407 lines
17 KiB
Rust
407 lines
17 KiB
Rust
use super::implicit_clone::is_clone_like;
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use super::unnecessary_iter_cloned::{self, is_into_iter};
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use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::source::snippet_opt;
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use clippy_utils::ty::{
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contains_ty, get_associated_type, get_iterator_item_ty, implements_trait, is_copy, peel_mid_ty_refs,
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};
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use clippy_utils::{fn_def_id, get_parent_expr, is_diag_item_method, is_diag_trait_item};
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use rustc_errors::Applicability;
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use rustc_hir::{def_id::DefId, BorrowKind, Expr, ExprKind};
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use rustc_lint::LateContext;
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use rustc_middle::mir::Mutability;
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use rustc_middle::ty::adjustment::{Adjust, Adjustment, OverloadedDeref};
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use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef};
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use rustc_middle::ty::{self, PredicateKind, ProjectionPredicate, TraitPredicate, Ty};
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use rustc_span::{sym, Symbol};
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use std::cmp::max;
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use super::UNNECESSARY_TO_OWNED;
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pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, method_name: Symbol, args: &'tcx [Expr<'tcx>]) {
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if_chain! {
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if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
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if let [receiver] = args;
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then {
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if is_cloned_or_copied(cx, method_name, method_def_id) {
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unnecessary_iter_cloned::check(cx, expr, method_name, receiver);
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} else if is_to_owned_like(cx, method_name, method_def_id) {
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// At this point, we know the call is of a `to_owned`-like function. The functions
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// `check_addr_of_expr` and `check_call_arg` determine whether the call is unnecessary
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// based on its context, that is, whether it is a referent in an `AddrOf` expression, an
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// argument in a `into_iter` call, or an argument in the call of some other function.
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if check_addr_of_expr(cx, expr, method_name, method_def_id, receiver) {
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return;
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}
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if check_into_iter_call_arg(cx, expr, method_name, receiver) {
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return;
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}
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check_other_call_arg(cx, expr, method_name, receiver);
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}
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}
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}
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}
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/// Checks whether `expr` is a referent in an `AddrOf` expression and, if so, determines whether its
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/// call of a `to_owned`-like function is unnecessary.
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#[allow(clippy::too_many_lines)]
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fn check_addr_of_expr(
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cx: &LateContext<'_>,
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expr: &Expr<'_>,
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method_name: Symbol,
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method_def_id: DefId,
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receiver: &Expr<'_>,
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) -> bool {
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if_chain! {
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if let Some(parent) = get_parent_expr(cx, expr);
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if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, _) = parent.kind;
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let adjustments = cx.typeck_results().expr_adjustments(parent).iter().collect::<Vec<_>>();
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if let Some(target_ty) = match adjustments[..]
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{
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// For matching uses of `Cow::from`
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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(_),
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target: target_ty,
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},
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]
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// For matching uses of arrays
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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(_),
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..
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},
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Adjustment {
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kind: Adjust::Pointer(_),
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target: target_ty,
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},
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]
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// For matching everything else
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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::Deref(Some(OverloadedDeref { .. })),
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..
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},
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Adjustment {
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kind: Adjust::Borrow(_),
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target: target_ty,
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},
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] => Some(target_ty),
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_ => None,
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};
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let receiver_ty = cx.typeck_results().expr_ty(receiver);
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// Only flag cases where the receiver is copyable or the method is `Cow::into_owned`. This
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// restriction is to ensure there is not overlap between `redundant_clone` and this lint.
