mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-12 14:22:45 +00:00
236 lines
9.4 KiB
Rust
236 lines
9.4 KiB
Rust
use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
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use clippy_utils::higher::VecArgs;
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use clippy_utils::source::snippet_opt;
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use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
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use clippy_utils::usage::local_used_after_expr;
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use clippy_utils::{higher, is_adjusted, path_to_local, path_to_local_id};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::def_id::DefId;
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use rustc_hir::{Closure, Expr, ExprKind, Param, PatKind, Unsafety};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow};
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use rustc_middle::ty::binding::BindingMode;
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use rustc_middle::ty::{self, Ty, TypeVisitable};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::symbol::sym;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for closures which just call another function where
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/// the function can be called directly. `unsafe` functions or calls where types
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/// get adjusted are ignored.
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///
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/// ### Why is this bad?
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/// Needlessly creating a closure adds code for no benefit
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/// and gives the optimizer more work.
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///
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/// ### Known problems
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/// If creating the closure inside the closure has a side-
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/// effect then moving the closure creation out will change when that side-
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/// effect runs.
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/// See [#1439](https://github.com/rust-lang/rust-clippy/issues/1439) for more details.
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///
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/// ### Example
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/// ```rust,ignore
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/// xs.map(|x| foo(x))
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/// ```
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///
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/// Use instead:
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/// ```rust,ignore
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/// // where `foo(_)` is a plain function that takes the exact argument type of `x`.
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/// xs.map(foo)
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub REDUNDANT_CLOSURE,
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style,
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"redundant closures, i.e., `|a| foo(a)` (which can be written as just `foo`)"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for closures which only invoke a method on the closure
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/// argument and can be replaced by referencing the method directly.
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///
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/// ### Why is this bad?
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/// It's unnecessary to create the closure.
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///
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/// ### Example
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/// ```rust,ignore
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/// Some('a').map(|s| s.to_uppercase());
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/// ```
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/// may be rewritten as
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/// ```rust,ignore
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/// Some('a').map(char::to_uppercase);
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/// ```
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#[clippy::version = "1.35.0"]
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pub REDUNDANT_CLOSURE_FOR_METHOD_CALLS,
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pedantic,
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"redundant closures for method calls"
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}
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declare_lint_pass!(EtaReduction => [REDUNDANT_CLOSURE, REDUNDANT_CLOSURE_FOR_METHOD_CALLS]);
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impl<'tcx> LateLintPass<'tcx> for EtaReduction {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if expr.span.from_expansion() {
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return;
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}
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let body = match expr.kind {
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ExprKind::Closure(&Closure { body, .. }) => cx.tcx.hir().body(body),
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_ => return,
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};
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if body.value.span.from_expansion() {
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if body.params.is_empty() {
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if let Some(VecArgs::Vec(&[])) = higher::VecArgs::hir(cx, body.value) {
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// replace `|| vec![]` with `Vec::new`
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span_lint_and_sugg(
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cx,
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REDUNDANT_CLOSURE,
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expr.span,
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"redundant closure",
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"replace the closure with `Vec::new`",
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"std::vec::Vec::new".into(),
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Applicability::MachineApplicable,
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);
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}
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}
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// skip `foo(|| macro!())`
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return;
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}
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let closure_ty = cx.typeck_results().expr_ty(expr);
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if_chain!(
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if !is_adjusted(cx, body.value);
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if let ExprKind::Call(callee, args) = body.value.kind;
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if let ExprKind::Path(_) = callee.kind;
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if check_inputs(cx, body.params, None, args);
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let callee_ty = cx.typeck_results().expr_ty_adjusted(callee);
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let call_ty = cx.typeck_results().type_dependent_def_id(body.value.hir_id)
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.map_or(callee_ty, |id| cx.tcx.type_of(id));
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if check_sig(cx, closure_ty, call_ty);
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let substs = cx.typeck_results().node_substs(callee.hir_id);
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// This fixes some false positives that I don't entirely understand
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if substs.is_empty() || !cx.typeck_results().expr_ty(expr).has_late_bound_regions();
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// A type param function ref like `T::f` is not 'static, however
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// it is if cast like `T::f as fn()`. This seems like a rustc bug.
