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Auto merge of #9424 - mikerite:fix-9351-4, r=xFrednet 

Fix `unnecessary_to_owned` false positive

Fixes #9351.

Note that this commit reworks that fix for #9317. The change
is to check that the type implements `AsRef<str>` before regarding
`to_string` as an equivalent of `to_owned`. This was suggested
by Jarcho in the #9317 issue comments.

The benefit of this is that it moves some complexity out of
`check_other_call_arg` and simplifies the module as a whole.

changelog: FP: [`unnecessary_to_owned`]: No longer lints, if type change would cause errors in the caller function
This commit is contained in:
bors 2022-09-04 15:14:58 +00:00
parent 99ab5fe53a 750a2d57bd
commit 46b7cb69cb
4 changed files with 262 additions and 71 deletions
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205
clippy_lints/src/methods/unnecessary_to_owned.rs
View File

@ -1,21 +1,25 @@
use super::implicit_clone::is_clone_like;
use super::unnecessary_iter_cloned::{self, is_into_iter};
use crate::rustc_middle::ty::Subst;
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_opt;
use clippy_utils::ty::{
get_associated_type, get_iterator_item_ty, implements_trait, is_copy, is_type_diagnostic_item, peel_mid_ty_refs,
};
use clippy_utils::{fn_def_id, get_parent_expr, is_diag_item_method, is_diag_trait_item};
use clippy_utils::ty::{get_associated_type, get_iterator_item_ty, implements_trait, is_copy, peel_mid_ty_refs};
use clippy_utils::visitors::find_all_ret_expressions;
use clippy_utils::{fn_def_id, get_parent_expr, is_diag_item_method, is_diag_trait_item, return_ty};
use clippy_utils::{meets_msrv, msrvs};
use rustc_errors::Applicability;
use rustc_hir::{def_id::DefId, BorrowKind, Expr, ExprKind};
use rustc_hir::{def_id::DefId, BorrowKind, Expr, ExprKind, ItemKind, Node};
use rustc_infer::infer::TyCtxtInferExt;
use rustc_lint::LateContext;
use rustc_middle::mir::Mutability;
use rustc_middle::ty::adjustment::{Adjust, Adjustment, OverloadedDeref};
use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef};
use rustc_middle::ty::{self, PredicateKind, ProjectionPredicate, TraitPredicate, Ty};
use rustc_middle::ty::EarlyBinder;
use rustc_middle::ty::{self, ParamTy, PredicateKind, ProjectionPredicate, TraitPredicate, Ty};
use rustc_semver::RustcVersion;
use rustc_span::{sym, Symbol};
use rustc_trait_selection::traits::{query::evaluate_obligation::InferCtxtExt as _, Obligation, ObligationCause};
use rustc_typeck::check::{FnCtxt, Inherited};
use std::cmp::max;
use super::UNNECESSARY_TO_OWNED;
@ -33,7 +37,7 @@ pub fn check<'tcx>(
then {
if is_cloned_or_copied(cx, method_name, method_def_id) {
unnecessary_iter_cloned::check(cx, expr, method_name, receiver);
} else if is_to_owned_like(cx, method_name, method_def_id) {
} else if is_to_owned_like(cx, expr, method_name, method_def_id) {
// At this point, we know the call is of a `to_owned`-like function. The functions
// `check_addr_of_expr` and `check_call_arg` determine whether the call is unnecessary
// based on its context, that is, whether it is a referent in an `AddrOf` expression, an
@ -245,12 +249,12 @@ fn check_other_call_arg<'tcx>(
) -> bool {
if_chain! {
if let Some((maybe_call, maybe_arg)) = skip_addr_of_ancestors(cx, expr);
if let Some((callee_def_id, call_substs, call_args)) = get_callee_substs_and_args(cx, maybe_call);
if let Some((callee_def_id, _, call_args)) = get_callee_substs_and_args(cx, maybe_call);
let fn_sig = cx.tcx.fn_sig(callee_def_id).skip_binder();
if let Some(i) = call_args.iter().position(|arg| arg.hir_id == maybe_arg.hir_id);
if let Some(input) = fn_sig.inputs().get(i);
let (input, n_refs) = peel_mid_ty_refs(*input);
if let (trait_predicates, projection_predicates) = get_input_traits_and_projections(cx, callee_def_id, input);
if let (trait_predicates, _) = get_input_traits_and_projections(cx, callee_def_id, input);
