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

   1 use crate::utils::{match_qpath, match_trait_method, paths, span_lint_and_sugg};
   2 use if_chain::if_chain;
   3 use rustc_errors::Applicability;
   4 use rustc_hir as hir;
   5 use rustc_lint::LateContext;
   6 use rustc_span::source_map::Span;
   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_args: &'tcx [hir::Expr<'_>],
  15     flat_map_span: Span,
  16 ) {
  17     if match_trait_method(cx, expr, &paths::ITERATOR) {
  18         let arg_node = &flat_map_args[1].kind;
  19
  20         let apply_lint = |message: &str| {
  21             span_lint_and_sugg(
  22                 cx,
  23                 FLAT_MAP_IDENTITY,
  24                 flat_map_span.with_hi(expr.span.hi()),
  25                 message,
  26                 "try",
  27                 "flatten()".to_string(),
  28                 Applicability::MachineApplicable,
  29             );
  30         };
  31
  32         if_chain! {
  33             if let hir::ExprKind::Closure(_, _, body_id, _, _) = arg_node;
  34             let body = cx.tcx.hir().body(*body_id);
  35
  36             if let hir::PatKind::Binding(_, _, binding_ident, _) = body.params[0].pat.kind;
  37             if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = body.value.kind;
  38
  39             if path.segments.len() == 1;
  40             if path.segments[0].ident.name == binding_ident.name;
  41
  42             then {
  43                 apply_lint("called `flat_map(|x| x)` on an `Iterator`");
  44             }
  45         }
  46
  47         if_chain! {
  48             if let hir::ExprKind::Path(ref qpath) = arg_node;
  49
  50             if match_qpath(qpath, &paths::STD_CONVERT_IDENTITY);
  51
  52             then {
  53                 apply_lint("called `flat_map(std::convert::identity)` on an `Iterator`");
  54             }
  55         }
  56     }
  57 }