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if is_copy(cx, receiver_ty) || is_cow_into_owned(cx, method_name, method_def_id);
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if let Some(receiver_snippet) = snippet_opt(cx, receiver.span);
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then {
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let (target_ty, n_target_refs) = peel_mid_ty_refs(*target_ty);
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let (receiver_ty, n_receiver_refs) = peel_mid_ty_refs(receiver_ty);
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if receiver_ty == target_ty && n_target_refs >= n_receiver_refs {
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span_lint_and_sugg(
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cx,
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UNNECESSARY_TO_OWNED,
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parent.span,
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&format!("unnecessary use of `{}`", method_name),
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"use",
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format!(
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"{:&>width$}{}",
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"",
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receiver_snippet,
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width = n_target_refs - n_receiver_refs
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),
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Applicability::MachineApplicable,
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);
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return true;
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}
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if_chain! {
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if let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref);
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if implements_trait(cx, receiver_ty, deref_trait_id, &[]);
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if get_associated_type(cx, receiver_ty, deref_trait_id, "Target") == Some(target_ty);
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then {
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if n_receiver_refs > 0 {
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span_lint_and_sugg(
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cx,
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UNNECESSARY_TO_OWNED,
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parent.span,
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&format!("unnecessary use of `{}`", method_name),
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"use",
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receiver_snippet,
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Applicability::MachineApplicable,
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);
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} else {
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span_lint_and_sugg(
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cx,
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UNNECESSARY_TO_OWNED,
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expr.span.with_lo(receiver.span.hi()),
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&format!("unnecessary use of `{}`", method_name),
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"remove this",
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String::new(),
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Applicability::MachineApplicable,
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);
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}
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return true;
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}
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}
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if_chain! {
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if let Some(as_ref_trait_id) = cx.tcx.get_diagnostic_item(sym::AsRef);
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if implements_trait(cx, receiver_ty, as_ref_trait_id, &[GenericArg::from(target_ty)]);
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then {
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span_lint_and_sugg(
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cx,
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UNNECESSARY_TO_OWNED,
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parent.span,
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&format!("unnecessary use of `{}`", method_name),
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"use",
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format!("{}.as_ref()", receiver_snippet),
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Applicability::MachineApplicable,
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);
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return true;
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}
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}
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}
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}
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false
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}
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/// Checks whether `expr` is an argument in an `into_iter` call and, if so, determines whether its
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/// call of a `to_owned`-like function is unnecessary.
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fn check_into_iter_call_arg(cx: &LateContext<'_>, expr: &Expr<'_>, method_name: Symbol, receiver: &Expr<'_>) -> bool {
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if_chain! {
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if let Some(parent) = get_parent_expr(cx, expr);
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if let Some(callee_def_id) = fn_def_id(cx, parent);
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if is_into_iter(cx, callee_def_id);
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if let Some(iterator_trait_id) = cx.tcx.get_diagnostic_item(sym::Iterator);
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let parent_ty = cx.typeck_results().expr_ty(parent);
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if implements_trait(cx, parent_ty, iterator_trait_id, &[]);
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if let Some(item_ty) = get_iterator_item_ty(cx, parent_ty);
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if let Some(receiver_snippet) = snippet_opt(cx, receiver.span);
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then {
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if unnecessary_iter_cloned::check_for_loop_iter(cx, parent, method_name, receiver, true) {
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return true;
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}
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let cloned_or_copied = if is_copy(cx, item_ty) { "copied" } else { "cloned" };
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// The next suggestion may be incorrect because the removal of the `to_owned`-like
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// function could cause the iterator to hold a reference to a resource that is used
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// mutably. See https://github.com/rust-lang/rust-clippy/issues/8148.
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span_lint_and_sugg(
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cx,
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UNNECESSARY_TO_OWNED,
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parent.span,
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&format!("unnecessary use of `{}`", method_name),
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"use",
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format!("{}.iter().{}()", receiver_snippet, cloned_or_copied),
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Applicability::MaybeIncorrect,
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);
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return true;
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}
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}
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false
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}
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/// Checks whether `expr` is an argument in a function call and, if so, determines whether its call
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/// of a `to_owned`-like function is unnecessary.
