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Diffstat (limited to 'src/tc/mod.rs')
| -rw-r--r-- | src/tc/mod.rs | 528 |
1 files changed, 528 insertions, 0 deletions
diff --git a/src/tc/mod.rs b/src/tc/mod.rs new file mode 100644 index 0000000000..b5acfac2b4 --- /dev/null +++ b/src/tc/mod.rs @@ -0,0 +1,528 @@ +use derive_more::From; +use itertools::Itertools; +use std::collections::HashMap; +use std::convert::{TryFrom, TryInto}; +use std::fmt::{self, Display}; +use std::result; +use thiserror::Error; + +use crate::ast::{self, hir, BinaryOperator, Ident, Literal}; +use crate::common::env::Env; + +#[derive(Debug, Error)] +pub enum Error { + #[error("Undefined variable {0}")] + UndefinedVariable(Ident<'static>), + + #[error("Mismatched types: expected {expected}, but got {actual}")] + TypeMismatch { expected: Type, actual: Type }, + + #[error("Mismatched types, expected numeric type, but got {0}")] + NonNumeric(Type), + + #[error("Ambiguous type {0}")] + AmbiguousType(TyVar), +} + +pub type Result<T> = result::Result<T, Error>; + +#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash)] +pub struct TyVar(u64); + +impl Display for TyVar { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "t{}", self.0) + } +} + +#[derive(Debug, PartialEq, Eq, Clone, Hash)] +pub struct NullaryType(String); + +impl Display for NullaryType { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.write_str(&self.0) + } +} + +#[derive(Debug, PartialEq, Eq, Clone, Copy)] +pub enum PrimType { + Int, + Float, + Bool, +} + +impl From<PrimType> for ast::Type { + fn from(pr: PrimType) -> Self { + match pr { + PrimType::Int => ast::Type::Int, + PrimType::Float => ast::Type::Float, + PrimType::Bool => ast::Type::Bool, + } + } +} + +impl Display for PrimType { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + match self { + PrimType::Int => f.write_str("int"), + PrimType::Float => f.write_str("float"), + PrimType::Bool => f.write_str("bool"), + } + } +} + +#[derive(Debug, PartialEq, Eq, Clone, From)] +pub enum Type { + #[from(ignore)] + Univ(TyVar), + #[from(ignore)] + Exist(TyVar), + Nullary(NullaryType), + Prim(PrimType), + Fun { + args: Vec<Type>, + ret: Box<Type>, + }, +} + +impl PartialEq<ast::Type> for Type { + fn eq(&self, other: &ast::Type) -> bool { + match (self, other) { + (Type::Univ(_), _) => todo!(), + (Type::Exist(_), _) => false, + (Type::Nullary(_), _) => todo!(), + (Type::Prim(pr), ty) => ast::Type::from(*pr) == *ty, + (Type::Fun { args, ret }, ast::Type::Function(ft)) => { + *args == ft.args && (**ret).eq(&*ft.ret) + } + (Type::Fun { .. }, _) => false, + } + } +} + +impl TryFrom<Type> for ast::Type { + type Error = Type; + + fn try_from(value: Type) -> result::Result<Self, Self::Error> { + match value { + Type::Univ(_) => todo!(), + Type::Exist(_) => Err(value), + Type::Nullary(_) => todo!