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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::msrvs::{self, Msrv};
   3 use clippy_utils::source::snippet_with_applicability;
   4 use clippy_utils::ty::{is_copy, is_type_diagnostic_item};
   5 use clippy_utils::{is_diag_trait_item, peel_blocks};
   6 use if_chain::if_chain;
   7 use rustc_errors::Applicability;
   8 use rustc_hir as hir;
   9 use rustc_lint::LateContext;
  10 use rustc_middle::mir::Mutability;
  11 use rustc_middle::ty;
  12 use rustc_middle::ty::adjustment::Adjust;
  13 use rustc_span::symbol::Ident;
  14 use rustc_span::{sym, Span};
  15
  16 use super::MAP_CLONE;
  17
  18 pub(super) fn check(cx: &LateContext<'_>, e: &hir::Expr<'_>, recv: &hir::Expr<'_>, arg: &hir::Expr<'_>, msrv: &Msrv) {
  19     if_chain! {
  20         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(e.hir_id);
  21         if cx.tcx.impl_of_method(method_id)
  22             .map_or(false, |id| is_type_diagnostic_item(cx, cx.tcx.type_of(id), sym::Option))
  23             || is_diag_trait_item(cx, method_id, sym::Iterator);
  24         if let hir::ExprKind::Closure(&hir::Closure{ body, .. }) = arg.kind;
  25         then {
  26             let closure_body = cx.tcx.hir().body(body);
  27             let closure_expr = peel_blocks(closure_body.value);
  28             match closure_body.params[0].pat.kind {
  29                 hir::PatKind::Ref(inner, hir::Mutability::Not) => if let hir::PatKind::Binding(
  30                     hir::BindingAnnotation::NONE, .., name, None
  31                 ) = inner.kind {
  32                     if ident_eq(name, closure_expr) {
  33                         lint_explicit_closure(cx, e.span, recv.span, true, msrv);
  34                     }
  35                 },
  36                 hir::PatKind::Binding(hir::BindingAnnotation::NONE, .., name, None) => {
  37                     match closure_expr.kind {
  38                         hir::ExprKind::Unary(hir::UnOp::Deref, inner) => {
  39                             if ident_eq(name, inner) {
  40                                 if let ty::Ref(.., Mutability::Not) = cx.typeck_results().expr_ty(inner).kind() {
  41                                     lint_explicit_closure(cx, e.span, recv.span, true, msrv);
  42                                 }
  43                             }
  44                         },
  45                         hir::ExprKind::MethodCall(method, obj, [], _) => if_chain! {
  46                             if ident_eq(name, obj) && method.ident.name == sym::clone;
  47                             if let Some(fn_id) = cx.typeck_results().type_dependent_def_id(closure_expr.hir_id);
  48                             if let Some(trait_id) = cx.tcx.trait_of_item(fn_id);
  49                             if cx.tcx.lang_items().clone_trait().map_or(false, |id| id == trait_id);
  50                             // no autoderefs
  51                             if !cx.typeck_results().expr_adjustments(obj).iter()
  52                                 .any(|a| matches!(a.kind, Adjust::Deref(Some(..))));
  53                             then {
  54                                 let obj_ty = cx.typeck_results().expr_ty(obj);
  55                                 if let ty::Ref(_, ty, mutability) = obj_ty.kind() {
  56                                     if matches!(mutability, Mutability::Not) {
  57                                         let copy = is_copy(cx, *ty);
  58                                         lint_explicit_closure(cx, e.span, recv.span, copy, msrv);
  59                                     }
  60                                 } else {
  61                                     lint_needless_cloning(cx, e.span, recv.span);
  62                                 }
  63                             }
  64                         },
  65                         _ => {},
  66                     }
  67                 },
  68                 _ => {},
  69             }
  70         }
  71     }
  72 }
  73
  74 fn ident_eq(name: Ident, path: &hir::Expr<'_>) -> bool {
  75     if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = path.kind {
  76         path.segments.len() == 1 && path.segments[0].ident == name
  77     } else {
  78         false
  79     }
  80 }
  81
  82 fn lint_needless_cloning(cx: &LateContext<'_>, root: Span, receiver: Span) {
  83     span_lint_and_sugg(
  84         cx,
  85         MAP_CLONE,
  86         root.trim_start(receiver).unwrap(),
  87         "you are needlessly cloning iterator elements",
  88         "remove the `map` call",
  89         String::new(),
  90         Applicability::MachineApplicable,
  91     );
  92 }
  93
  94 fn lint_explicit_closure(cx: &LateContext<'_>, replace: Span, root: Span, is_copy: bool, msrv: &Msrv) {
  95     let mut applicability = Applicability::MachineApplicable;
  96
  97     let (message, sugg_method) = if is_copy && msrv.meets(msrvs::ITERATOR_COPIED) {
  98         ("you are using an explicit closure for copying elements", "copied")
  99     } else {
 100         ("you are using an explicit closure for cloning elements", "cloned")
 101     };
 102
 103     span_lint_and_sugg(
 104         cx,
 105         MAP_CLONE,
 106         replace,
 107         message,
 108         &format!("consider calling the dedicated `{sugg_method}` method"),
 109         format!(
 110             "{}.{sugg_method}()",
 111             snippet_with_applicability(cx, root, "..", &mut applicability),
 112         ),
 113         applicability,
 114     );
 115 }