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use crate::{abort_now, check_correctness, sealed::Sealed, SpanRange};
use proc_macro2::Span;
use proc_macro2::TokenStream;
use quote::{quote_spanned, ToTokens};
/// Represents a diagnostic level
///
/// # Warnings
///
/// Warnings are ignored on stable/beta
#[derive(Debug, PartialEq)]
pub enum Level {
Error,
Warning,
#[doc(hidden)]
NonExhaustive,
}
/// Represents a single diagnostic message
#[derive(Debug)]
pub struct Diagnostic {
pub(crate) level: Level,
pub(crate) span_range: SpanRange,
pub(crate) msg: String,
pub(crate) suggestions: Vec<(SuggestionKind, String, Option<SpanRange>)>,
pub(crate) children: Vec<(SpanRange, String)>,
}
/// A collection of methods that do not exist in `proc_macro::Diagnostic`
/// but still useful to have around.
///
/// This trait is sealed and cannot be implemented outside of `proc_macro_error`.
pub trait DiagnosticExt: Sealed {
/// Create a new diagnostic message that points to the `span_range`.
///
/// This function is the same as `Diagnostic::spanned` but produces considerably
/// better error messages for multi-token spans on stable.
fn spanned_range(span_range: SpanRange, level: Level, message: String) -> Self;
/// Add another error message to self such that it will be emitted right after
/// the main message.
///
/// This function is the same as `Diagnostic::span_error` but produces considerably
/// better error messages for multi-token spans on stable.
fn span_range_error(self, span_range: SpanRange, msg: String) -> Self;
/// Attach a "help" note to your main message, the note will have it's own span on nightly.
///
/// This function is the same as `Diagnostic::span_help` but produces considerably
/// better error messages for multi-token spans on stable.
///
/// # Span
///
/// The span is ignored on stable, the note effectively inherits its parent's (main message) span
fn span_range_help(self, span_range: SpanRange, msg: String) -> Self;
/// Attach a note to your main message, the note will have it's own span on nightly.
///
/// This function is the same as `Diagnostic::span_note` but produces considerably
/// better error messages for multi-token spans on stable.
///
/// # Span
///
/// The span is ignored on stable, the note effectively inherits its parent's (main message) span
fn span_range_note(self, span_range: SpanRange, msg: String) -> Self;
}
impl DiagnosticExt for Diagnostic {
fn spanned_range(span_range: SpanRange, level: Level, message: String) -> Self {
Diagnostic {
level,
span_range,
msg: message,
suggestions: vec![],
children: vec![],
}
}
fn span_range_error(mut self, span_range: SpanRange, msg: String) -> Self {
self.children.push((span_range, msg));
self
}
fn span_range_help(mut self, span_range: SpanRange, msg: String) -> Self {
self.suggestions
.push((SuggestionKind::Help, msg, Some(span_range)));
self
}
fn span_range_note(mut self, span_range: SpanRange, msg: String) -> Self {
self.suggestions
.push((SuggestionKind::Note, msg, Some(span_range)));
self
}
}
impl Diagnostic {
/// Create a new diagnostic message that points to `Span::call_site()`
pub fn new(level: Level, message: String) -> Self {
Diagnostic::spanned(Span::call_site(), level, message)
}
/// Create a new diagnostic message that points to the `span`
pub fn spanned(span: Span, level: Level, message: String) -> Self {
Diagnostic::spanned_range(
SpanRange {
first: span,
last: span,
},
level,
message,
)
}
/// Add another error message to self such that it will be emitted right after
/// the main message.
pub fn span_error(self, span: Span, msg: String) -> Self {
self.span_range_error(
SpanRange {
first: span,
last: span,
},
msg,
)
}
/// Attach a "help" note to your main message, the note will have it's own span on nightly.
///
/// # Span
///
/// The span is ignored on stable, the note effectively inherits its parent's (main message) span
pub fn span_help(self, span: Span, msg: String) -> Self {
self.span_range_help(
SpanRange {
first: span,
last: span,
},
msg,
)
}
/// Attach a "help" note to your main message.
pub fn help(mut self, msg: String) -> Self {
self.suggestions.push((SuggestionKind::Help, msg, None));
self
}
/// Attach a note to your main message, the note will have it's own span on nightly.
///
/// # Span
///
/// The span is ignored on stable, the note effectively inherits its parent's (main message) span
pub fn span_note(self, span: Span, msg: String) -> Self {
self.span_range_note(
SpanRange {
first: span,
last: span,
},
msg,
)
}
/// Attach a note to your main message
pub fn note(mut self, msg: String) -> Self {
self.suggestions.push((SuggestionKind::Note, msg, None));
self
}
/// The message of main warning/error (no notes attached)
pub fn message(&self) -> &str {
&self.msg
}
/// Abort the proc-macro's execution and display the diagnostic.