(), + Type::Prim(p) => Ok(p.into()), + Type::Fun { ref args, ref ret } => Ok(ast::Type::Function(ast::FunctionType { + args: args + .clone() + .into_iter() + .map(Self::try_from) + .try_collect() + .map_err(|_| value.clone())?, + ret: Box::new((*ret.clone()).try_into().map_err(|_| value.clone())?), + })), + } + } +} + +const INT: Type = Type::Prim(PrimType::Int); +const FLOAT: Type = Type::Prim(PrimType::Float); +const BOOL: Type = Type::Prim(PrimType::Bool); + +impl Display for Type { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + match self { + Type::Nullary(nt) => nt.fmt(f), + Type::Prim(p) => p.fmt(f), + Type::Univ(TyVar(n)) => write!(f, "∀{}", n), + Type::Exist(TyVar(n)) => write!(f, "∃{}", n), + Type::Fun { args, ret } => write!(f, "fn {} -> {}", args.iter().join(", "), ret), + } + } +} + +impl From<ast::Type> for Type { + fn from(type_: ast::Type) -> Self { + match type_ { + ast::Type::Int => INT, + ast::Type::Float => FLOAT, + ast::Type::Bool => BOOL, + ast::Type::Function(ast::FunctionType { args, ret }) => Type::Fun { + args: args.into_iter().map(Self::from).collect(), + ret: Box::new(Self::from(*ret)), + }, + } + } +} + +struct Typechecker<'ast> { + ty_var_counter: u64, + ctx: HashMap<TyVar, Type>, + env: Env<Ident<'ast>, Type>, +} + +impl<'ast> Typechecker<'ast> { + fn new() -> Self { + Self { + ty_var_counter: 0, + ctx: Default::default(), + env: Default::default(), + } + } + + pub(crate) fn tc_expr(&mut self, expr: ast::Expr<'ast>) -> Result<hir::Expr<'ast, Type>> { + match expr { + ast::Expr::Ident(ident) => { + let type_ = self + .env + .resolve(&ident) + .ok_or_else(|| Error::UndefinedVariable(ident.to_owned()))? + .clone(); + Ok(hir::Expr::Ident(ident, type_)) + } + ast::Expr::Literal(lit) => { + let type_ = match lit { + Literal::Int(_) => Type::Prim(PrimType::Int), + Literal::Bool(_) => Type::Prim(PrimType::Bool), + }; + Ok(hir::Expr::Literal(lit, type_)) + } + ast::Expr::UnaryOp { op, rhs } => todo!(), + ast::Expr::BinaryOp { lhs, op, rhs } => { + let lhs = self.tc_expr(*lhs)?; + let rhs = self.tc_expr(*rhs)?; + let type_ = match op { + BinaryOperator::Equ | BinaryOperator::Neq => { + self.unify(lhs.type_(), rhs.type_())?; + Type::Prim(PrimType::Bool) + } + BinaryOperator::Add | BinaryOperator::Sub | BinaryOperator::Mul => { + let ty = self.unify(lhs.type_(), rhs.type_())?; + // if !matches!(ty, Type::Int | Type::Float) { + // return Err(Error::NonNumeric(ty)); + // } + ty + } + BinaryOperator::Div => todo!(), + BinaryOperator::Pow => todo!(), + }; + Ok(hir::Expr::BinaryOp { + lhs: Box::new(lhs), + op, + rhs: Box::new(rhs), + type_, + }) + } + ast::Expr::Let { bindings, body } => { + self.env.push(); + let bindings = bindings + .into_iter() + .map( + |ast::Binding { ident, type_, body }| -> Result<hir::Binding<Type>> { + let body = self.tc_expr(body)?; + if let Some(type_) = type_ { + self.unify(body.type_(), &type_.into())?; + } + self.env.set(ident.clone(), body.type_().clone()); + Ok(hir::Binding { + ident, + type_: body.type_().clone(), + body, + }) + }, + ) + .collect::<Result<Vec<hir::Binding<Type>>>>()?; + let body = self.tc_expr(*body)?; + self.env.pop(); + Ok(hir::Expr::Let { + bindings, + type_: body.type_().clone(), + body: Box::new(body), + }) + } + ast::Expr::If { + condition, + then, + else_, + } => { + let condition = self.tc_expr(*condition)?; + self.unify(&Type::Prim(PrimType::Bool), condition.type_())?; + let then = self.tc_expr(*then)?; + let else_ = self.tc_expr(*else_)?; + let