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if !substs.types().any(|t| matches!(t.kind(), ty::Param(_)));
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let callee_ty_unadjusted = cx.typeck_results().expr_ty(callee).peel_refs();
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if !is_type_diagnostic_item(cx, callee_ty_unadjusted, sym::Arc);
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if !is_type_diagnostic_item(cx, callee_ty_unadjusted, sym::Rc);
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then {
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span_lint_and_then(cx, REDUNDANT_CLOSURE, expr.span, "redundant closure", |diag| {
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if let Some(mut snippet) = snippet_opt(cx, callee.span) {
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if let Some(fn_mut_id) = cx.tcx.lang_items().fn_mut_trait()
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&& implements_trait(cx, callee_ty.peel_refs(), fn_mut_id, &[])
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&& path_to_local(callee).map_or(false, |l| local_used_after_expr(cx, l, expr))
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{
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// Mutable closure is used after current expr; we cannot consume it.
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snippet = format!("&mut {snippet}");
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}
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diag.span_suggestion(
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expr.span,
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"replace the closure with the function itself",
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snippet,
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Applicability::MachineApplicable,
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);
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}
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});
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}
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);
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if_chain!(
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if !is_adjusted(cx, body.value);
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if let ExprKind::MethodCall(path, receiver, args, _) = body.value.kind;
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if check_inputs(cx, body.params, Some(receiver), args);
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let method_def_id = cx.typeck_results().type_dependent_def_id(body.value.hir_id).unwrap();
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let substs = cx.typeck_results().node_substs(body.value.hir_id);
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let call_ty = cx.tcx.bound_type_of(method_def_id).subst(cx.tcx, substs);
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if check_sig(cx, closure_ty, call_ty);
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then {
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span_lint_and_then(cx, REDUNDANT_CLOSURE_FOR_METHOD_CALLS, expr.span, "redundant closure", |diag| {
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let name = get_ufcs_type_name(cx, method_def_id);
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diag.span_suggestion(
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expr.span,
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"replace the closure with the method itself",
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format!("{name}::{}", path.ident.name),
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Applicability::MachineApplicable,
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);
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})
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}
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);
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}
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}
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fn check_inputs(
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cx: &LateContext<'_>,
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params: &[Param<'_>],
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receiver: Option<&Expr<'_>>,
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call_args: &[Expr<'_>],
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) -> bool {
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if receiver.map_or(params.len() != call_args.len(), |_| params.len() != call_args.len() + 1) {
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return false;
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}
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let binding_modes = cx.typeck_results().pat_binding_modes();
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let check_inputs = |param: &Param<'_>, arg| {
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match param.pat.kind {
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PatKind::Binding(_, id, ..) if path_to_local_id(arg, id) => {},
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_ => return false,
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}
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// checks that parameters are not bound as `ref` or `ref mut`
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if let Some(BindingMode::BindByReference(_)) = binding_modes.get(param.pat.hir_id) {
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return false;
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}
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match *cx.typeck_results().expr_adjustments(arg) {
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[] => true,
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[
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Adjustment {
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kind: Adjust::Deref(None),
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..
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},
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Adjustment {
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kind: Adjust::Borrow(AutoBorrow::Ref(_, mu2)),
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..
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},
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] => {
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// re-borrow with the same mutability is allowed
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let ty = cx.typeck_results().expr_ty(arg);
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matches!(*ty.kind(), ty::Ref(.., mu1) if mu1 == mu2.into())
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},
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_ => false,
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}
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};
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std::iter::zip(params, receiver.into_iter().chain(call_args.iter())).all(|(param, arg)| check_inputs(param, arg))
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}
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fn check_sig<'tcx>(cx: &LateContext<'tcx>, closure_ty: Ty<'tcx>, call_ty: Ty<'tcx>) -> bool {
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let call_sig = call_ty.fn_sig(cx.tcx);
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if call_sig.unsafety() == Unsafety::Unsafe {
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return false;
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}
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if !closure_ty.has_late_bound_regions() {
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return true;
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}
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let ty::Closure(_, substs) = closure_ty.kind() else {
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return false;
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};
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let closure_sig = cx.tcx.signature_unclosure(substs.as_closure().sig(), Unsafety::Normal);
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cx.tcx.erase_late_bound_regions(closure_sig) == cx.tcx.erase_late_bound_regions(call_sig)
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}
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fn get_ufcs_type_name(cx: &LateContext<'_>, method_def_id: DefId) -> String {
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let assoc_item = cx.tcx.associated_item(method_def_id);
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let def_id = assoc_item.container_id(cx.tcx);
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match assoc_item.container {
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ty::TraitContainer => cx.tcx.def_path_str(def_id),
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ty::ImplContainer => {
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let ty = cx.tcx.type_of(def_id);
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match ty.kind() {
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ty::Adt(adt, _) => cx.tcx.def_path_str(adt.did()),
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_ => ty.to_string(),
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}
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},
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}
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}
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