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use clippy_utils::diagnostics::span_lint_and_note;
use clippy_utils::macros::{is_panic, root_macro_call};
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::visitors::is_local_used;
use clippy_utils::{is_wild, peel_blocks_with_stmt};
use rustc_hir::{Arm, Expr, PatKind};
use rustc_lint::LateContext;
use rustc_span::symbol::{kw, sym};
use super::MATCH_WILD_ERR_ARM;
pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, ex: &Expr<'tcx>, arms: &[Arm<'tcx>]) {
let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
if is_type_diagnostic_item(cx, ex_ty, sym::Result) {
for arm in arms {
if let PatKind::TupleStruct(ref path, inner, _) = arm.pat.kind {
let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
if path_str == "Err" {
let mut matching_wild = inner.iter().any(is_wild);
let mut ident_bind_name = kw::Underscore;
if !matching_wild {
// Looking for unused bindings (i.e.: `_e`)
for pat in inner.iter() {
if let PatKind::Binding(_, id, ident, None) = pat.kind {
if ident.as_str().starts_with('_') && !is_local_used(cx, arm.body, id) {
ident_bind_name = ident.name;
matching_wild = true;
}
}
}
}
if_chain! {
if matching_wild;
if let Some(macro_call) = root_macro_call(peel_blocks_with_stmt(arm.body).span);
if is_panic(cx, macro_call.def_id);
then {
// `Err(_)` or `Err(_e)` arm with `panic!` found
span_lint_and_note(cx,
MATCH_WILD_ERR_ARM,
arm.pat.span,
&format!("`Err({})` matches all errors", ident_bind_name),
None,
"match each error separately or use the error output, or use `.expect(msg)` if the error case is unreachable",
);
}
}
}
}
}
}
}
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