src/tools/clippy/clippy_lints/src/matches/match_wild_err_arm.rs

   1 use clippy_utils::diagnostics::span_lint_and_note;
   2 use clippy_utils::macros::{is_panic, root_macro_call};
   3 use clippy_utils::ty::is_type_diagnostic_item;
   4 use clippy_utils::visitors::is_local_used;
   5 use clippy_utils::{is_wild, peel_blocks_with_stmt};
   6 use rustc_hir::{Arm, Expr, PatKind};
   7 use rustc_lint::LateContext;
   8 use rustc_span::symbol::{kw, sym};
   9
  10 use super::MATCH_WILD_ERR_ARM;
  11
  12 pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, ex: &Expr<'tcx>, arms: &[Arm<'tcx>]) {
  13     let ex_ty = cx.typeck_results().expr_ty(ex).peel_refs();
  14     if is_type_diagnostic_item(cx, ex_ty, sym::Result) {
  15         for arm in arms {
  16             if let PatKind::TupleStruct(ref path, inner, _) = arm.pat.kind {
  17                 let path_str = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| s.print_qpath(path, false));
  18                 if path_str == "Err" {
  19                     let mut matching_wild = inner.iter().any(is_wild);
  20                     let mut ident_bind_name = kw::Underscore;
  21                     if !matching_wild {
  22                         // Looking for unused bindings (i.e.: `_e`)
  23                         for pat in inner.iter() {
  24                             if let PatKind::Binding(_, id, ident, None) = pat.kind {
  25                                 if ident.as_str().starts_with('_') && !is_local_used(cx, arm.body, id) {
  26                                     ident_bind_name = ident.name;
  27                                     matching_wild = true;
  28                                 }
  29                             }
  30                         }
  31                     }
  32                     if_chain! {
  33                         if matching_wild;
  34                         if let Some(macro_call) = root_macro_call(peel_blocks_with_stmt(arm.body).span);
  35                         if is_panic(cx, macro_call.def_id);
  36                         then {
  37                             // `Err(_)` or `Err(_e)` arm with `panic!` found
  38                             span_lint_and_note(cx,
  39                                 MATCH_WILD_ERR_ARM,
  40                                 arm.pat.span,
  41                                 &format!("`Err({})` matches all errors", ident_bind_name),
  42                                 None,
  43                                 "match each error separately or use the error output, or use `.expect(msg)` if the error case is unreachable",
  44                             );
  45                         }
  46                     }
  47                 }
  48             }
  49         }
  50     }
  51 }