type_ = self.unify(then.type_(), else_.type_())?; + Ok(hir::Expr::If { + condition: Box::new(condition), + then: Box::new(then), + else_: Box::new(else_), + type_, + }) + } + ast::Expr::Fun(f) => { + let ast::Fun { args, body } = *f; + self.env.push(); + let args: Vec<_> = args + .into_iter() + .map(|id| { + let ty = self.fresh_ex(); + self.env.set(id.clone(), ty.clone()); + (id, ty) + }) + .collect(); + let body = self.tc_expr(body)?; + self.env.pop(); + Ok(hir::Expr::Fun { + type_: Type::Fun { + args: args.iter().map(|(_, ty)| ty.clone()).collect(), + ret: Box::new(body.type_().clone()), + }, + args, + body: Box::new(body), + }) + } + ast::Expr::Call { fun, args } => { + let ret_ty = self.fresh_ex(); + let arg_tys = args.iter().map(|_| self.fresh_ex()).collect::<Vec<_>>(); + let ft = Type::Fun { + args: arg_tys.clone(), + ret: Box::new(ret_ty.clone()), + }; + let fun = self.tc_expr(*fun)?; + self.unify(&ft, fun.type_())?; + let args = args + .into_iter() + .zip(arg_tys) + .map(|(arg, ty)| { + let arg = self.tc_expr(arg)?; + self.unify(&ty, arg.type_())?; + Ok(arg) + }) + .try_collect()?; + Ok(hir::Expr::Call { + fun: Box::new(fun), + args, + type_: ret_ty, + }) + } + ast::Expr::Ascription { expr, type_ } => { + let expr = self.tc_expr(*expr)?; + self.unify(expr.type_(), &type_.into())?; + Ok(expr) + } + } + } + + pub(crate) fn tc_decl(&mut self, decl: ast::Decl<'ast>) -> Result<hir::Decl<'ast, Type>> { + match decl { + ast::Decl::Fun { name, body } => { + let body = self.tc_expr(ast::Expr::Fun(Box::new(body)))?; + let type_ = body.type_().clone(); + self.env.set(name.clone(), type_); + match body { + hir::Expr::Fun { args, body, type_ } => Ok(hir::Decl::Fun { + name, + args, + body, + type_, + }), + _ => unreachable!(), + } + } + } + } + + fn fresh_tv(&mut self) -> TyVar { + self.ty_var_counter += 1; + TyVar(self.ty_var_counter) + } + + fn fresh_ex(&mut self) -> Type { + Type::Exist(self.fresh_tv()) + } + + fn fresh_univ(&mut self) -> Type { + Type::Exist(self.fresh_tv()) + } + + fn universalize<'a>(&mut self, expr: hir::Expr<'a, Type>) -> hir::Expr<'a, Type> { + // TODO + expr + } + + fn unify(&mut self, ty1: &Type, ty2: &Type) -> Result<Type> { + match (ty1, ty2) { + (Type::Prim(p1), Type::Prim(p2)) if p1 == p2 => Ok(ty2.clone()), + (Type::Exist(tv), ty) | (ty, Type::Exist(tv)) => match self.resolve_tv(*tv) { + Some(existing_ty) if *ty == existing_ty => Ok(ty.clone()), + Some(existing_ty) => Err(Error::TypeMismatch { + expected: ty.clone(), + actual: existing_ty.into(), + }), + None => match self.ctx.insert(*tv, ty.clone()) { + Some(existing) => self.unify(&existing, ty), + None => Ok(ty.clone()), + }, + }, + (Type::Univ(u1), Type::Univ(u2)) if u1 == u2 => Ok(ty2.clone()), + ( + Type::Fun { + args: args1, + ret: ret1, + }, + Type::Fun { + args: args2, + ret: ret2, + }, + ) => { + let args = args1 + .iter() + .zip(args2) + .map(|(t1, t2)| self.unify(t1, t2)) + .try_collect()?; + let ret = self.unify(ret1, ret2)?; + Ok(Type::Fun { + args, + ret: Box::new(ret), + }) + } + (Type::Nullary(_), _) | (_, Type::Nullary(_)) => todo!