if let Some(sized_def_id) = cx.tcx.lang_items().sized_trait();
if let [trait_predicate] = trait_predicates
.iter()
@ -258,52 +262,13 @@ fn check_other_call_arg<'tcx>(
.collect::<Vec<_>>()[..];
if let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref);
if let Some(as_ref_trait_id) = cx.tcx.get_diagnostic_item(sym::AsRef);
if trait_predicate.def_id() == deref_trait_id || trait_predicate.def_id() == as_ref_trait_id;
let receiver_ty = cx.typeck_results().expr_ty(receiver);
// If the callee has type parameters, they could appear in `projection_predicate.ty` or the
// types of `trait_predicate.trait_ref.substs`.
if if trait_predicate.def_id() == deref_trait_id {
if let [projection_predicate] = projection_predicates[..] {
let normalized_ty =
cx.tcx
.subst_and_normalize_erasing_regions(call_substs, cx.param_env, projection_predicate.term);
implements_trait(cx, receiver_ty, deref_trait_id, &[])
&& get_associated_type(cx, receiver_ty, deref_trait_id, "Target")
.map_or(false, |ty| ty::Term::Ty(ty) == normalized_ty)
} else {
false
}
} else if trait_predicate.def_id() == as_ref_trait_id {
let composed_substs = compose_substs(
cx,
&trait_predicate.trait_ref.substs.iter().skip(1).collect::<Vec<_>>()[..],
call_substs,
);
// if `expr` is a `String` and generic target is [u8], skip
// (https://github.com/rust-lang/rust-clippy/issues/9317).
if let [subst] = composed_substs[..]
&& let GenericArgKind::Type(arg_ty) = subst.unpack()
&& arg_ty.is_slice()
&& let inner_ty = arg_ty.builtin_index().unwrap()
&& let ty::Uint(ty::UintTy::U8) = inner_ty.kind()
&& let self_ty = cx.typeck_results().expr_ty(expr).peel_refs()
&& is_type_diagnostic_item(cx, self_ty, sym::String) {
false
} else {
implements_trait(cx, receiver_ty, as_ref_trait_id, &composed_substs)
}
} else {
false
};
if can_change_type(cx, maybe_arg, receiver_ty);
// We can't add an `&` when the trait is `Deref` because `Target = &T` won't match
// `Target = T`.
if n_refs > 0 || is_copy(cx, receiver_ty) || trait_predicate.def_id() != deref_trait_id;
let n_refs = max(n_refs, if is_copy(cx, receiver_ty) { 0 } else { 1 });
// If the trait is `AsRef` and the input type variable `T` occurs in the output type, then
// `T` must not be instantiated with a reference
// (https://github.com/rust-lang/rust-clippy/issues/8507).
if (n_refs == 0 && !receiver_ty.is_ref())
|| trait_predicate.def_id() != as_ref_trait_id
|| !fn_sig.output().contains(input);
if let Some(receiver_snippet) = snippet_opt(cx, receiver.span);
then {
span_lint_and_sugg(
@ -389,22 +354,102 @@ fn get_input_traits_and_projections<'tcx>(
(trait_predicates, projection_predicates)
}
/// Composes two substitutions by applying the latter to the types of the former.
fn compose_substs<'tcx>(
cx: &LateContext<'tcx>,
left: &[GenericArg<'tcx>],
right: SubstsRef<'tcx>,
) -> Vec<GenericArg<'tcx>> {
left.iter()
.map(|arg| {
if let GenericArgKind::Type(arg_ty) = arg.unpack() {
let normalized_ty = cx.tcx.subst_and_normalize_erasing_regions(right, cx.param_env, arg_ty);
GenericArg::from(normalized_ty)
} else {
*arg
fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<'a>) -> bool {
for (_, node) in cx.tcx.hir().parent_iter(expr.hir_id) {
match node {
Node::Stmt(_) => return true,
Node::Block(..) => continue,
Node::Item(item) => {
if let ItemKind::Fn(_, _, body_id) = &item.kind
&& let output_ty = return_ty(cx, item.hir_id())
&& let local_def_id = cx.tcx.hir().local_def_id(item.hir_id())
&& Inherited::build(cx.tcx, local_def_id).enter(|inherited| {
let fn_ctxt = FnCtxt::new(&inherited, cx.param_env, item.hir_id());
fn_ctxt.can_coerce(ty, output_ty)
}) {
if has_lifetime(output_ty) && has_lifetime(ty) {
return false;
}
let body = cx.tcx.hir().body(*body_id);
let body_expr = &body.value;
let mut count = 0;
return find_all_ret_expressions(cx, body_expr, |_| { count += 1; count <= 1 });
