),
-                        )]))
-                        .unwrap();
-                }
-            }
         }
 
         parse_errs

src/parse/parser.rs

@@ -178,8 +178,6 @@ pub enum BinaryOp {
 }
 
 pub type Spanned<T> = (T, Span);
-type Binding<'src> =
-    (&'src str, Option<Type>, Spanned<Box<Expr<'src>>>);
 
 // Clone is needed for type checking since the type checking
 // algorithm is recursive and sometimes consume the AST.
@@ -200,10 +198,16 @@ pub enum Expr<'src> {
         f: Spanned<Box<Self>>,
     },
     Let {
-        bindings: Vec<Binding<'src>>,
+        name: &'src str,
+        ty: Option<Type>,
+        value: Spanned<Box<Self>>,
         body: Spanned<Box<Self>>,
     },
-    Assign(Vec<Binding<'src>>),
+    Define {
+        name: &'src str,
+        ty: Option<Type>,
+        value: Spanned<Box<Self>>,
+    },
     Block {
         exprs: Vec<Spanned<Box<Self>>>,
         void: bool, // True if last expression is discarded (ends with semicolon).
@@ -268,8 +272,8 @@ pub fn expr_parser<'tokens, 'src: 'tokens>() -> impl Parser<
             .then(expr.clone())
             .map(|(args, body)| Expr::Lambda(args, boxspan(body)));
 
-        // (ident (: type)?)*
+        // ident (: type)?
-        let binds = symbol
+        let bind = symbol
             .then(
                 just(Token::Colon)
                     .ignore_then(type_parser())
@@ -277,21 +281,18 @@ pub fn expr_parser<'tokens, 'src: 'tokens>() -> impl Parser<
             )
             .then_ignore(just(Token::Assign))
             .then(expr.clone())
-            .map(|((name, ty), expr)| (name, ty, boxspan(expr)))
+            .map(|((name, ty), expr)| (name, ty, boxspan(expr)));
-            .separated_by(just(Token::Comma))
-            .allow_trailing()
-            .collect::<Vec<_>>();
 
-        let let_or_assign = just(Token::Let)
+        let let_or_define = just(Token::Let)
-            .ignore_then(binds)
+            .ignore_then(bind)
             .then(
                 just(Token::In)
                     .ignore_then(expr.clone())
                     .or_not()
             )
-            .map(|(bindings, body)| match body {
+            .map(|((name, ty, expr), body)| match body {
-                Some(body) => Expr::Let { bindings, body: boxspan(body) },
+                Some(body) => Expr::Let { name, ty, value: expr, body: boxspan(body) },
-                None => Expr::Assign(bindings),
+                None => Expr::Define { name, ty, value: expr },
             });
 
         let if_ = just(Token::If)
@@ -333,7 +334,7 @@ pub fn expr_parser<'tokens, 'src: 'tokens>() -> impl Parser<
             .or(ident)
             .or(paren_expr)
             .or(lambda)
-            .or(let_or_assign)
+            .or(let_or_define)
             .or(if_)
             .or(block)
             .map_with_span(|e, s| (e, s))

