src/tools/clippy/clippy_lints/src/methods/map_identity.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::ty::is_type_diagnostic_item;
   3 use clippy_utils::{is_expr_identity_function, is_trait_method};
   4 use rustc_errors::Applicability;
   5 use rustc_hir as hir;
   6 use rustc_lint::LateContext;
   7 use rustc_span::{source_map::Span, sym};
   8
   9 use super::MAP_IDENTITY;
  10
  11 pub(super) fn check(
  12     cx: &LateContext<'_>,
  13     expr: &hir::Expr<'_>,
  14     caller: &hir::Expr<'_>,
  15     map_arg: &hir::Expr<'_>,
  16     name: &str,
  17     _map_span: Span,
  18 ) {
  19     let caller_ty = cx.typeck_results().expr_ty(caller);
  20
  21     if_chain! {
  22         if is_trait_method(cx, expr, sym::Iterator)
  23             || is_type_diagnostic_item(cx, caller_ty, sym::Result)
  24             || is_type_diagnostic_item(cx, caller_ty, sym::Option);
  25         if is_expr_identity_function(cx, map_arg);
  26         if let Some(sugg_span) = expr.span.trim_start(caller.span);
  27         then {
  28             span_lint_and_sugg(
  29                 cx,
  30                 MAP_IDENTITY,
  31                 sugg_span,
  32                 "unnecessary map of the identity function",
  33                 &format!("remove the call to `{name}`"),
  34                 String::new(),
  35                 Applicability::MachineApplicable,
  36             )
  37         }
  38     }
  39 }