81 lines
2.3 KiB
Rust
81 lines
2.3 KiB
Rust
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// Copyright (c) 2024 Jonas Schäfer <jonas@zombofant.net>
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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//! Infrastructure for contextual error messages
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use std::fmt;
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use syn::*;
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/// Reference to a compound field's parent
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///
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/// This reference can be converted to a hopefully-useful human-readable
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/// string via [`std::fmt::Display`].
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#[derive(Clone, Debug)]
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pub(super) enum ParentRef {
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/// The parent is addressable by a path, e.g. a struct type or enum
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/// variant.
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Named(Path),
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}
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impl From<Path> for ParentRef {
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fn from(other: Path) -> Self {
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Self::Named(other)
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}
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}
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impl From<&Path> for ParentRef {
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fn from(other: &Path) -> Self {
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Self::Named(other.clone())
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}
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}
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impl fmt::Display for ParentRef {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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match self {
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Self::Named(name) => {
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let mut first = true;
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for segment in name.segments.iter() {
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if !first || name.leading_colon.is_some() {
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write!(f, "::")?;
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}
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first = false;
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write!(f, "{}", segment.ident)?;
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}
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write!(f, " element")
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}
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}
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}
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}
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/// Ephemeral struct to create a nice human-readable representation of
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/// [`syn::Member`].
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///
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/// It implements [`std::fmt::Display`] for that purpose and is otherwise of
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/// little use.
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#[repr(transparent)]
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struct FieldName<'x>(&'x Member);
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impl fmt::Display for FieldName<'_> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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match self.0 {
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Member::Named(v) => write!(f, "field '{}'", v),
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Member::Unnamed(v) => write!(f, "unnamed field {}", v.index),
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}
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}
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}
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/// Create a string error message for a missing attribute.
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///
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/// `parent_name` should point at the compound which is being parsed and
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/// `field` should be the field to which the attribute belongs.
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pub(super) fn on_missing_attribute(parent_name: &ParentRef, field: &Member) -> String {
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format!(
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"Required attribute {} on {} missing.",
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FieldName(&field),
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parent_name
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)
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}
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