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Add machine-applicable suggestions 

This avoids the need for tools like rust-analyzer to implement these
suggestions themselves.
This commit is contained in:
Jacob Pratt 2021-07-12 02:26:14 -04:00
parent c70147fd66
commit eef2856eaf
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GPG Key ID: B80E19E4662B5AA4
1 changed files with 42 additions and 8 deletions
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50
compiler/rustc_builtin_macros/src/deriving/default.rs
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@ -132,18 +132,52 @@ fn extract_default_variant<'a>(
let variant = match default_variants.as_slice() {
[variant] => variant,
[] => {
cx.struct_span_err(trait_span, "no default declared")
.help("make a unit variant default by placing `#[default]` above it")
.emit();
let possible_defaults = enum_def
.variants
.iter()
.filter(|variant| matches!(variant.data, VariantData::Unit(..)))
.filter(|variant| !cx.sess.contains_name(&variant.attrs, sym::non_exhaustive));
let mut diag = cx.struct_span_err(trait_span, "no default declared");
diag.help("make a unit variant default by placing `#[default]` above it");
for variant in possible_defaults {
// Suggest making each unit variant default.
diag.tool_only_span_suggestion(
variant.span,
&format!("make `{}` default", variant.ident),
format!("#[default] {}", variant.ident),
Applicability::MaybeIncorrect,
);
}
diag.emit();
return Err(());
}
[first, rest @ ..] => {
cx.struct_span_err(trait_span, "multiple declared defaults")
.span_label(first.span, "first default")
.span_labels(rest.iter().map(|variant| variant.span), "additional default")
.note("only one variant can be default")
.emit();
let mut diag = cx.struct_span_err(trait_span, "multiple declared defaults");
diag.span_label(first.span, "first default");
diag.span_labels(rest.iter().map(|variant| variant.span), "additional default");
diag.note("only one variant can be default");
for variant in &default_variants {
// Suggest making each variant already tagged default.
let suggestion = default_variants
.iter()
.filter_map(|v| {
if v.ident == variant.ident {
None
} else {
Some((cx.sess.find_by_name(&v.attrs, kw::Default)?.span, String::new()))
}
})
.collect();
diag.tool_only_multipart_suggestion(
&format!("make `{}` default", variant.ident),
suggestion,
Applicability::MaybeIncorrect,
);
}
diag.emit();
return Err(());
}