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
|
// SPDX-License-Identifier: Apache-2.0 OR MIT
use std::cell::RefCell;
use std::fmt::Display;
use std::marker::PhantomData;
use proc_macro2::{Span, TokenStream};
use quote::{quote, quote_spanned};
use syn::{spanned::Spanned, Error};
pub(crate) struct DiagCtxt(PhantomData<*mut ()>);
pub(crate) struct ErrorGuaranteed(());
struct DiagCtxtData {
diag: TokenStream,
}
thread_local! {
static DIAGNOSTICS: RefCell<Option<DiagCtxtData>> = const { RefCell::new(None) };
}
// Allows `syn::Error` to be emitted into the current diagnostic context with just `?`.
impl From<syn::Error> for ErrorGuaranteed {
fn from(error: syn::Error) -> Self {
DIAGNOSTICS.with_borrow_mut(|data| {
data.as_mut()
.unwrap()
.diag
.extend(error.into_compile_error());
});
Self(())
}
}
impl DiagCtxt {
pub(crate) fn error(&self, span: impl Spanned, msg: impl Display) -> ErrorGuaranteed {
Error::new(span.span(), msg).into()
}
pub(crate) fn warn(&self, span: impl Spanned, msg: impl Display) {
// Have the message start on a new line for visual clarity.
let msg = format!("\n{}", msg);
DIAGNOSTICS.with_borrow_mut(|data| {
data.as_mut()
.unwrap()
.diag
.extend(quote_spanned!(span.span() =>
// Approximate using deprecated warning while `proc_macro_diagnostic` is
// unstable.
const _: () = {
#[deprecated = #msg]
const fn warn() {}
warn();
};
))
});
}
/// Execute the provided function with the current diagnostic context.
pub(crate) fn current<R>(f: impl FnOnce(&DiagCtxt) -> R) -> R {
DIAGNOSTICS.with_borrow(|data| {
assert!(data.is_some(), "No active `DiagCtxt`");
});
f(&DiagCtxt(PhantomData))
}
fn with(
f: impl FnOnce(&mut DiagCtxt) -> Result<TokenStream, ErrorGuaranteed>,
merge_diag: impl FnOnce(TokenStream, TokenStream) -> TokenStream,
convert_diag: impl FnOnce(TokenStream) -> TokenStream,
) -> TokenStream {
DIAGNOSTICS.with_borrow_mut(|data| {
assert!(data.is_none(), "`DiagCtxt` cannot be nested");
*data = Some(DiagCtxtData {
diag: TokenStream::new(),
});
});
let mut dcx = DiagCtxt(PhantomData);
let result = match std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| f(&mut dcx))) {
Ok(result) => result,
Err(payload) => {
// Robustness against panicking in macros.
//
// Ensure that any error messages are still emitted when this happens.
let message = if let Some(&s) = payload.downcast_ref::<&'static str>() {
s
} else if let Some(s) = payload.downcast_ref::<String>() {
s.as_str()
} else {
"Box<dyn Any>"
};
Err(dcx.error(
Span::mixed_site(),
format!("proc macro panicked: {message}"),
))
}
};
let data = DIAGNOSTICS.with_borrow_mut(|data| data.take().unwrap());
match result {
Ok(stream) => {
if data.diag.is_empty() {
stream
} else {
merge_diag(stream, data.diag)
}
}
Err(ErrorGuaranteed(())) => convert_diag(data.diag),
}
}
pub(crate) fn for_item(
f: impl FnOnce(&mut DiagCtxt) -> Result<TokenStream, ErrorGuaranteed>,
) -> TokenStream {
Self::with(
f,
|mut out, diag| {
out.extend(diag);
out
},
std::convert::identity,
)
}
pub(crate) fn for_expr(
f: impl FnOnce(&mut DiagCtxt) -> Result<TokenStream, ErrorGuaranteed>,
) -> TokenStream {
Self::with(
f,
|out, diag| {
// Diagnostics that we generate are always items.
// So for expressions create a block to place diagnostics in item position.
quote!({
#diag
#out
})
},
|diag| {
quote!({
#diag
})
},
)
}
}
|
