rust/compiler/rustc_hir/src/lints.rs

use rustc_data_structures::fingerprint::Fingerprint;
use rustc_macros::HashStable_Generic;
use rustc_span::Span;

use crate::{AttrPath, HirId, Target};

#[derive(Debug)]
pub struct DelayedLints {
    pub lints: Box<[DelayedLint]>,
    // Only present when the crate hash is needed.
    pub opt_hash: Option<Fingerprint>,
}

/// During ast lowering, no lints can be emitted.
/// That is because lints attach to nodes either in the AST, or on the built HIR.
/// When attached to AST nodes, they're emitted just before building HIR,
/// and then there's a gap where no lints can be emitted until HIR is done.
/// The variants in this enum represent lints that are temporarily stashed during
/// AST lowering to be emitted once HIR is built.
#[derive(Clone, Debug, HashStable_Generic)]
pub enum DelayedLint {
    AttributeParsing(AttributeLint<HirId>),
}

#[derive(Clone, Debug, HashStable_Generic)]
pub struct AttributeLint<Id> {
    pub id: Id,
    pub span: Span,
    pub kind: AttributeLintKind,
}

#[derive(Clone, Debug, HashStable_Generic)]
pub enum AttributeLintKind {
    UnusedDuplicate { this: Span, other: Span, warning: bool },
    IllFormedAttributeInput { suggestions: Vec<String> },
    EmptyAttribute { first_span: Span },
    InvalidTarget { name: AttrPath, target: Target, applied: Vec<String>, only: &'static str },
}