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Validate #[from] attribute

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David Tolnay 2019-10-12 16:50:41 -07:00
parent 8cbc50e05a
commit 2305f75976
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GPG key ID: F9BA143B95FF6D82
3 changed files with 54 additions and 9 deletions
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47
impl/src/valid.rs
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@ -1,6 +1,6 @@
use crate::ast::{Enum, Field, Input, Struct, Variant};
use crate::attr::Attrs;
use syn::{Error, Result};
use syn::{Error, Member, Result};
pub(crate) const CHECKED: &str = "checked in validation";
@ -65,6 +65,12 @@ impl Field<'_> {
}
fn check_non_field_attrs(attrs: &Attrs) -> Result<()> {
if let Some(from) = &attrs.from {
return Err(Error::new_spanned(
from,
"not expected here; the #[from] attribute belongs on a specific field",
));
}
if let Some(source) = &attrs.source {
return Err(Error::new_spanned(
source,
@ -81,24 +87,47 @@ fn check_non_field_attrs(attrs: &Attrs) -> Result<()> {
}
fn check_field_attrs(fields: &[Field]) -> Result<()> {
let mut has_source = false;
let mut has_backtrace = false;
let mut from_field = None;
let mut source_field = None;
let mut backtrace_field = None;
for field in fields {
if let Some(source) = &field.attrs.source {
if has_source {
if let Some(from) = field.attrs.from {
if from_field.is_some() {
return Err(Error::new_spanned(from, "duplicate #[from] attribute"));
}
from_field = Some(field);
}
if let Some(source) = field.attrs.source {
if source_field.is_some() {
return Err(Error::new_spanned(source, "duplicate #[source] attribute"));
}
has_source = true;
source_field = Some(field);
}
if let Some(backtrace) = &field.attrs.backtrace {
if has_backtrace {
if let Some(backtrace) = field.attrs.backtrace {
if backtrace_field.is_some() {
return Err(Error::new_spanned(
backtrace,
"duplicate #[backtrace] attribute",
));
}
has_backtrace = true;
backtrace_field = Some(field);
}
}
if let (Some(from_field), Some(source_field)) = (from_field, source_field) {
if !same_member(from_field, source_field) {
return Err(Error::new_spanned(
from_field.attrs.from,
"#[from] is only supported on the source field, not any other field",
));
}
}
Ok(())
}
fn same_member(one: &Field, two: &Field) -> bool {
match (&one.member, &two.member) {
(Member::Named(one), Member::Named(two)) => one == two,
(Member::Unnamed(one), Member::Unnamed(two)) => one.index == two.index,
_ => unreachable!(),
}
}