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Auto merge of #9134 - Jarcho:while_let_iter_closure, r=dswij

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Improve `while_let_on_iterator` suggestion inside an `FnOnce` closure

changelog: Improve `while_let_on_iterator` suggestion inside an `FnOnce` closure
This commit is contained in:
bors 2022-07-13 16:20:14 +00:00
commit a7162f29b4
6 changed files with 240 additions and 57 deletions
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19
clippy_lints/src/loops/while_let_on_iterator.rs
View file

@ -3,13 +3,15 @@ use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::higher;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::{
get_enclosing_loop_or_closure, is_refutable, is_trait_method, match_def_path, paths, visitors::is_res_used,
get_enclosing_loop_or_multi_call_closure, is_refutable, is_trait_method, match_def_path, paths,
visitors::is_res_used,
};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::intravisit::{walk_expr, Visitor};
use rustc_hir::{def::Res, Expr, ExprKind, HirId, Local, Mutability, PatKind, QPath, UnOp};
use rustc_lint::LateContext;
use rustc_middle::hir::nested_filter::OnlyBodies;
use rustc_middle::ty::adjustment::Adjust;
use rustc_span::{symbol::sym, Symbol};
@ -249,6 +251,11 @@ fn needs_mutable_borrow(cx: &LateContext<'_>, iter_expr: &IterExpr, loop_expr: &
used_iter: bool,
}
impl<'tcx> Visitor<'tcx> for AfterLoopVisitor<'_, '_, 'tcx> {
type NestedFilter = OnlyBodies;
fn nested_visit_map(&mut self) -> Self::Map {
self.cx.tcx.hir()
}
fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
if self.used_iter {
return;
@ -283,6 +290,11 @@ fn needs_mutable_borrow(cx: &LateContext<'_>, iter_expr: &IterExpr, loop_expr: &
used_after: bool,
}
impl<'a, 'b, 'tcx> Visitor<'tcx> for NestedLoopVisitor<'a, 'b, 'tcx> {
type NestedFilter = OnlyBodies;
fn nested_visit_map(&mut self) -> Self::Map {
self.cx.tcx.hir()
}
fn visit_local(&mut self, l: &'tcx Local<'_>) {
if !self.after_loop {
l.pat.each_binding_or_first(&mut |_, id, _, _| {
@ -320,10 +332,7 @@ fn needs_mutable_borrow(cx: &LateContext<'_>, iter_expr: &IterExpr, loop_expr: &
}
}
if let Some(e) = get_enclosing_loop_or_closure(cx.tcx, loop_expr) {
// The iterator expression will be used on the next iteration (for loops), or on the next call (for
// closures) unless it is declared within the enclosing expression. TODO: Check for closures
// used where an `FnOnce` type is expected.
if let Some(e) = get_enclosing_loop_or_multi_call_closure(cx, loop_expr) {
let local_id = match iter_expr.path {
Res::Local(id) => id,
_ => return true,

