1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
extern crate proc_macro;
use dhall_core::context::Context;
use dhall_core::*;
use proc_macro2::Literal;
use proc_macro2::TokenStream;
use quote::quote;
#[proc_macro]
pub fn dhall(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input_str = input.to_string();
let expr: Box<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::<&str>(&expr, &Context::new());
output.into()
}
// Returns an expression of type Expr<_, _>. Expects input variables
// to be of type Box<Expr<_, _>> (future-proof for structural sharing).
fn dhall_to_tokenstream<L: StringLike>(
expr: &Expr_<L, X, X>,
ctx: &Context<L, ()>,
) -> TokenStream {
use dhall_core::Expr_::*;
match expr {
e @ Var(_) => {
let v = dhall_to_tokenstream_bx(e, ctx);
quote! { *#v }
}
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 = Literal::string(&x.clone().into());
quote! { Lam(#x.to_owned().into(), #t, #b) }
}
App(f, a) => {
let f = dhall_to_tokenstream_bx(f, ctx);
let a = dhall_to_tokenstream_bx(a, ctx);
quote! { App(#f, #a) }
}
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) }
}
OptionalLit(t, es) => {
let t = option_tks(
t.as_ref()
.map(deref)
.map(|x| dhall_to_tokenstream_bx(x, ctx)),
);
let es =
vec_tks(es.into_iter().map(|x| dhall_to_tokenstream(x, ctx)));
quote! { OptionalLit(#t, #es) }
}
ListLit(t, es) => {
let t = option_tks(
t.as_ref()
.map(deref)
.map(|x| dhall_to_tokenstream_bx(x, ctx)),
);
let es =
vec_tks(es.into_iter().map(|x| dhall_to_tokenstream(x, ctx)));
quote! { ListLit(#t, #es) }
}
e => unimplemented!("{:?}", e),
}
}
// Returns an expression of type Box<Expr<_, _>>
fn dhall_to_tokenstream_bx<L: StringLike>(
expr: &Expr_<L, X, X>,
ctx: &Context<L, ()>,
) -> 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.to_owned().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: Box<Expr_<_, _, _>> = #v.clone();
x
} }
}
}
}
e => bx(dhall_to_tokenstream(e, ctx)),
}
}
fn builtin_to_tokenstream(b: &Builtin) -> TokenStream {
format!("{:?}", b).parse().unwrap()
}
fn binop_to_tokenstream(b: &BinOp) -> TokenStream {
format!("{:?}", b).parse().unwrap()
}
fn deref<T>(x: &Box<T>) -> &T {
&*x
}
fn bx(x: TokenStream) -> TokenStream {
quote! { bx(#x) }
}
fn option_tks(x: Option<TokenStream>) -> TokenStream {
match x {
Some(x) => quote! { Some(#x) },
None => quote! { None },
}
}
fn vec_tks<T>(x: T) -> TokenStream
where
T: Iterator<Item = TokenStream>,
{
quote! { vec![ #(#x),* ] }
}
|
