clippy_lints/src/methods/extend_with_drain.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::source::snippet_with_applicability;
   3 use clippy_utils::ty::{is_type_diagnostic_item, is_type_lang_item};
   4 use if_chain::if_chain;
   5 use rustc_errors::Applicability;
   6 use rustc_hir::{Expr, ExprKind, LangItem};
   7 use rustc_lint::LateContext;
   8 use rustc_span::symbol::sym;
   9
  10 use super::EXTEND_WITH_DRAIN;
  11
  12 pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, arg: &Expr<'_>) {
  13     let ty = cx.typeck_results().expr_ty(recv).peel_refs();
  14     if_chain! {
  15         if is_type_diagnostic_item(cx, ty, sym::Vec);
  16         //check source object
  17         if let ExprKind::MethodCall(src_method, drain_vec, [drain_arg], _) = &arg.kind;
  18         if src_method.ident.as_str() == "drain";
  19         let src_ty = cx.typeck_results().expr_ty(drain_vec);
  20         //check if actual src type is mutable for code suggestion
  21         let immutable = src_ty.is_mutable_ptr();
  22         let src_ty = src_ty.peel_refs();
  23         if is_type_diagnostic_item(cx, src_ty, sym::Vec);
  24         //check drain range
  25         if let src_ty_range = cx.typeck_results().expr_ty(drain_arg).peel_refs();
  26         if is_type_lang_item(cx, src_ty_range, LangItem::RangeFull);
  27         then {
  28             let mut applicability = Applicability::MachineApplicable;
  29             span_lint_and_sugg(
  30                 cx,
  31                 EXTEND_WITH_DRAIN,
  32                 expr.span,
  33                 "use of `extend` instead of `append` for adding the full range of a second vector",
  34                 "try this",
  35                 format!(
  36                     "{}.append({}{})",
  37                     snippet_with_applicability(cx, recv.span, "..", &mut applicability),
  38                     if immutable { "" } else { "&mut " },
  39                     snippet_with_applicability(cx, drain_vec.span, "..", &mut applicability)
  40                 ),
  41                 applicability,
  42             );
  43         }
  44     }
  45 }