src/typing/check.rs

@@ -1,425 +0,0 @@
-use crate::parse::parser::{
-    Span, Spanned,
-    UnaryOp, BinaryOp, Lit, Expr,
-};
-use super::{ty::Type, typed::TExpr};
-
-#[derive(Clone, Debug)]
-struct TypeContext<'src> {
-    bindings: Vec<(&'src str, Type)>,
-    funcs: Vec<(&'src str, Vec<Type>, Type)>,
-}
-
-impl<'src> TypeContext<'src> {
-    fn new() -> Self {
-        Self {
-            bindings: Vec::new(),
-            funcs: Vec::new(),
-        }
-    }
-
-    /// Bind a type to a name.
-    fn bind(&mut self, name: &'src str, ty: Type) {
-        self.bindings.push((name, ty));
-    }
-
-    /// Bind a function (parameters and return type) to a name.
-    fn bind_func(&mut self, name: &'src str, args: Vec<Type>, ret_ty: Type) {
-        self.funcs.push((name, args, ret_ty));
-    }
-
-    fn lookup(&self, name: &str) -> Option<Type> {
-        self.bindings.iter()
-            .rev()
-            .find(|(n, _)| *n == name)
-            .map(|(_, t)| t.clone())
-    }
-
-    fn lookup_func(&self, name: &str) -> Option<(Vec<Type>, Type)> {
-        self.funcs.iter()
-            .rev()
-            .find(|(n, _, _)| *n == name)
-            .map(|(_, args, ret_ty)| (args.clone(), ret_ty.clone()))
-    }
-}
-
-#[derive(Debug)]
-pub struct TypeError {
-    pub msg: String,
-    pub note: Option<String>,
-    pub hint: Option<(String, Span)>,
-    pub loc: Span,
-}
-
-impl TypeError {
-    fn new(msg: String, loc: Span) -> Self {
-        Self {
-            msg,
-            note: None,
-            hint: None,
-            loc,
-        }
-    }
-
-    fn with_note(mut self, note: String) -> Self {
-        self.note = Some(note);
-        self
-    }
-
-    fn with_hint(mut self, hint: String, loc: Span) -> Self {
-        self.hint = Some((hint, loc));
-        self
-    }
-}
-
-fn type_expr<'src>(
-    env: &mut TypeContext<'src>, expr: Spanned<Expr<'src>>
-) -> Result<Spanned<TExpr<'src>>, TypeError> {
-    macro_rules! oks { // Spanned Ok macro.
-        ($e:expr $(,)?) => {
-            Ok(($e, expr.1))
-        };
-    }
-    macro_rules! unbox { // Unbox a Spanned<Box<T>> into a Spanned<T>.
-        ($e:expr) => {
-            (*$e.0, $e.1)
-        };
-    }
-    macro_rules! sbox { // Box the first value of a Spanned<T>.
-        ($e:expr) => {
-            (Box::new($e.0), $e.1)
-        };
-    }
-
-    match expr.0 {
-        Expr::Lit(lit) => match lit {
-            Lit::Unit    => oks!(TExpr::Lit(Lit::Unit)),
-            Lit::Bool(x) => oks!(TExpr::Lit(Lit::Bool(x))),
-            Lit::Num(x)  => oks!(TExpr::Lit(Lit::Num(x))),
-            Lit::Str(x)  => oks!(TExpr::Lit(Lit::Str(x))),
-        }
-
-        Expr::Ident(name) => {
-            let ty = env.lookup(name)
-                .ok_or(TypeError::new(format!("Unknown identifier `{}`", name), expr.1))?;
-            oks!(TExpr::Ident(name, ty))
-        }
-
-        Expr::Unary(op, e) => {
-            let te = type_expr(env, unbox!(e))?;
-            let ret_ty = match op {
-                UnaryOp::Neg => Type::Num,
-                UnaryOp::Not => Type::Bool,
-            };
-
-            if te.0.ty() != &ret_ty {
-                return Err(TypeError::new(format!("Expected `{}` but found `{}`", ret_ty, te.0.ty()), te.1)
-                    .with_note(format!("This have type `{}`", te.0.ty()))
-                    .with_hint(format!("This operator requires a `{}`", ret_ty), (te.1.start-1..te.1.start).into()));
-            }
-
-            oks!(TExpr::Unary {
-                op,
-                expr: sbox!(te),
-                ret_ty,
-            })
-        }
-
-        Expr::Binary(op, lhs, rhs) => {
-            let tlhs = type_expr(env, unbox!(lhs))?;
-            let trhs = type_expr(env, unbox!(rhs))?;
-            let op_ty = match op {
-                BinaryOp::Add
-                | BinaryOp::Sub
-                | BinaryOp::Mul
-                | BinaryOp::Div
-                | BinaryOp::Rem => Some(Type::Num),
-                BinaryOp::And
-                | BinaryOp::Or => Some(Type::Bool),
-                BinaryOp::Eq
-                | BinaryOp::Ne
-                | BinaryOp::Lt
-                | BinaryOp::Le
-                | BinaryOp::Gt
-                | BinaryOp::Ge => None,
-            };
-
-            let ret_ty;
-            if let Some(op_ty) = op_ty {
-                if tlhs.0.ty() != &op_ty {
-                    return Err(TypeError::new(format!("Expected `{}` but found `{}`", op_ty, tlhs.0.ty()), tlhs.1)
-                        .with_note(format!("This have type `{}`", tlhs.0.ty()))
-                        .with_hint(format!("This operator requires a `{}`", op_ty), (tlhs.1.start-1..tlhs.1.start).into()));
-                }
-                if trhs.0.ty() != &op_ty {
-                    return Err(TypeError::new(format!("Expected `{}` but found `{}`", op_ty, trhs.0.ty()), trhs.1)
