clippy_lints/src/methods/filter_map_identity.rs

   1 use crate::utils::{match_qpath, match_trait_method, path_to_local_id, 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::FILTER_MAP_IDENTITY;
   9
  10 pub(super) fn check(
  11     cx: &LateContext<'_>,
  12     expr: &hir::Expr<'_>,
  13     filter_map_args: &[hir::Expr<'_>],
  14     filter_map_span: Span,
  15 ) {
  16     if match_trait_method(cx, expr, &paths::ITERATOR) {
  17         let arg_node = &filter_map_args[1].kind;
  18
  19         let apply_lint = |message: &str| {
  20             span_lint_and_sugg(
  21                 cx,
  22                 FILTER_MAP_IDENTITY,
  23                 filter_map_span.with_hi(expr.span.hi()),
  24                 message,
  25                 "try",
  26                 "flatten()".to_string(),
  27                 Applicability::MachineApplicable,
  28             );
  29         };
  30
  31         if_chain! {
  32             if let hir::ExprKind::Closure(_, _, body_id, _, _) = arg_node;
  33             let body = cx.tcx.hir().body(*body_id);
  34
  35             if let hir::PatKind::Binding(_, binding_id, ..) = body.params[0].pat.kind;
  36             if path_to_local_id(&body.value, binding_id);
  37             then {
  38                 apply_lint("called `filter_map(|x| x)` on an `Iterator`");
  39             }
  40         }
  41
  42         if_chain! {
  43             if let hir::ExprKind::Path(ref qpath) = arg_node;
  44
  45             if match_qpath(qpath, &paths::STD_CONVERT_IDENTITY);
  46
  47             then {
  48                 apply_lint("called `filter_map(std::convert::identity)` on an `Iterator`");
  49             }
  50         }
  51     }
  52 }