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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::{is_expr_identity_function, is_trait_method};
   3 use rustc_errors::Applicability;
   4 use rustc_hir as hir;
   5 use rustc_lint::LateContext;
   6 use rustc_span::{source_map::Span, sym};
   7
   8 use super::FLAT_MAP_IDENTITY;
   9
  10 /// lint use of `flat_map` for `Iterators` where `flatten` would be sufficient
  11 pub(super) fn check<'tcx>(
  12     cx: &LateContext<'tcx>,
  13     expr: &'tcx hir::Expr<'_>,
  14     flat_map_arg: &'tcx hir::Expr<'_>,
  15     flat_map_span: Span,
  16 ) {
  17     if is_trait_method(cx, expr, sym::Iterator) && is_expr_identity_function(cx, flat_map_arg) {
  18         span_lint_and_sugg(
  19             cx,
  20             FLAT_MAP_IDENTITY,
  21             flat_map_span.with_hi(expr.span.hi()),
  22             "use of `flat_map` with an identity function",
  23             "try",
  24             "flatten()".to_string(),
  25             Applicability::MachineApplicable,
  26         );
  27     }
  28 }