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use proc_macro::Span;
use syn::Token;
use syn::punctuated::Punctuated;
use syn::parse::{Parse as SynParse, ParseStream as SynParseStream};
use proc_macro2::Delimiter;
use spanned::Spanned;
#[derive(Debug)]
crate struct Diagnostic(crate ::proc_macro::Diagnostic);
impl Diagnostic {
pub fn emit(self) {
self.0.emit();
}
}
impl From<::proc_macro::Diagnostic> for Diagnostic {
fn from(original: ::proc_macro::Diagnostic) -> Diagnostic {
Diagnostic(original)
}
}
impl From<::syn::parse::Error> for Diagnostic {
fn from(e: ::syn::parse::Error) -> Diagnostic {
let inner = ::proc_macro::Diagnostic::spanned(
e.span().unstable(), ::proc_macro::Level::Error, e.to_string());
Diagnostic(inner)
}
}
impl Into<::syn::parse::Error> for Diagnostic {
fn into(self) -> ::syn::parse::Error {
let span = if self.0.spans().is_empty() {
Span::call_site()
} else {
self.0.spans()[0]
};
::syn::parse::Error::new(span.into(), self.0.message())
}
}
impl ::std::ops::Deref for Diagnostic {
type Target = ::proc_macro::Diagnostic;
fn deref(&self) -> &Self::Target {
&self.0
}
}
crate type PResult<T> = Result<T, Diagnostic>;
crate trait Parse: Sized {
fn parse(input: syn::parse::ParseStream) -> PResult<Self>;
fn syn_parse(input: syn::parse::ParseStream) -> syn::parse::Result<Self> {
Self::parse(input).map_err(|e| e.into())
}
}
trait ParseStreamExt {
fn parse_group<F, G>(self, delimiter: Delimiter, parser: F) -> syn::parse::Result<G>
where F: FnOnce(SynParseStream) -> syn::parse::Result<G>;
fn try_parse<F, G>(self, parser: F) -> syn::parse::Result<G>
where F: Fn(SynParseStream) -> syn::parse::Result<G>;
}
impl<'a> ParseStreamExt for SynParseStream<'a> {
fn parse_group<F, G>(self, delimiter: Delimiter, parser: F) -> syn::parse::Result<G>
where F: FnOnce(SynParseStream) -> syn::parse::Result<G>
{
let content;
match delimiter {
Delimiter::Brace => { syn::braced!(content in self); },
Delimiter::Bracket => { syn::bracketed!(content in self); },
Delimiter::Parenthesis => { syn::parenthesized!(content in self); },
Delimiter::None => return parser(self),
}
parser(&content)
}
fn try_parse<F, G>(self, parser: F) -> syn::parse::Result<G>
where F: Fn(SynParseStream) -> syn::parse::Result<G>
{
let input = self.fork();
parser(&input)?;
parser(self)
}
}
#[derive(Debug)]
crate struct CallPattern {
crate name: Option<syn::Ident>,
crate expr: syn::ExprCall,
}
impl syn::parse::Parse for CallPattern {
fn parse(input: syn::parse::ParseStream) -> syn::parse::Result<Self> {
Self::syn_parse(input)
}
}
impl Spanned for CallPattern {
fn span(&self) -> Span {
self.name.as_ref()
.and_then(|name| name.span().unstable().join(self.expr.span()))
.unwrap_or_else(|| self.expr.span())
}
}
#[derive(Debug)]
crate enum Pattern {
Wild(Token![_]),
Calls(Punctuated<CallPattern, Token![|]>)
}
#[derive(Debug)]
crate struct Case {
crate pattern: Pattern,
crate expr: syn::Expr,
crate span: Span,
}
#[derive(Debug)]
crate struct Switch {
crate parser_name: syn::Ident,
crate input: syn::Expr,
crate cases: Punctuated<Case, Token![,]>
}
fn parse_expr_call(input: SynParseStream) -> syn::parse::Result<syn::ExprCall> {
let path: syn::ExprPath = input.parse()?;
let paren_span = input.cursor().span();
let args: Punctuated<syn::Expr, Token![,]> = input.parse_group(Delimiter::Parenthesis, |i| {
i.parse_terminated(syn::Expr::parse)
})?;
Ok(syn::ExprCall {
attrs: vec![],
func: Box::new(syn::Expr::Path(path)),
paren_token: syn::token::Paren(paren_span),
args: args
})
}
impl Parse for CallPattern {
fn parse(input: SynParseStream) -> PResult<Self> {
let name = input.try_parse(|input| {
let ident: syn::Ident = input.parse()?;
input.parse::<Token![@]>()?;
Ok(ident)
}).ok();
Ok(CallPattern { name, expr: parse_expr_call(input)? })
}
}
impl Pattern {
fn validate(&self) -> PResult<()> {
let mut prev = None;
if let Pattern::Calls(ref calls) = self {
for call in calls.iter() {
if prev.is_none() { prev = Some(call.name.clone()); }
let prev_name = prev.as_ref().unwrap();
if prev_name != &call.name {
let mut err = if let Some(ref ident) = call.name {
ident.span().unstable()
.error("captured name differs from declaration")
} else {
call.expr.span()
.error("expected capture name due to previous declaration")
};
err = match prev_name {
Some(p) => err.span_note(p.span().unstable(), "declared here"),
None => err
};
return Err(err.into());
}
}
}
Ok(())
}
}
impl Parse for Case {
fn parse(input: SynParseStream) -> PResult<Self> {
let case_span_start = input.cursor().span().unstable();
let pattern = if let Ok(wild) = input.parse::<Token![_]>() {
Pattern::Wild(wild)
} else {
let call_patterns =
input.call(<Punctuated<CallPattern, Token![|]>>::parse_separated_nonempty)?;
Pattern::Calls(call_patterns)
};
pattern.validate()?;
input.parse::<Token![=>]>()?;
let expr: syn::Expr = input.parse()?;
let span = case_span_start
.join(input.cursor().span().unstable())
.unwrap_or(case_span_start);
Ok(Case { pattern, expr, span })
}
}
impl Parse for Switch {
fn parse(stream: SynParseStream) -> PResult<Switch> {
let (parser_name, input) = stream.parse_group(Delimiter::Bracket, |inner| {
let name: syn::Ident = inner.parse()?;
inner.parse::<Token![;]>()?;
let input: syn::Expr = inner.parse()?;
Ok((name, input))
})?;
let cases: Punctuated<Case, Token![,]> = stream.parse_terminated(Case::syn_parse)?;
if !stream.is_empty() {
Err(stream.error("trailing characters; expected eof"))?;
}
if cases.is_empty() {
Err(stream.error("switch cannot be empty"))?;
}
for case in cases.iter().take(cases.len() - 1) {
if let Pattern::Wild(..) = case.pattern {
Err(case.span.error("`_` matches can only appear as the last case"))?;
}
}
Ok(Switch { parser_name, input, cases })
}
}