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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::{is_expr_path_def_path, is_trait_method, path_to_local_id, paths};
   3 use if_chain::if_chain;
   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::FILTER_MAP_IDENTITY;
  10
  11 pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, filter_map_arg: &hir::Expr<'_>, filter_map_span: Span) {
  12     if is_trait_method(cx, expr, sym::Iterator) {
  13         let apply_lint = |message: &str| {
  14             span_lint_and_sugg(
  15                 cx,
  16                 FILTER_MAP_IDENTITY,
  17                 filter_map_span.with_hi(expr.span.hi()),
  18                 message,
  19                 "try",
  20                 "flatten()".to_string(),
  21                 Applicability::MachineApplicable,
  22             );
  23         };
  24
  25         if_chain! {
  26             if let hir::ExprKind::Closure(_, _, body_id, _, _) = filter_map_arg.kind;
  27             let body = cx.tcx.hir().body(body_id);
  28
  29             if let hir::PatKind::Binding(_, binding_id, ..) = body.params[0].pat.kind;
  30             if path_to_local_id(&body.value, binding_id);
  31             then {
  32                 apply_lint("called `filter_map(|x| x)` on an `Iterator`");
  33             }
  34         }
  35
  36         if is_expr_path_def_path(cx, filter_map_arg, &paths::CONVERT_IDENTITY) {
  37             apply_lint("called `filter_map(std::convert::identity)` on an `Iterator`");
  38         }
  39     }
  40 }