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     _map_span: Span,
  17 ) {
  18     let caller_ty = cx.typeck_results().expr_ty(caller);
  19
  20     if_chain! {
  21         if is_trait_method(cx, expr, sym::Iterator)
  22             || is_type_diagnostic_item(cx, caller_ty, sym::Result)
  23             || is_type_diagnostic_item(cx, caller_ty, sym::Option);
  24         if is_expr_identity_function(cx, map_arg);
  25         if let Some(sugg_span) = expr.span.trim_start(caller.span);
  26         then {
  27             span_lint_and_sugg(
  28                 cx,
  29                 MAP_IDENTITY,
  30                 sugg_span,
  31                 "unnecessary map of the identity function",
  32                 "remove the call to `map`",
  33                 String::new(),
  34                 Applicability::MachineApplicable,
  35             )
  36         }
  37     }
  38 }