}
}
})
.collect()
Node::Expr(parent_expr) => {
if let Some((callee_def_id, call_substs, call_args)) = get_callee_substs_and_args(cx, parent_expr) {
let fn_sig = cx.tcx.fn_sig(callee_def_id).skip_binder();
if let Some(arg_index) = call_args.iter().position(|arg| arg.hir_id == expr.hir_id)
&& let Some(param_ty) = fn_sig.inputs().get(arg_index)
&& let ty::Param(ParamTy { index: param_index , ..}) = param_ty.kind()
{
if fn_sig
.inputs()
.iter()
.enumerate()
.filter(|(i, _)| *i != arg_index)
.any(|(_, ty)| ty.contains(*param_ty))
{
return false;
}
let mut trait_predicates = cx.tcx.param_env(callee_def_id)
.caller_bounds().iter().filter(|predicate| {
if let PredicateKind::Trait(trait_predicate) = predicate.kind().skip_binder()
&& trait_predicate.trait_ref.self_ty() == *param_ty {
true
} else {
false
}
});
let new_subst = cx.tcx.mk_substs(
call_substs.iter()
.enumerate()
.map(|(i, t)|
if i == (*param_index as usize) {
GenericArg::from(ty)
} else {
t
}));
if trait_predicates.any(|predicate| {
let predicate = EarlyBinder(predicate).subst(cx.tcx, new_subst);
let obligation = Obligation::new(ObligationCause::dummy(), cx.param_env, predicate);
!cx.tcx
.infer_ctxt()
.enter(|infcx| infcx.predicate_must_hold_modulo_regions(&obligation))
}) {
return false;
}
let output_ty = fn_sig.output();
if output_ty.contains(*param_ty) {
if let Ok(new_ty) = cx.tcx.try_subst_and_normalize_erasing_regions(
new_subst, cx.param_env, output_ty) {
expr = parent_expr;
ty = new_ty;
continue;
}
return false;
}
return true;
}
} else if let ExprKind::Block(..) = parent_expr.kind {
continue;
}
return false;
},
_ => return false,
}
}
false
}
fn has_lifetime(ty: Ty<'_>) -> bool {
ty.walk().any(|t| matches!(t.unpack(), GenericArgKind::Lifetime(_)))
}
/// Returns true if the named method is `Iterator::cloned` or `Iterator::copied`.
@ -415,10 +460,10 @@ fn is_cloned_or_copied(cx: &LateContext<'_>, method_name: Symbol, method_def_id:
/// Returns true if the named method can be used to convert the receiver to its "owned"
/// representation.
fn is_to_owned_like(cx: &LateContext<'_>, method_name: Symbol, method_def_id: DefId) -> bool {
fn is_to_owned_like<'a>(cx: &LateContext<'a>, call_expr: &Expr<'a>, method_name: Symbol, method_def_id: DefId) -> bool {
is_clone_like(cx, method_name.as_str(), method_def_id)
|| is_cow_into_owned(cx, method_name, method_def_id)
|| is_to_string(cx, method_name, method_def_id)
|| is_to_string_on_string_like(cx, call_expr, method_name, method_def_id)
}
/// Returns true if the named method is `Cow::into_owned`.
@ -426,7 +471,27 @@ fn is_cow_into_owned(cx: &LateContext<'_>, method_name: Symbol, method_def_id: D
method_name.as_str() == "into_owned" && is_diag_item_method(cx, method_def_id, sym::Cow)
}
/// Returns true if the named method is `ToString::to_string`.
fn is_to_string(cx: &LateContext<'_>, method_name: Symbol, method_def_id: DefId) -> bool {
method_name == sym::to_string && is_diag_trait_item(cx, method_def_id, sym::ToString)
/// Returns true if the named method is `ToString::to_string` and it's called on a type that
/// is string-like i.e. implements `AsRef<str>` or `Deref<str>`.
fn is_to_string_on_string_like<'a>(
cx: &LateContext<'_>,
call_expr: &'a Expr<'a>,
method_name: Symbol,
method_def_id: DefId,
) -> bool {
if method_name != sym::to_string || !is_diag_trait_item(cx, method_def_id, sym::ToString) {
return false;
}
if let Some(substs) = cx.typeck_results().node_substs_opt(call_expr.hir_id)
&& let [generic_arg] = substs.as_slice()
&& let GenericArgKind::Type(ty) = generic_arg.unpack()
&& let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref)
&& let Some(as_ref_trait_id) = cx.tcx.get_diagnostic_item(sym::AsRef)
&& (implements_trait(cx, ty, deref_trait_id, &[cx.tcx.types.str_.into()]) ||
implements_trait(cx, ty, as_ref_trait_id, &[cx.tcx.types.str_.into()])) {
true
} else {
false
}
}

