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Improve dyn/impl-related parse errors

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This commit is contained in:
David Tolnay 2022-11-30 19:15:08 -08:00
parent b8b0761cb8
commit db874ddf9b
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GPG Key ID: F9BA143B95FF6D82
1 changed files with 56 additions and 23 deletions
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79
src/ty.rs
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@ -337,7 +337,7 @@ pub mod parsing {
use crate::ext::IdentExt;
use crate::parse::{Parse, ParseStream, Result};
use crate::path;
use proc_macro2::{Punct, Spacing, TokenTree};
use proc_macro2::{Punct, Spacing, Span, TokenTree};
#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
impl Parse for Type {
@ -546,13 +546,17 @@ pub mod parsing {
|| lookahead.peek(Token![<])
{
let dyn_token: Option<Token![dyn]> = input.parse()?;
if dyn_token.is_some() {
if let Some(dyn_token) = dyn_token {
let dyn_span = dyn_token.span;
let star_token: Option<Token![*]> = input.parse()?;
let bounds = TypeTraitObject::parse_bounds(input, allow_plus)?;
let bounds = TypeTraitObject::parse_bounds(dyn_span, input, allow_plus)?;
return Ok(if star_token.is_some() {
Type::Verbatim(verbatim::between(begin, input))
} else {
Type::TraitObject(TypeTraitObject { dyn_token, bounds })
Type::TraitObject(TypeTraitObject {
dyn_token: Some(dyn_token),
bounds,
})
});
}
@ -896,15 +900,6 @@ pub mod parsing {
}
}
fn at_least_one_type(bounds: &Punctuated<TypeParamBound, Token![+]>) -> bool {
for bound in bounds {
if let TypeParamBound::Trait(_) = *bound {
return true;
}
}
false
}
impl TypeTraitObject {
#[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
pub fn without_plus(input: ParseStream) -> Result<Self> {
@ -914,20 +909,38 @@ pub mod parsing {
// Only allow multiple trait references if allow_plus is true.
pub(crate) fn parse(input: ParseStream, allow_plus: bool) -> Result<Self> {
Ok(TypeTraitObject {
dyn_token: input.parse()?,
bounds: Self::parse_bounds(input, allow_plus)?,
})
let dyn_token: Option<Token![dyn]> = input.parse()?;
let dyn_span = match &dyn_token {
Some(token) => token.span,
None => input.span(),
};
let bounds = Self::parse_bounds(dyn_span, input, allow_plus)?;
Ok(TypeTraitObject { dyn_token, bounds })
}
fn parse_bounds(
dyn_span: Span,
input: ParseStream,
allow_plus: bool,
) -> Result<Punctuated<TypeParamBound, Token![+]>> {
let bounds = TypeParamBound::parse_multiple(input, allow_plus)?;
let mut last_lifetime_span = None;
let mut at_least_one_trait = false;
for bound in &bounds {
match bound {
TypeParamBound::Trait(_) => {
at_least_one_trait = true;
break;
}
TypeParamBound::Lifetime(lifetime) => {
last_lifetime_span = Some(lifetime.ident.span());
}
}
}
// Just lifetimes like `'a + 'b` is not a TraitObject.
if !at_least_one_type(&bounds) {
return Err(input.error("expected at least one type"));
if !at_least_one_trait {
let msg = "at least one trait is required for an object type";
return Err(error::new2(dyn_span, last_lifetime_span.unwrap(), msg));
}
Ok(bounds)
}
@ -949,10 +962,30 @@ pub mod parsing {
}
pub(crate) fn parse(input: ParseStream, allow_plus: bool) -> Result<Self> {
Ok(TypeImplTrait {
impl_token: input.parse()?,
bounds: TypeTraitObject::parse_bounds(input, allow_plus)?,
})
let impl_token: Token![impl] = input.parse()?;
let bounds = TypeParamBound::parse_multiple(input, allow_plus)?;
let mut last_lifetime_span = None;
let mut at_least_one_trait = false;
for bound in &bounds {
match bound {
TypeParamBound::Trait(_) => {
at_least_one_trait = true;
break;
}
TypeParamBound::Lifetime(lifetime) => {
last_lifetime_span = Some(lifetime.ident.span());
}
}
}
if !at_least_one_trait {
let msg = "at least one trait must be specified";
return Err(error::new2(
impl_token.span,
last_lifetime_span.unwrap(),
msg,
));
}
Ok(TypeImplTrait { impl_token, bounds })
}
}