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macros: spanless subdiagnostics from () fields

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Type attributes could previously be used to support spanless
subdiagnostics but these couldn't easily be made optional in the same
way that spanned subdiagnostics could by using a field attribute on a
field with an `Option<Span>` type. Spanless subdiagnostics can now be
specified on fields with `()` type or `Option<()>` type.

Signed-off-by: David Wood <david.wood@huawei.com>
This commit is contained in:
David Wood
2022-05-07 06:02:11 +01:00
parent 1d2ea98cff
commit 7b7061dd89
4 changed files with 97 additions and 33 deletions
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54
compiler/rustc_macros/src/diagnostics/utils.rs
View File

@@ -4,7 +4,7 @@ use proc_macro2::TokenStream;
use quote::{format_ident, quote, ToTokens};
use std::collections::BTreeSet;
use std::str::FromStr;
use syn::{spanned::Spanned, Attribute, Meta, Type, Visibility};
use syn::{spanned::Spanned, Attribute, Meta, Type, TypeTuple, Visibility};
use synstructure::BindingInfo;
/// Checks whether the type name of `ty` matches `name`.
@@ -25,7 +25,35 @@ pub(crate) fn type_matches_path(ty: &Type, name: &[&str]) -> bool {
}
}
/// Reports an error if the field's type is not `Applicability`.
/// Checks whether the type `ty` is `()`.
pub(crate) fn type_is_unit(ty: &Type) -> bool {
if let Type::Tuple(TypeTuple { elems, .. }) = ty { elems.is_empty() } else { false }
}
/// Reports a type error for field with `attr`.
pub(crate) fn report_type_error(
attr: &Attribute,
ty_name: &str,
) -> Result<!, SessionDiagnosticDeriveError> {
let name = attr.path.segments.last().unwrap().ident.to_string();
let meta = attr.parse_meta()?;
throw_span_err!(
attr.span().unwrap(),
&format!(
"the `#[{}{}]` attribute can only be applied to fields of type {}",
name,
match meta {
Meta::Path(_) => "",
Meta::NameValue(_) => " = ...",
Meta::List(_) => "(...)",
},
ty_name
)
);
}
/// Reports an error if the field's type does not match `path`.
fn report_error_if_not_applied_to_ty(
attr: &Attribute,
info: &FieldInfo<'_>,
@@ -33,23 +61,7 @@ fn report_error_if_not_applied_to_ty(
ty_name: &str,
) -> Result<(), SessionDiagnosticDeriveError> {
if !type_matches_path(&info.ty, path) {
let name = attr.path.segments.last().unwrap().ident.to_string();
let name = name.as_str();
let meta = attr.parse_meta()?;
throw_span_err!(
attr.span().unwrap(),
&format!(
"the `#[{}{}]` attribute can only be applied to fields of type `{}`",
name,
match meta {
Meta::Path(_) => "",
Meta::NameValue(_) => " = ...",
Meta::List(_) => "(...)",
},
ty_name
)
);
report_type_error(attr, ty_name)?;
}
Ok(())
@@ -64,7 +76,7 @@ pub(crate) fn report_error_if_not_applied_to_applicability(
attr,
info,
&["rustc_errors", "Applicability"],
"Applicability",
"`Applicability`",
)
}
@@ -73,7 +85,7 @@ pub(crate) fn report_error_if_not_applied_to_span(
attr: &Attribute,
info: &FieldInfo<'_>,
) -> Result<(), SessionDiagnosticDeriveError> {
report_error_if_not_applied_to_ty(attr, info, &["rustc_span", "Span"], "Span")
report_error_if_not_applied_to_ty(attr, info, &["rustc_span", "Span"], "`Span`")
}
/// Inner type of a field and type of wrapper.