-                        .with_note(format!("This have type `{}`", trhs.0.ty()))
-                        .with_hint(format!("This operator requires a `{}`", op_ty), (trhs.1.start-1..trhs.1.start).into()));
-                }
-                ret_ty = op_ty;
-            } else {
-                if tlhs.0.ty() != trhs.0.ty() {
-                    return Err(TypeError::new(format!("Expected `{}` but found `{}`", tlhs.0.ty(), trhs.0.ty()), trhs.1)
-                        .with_hint(
-                            format!("Both have to be the same type. Got `{}` and `{}`", tlhs.0.ty(), trhs.0.ty()),
-                            (tlhs.1.start..trhs.1.end).into(),
-                        ));
-                }
-                ret_ty = Type::Bool;
-            }
-
-            oks!(TExpr::Binary {
-                op,
-                lhs: sbox!(tlhs),
-                rhs: sbox!(trhs),
-                ret_ty,
-            })
-        }
-
-        Expr::Lambda(args, body) => {
-            // Create a new type environment.
-            let mut new_env = env.clone();
-
-            // Bind the arguments to the new environment.
-            let mut arg_tys = Vec::new();
-            for (arg, maybe_ty) in args {
-                let ty = match maybe_ty {
-                    Some(ty) => ty,
-                    None => todo!(), // TODO: infer the type of the argument after type checking the body.
-                };
-                arg_tys.push((arg, ty.clone()));
-                new_env.bind(arg, ty);
-            }
-
-            // Type check the body.
-            let tbody = type_expr(&mut new_env, unbox!(body))?;
-
-            // Return the typed lambda expression.
-            oks!(TExpr::Lambda {
-                params: arg_tys,
-                body: sbox!(tbody.clone()),
-                ret_ty: tbody.0.ty().clone(),
-            })
-        }
-
-        Expr::Call(func, cargs) => {
-            // Get span of the arguments.
-            let args_span = cargs.iter()
-                .map(|arg| arg.1.into_range())
-                .fold(None, |acc: Option<std::ops::Range<usize>>, range| match acc {
-                    Some(acc) => Some(acc.start..range.end),
-                    None => Some(range),
-                })
-                .unwrap_or(func.1.end..func.1.end+2);
-
-            // Type check the arguments.
-            let mut targs = Vec::new();
-            for arg in cargs {
-                let targ = type_expr(env, arg)?;
-                targs.push(targ);
-            }
-
-            // Type check the function (callee).
-            let tfunc = type_expr(env, unbox!(func))?;
-
-            // Get the function type of the callee. (if any).
-            if let Some((param_tys, ret_ty)) = tfunc.0.clone().as_fn() {
-
-                // Check if the number of arguments match the number of parameters.
-                if param_tys.len() != targs.len() {
-                    return Err(TypeError::new(
-                        format!(
-                            "Expected {} arguments, got {}",
-                            param_tys.len(),
-                            targs.len(),
-                        ),
-                        args_span.into(),
-                    ).with_note(format!(
-                        "Expected {} arguments",
-                        param_tys.len(),
-                    )).with_hint(
-                        format!(
-                            "This expect arguments of type `{}`",
-                            param_tys.iter().map(|ty| ty.to_string()).collect::<Vec<_>>().join(", ")
-                        ),
-                        func.1,
-                    ));
-                }
-
-                // Check if the types of the arguments match the types of the parameters.
-                for (arg, param) in targs.iter().zip(param_tys.iter()) {
-                    if arg.0.ty() != param {
-                        return Err(TypeError::new(
-                            format!(
-                                "Expected argument of type `{}`, got `{}`",
-                                param,
-                                arg.0.ty(),
-                            ),
-                            arg.1,
-                        ).with_note(format!(
-                            "Expected argument of type `{}`",
-                            param,
-                        )));
-                    }
-                }
-
-                // Return the typed call expression.
-                oks!(TExpr::Call {
-                    func: sbox!(tfunc),
-                    args: targs,
-                    ret_ty,
-                })
-            } else {
-                Err(TypeError::new(
-                    format!("Expected function, got `{}`", tfunc.0.ty()),
-                    tfunc.1,
-                ))
-            }
-        }
-
-        Expr::If { cond, t, f } => {
-            let tcond = type_expr(env, unbox!(cond))?;
