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use clippy_utils::diagnostics::span_lint;
use clippy_utils::paths;
use rustc_hir::{Impl, Item, ItemKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::declare_lint_pass;
declare_clippy_lint! {
/// ### What it does
/// Checks for misuses of the serde API.
///
/// ### Why is this bad?
/// Serde is very finicky about how its API should be
/// used, but the type system can't be used to enforce it (yet?).
///
/// ### Example
/// Implementing `Visitor::visit_string` but not
/// `Visitor::visit_str`.
#[clippy::version = "pre 1.29.0"]
pub SERDE_API_MISUSE,
correctness,
"various things that will negatively affect your serde experience"
}
declare_lint_pass!(SerdeApi => [SERDE_API_MISUSE]);
impl<'tcx> LateLintPass<'tcx> for SerdeApi {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
if let ItemKind::Impl(Impl {
of_trait: Some(trait_ref),
items,
..
}) = item.kind
{
let did = trait_ref.path.res.def_id();
if paths::SERDE_DE_VISITOR.matches(cx, did) {
let mut seen_str = None;
let mut seen_string = None;
for item in *items {
match item.ident.as_str() {
"visit_str" => seen_str = Some(item.span),
"visit_string" => seen_string = Some(item.span),
_ => {},
}
}
if let Some(span) = seen_string
&& seen_str.is_none()
{
span_lint(
cx,
SERDE_API_MISUSE,
span,
"you should not implement `visit_string` without also implementing `visit_str`",
);
}
}
}
}
}
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