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use std::borrow::Cow;
use std::fmt;
use proc_macro::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
trait WithSpan {
fn with_span(self, span: Span) -> Self;
}
impl WithSpan for TokenTree {
fn with_span(mut self, span: Span) -> Self {
self.set_span(span);
self
}
}
pub(crate) enum Error {
MissingComponent {
name: &'static str,
span_start: Option<Span>,
span_end: Option<Span>,
},
InvalidComponent {
name: &'static str,
value: String,
span_start: Option<Span>,
span_end: Option<Span>,
},
#[cfg(any(feature = "formatting", feature = "parsing"))]
ExpectedString {
span_start: Option<Span>,
span_end: Option<Span>,
},
UnexpectedToken {
tree: TokenTree,
},
UnexpectedEndOfInput,
Custom {
message: Cow<'static, str>,
span_start: Option<Span>,
span_end: Option<Span>,
},
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::MissingComponent { name, .. } => write!(f, "missing component: {name}"),
Self::InvalidComponent { name, value, .. } => {
write!(f, "invalid component: {name} was {value}")
}
#[cfg(any(feature = "formatting", feature = "parsing"))]
Self::ExpectedString { .. } => f.write_str("expected string literal"),
Self::UnexpectedToken { tree } => write!(f, "unexpected token: {tree}"),
Self::UnexpectedEndOfInput => f.write_str("unexpected end of input"),
Self::Custom { message, .. } => f.write_str(message),
}
}
}
impl Error {
fn span_start(&self) -> Span {
match self {
Self::MissingComponent { span_start, .. }
| Self::InvalidComponent { span_start, .. }
| Self::Custom { span_start, .. } => *span_start,
#[cfg(any(feature = "formatting", feature = "parsing"))]
Self::ExpectedString { span_start, .. } => *span_start,
Self::UnexpectedToken { tree } => Some(tree.span()),
Self::UnexpectedEndOfInput => Some(Span::mixed_site()),
}
.unwrap_or_else(Span::mixed_site)
}
fn span_end(&self) -> Span {
match self {
Self::MissingComponent { span_end, .. }
| Self::InvalidComponent { span_end, .. }
| Self::Custom { span_end, .. } => *span_end,
#[cfg(any(feature = "formatting", feature = "parsing"))]
Self::ExpectedString { span_end, .. } => *span_end,
Self::UnexpectedToken { tree, .. } => Some(tree.span()),
Self::UnexpectedEndOfInput => Some(Span::mixed_site()),
}
.unwrap_or_else(|| self.span_start())
}
pub(crate) fn to_compile_error(&self) -> TokenStream {
let (start, end) = (self.span_start(), self.span_end());
[
TokenTree::from(Punct::new(':', Spacing::Joint)).with_span(start),
TokenTree::from(Punct::new(':', Spacing::Alone)).with_span(start),
TokenTree::from(Ident::new("core", start)),
TokenTree::from(Punct::new(':', Spacing::Joint)).with_span(start),
TokenTree::from(Punct::new(':', Spacing::Alone)).with_span(start),
TokenTree::from(Ident::new("compile_error", start)),
TokenTree::from(Punct::new('!', Spacing::Alone)).with_span(start),
TokenTree::from(Group::new(
Delimiter::Parenthesis,
TokenStream::from(
TokenTree::from(Literal::string(&self.to_string())).with_span(end),
),
))
.with_span(end),
]
.iter()
.cloned()
.collect()
}
/// Like `to_compile_error`, but for use in macros that produce items.
#[cfg(all(feature = "serde", any(feature = "formatting", feature = "parsing")))]
pub(crate) fn to_compile_error_standalone(&self) -> TokenStream {
let end = self.span_end();
self.to_compile_error()
.into_iter()
.chain(std::iter::once(
TokenTree::from(Punct::new(';', Spacing::Alone)).with_span(end),
))
.collect()
}
}