-            let tt = type_expr(env, unbox!(t))?;
-            let tf = type_expr(env, unbox!(f))?;
-
-            // Check if the condition is of type `bool`.
-            if tcond.0.ty() != &Type::Bool {
-                return Err(TypeError::new(
-                    format!("Expected condition of type `bool`, got `{}`", tcond.0.ty()),
-                    tcond.1,
-                ));
-            }
-
-            // Check if the true and false branches have the same type.
-            if tt.0.ty() != tf.0.ty() {
-                return Err(TypeError::new(
-                    format!(
-                        "Expected the branches to have the same type, got `{}` and `{}`",
-                        tt.0.ty(),
-                        tf.0.ty(),
-                    ),
-                    tf.1,
-                ).with_note(format!(
-                    "Expected this branch to be type of `{}`",
-                    tt.0.ty(),
-                )));
-            }
-
-            oks!(TExpr::If {
-                cond: sbox!(tcond),
-                br_ty: tt.0.ty().clone(),
-                t: sbox!(tt),
-                f: sbox!(tf),
-            })
-        }
-
-        Expr::Let { bindings, body } => {
-            // Create a new type environment.
-            let mut new_env = env.clone();
-
-            // Type check the bindings.
-            let mut tbindings = Vec::new();
-            for (name, maybe_ty, expr) in bindings {
-                let ty = match maybe_ty {
-                    Some(ty) => ty,
-                    None => todo!("Type inferrence"), // TODO: infer.
-                };
-                let texpr = type_expr(&mut new_env, unbox!(expr))?;
-
-                // Check if the type of the binding matches the type of the expression.
-                if texpr.0.ty() != &ty {
-                    return Err(TypeError::new(
-                        format!(
-                            "Expected the value to be of type `{}`, got `{}`",
-                            ty,
-                            texpr.0.ty(),
-                        ),
-                        texpr.1,
-                    ).with_note(format!(
-                        "Expected this value to be of type `{}`",
-                        ty,
-                    )));
-                }
-
-                tbindings.push((name, ty.clone(), sbox!(texpr)));
-                new_env.bind(name, ty);
-            }
-
-            // Type check the body.
-            let tbody = type_expr(&mut new_env, unbox!(body))?;
-
-            // Return the typed let expression.
-            oks!(TExpr::Let {
-                bindings: tbindings,
-                body: sbox!(tbody),
-            })
-        }
-
-        Expr::Assign(bindings) => {
-            // Type check the bindings.
-            let mut tbindings = Vec::new();
-            for (name, maybe_ty, expr) in bindings {
-                let ty = match maybe_ty {
-                    Some(ty) => ty,
-                    None => todo!("Type inferrence"), // TODO: infer.
-                };
-                let texpr = type_expr(env, unbox!(expr))?;
-
-                // Check if the type of the binding matches the type of the expression.
-                if texpr.0.ty() != &ty {
-                    return Err(TypeError::new(
-                        format!(
-                            "Expected the binding to be of type `{}`, got `{}`",
-                            ty,
-                            texpr.0.ty(),
-                        ),
-                        texpr.1,
-                    ).with_note(format!(
-                        "Expected this binding to be of type `{}`",
-                        ty,
-                    )));
-                }
-
-                tbindings.push((name, ty.clone(), sbox!(texpr)));
-                env.bind(name, ty);
-            }
-
-            // Return the typed assign expression.
-            oks!(TExpr::Assign(tbindings))
-        }
-
-        Expr::Block { exprs, void } => {
-            let texprs = exprs
-                .into_iter()
-                .map(|e| type_expr(env, unbox!(e)))
-                .collect::<Result<Vec<_>, _>>()?;
-
-            let ret_ty = if void {
-                Type::Unit
-            } else if let Some(texpr) = texprs.last() {
-                texpr.0.ty().clone()
-            } else {
-                Type::Unit
-            };
-
-            oks!(TExpr::Block {
-                exprs: texprs,
-                void,
-                ret_ty,
-            })
-        }
-
-        #[allow(unreachable_patterns)]
-        _ => todo!(),
-    }
-}
-
-pub fn check(es: Vec<Spanned<Expr<'_>>>) -> Result<Vec<Spanned<TExpr<'_>>>, TypeError> {
-    let mut env = TypeContext::new();
-    let mut tes = Vec::new();
-    for e in es {
-        let te = type_expr(&mut env, e)?;
-        tes.push(te);
-    }
-    Ok(tes)
-}