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fn check_other_call_arg<'tcx>(
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cx: &LateContext<'tcx>,
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expr: &'tcx Expr<'tcx>,
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method_name: Symbol,
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receiver: &'tcx Expr<'tcx>,
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) -> bool {
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if_chain! {
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if let Some((maybe_call, maybe_arg)) = skip_addr_of_ancestors(cx, expr);
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if let Some((callee_def_id, call_substs, call_args)) = get_callee_substs_and_args(cx, maybe_call);
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let fn_sig = cx.tcx.fn_sig(callee_def_id).skip_binder();
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if let Some(i) = call_args.iter().position(|arg| arg.hir_id == maybe_arg.hir_id);
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if let Some(input) = fn_sig.inputs().get(i);
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let (input, n_refs) = peel_mid_ty_refs(*input);
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if let (trait_predicates, projection_predicates) = get_input_traits_and_projections(cx, callee_def_id, input);
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if let Some(sized_def_id) = cx.tcx.lang_items().sized_trait();
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if let [trait_predicate] = trait_predicates
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.iter()
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.filter(|trait_predicate| trait_predicate.def_id() != sized_def_id)
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.collect::<Vec<_>>()[..];
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if let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref);
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if let Some(as_ref_trait_id) = cx.tcx.get_diagnostic_item(sym::AsRef);
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let receiver_ty = cx.typeck_results().expr_ty(receiver);
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// If the callee has type parameters, they could appear in `projection_predicate.ty` or the
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// types of `trait_predicate.trait_ref.substs`.
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if if trait_predicate.def_id() == deref_trait_id {
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if let [projection_predicate] = projection_predicates[..] {
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let normalized_ty =
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cx.tcx
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.subst_and_normalize_erasing_regions(call_substs, cx.param_env, projection_predicate.term);
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implements_trait(cx, receiver_ty, deref_trait_id, &[])
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&& get_associated_type(cx, receiver_ty, deref_trait_id, "Target")
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.map_or(false, |ty| ty::Term::Ty(ty) == normalized_ty)
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} else {
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false
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}
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} else if trait_predicate.def_id() == as_ref_trait_id {
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let composed_substs = compose_substs(
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cx,
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&trait_predicate.trait_ref.substs.iter().skip(1).collect::<Vec<_>>()[..],
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call_substs,
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);
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implements_trait(cx, receiver_ty, as_ref_trait_id, &composed_substs)
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} else {
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false
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};
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// We can't add an `&` when the trait is `Deref` because `Target = &T` won't match
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// `Target = T`.
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if n_refs > 0 || is_copy(cx, receiver_ty) || trait_predicate.def_id() != deref_trait_id;
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let n_refs = max(n_refs, if is_copy(cx, receiver_ty) { 0 } else { 1 });
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// If the trait is `AsRef` and the input type variable `T` occurs in the output type, then
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// `T` must not be instantiated with a reference
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// (https://github.com/rust-lang/rust-clippy/issues/8507).
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if (n_refs == 0 && !receiver_ty.is_ref())
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|| trait_predicate.def_id() != as_ref_trait_id
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|| !contains_ty(fn_sig.output(), input);
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if let Some(receiver_snippet) = snippet_opt(cx, receiver.span);
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then {
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span_lint_and_sugg(
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cx,
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UNNECESSARY_TO_OWNED,
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maybe_arg.span,
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&format!("unnecessary use of `{}`", method_name),
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"use",
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format!("{:&>width$}{}", "", receiver_snippet, width = n_refs),
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Applicability::MachineApplicable,
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);
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return true;
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}
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}
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false
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}
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/// Walks an expression's ancestors until it finds a non-`AddrOf` expression. Returns the first such
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/// expression found (if any) along with the immediately prior expression.
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fn skip_addr_of_ancestors<'tcx>(
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cx: &LateContext<'tcx>,
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mut expr: &'tcx Expr<'tcx>,
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) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> {
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while let Some(parent) = get_parent_expr(cx, expr) {
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if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, _) = parent.kind {
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expr = parent;
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} else {
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return Some((parent, expr));
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}
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}
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None
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}
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/// Checks whether an expression is a function or method call and, if so, returns its `DefId`,
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/// `Substs`, and arguments.
