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extern crate proc_macro;
use dhall_core::context::Context;
use dhall_core::*;
use proc_macro2::TokenStream;
use quote::quote;
use std::collections::BTreeMap;
use std::rc::Rc;
#[proc_macro]
pub fn dhall_expr(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input_str = input.to_string();
let expr: Rc<Expr<X, Import>> = parser::parse_expr(&input_str).unwrap();
let no_import =
|_: &Import| -> X { panic!("Don't use import in dhall!()") };
let expr = expr.map_embed(&no_import);
let output = dhall_to_tokenstream_bx(&expr, &Context::new());
output.into()
}
// Returns an expression of type Expr<_, _>. Expects interpolated variables
// to be of type Rc<Expr<_, _>>.
fn dhall_to_tokenstream(
expr: &Expr<X, X>,
ctx: &Context<Label, ()>,
) -> TokenStream {
use dhall_core::Expr::*;
match expr {
e @ Var(_) => {
let v = dhall_to_tokenstream_bx(e, ctx);
quote! { *#v }
}
Pi(x, t, b) => {
let t = dhall_to_tokenstream_bx(t, ctx);
let b = dhall_to_tokenstream_bx(b, &ctx.insert(x.clone(), ()));
let x = label_to_tokenstream(x);
quote! { Pi(#x, #t, #b) }
}
Lam(x, t, b) => {
let t = dhall_to_tokenstream_bx(t, ctx);
let b = dhall_to_tokenstream_bx(b, &ctx.insert(x.clone(), ()));
let x = label_to_tokenstream(x);
quote! { Lam(#x, #t, #b) }
}
App(f, a) => {
let f = dhall_to_tokenstream_bx(f, ctx);
let a = vec_to_tokenstream(a, ctx);
quote! { App(#f, #a) }
}
Const(c) => {
let c = const_to_tokenstream(*c);
quote! { Const(#c) }
}
Builtin(b) => {
let b = builtin_to_tokenstream(*b);
quote! { Builtin(#b) }
}
BinOp(o, a, b) => {
let o = binop_to_tokenstream(*o);
let a = dhall_to_tokenstream_bx(a, ctx);
let b = dhall_to_tokenstream_bx(b, ctx);
quote! { BinOp(#o, #a, #b) }
}
NaturalLit(n) => {
quote! { NaturalLit(#n) }
}
OptionalLit(t, e) => {
let t = option_to_tokenstream(t, ctx);
let e = option_to_tokenstream(e, ctx);
quote! { OptionalLit(#t, #e) }
}
EmptyListLit(t) => {
let t = dhall_to_tokenstream_bx(t, ctx);
quote! { EmptyListLit(#t) }
}
NEListLit(es) => {
let es = vec_to_tokenstream(es, ctx);
quote! { NEListLit(#es) }
}
Record(m) => {
let m = map_to_tokenstream(m, ctx);
quote! { Record(#m) }
}
RecordLit(m) => {
let m = map_to_tokenstream(m, ctx);
quote! { RecordLit(#m) }
}
e => unimplemented!("{:?}", e),
}
}
// Returns an expression of type Rc<Expr<_, _>>
fn dhall_to_tokenstream_bx(
expr: &Expr<X, X>,
ctx: &Context<Label, ()>,
) -> TokenStream {
use dhall_core::Expr::*;
match expr {
Var(V(s, n)) => {
match ctx.lookup(&s, *n) {
// Non-free variable; interpolates as itself
Some(()) => {
let s: String = s.clone().into();
quote! { bx(Var(V(#s.into(), #n))) }
}
// Free variable; interpolates as a rust variable
None => {
let s: String = s.clone().into();
// TODO: insert appropriate shifts ?
let v: TokenStream = s.parse().unwrap();
quote! { {
let x: Rc<Expr<_, _>> = #v.clone();
x
} }
}
}
}
e => bx(dhall_to_tokenstream(e, ctx)),
}
}
fn builtin_to_tokenstream(b: Builtin) -> TokenStream {
format!("{:?}", b).parse().unwrap()
}
fn const_to_tokenstream(c: Const) -> TokenStream {
format!("{:?}", c).parse().unwrap()
}
fn binop_to_tokenstream(b: BinOp) -> TokenStream {
format!("{:?}", b).parse().unwrap()
}
fn label_to_tokenstream(l: &Label) -> TokenStream {
let l = String::from(l.clone());
quote! { #l.into() }
}
fn map_to_tokenstream(
m: &BTreeMap<Label, Rc<Expr<X, X>>>,
ctx: &Context<Label, ()>,
) -> TokenStream {
let (keys, values): (Vec<TokenStream>, Vec<TokenStream>) = m
.iter()
.map(|(k, v)| {
(label_to_tokenstream(k), dhall_to_tokenstream_bx(&*v, ctx))
})
.unzip();
quote! { {
use std::collections::BTreeMap;
let mut m = BTreeMap::new();
#( m.insert(#keys, #values); )*
m
} }
}
fn option_to_tokenstream(
e: &Option<Rc<Expr<X, X>>>,
ctx: &Context<Label, ()>,
) -> TokenStream {
let e = e.as_ref().map(|x| dhall_to_tokenstream_bx(x, ctx));
match e {
Some(x) => quote! { Some(#x) },
None => quote! { None },
}
}
fn vec_to_tokenstream(
e: &Vec<Rc<Expr<X, X>>>,
ctx: &Context<Label, ()>,
) -> TokenStream {
let e = e.iter().map(|x| dhall_to_tokenstream_bx(&**x, ctx));
quote! { vec![ #(#e),* ] }
}
fn bx(x: TokenStream) -> TokenStream {
quote! { bx(#x) }
}
|