(), + _ => Err(Error::TypeMismatch { + expected: ty1.clone(), + actual: ty2.clone(), + }), + } + } + + fn finalize_expr(&self, expr: hir::Expr<'ast, Type>) -> Result<hir::Expr<'ast, ast::Type>> { + expr.traverse_type(|ty| self.finalize_type(ty)) + } + + fn finalize_decl(&self, decl: hir::Decl<'ast, Type>) -> Result<hir::Decl<'ast, ast::Type>> { + decl.traverse_type(|ty| self.finalize_type(ty)) + } + + fn finalize_type(&self, ty: Type) -> Result<ast::Type> { + match ty { + Type::Exist(tv) => self.resolve_tv(tv).ok_or(Error::AmbiguousType(tv)), + Type::Univ(tv) => todo!(), + Type::Nullary(_) => todo!(), + Type::Prim(pr) => Ok(pr.into()), + Type::Fun { args, ret } => Ok(ast::Type::Function(ast::FunctionType { + args: args + .into_iter() + .map(|ty| self.finalize_type(ty)) + .try_collect()?, + ret: Box::new(self.finalize_type(*ret)?), + })), + } + } + + fn resolve_tv(&self, tv: TyVar) -> Option<ast::Type> { + let mut res = &Type::Exist(tv); + loop { + match res { + Type::Exist(tv) => { + res = self.ctx.get(tv)?; + } + Type::Univ(_) => todo!(), + Type::Nullary(_) => todo!(), + Type::Prim(pr) => break Some((*pr).into()), + Type::Fun { args, ret } => todo!(), + } + } + } +} + +pub fn typecheck_expr(expr: ast::Expr) -> Result<hir::Expr<ast::Type>> { + let mut typechecker = Typechecker::new(); + let typechecked = typechecker.tc_expr(expr)?; + typechecker.finalize_expr(typechecked) +} + +pub fn typecheck_toplevel(decls: Vec<ast::Decl>) -> Result<Vec<hir::Decl<ast::Type>>> { + let mut typechecker = Typechecker::new(); + decls + .into_iter() + .map(|decl| { + let decl = typechecker.tc_decl(decl)?; + typechecker.finalize_decl(decl) + }) + .try_collect() +} + +#[cfg(test)] +mod tests { + use super::*; + + macro_rules! assert_type { + ($expr: expr, $type: expr) => { + use crate::parser::{expr, type_}; + let parsed_expr = test_parse!(expr, $expr); + let parsed_type = test_parse!(type_, $type); + let res = typecheck_expr(parsed_expr).unwrap_or_else(|e| panic!("{}", e)); + assert_eq!(res.type_(), &parsed_type); + }; + } + + macro_rules! assert_type_error { + ($expr: expr) => { + use crate::parser::expr; + let parsed_expr = test_parse!(expr, $expr); + let res = typecheck_expr(parsed_expr); + assert!( + res.is_err(), + "Expected type error, but got type: {}", + res.unwrap().type_() + ); + }; + } + + #[test] + fn literal_int() { + assert_type!("1", "int"); + } + + #[test] + fn conditional() { + assert_type!("if 1 == 2 then 3 else 4", "int"); + } + + #[test] + #[ignore] + fn add_bools() { + assert_type_error!("true + false"); + } + + #[test] + fn call_generic_function() { + assert_type!("(fn x = x) 1", "int"); + } + + #[test] + #[ignore] + fn generic_function() { + assert_type!("fn x = x", "fn x, y -> x"); + } + + #[test] + #[ignore] + fn let_generalization() { + assert_type!("let id = fn x = x in if id true then id 1 else 2", "int"); + } + + #[test] + fn concrete_function() { + assert_type!("fn x = x + 1", "fn int -> int"); + } + + #[test] + fn call_concrete_function() { + assert_type!("(fn x = x + 1) 2", "int"); + } + + #[test] + fn conditional_non_bool() { + assert_type_error!("if 3 then true else false"); + } + + #[test] + fn let_int() { + assert_type!("let x = 1 in x", "int"); + } +} |