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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::source::snippet_with_applicability;
   3 use clippy_utils::ty::{is_copy, is_type_diagnostic_item};
   4 use clippy_utils::{is_diag_trait_item, meets_msrv, msrvs, peel_blocks};
   5 use if_chain::if_chain;
   6 use rustc_errors::Applicability;
   7 use rustc_hir as hir;
   8 use rustc_lint::LateContext;
   9 use rustc_middle::mir::Mutability;
  10 use rustc_middle::ty;
  11 use rustc_middle::ty::adjustment::Adjust;
  12 use rustc_semver::RustcVersion;
  13 use rustc_span::symbol::Ident;
  14 use rustc_span::{sym, Span};
  15
  16 use super::MAP_CLONE;
  17
  18 pub(super) fn check(
  19     cx: &LateContext<'_>,
  20     e: &hir::Expr<'_>,
  21     recv: &hir::Expr<'_>,
  22     arg: &hir::Expr<'_>,
  23     msrv: Option<RustcVersion>,
  24 ) {
  25     if_chain! {
  26         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(e.hir_id);
  27         if cx.tcx.impl_of_method(method_id)
  28             .map_or(false, |id| is_type_diagnostic_item(cx, cx.tcx.type_of(id), sym::Option))
  29             || is_diag_trait_item(cx, method_id, sym::Iterator);
  30         if let hir::ExprKind::Closure(&hir::Closure{ body, .. }) = arg.kind;
  31         then {
  32             let closure_body = cx.tcx.hir().body(body);
  33             let closure_expr = peel_blocks(closure_body.value);
  34             match closure_body.params[0].pat.kind {
  35                 hir::PatKind::Ref(inner, hir::Mutability::Not) => if let hir::PatKind::Binding(
  36                     hir::BindingAnnotation::NONE, .., name, None
  37                 ) = inner.kind {
  38                     if ident_eq(name, closure_expr) {
  39                         lint_explicit_closure(cx, e.span, recv.span, true, msrv);
  40                     }
  41                 },
  42                 hir::PatKind::Binding(hir::BindingAnnotation::NONE, .., name, None) => {
  43                     match closure_expr.kind {
  44                         hir::ExprKind::Unary(hir::UnOp::Deref, inner) => {
  45                             if ident_eq(name, inner) {
  46                                 if let ty::Ref(.., Mutability::Not) = cx.typeck_results().expr_ty(inner).kind() {
  47                                     lint_explicit_closure(cx, e.span, recv.span, true, msrv);
  48                                 }
  49                             }
  50                         },
  51                         hir::ExprKind::MethodCall(method, obj, [], _) => if_chain! {
  52                             if ident_eq(name, obj) && method.ident.name == sym::clone;
  53                             if let Some(fn_id) = cx.typeck_results().type_dependent_def_id(closure_expr.hir_id);
  54                             if let Some(trait_id) = cx.tcx.trait_of_item(fn_id);
  55                             if cx.tcx.lang_items().clone_trait().map_or(false, |id| id == trait_id);
  56                             // no autoderefs
  57                             if !cx.typeck_results().expr_adjustments(obj).iter()
  58                                 .any(|a| matches!(a.kind, Adjust::Deref(Some(..))));
  59                             then {
  60                                 let obj_ty = cx.typeck_results().expr_ty(obj);
  61                                 if let ty::Ref(_, ty, mutability) = obj_ty.kind() {
  62                                     if matches!(mutability, Mutability::Not) {
  63                                         let copy = is_copy(cx, *ty);
  64                                         lint_explicit_closure(cx, e.span, recv.span, copy, msrv);
  65                                     }
  66                                 } else {
  67                                     lint_needless_cloning(cx, e.span, recv.span);
  68                                 }
  69                             }
  70                         },
  71                         _ => {},
  72                     }
  73                 },
  74                 _ => {},
  75             }
  76         }
  77     }
  78 }
  79
  80 fn ident_eq(name: Ident, path: &hir::Expr<'_>) -> bool {
  81     if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = path.kind {
  82         path.segments.len() == 1 && path.segments[0].ident == name
  83     } else {
  84         false
  85     }
  86 }
  87
  88 fn lint_needless_cloning(cx: &LateContext<'_>, root: Span, receiver: Span) {
  89     span_lint_and_sugg(
  90         cx,
  91         MAP_CLONE,
  92         root.trim_start(receiver).unwrap(),
  93         "you are needlessly cloning iterator elements",
  94         "remove the `map` call",
  95         String::new(),
  96         Applicability::MachineApplicable,
  97     );
  98 }
  99
 100 fn lint_explicit_closure(cx: &LateContext<'_>, replace: Span, root: Span, is_copy: bool, msrv: Option<RustcVersion>) {
 101     let mut applicability = Applicability::MachineApplicable;
 102
 103     let (message, sugg_method) = if is_copy && meets_msrv(msrv, msrvs::ITERATOR_COPIED) {
 104         ("you are using an explicit closure for copying elements", "copied")
 105     } else {
 106         ("you are using an explicit closure for cloning elements", "cloned")
 107     };
 108
 109     span_lint_and_sugg(
 110         cx,
 111         MAP_CLONE,
 112         replace,
 113         message,
 114         &format!("consider calling the dedicated `{sugg_method}` method"),
 115         format!(
 116             "{}.{sugg_method}()",
 117             snippet_with_applicability(cx, root, "..", &mut applicability),
 118         ),
 119         applicability,
 120     );
 121 }