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fn get_callee_substs_and_args<'tcx>(
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cx: &LateContext<'tcx>,
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expr: &'tcx Expr<'tcx>,
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) -> Option<(DefId, SubstsRef<'tcx>, &'tcx [Expr<'tcx>])> {
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if_chain! {
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if let ExprKind::Call(callee, args) = expr.kind;
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let callee_ty = cx.typeck_results().expr_ty(callee);
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if let ty::FnDef(callee_def_id, _) = callee_ty.kind();
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then {
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let substs = cx.typeck_results().node_substs(callee.hir_id);
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return Some((*callee_def_id, substs, args));
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}
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}
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if_chain! {
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if let ExprKind::MethodCall(_, args, _) = expr.kind;
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if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
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then {
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let substs = cx.typeck_results().node_substs(expr.hir_id);
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return Some((method_def_id, substs, args));
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}
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}
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None
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}
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/// Returns the `TraitPredicate`s and `ProjectionPredicate`s for a function's input type.
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fn get_input_traits_and_projections<'tcx>(
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cx: &LateContext<'tcx>,
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callee_def_id: DefId,
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input: Ty<'tcx>,
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) -> (Vec<TraitPredicate<'tcx>>, Vec<ProjectionPredicate<'tcx>>) {
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let mut trait_predicates = Vec::new();
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let mut projection_predicates = Vec::new();
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for (predicate, _) in cx.tcx.predicates_of(callee_def_id).predicates.iter() {
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// `substs` should have 1 + n elements. The first is the type on the left hand side of an
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// `as`. The remaining n are trait parameters.
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let is_input_substs = |substs: SubstsRef<'tcx>| {
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if_chain! {
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if let Some(arg) = substs.iter().next();
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if let GenericArgKind::Type(arg_ty) = arg.unpack();
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if arg_ty == input;
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then { true } else { false }
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}
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};
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match predicate.kind().skip_binder() {
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PredicateKind::Trait(trait_predicate) => {
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if is_input_substs(trait_predicate.trait_ref.substs) {
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trait_predicates.push(trait_predicate);
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}
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},
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PredicateKind::Projection(projection_predicate) => {
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if is_input_substs(projection_predicate.projection_ty.substs) {
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projection_predicates.push(projection_predicate);
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}
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},
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_ => {},
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}
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}
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(trait_predicates, projection_predicates)
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}
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/// Composes two substitutions by applying the latter to the types of the former.
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fn compose_substs<'tcx>(
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cx: &LateContext<'tcx>,
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left: &[GenericArg<'tcx>],
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right: SubstsRef<'tcx>,
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) -> Vec<GenericArg<'tcx>> {
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left.iter()
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.map(|arg| {
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if let GenericArgKind::Type(arg_ty) = arg.unpack() {
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let normalized_ty = cx.tcx.subst_and_normalize_erasing_regions(right, cx.param_env, arg_ty);
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GenericArg::from(normalized_ty)
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} else {
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*arg
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}
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})
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.collect()
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}
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/// Returns true if the named method is `Iterator::cloned` or `Iterator::copied`.
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fn is_cloned_or_copied(cx: &LateContext<'_>, method_name: Symbol, method_def_id: DefId) -> bool {
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(method_name.as_str() == "cloned" || method_name.as_str() == "copied")
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&& is_diag_trait_item(cx, method_def_id, sym::Iterator)
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}
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/// Returns true if the named method can be used to convert the receiver to its "owned"
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/// representation.
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fn is_to_owned_like(cx: &LateContext<'_>, method_name: Symbol, method_def_id: DefId) -> bool {
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is_clone_like(cx, &*method_name.as_str(), method_def_id)
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|| is_cow_into_owned(cx, method_name, method_def_id)
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|| is_to_string(cx, method_name, method_def_id)
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}
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/// Returns true if the named method is `Cow::into_owned`.
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fn is_cow_into_owned(cx: &LateContext<'_>, method_name: Symbol, method_def_id: DefId) -> bool {
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method_name.as_str() == "into_owned" && is_diag_item_method(cx, method_def_id, sym::Cow)
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}
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/// Returns true if the named method is `ToString::to_string`.
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fn is_to_string(cx: &LateContext<'_>, method_name: Symbol, method_def_id: DefId) -> bool {
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method_name.as_str() == "to_string" && is_diag_trait_item(cx, method_def_id, sym::ToString)
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}
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