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
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
|
extern crate proc_macro;
use proc_macro::TokenStream;
use proc_macro2::Span;
use quote::{quote_spanned, ToTokens};
use syn::parse::Parse;
use syn::spanned::Spanned;
use syn::{
parse_macro_input, parse_quote, FnArg, Ident, Item, ItemMod, LitStr, Pat, PatIdent, PatType,
};
struct BuiltinArgs {
name: LitStr,
}
impl Parse for BuiltinArgs {
fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
Ok(BuiltinArgs {
name: input.parse()?,
})
}
}
/// Mark the annotated module as a module for defining Nix builtins.
///
/// A function `fn builtins() -> Vec<Builtin>` will be defined within the annotated module,
/// returning a list of [`tvix_eval::Builtin`] for each function annotated with the `#[builtin]`
/// attribute within the module.
///
/// Each invocation of the `#[builtin]` annotation within the module should be passed a string
/// literal for the name of the builtin.
///
/// # Examples
/// ```ignore
/// # use tvix_eval_builtin_macros::builtins;
/// # mod value {
/// # pub use tvix_eval::Builtin;
/// # }
///
/// #[builtins]
/// mod builtins {
/// use tvix_eval::{ErrorKind, Value, VM};
///
/// #[builtin("identity")]
/// pub fn builtin_identity(_vm: &mut VM, x: Value) -> Result<Value, ErrorKind> {
/// Ok(x)
/// }
///
/// // Builtins can request their argument not be forced before being called by annotating the
/// // argument with the `#[lazy]` attribute
///
/// #[builtin("tryEval")]
/// pub fn builtin_try_eval(vm: &mut VM, #[lazy] x: Value) -> Result<Value, ErrorKind> {
/// todo!()
/// }
/// }
/// ```
#[proc_macro_attribute]
pub fn builtins(_args: TokenStream, item: TokenStream) -> TokenStream {
let mut module = parse_macro_input!(item as ItemMod);
let (_, items) = match &mut module.content {
Some(content) => content,
None => {
return (quote_spanned!(module.span() =>
compile_error!("Builtin modules must be defined in-line")
))
.into();
}
};
let mut builtins = vec![];
for item in items.iter_mut() {
if let Item::Fn(f) = item {
if let Some(builtin_attr_pos) = f
.attrs
.iter()
.position(|attr| attr.path.get_ident().iter().any(|id| *id == "builtin"))
{
let builtin_attr = f.attrs.remove(builtin_attr_pos);
let BuiltinArgs { name } = match builtin_attr.parse_args() {
Ok(args) => args,
Err(err) => return err.into_compile_error().into(),
};
if f.sig.inputs.len() <= 1 {
return (quote_spanned!(
f.sig.inputs.span() =>
compile_error!("Builtin functions must take at least two arguments")
))
.into();
}
let builtin_arguments = f
.sig
.inputs
.iter_mut()
.skip(1)
.map(|arg| {
let mut strict = true;
let name = match arg {
FnArg::Receiver(_) => {
return Err(quote_spanned!(arg.span() => {
compile_error!("Unexpected receiver argument in builtin")
}))
}
FnArg::Typed(PatType { attrs, pat, .. }) => {
attrs.retain(|attr| {
attr.path.get_ident().into_iter().any(|id| {
if id == "lazy" {
strict = false;
false
} else {
true
}
})
});
match pat.as_ref() {
Pat::Ident(PatIdent { ident, .. }) => ident.to_string(),
_ => "unknown".to_string(),
}
}
};
Ok(quote_spanned!(arg.span() => {
crate::internal::BuiltinArgument {
strict: #strict,
name: #name,
}
}))
})
.collect::<Result<Vec<_>, _>>();
let builtin_arguments = match builtin_arguments {
Ok(args) => args,
Err(err) => return err.into(),
};
let fn_name = f.sig.ident.clone();
let num_args = f.sig.inputs.len() - 1;
let args = (0..num_args)
.map(|n| Ident::new(&format!("arg_{n}"), Span::call_site()))
.collect::<Vec<_>>();
let mut reversed_args = args.clone();
reversed_args.reverse();
builtins.push(quote_spanned! { builtin_attr.span() => {
crate::internal::Builtin::new(
#name,
&[#(#builtin_arguments),*],
|mut args: Vec<crate::Value>, vm: &mut crate::internal::VM| {
#(let #reversed_args = args.pop().unwrap();)*
#fn_name(vm, #(#args),*)
}
)
}});
}
}
}
items.push(parse_quote! {
pub fn builtins() -> Vec<crate::internal::Builtin> {
vec![#(#builtins),*]
}
});
module.into_token_stream().into()
}
|
