bjoernager/rust
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Tweak output and add test cases

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This commit is contained in:
Esteban Küber 2020-09-22 19:19:33 -07:00
parent 711760c8ec
commit 5217007a20
3 changed files with 223 additions and 17 deletions
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58
compiler/rustc_resolve/src/late/diagnostics.rs
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@ -19,7 +19,7 @@ use rustc_session::config::nightly_options;
use rustc_session::parse::feature_err;
use rustc_span::hygiene::MacroKind;
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::{BytePos, Span, DUMMY_SP};
use rustc_span::{BytePos, MultiSpan, Span, DUMMY_SP};
use tracing::debug;
@ -446,12 +446,58 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
err.span_label(base_span, fallback_label);
if let PathSource::Trait(AliasPossibility::Maybe) = source {
if let Some([start, .., end]) = self.diagnostic_metadata.current_trait_object {
err.span_help(
start.span().to(end.span()),
"`+` can be used to constrain a \"trait object\" type with lifetimes or \
auto-traits, structs and enums can't be bound in that way",
if let Some(bounds @ [_, .., _]) = self.diagnostic_metadata.current_trait_object {
let spans: Vec<Span> = bounds
.iter()
.map(|bound| bound.span())
.filter(|&sp| sp != base_span)
.collect();
let start_span = bounds.iter().map(|bound| bound.span()).next().unwrap();
// `end_span` is the end of the poly trait ref (Foo + 'baz + Bar><)
let end_span = bounds.iter().map(|bound| bound.span()).last().unwrap();
// `last_bound_span` is the last bound of the poly trait ref (Foo + >'baz< + Bar)
let last_bound_span = spans.last().cloned().unwrap();
let mut multi_span: MultiSpan = spans.clone().into();
for sp in spans {
let msg = if sp == last_bound_span {
format!(
"...because of {} bound{}",
if bounds.len() <= 2 { "this" } else { "these" },
if bounds.len() <= 2 { "" } else { "s" },
)
} else {
String::new()
};
multi_span.push_span_label(sp, msg);
}
multi_span.push_span_label(
base_span,
"expected this type to be a trait...".to_string(),
);
err.span_help(
multi_span,
"`+` is used to constrain a \"trait object\" type with lifetimes or \
auto-traits; structs and enums can't be bound in that way",
);
if bounds.iter().all(|bound| match bound {
ast::GenericBound::Outlives(_) => true,
ast::GenericBound::Trait(tr, _) => tr.span == base_span,
}) {
let mut sugg = vec![];
if base_span != start_span {
sugg.push((start_span.until(base_span), String::new()));
}
if base_span != end_span {
sugg.push((base_span.shrink_to_hi().to(end_span), String::new()));
}
err.multipart_suggestion(
"if you meant to use a type and not a trait here, remove the bounds",
sugg,
Applicability::MaybeIncorrect,
);
}
}
}
match self.diagnostic_metadata.current_let_binding {