flux_macros/diagnostics/
error.rs

1use proc_macro::{Diagnostic, Level, MultiSpan};
2use proc_macro2::TokenStream;
3use quote::quote;
4use syn::{Attribute, Error as SynError, Meta, spanned::Spanned};
5
6#[derive(Debug)]
7pub(crate) enum DiagnosticDeriveError {
8    SynError(SynError),
9    ErrorHandled,
10}
11
12impl DiagnosticDeriveError {
13    pub(crate) fn to_compile_error(self) -> TokenStream {
14        match self {
15            DiagnosticDeriveError::SynError(e) => e.to_compile_error(),
16            DiagnosticDeriveError::ErrorHandled => {
17                // Return ! to avoid having to create a blank Diag to return when an
18                // error has already been emitted to the compiler.
19                quote! {
20                    { unreachable!(); }
21                }
22            }
23        }
24    }
25}
26
27impl From<SynError> for DiagnosticDeriveError {
28    fn from(e: SynError) -> Self {
29        DiagnosticDeriveError::SynError(e)
30    }
31}
32
33/// Helper function for use with `throw_*` macros - constraints `$f` to an `impl FnOnce`.
34pub(crate) fn _throw_err(
35    diag: Diagnostic,
36    f: impl FnOnce(Diagnostic) -> Diagnostic,
37) -> DiagnosticDeriveError {
38    f(diag).emit();
39    DiagnosticDeriveError::ErrorHandled
40}
41
42/// Helper function for printing `syn::Path` - doesn't handle arguments in paths and these are
43/// unlikely to come up much in use of the macro.
44fn path_to_string(path: &syn::Path) -> String {
45    let mut out = String::new();
46    for (i, segment) in path.segments.iter().enumerate() {
47        if i > 0 || path.leading_colon.is_some() {
48            out.push_str("::");
49        }
50        out.push_str(&segment.ident.to_string());
51    }
52    out
53}
54
55/// Returns an error diagnostic on span `span` with msg `msg`.
56#[must_use]
57pub(crate) fn span_err<T: Into<String>>(span: impl MultiSpan, msg: T) -> Diagnostic {
58    Diagnostic::spanned(span, Level::Error, msg)
59}
60
61/// Emit a diagnostic on span `$span` with msg `$msg` (optionally performing additional decoration
62/// using the `FnOnce` passed in `diag`) and return `Err(ErrorHandled)`.
63///
64/// For methods that return a `Result<_, DiagnosticDeriveError>`:
65macro_rules! throw_span_err {
66    ($span:expr, $msg:expr) => {{ throw_span_err!($span, $msg, |diag| diag) }};
67    ($span:expr, $msg:expr, $f:expr) => {{
68        let diag = span_err($span, $msg);
69        return Err(crate::diagnostics::error::_throw_err(diag, $f));
70    }};
71}
72
73pub(crate) use throw_span_err;
74
75/// Returns an error diagnostic for an invalid attribute.
76pub(crate) fn invalid_attr(attr: &Attribute) -> Diagnostic {
77    let span = attr.span().unwrap();
78    let path = path_to_string(attr.path());
79    match attr.meta {
80        Meta::Path(_) => span_err(span, format!("`#[{path}]` is not a valid attribute")),
81        Meta::NameValue(_) => span_err(span, format!("`#[{path} = ...]` is not a valid attribute")),
82        Meta::List(_) => span_err(span, format!("`#[{path}(...)]` is not a valid attribute")),
83    }
84}
85
86/// Emit an error diagnostic for an invalid attribute (optionally performing additional decoration
87/// using the `FnOnce` passed in `diag`) and return `Err(ErrorHandled)`.
88///
89/// For methods that return a `Result<_, DiagnosticDeriveError>`:
90macro_rules! throw_invalid_attr {
91    ($attr:expr) => {{ throw_invalid_attr!($attr, |diag| diag) }};
92    ($attr:expr, $f:expr) => {{
93        let diag = crate::diagnostics::error::invalid_attr($attr);
94        return Err(crate::diagnostics::error::_throw_err(diag, $f));
95    }};
96}
97
98pub(crate) use throw_invalid_attr;
flux_macros/diagnostics/error.rs

flux_macros/diagnostics/
error.rs