///
/// # Warnings
///
/// Warnings are not emitted on stable and beta, but this function will abort anyway.
pub fn abort(self) -> ! {
self.emit();
abort_now()
}
/// Display the diagnostic while not aborting macro execution.
///
/// # Warnings
///
/// Warnings are ignored on stable/beta
pub fn emit(self) {
check_correctness();
crate::imp::emit_diagnostic(self);
}
}
/// **NOT PUBLIC API! NOTHING TO SEE HERE!!!**
#[doc(hidden)]
impl Diagnostic {
pub fn span_suggestion(self, span: Span, suggestion: &str, msg: String) -> Self {
match suggestion {
"help" | "hint" => self.span_help(span, msg),
_ => self.span_note(span, msg),
}
}
pub fn suggestion(self, suggestion: &str, msg: String) -> Self {
match suggestion {
"help" | "hint" => self.help(msg),
_ => self.note(msg),
}
}
}
impl ToTokens for Diagnostic {
fn to_tokens(&self, ts: &mut TokenStream) {
use std::borrow::Cow;
fn ensure_lf(buf: &mut String, s: &str) {
if s.ends_with('\n') {
buf.push_str(s);
} else {
buf.push_str(s);
buf.push('\n');
}
}
fn diag_to_tokens(
span_range: SpanRange,
level: &Level,
msg: &str,
suggestions: &[(SuggestionKind, String, Option<SpanRange>)],
) -> TokenStream {
if *level == Level::Warning {
return TokenStream::new();
}
let message = if suggestions.is_empty() {
Cow::Borrowed(msg)
} else {
let mut message = String::new();
ensure_lf(&mut message, msg);
message.push('\n');
for (kind, note, _span) in suggestions {
message.push_str(" = ");
message.push_str(kind.name());
message.push_str(": ");
ensure_lf(&mut message, note);
}
message.push('\n');
Cow::Owned(message)
};
let mut msg = proc_macro2::Literal::string(&message);
msg.set_span(span_range.last);
let group = quote_spanned!(span_range.last=> { #msg } );
quote_spanned!(span_range.first=> compile_error!#group)
}
ts.extend(diag_to_tokens(
self.span_range,
&self.level,
&self.msg,
&self.suggestions,
));
ts.extend(
self.children
.iter()
.map(|(span_range, msg)| diag_to_tokens(*span_range, &Level::Error, &msg, &[])),
);
}
}
#[derive(Debug)]
pub(crate) enum SuggestionKind {
Help,
Note,
}
impl SuggestionKind {
fn name(&self) -> &'static str {
match self {
SuggestionKind::Note => "note",
SuggestionKind::Help => "help",
}
}
}
#[cfg(feature = "syn-error")]
impl From<syn::Error> for Diagnostic {
fn from(err: syn::Error) -> Self {
use proc_macro2::{Delimiter, TokenTree};
fn gut_error(ts: &mut impl Iterator<Item = TokenTree>) -> Option<(SpanRange, String)> {
let first = match ts.next() {
// compile_error
None => return None,
Some(tt) => tt.span(),
};
ts.next().unwrap(); // !
let lit = match ts.next().unwrap() {
TokenTree::Group(group) => {
// Currently `syn` builds `compile_error!` invocations
// exclusively in `ident{"..."}` (braced) form which is not
// followed by `;` (semicolon).
//
// But if it changes to `ident("...");` (parenthesized)
// or `ident["..."];` (bracketed) form,
// we will need to skip the `;` as well.
// Highly unlikely, but better safe than sorry.
if group.delimiter() == Delimiter::Parenthesis
|| group.delimiter() == Delimiter::Bracket
{
ts.next().unwrap(); // ;
}
match group.stream().into_iter().next().unwrap() {
TokenTree::Literal(lit) => lit,
_ => unreachable!(),
}
}
_ => unreachable!(),
};
let last = lit.span();
let mut msg = lit.to_string();
// "abc" => abc
msg.pop();
msg.remove(0);
Some((SpanRange { first, last }, msg))
}
let mut ts = err.to_compile_error().into_iter();
let (span_range, msg) = gut_error(&mut ts).unwrap();
let mut res = Diagnostic::spanned_range(span_range, Level::Error, msg);
while let Some((span_range, msg)) = gut_error(&mut ts) {
res = res.span_range_error(span_range, msg);
}
res
}
}