60
tests/ui/unnecessary_to_owned.fixed
View File

@ -357,3 +357,63 @@ mod issue_9317 {
consume(b.to_string());
}
}
mod issue_9351 {
#![allow(dead_code)]
use std::ops::Deref;
use std::path::{Path, PathBuf};
fn require_deref_path<T: Deref<Target = std::path::Path>>(x: T) -> T {
x
}
fn generic_arg_used_elsewhere<T: AsRef<Path>>(_x: T, _y: T) {}
fn id<T: AsRef<str>>(x: T) -> T {
x
}
fn predicates_are_satisfied(_x: impl std::fmt::Write) {}
// Should lint
fn single_return() -> impl AsRef<str> {
id("abc")
}
// Should not lint
fn multiple_returns(b: bool) -> impl AsRef<str> {
if b {
return String::new();
}
id("abc".to_string())
}
struct S1(String);
// Should not lint
fn fields1() -> S1 {
S1(id("abc".to_string()))
}
struct S2 {
s: String,
}
// Should not lint
fn fields2() {
let mut s = S2 { s: "abc".into() };
s.s = id("abc".to_string());
}
pub fn main() {
let path = std::path::Path::new("x");
let path_buf = path.to_owned();
// Should not lint.
let _x: PathBuf = require_deref_path(path.to_owned());
generic_arg_used_elsewhere(path.to_owned(), path_buf);
predicates_are_satisfied(id("abc".to_string()));
}
}

60
tests/ui/unnecessary_to_owned.rs
View File

@ -357,3 +357,63 @@ mod issue_9317 {
consume(b.to_string());
}
}
mod issue_9351 {
#![allow(dead_code)]
use std::ops::Deref;
use std::path::{Path, PathBuf};
fn require_deref_path<T: Deref<Target = std::path::Path>>(x: T) -> T {
x
}
fn generic_arg_used_elsewhere<T: AsRef<Path>>(_x: T, _y: T) {}
fn id<T: AsRef<str>>(x: T) -> T {
x
}
fn predicates_are_satisfied(_x: impl std::fmt::Write) {}
// Should lint
fn single_return() -> impl AsRef<str> {
id("abc".to_string())
}
// Should not lint
fn multiple_returns(b: bool) -> impl AsRef<str> {
if b {
return String::new();
}
id("abc".to_string())
}
struct S1(String);
// Should not lint
fn fields1() -> S1 {
S1(id("abc".to_string()))
}
struct S2 {
s: String,
}
// Should not lint
fn fields2() {
let mut s = S2 { s: "abc".into() };
s.s = id("abc".to_string());
}
pub fn main() {
let path = std::path::Path::new("x");
let path_buf = path.to_owned();
// Should not lint.
let _x: PathBuf = require_deref_path(path.to_owned());
generic_arg_used_elsewhere(path.to_owned(), path_buf);
predicates_are_satisfied(id("abc".to_string()));
}
}

8
tests/ui/unnecessary_to_owned.stderr
View File

@ -509,5 +509,11 @@ error: unnecessary use of `to_string`
LL | Box::new(build(y.to_string()))
| ^^^^^^^^^^^^^ help: use: `y`
error: aborting due to 78 previous errors
error: unnecessary use of `to_string`
--> $DIR/unnecessary_to_owned.rs:381:12
|
LL | id("abc".to_string())
| ^^^^^^^^^^^^^^^^^ help: use: `"abc"`
error: aborting due to 79 previous errors