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// Copyright ⓒ 2017 David Li.
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
use ::ast::{self, WithLocation};
use super::environment;
use super::types::{self, Ty};
#[derive(Debug)]
pub enum TypeError {
Unimplemented,
Mismatch {
expected: Ty,
actual: Ty,
},
UnboundName,
}
type TypeEnvironment<'a> = environment::Environment<'a, String, Ty>;
pub type Result = ::std::result::Result<Ty, WithLocation<TypeError>>;
pub fn translate(program: &ast::Program) -> Result {
let mut venv = TypeEnvironment::new(None);
let mut tenv = TypeEnvironment::new(None);
tenv.add_binding("int".into(), Ty::Int);
tenv.add_binding("string".into(), Ty::String);
trans_exp(&mut venv, &mut tenv, &*program.0)
}
macro_rules! err {
($exp: expr, $err: expr) => {
Err(WithLocation::new($err, $exp.start, $exp.end))
}
}
fn trans_ty<'a>(
venv: &mut TypeEnvironment<'a>,
tenv: &mut TypeEnvironment<'a>,
ty: &WithLocation<ast::Ty>) -> Result {
match ty.value {
ast::Ty::Name(ref name) => {
tenv.lookup(&name)
.map(|v| v.clone())
.ok_or(WithLocation::new(TypeError::UnboundName, ty.start, ty.end))
}
ast::Ty::Array(ref inner_ty) => {
trans_ty(venv, tenv, &inner_ty)
},
ast::Ty::Record(ref fields) => {
let mut result = vec![];
for field in fields {
result.push(types::RecordField::new(
field.name.clone(),
trans_ty(venv, tenv, &field.ty)?));
}
Ok(Ty::Record(result))
},
}
}
fn trans_decl<'a>(
venv: &mut TypeEnvironment<'a>,
tenv: &mut TypeEnvironment<'a>,
decl: &WithLocation<ast::Declaration>) -> Result {
match decl.declaration {
ast::DeclarationBody::Fun { .. } => {
err!(decl, TypeError::Unimplemented)
}
ast::DeclarationBody::Ty { ref ty } => {
trans_ty(venv, tenv, ty)
}
ast::DeclarationBody::Var { ref ty, ref value } => {
let actual_ty = trans_exp(venv, tenv, &value)?;
if let &Some(ref ty) = ty {
let decl_ty = trans_ty(venv, tenv, &ty)?;
if decl_ty != actual_ty {
return err!(ty, TypeError::Mismatch {
expected: decl_ty,
actual: actual_ty,
});
}
}
Ok(actual_ty)
}
}
}
fn trans_exp<'a>(
venv: &mut TypeEnvironment<'a>,
tenv: &mut TypeEnvironment<'a>,
exp: &WithLocation<ast::Expression>) -> Result {
use ast::Expression::*;
match &exp.value {
&Let(ref decls, ref body) => {
let mut new_venv = TypeEnvironment::new(Some(venv));
let mut new_tenv = TypeEnvironment::new(Some(tenv));
for decl in decls.iter() {
let decl_ty = trans_decl(&mut new_venv, &mut new_tenv, decl)?;
match decl.declaration {
ast::DeclarationBody::Fun { .. } | ast::DeclarationBody::Var { .. } => {
new_venv.add_binding(decl.name.clone(), decl_ty);
}
ast::DeclarationBody::Ty { .. } => {
new_tenv.add_binding(decl.name.clone(), decl_ty);
}
}
}
trans_exp(&mut new_venv, &mut new_tenv, &*body)
},
&UnaryOp(ref op, ref operand) => {
use ast::UnaryOp::*;
let operand_ty = trans_exp(venv, tenv, operand)?;
match op {
&Neg | &Pos => {
match operand_ty {
Ty::Int => {
Ok(Ty::Int)
}
other => {
err!(operand, TypeError::Mismatch {
expected: Ty::Int,
actual: other,
})
}
}
}
&Not => {
err!(exp, TypeError::Unimplemented)
}
}
},
&BinOp(ref op, ref left, ref right) => {
use ast::BinOp::*;
let left_ty = trans_exp(venv, tenv, left)?;
let right_ty = trans_exp(venv, tenv, right)?;
match op {
&Add => {
match (left_ty, right_ty) {
(Ty::Int, Ty::Int) => {
Ok(Ty::Int)
}
(Ty::String, Ty::String) => {
Ok(Ty::String)
}
(Ty::Int, other) => {
err!(right, TypeError::Mismatch {
expected: Ty::Int,
actual: other,
})
}
(Ty::String, other) => {
err!(right, TypeError::Mismatch {
expected: Ty::String,
actual: other,
})
}
_ => {
err!(exp, TypeError::Unimplemented)
}
}
}
_ => {
err!(exp, TypeError::Unimplemented)
}
}
},
&Number(_) => Ok(Ty::Int),
&String(_) => Ok(Ty::String),
&Name(ref name) => {
if let Some(ty) = venv.lookup(name) {
Ok(ty.clone())
}
else {
err!(exp, TypeError::UnboundName)
}
},
&Nil => {
Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
},
}
}
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