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|
use ::ast::{self, WithLocation};
use super::environment;
use super::types::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 env = TypeEnvironment::new(None);
trans_exp(&mut env, &*program.0)
}
macro_rules! err {
($exp: expr, $err: expr) => {
Err(WithLocation::new($err, $exp.start, $exp.end))
}
}
fn trans_exp<'a>(venv: &mut TypeEnvironment<'a>, exp: &WithLocation<ast::Expression>) -> Result {
use ast::Expression::*;
match &exp.value {
&Let(ref decls, ref body) => {
let mut new_env = TypeEnvironment::new(None);
for decl in decls.iter() {
let decl_ty = trans_exp(venv, &*decl.value.value)?;
if let Some(_) = decl.value.type_ {
return err!(decl, TypeError::Unimplemented);
}
else {
new_env.add_binding(decl.value.name.value.clone(), decl_ty);
}
}
new_env.set_parent(venv);
trans_exp(&mut new_env, &*body)
},
&UnaryOp(ref op, ref operand) => {
use ast::UnaryOp::*;
let operand_ty = trans_exp(venv, 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, left)?;
let right_ty = trans_exp(venv, 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)
}
else {
err!(exp, TypeError::UnboundName)
}
},
&Nil => {
Err(WithLocation::new(TypeError::Unimplemented, exp.start, exp.end))
},
}
}
|