src/typing/mod.rs

@@ -1,3 +1,2 @@
 pub mod ty;
-pub mod check;
 pub mod typed;

src/typing/typed.rs

@@ -6,14 +6,11 @@ use crate::parse::parser::{
     Spanned,
 };
 
-type TypedBinding<'src> =
-    (&'src str, Type, Spanned<Box<TExpr<'src>>>);
-
 // Typed version of the expression.
 #[derive(Clone, Debug)]
 pub enum TExpr<'src> {
     Lit(Lit<'src>),
-    Ident(&'src str, Type),
+    Ident(&'src str),
 
     Unary {
         op: UnaryOp,
@@ -35,7 +32,6 @@ pub enum TExpr<'src> {
     Call {
         func: Spanned<Box<Self>>,
         args: Vec<Spanned<Self>>,
-        ret_ty: Type,
     },
     If {
         cond: Spanned<Box<Self>>,
@@ -44,52 +40,19 @@ pub enum TExpr<'src> {
         br_ty: Type,
     },
     Let {
-        bindings: Vec<TypedBinding<'src>>,
+        name: &'src str,
+        ty: Type,
+        value: Spanned<Box<Self>>,
         body: Spanned<Box<Self>>,
     },
-    Assign(Vec<TypedBinding<'src>>),
+    Define {
+        name: &'src str,
+        ty: Type,
+        value: Spanned<Box<Self>>,
+    },
     Block {
         exprs: Vec<Spanned<Self>>,
         void: bool,
         ret_ty: Type,
     },
 }
-
-impl<'src> TExpr<'src> {
-    pub fn ty(&self) -> &Type {
-        match self {
-            TExpr::Lit(lit) => match lit {
-                Lit::Unit    => &Type::Unit,
-                Lit::Bool(_) => &Type::Bool,
-                Lit::Num(_)  => &Type::Num,
-                Lit::Str(_)  => &Type::Str,
-            },
-            TExpr::Ident(_, ty)          => ty,
-            TExpr::Unary { ret_ty, .. }  => ret_ty,
-            TExpr::Binary { ret_ty, .. } => ret_ty,
-            TExpr::Lambda { ret_ty, .. } => ret_ty,
-            TExpr::Call { ret_ty, .. }   => ret_ty,
-            TExpr::If { br_ty, .. }      => br_ty,
-            // Get the type from the body.
-            TExpr::Let { body, .. }      => body.0.ty(),
-            // Assignment is always unit.
-            TExpr::Assign { .. }         => &Type::Unit,
-            // Get the type from the last expression in the block
-            // if the expression is not ended with a semicolon.
-            TExpr::Block { ret_ty, .. }  => ret_ty,
-        }
-    }
-
-    pub fn as_fn(self) -> Option<(Vec<Type>, Type)> {
-        match self {
-            TExpr::Ident(_, Type::Func(params, ret_ty)) => Some((params, *ret_ty)),
-            TExpr::Lambda { params, ret_ty, .. } => {
-                let p = params.into_iter()
-                    .map(|(_, ty)| ty)
-                    .collect();
-                Some((p, ret_ty))
-            }
-            _ => None,
-        }
-    }
-}