60
clippy_utils/src/lib.rs
View file

@ -93,7 +93,9 @@ use rustc_middle::ty::fast_reject::SimplifiedTypeGen::{
ArraySimplifiedType, BoolSimplifiedType, CharSimplifiedType, FloatSimplifiedType, IntSimplifiedType,
PtrSimplifiedType, SliceSimplifiedType, StrSimplifiedType, UintSimplifiedType,
};
use rustc_middle::ty::{layout::IntegerExt, BorrowKind, DefIdTree, Ty, TyCtxt, TypeAndMut, TypeFoldable, UpvarCapture};
use rustc_middle::ty::{
layout::IntegerExt, BorrowKind, ClosureKind, DefIdTree, Ty, TyCtxt, TypeAndMut, TypeFoldable, UpvarCapture,
};
use rustc_middle::ty::{FloatTy, IntTy, UintTy};
use rustc_semver::RustcVersion;
use rustc_session::Session;
@ -105,7 +107,7 @@ use rustc_span::{Span, DUMMY_SP};
use rustc_target::abi::Integer;
use crate::consts::{constant, Constant};
use crate::ty::{can_partially_move_ty, is_copy, is_recursively_primitive_type};
use crate::ty::{can_partially_move_ty, expr_sig, is_copy, is_recursively_primitive_type, ty_is_fn_once_param};
use crate::visitors::expr_visitor_no_bodies;
pub fn parse_msrv(msrv: &str, sess: Option<&Session>, span: Option<Span>) -> Option<RustcVersion> {
@ -1197,16 +1199,54 @@ pub fn get_enclosing_block<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId) -> Optio
}
/// Gets the loop or closure enclosing the given expression, if any.
pub fn get_enclosing_loop_or_closure<'tcx>(tcx: TyCtxt<'tcx>, expr: &Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
for (_, node) in tcx.hir().parent_iter(expr.hir_id) {
pub fn get_enclosing_loop_or_multi_call_closure<'tcx>(
cx: &LateContext<'tcx>,
expr: &Expr<'_>,
) -> Option<&'tcx Expr<'tcx>> {
for (_, node) in cx.tcx.hir().parent_iter(expr.hir_id) {
match node {
Node::Expr(
e @ Expr {
kind: ExprKind::Loop(..) | ExprKind::Closure { .. },
..
Node::Expr(e) => match e.kind {
ExprKind::Closure { .. } => {
if let rustc_ty::Closure(_, subs) = cx.typeck_results().expr_ty(e).kind()
&& subs.as_closure().kind() == ClosureKind::FnOnce
{
continue;
}
let is_once = walk_to_expr_usage(cx, e, |node, id| {
let Node::Expr(e) = node else {
return None;
};
match e.kind {
ExprKind::Call(f, _) if f.hir_id == id => Some(()),
ExprKind::Call(f, args) => {
let i = args.iter().position(|arg| arg.hir_id == id)?;
let sig = expr_sig(cx, f)?;
let predicates = sig
.predicates_id()
.map_or(cx.param_env, |id| cx.tcx.param_env(id))
.caller_bounds();
sig.input(i).and_then(|ty| {
ty_is_fn_once_param(cx.tcx, ty.skip_binder(), predicates).then_some(())
})
},
) => return Some(e),
Node::Expr(_) | Node::Stmt(_) | Node::Block(_) | Node::Local(_) | Node::Arm(_) => (),
ExprKind::MethodCall(_, args, _) => {
let i = args.iter().position(|arg| arg.hir_id == id)?;
let id = cx.typeck_results().type_dependent_def_id(e.hir_id)?;
let ty = cx.tcx.fn_sig(id).skip_binder().inputs()[i];
ty_is_fn_once_param(cx.tcx, ty, cx.tcx.param_env(id).caller_bounds()).then_some(())
},
_ => None,
}
})
.is_some();
if !is_once {
return Some(e);
}
},
ExprKind::Loop(..) => return Some(e),
_ => (),
},
Node::Stmt(_) | Node::Block(_) | Node::Local(_) | Node::Arm(_) => (),
_ => break,
}
}

48
clippy_utils/src/ty.rs
View file

@ -501,7 +501,7 @@ pub fn all_predicates_of(tcx: TyCtxt<'_>, id: DefId) -> impl Iterator<Item = &(P
/// A signature for a function like type.
#[derive(Clone, Copy)]
pub enum ExprFnSig<'tcx> {
Sig(Binder<'tcx, FnSig<'tcx>>),
Sig(Binder<'tcx, FnSig<'tcx>>, Option<DefId>),
Closure(Option<&'tcx FnDecl<'tcx>>, Binder<'tcx, FnSig<'tcx>>),
Trait(Binder<'tcx, Ty<'tcx>>, Option<Binder<'tcx, Ty<'tcx>>>),
}
@ -510,7 +510,7 @@ impl<'tcx> ExprFnSig<'tcx> {
/// bounds only for variadic functions, otherwise this will panic.
pub fn input(self, i: usize) -> Option<Binder<'tcx, Ty<'tcx>>> {
match self {
Self::Sig(sig) => {
Self::Sig(sig, _) => {
if sig.c_variadic() {
sig.inputs().map_bound(|inputs| inputs.get(i).copied()).transpose()
} else {
@ -527,7 +527,7 @@ impl<'tcx> ExprFnSig<'tcx> {
/// functions, otherwise this will panic.
pub fn input_with_hir(self, i: usize) -> Option<(Option<&'tcx hir::Ty<'tcx>>, Binder<'tcx, Ty<'tcx>>)> {
match self {
Self::Sig(sig) => {
Self::Sig(sig, _) => {
if sig.c_variadic() {
sig.inputs()
.map_bound(|inputs| inputs.get(i).copied())
@ -549,16 +549,20 @@ impl<'tcx> ExprFnSig<'tcx> {
/// specified.
pub fn output(self) -> Option<Binder<'tcx, Ty<'tcx>>> {
match self {
Self::Sig(sig) | Self::Closure(_, sig) => Some(sig.output()),
Self::Sig(sig, _) | Self::Closure(_, sig) => Some(sig.output()),
Self::Trait(_, output) => output,
}
}
pub fn predicates_id(&self) -> Option<DefId> {
if let ExprFnSig::Sig(_, id) = *self { id } else { None }
}
}
/// If the expression is function like, get the signature for it.
pub fn expr_sig<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> Option<ExprFnSig<'tcx>> {
if let Res::Def(DefKind::Fn | DefKind::Ctor(_, CtorKind::Fn) | DefKind::AssocFn, id) = path_res(cx, expr) {
Some(ExprFnSig::Sig(cx.tcx.fn_sig(id)))
Some(ExprFnSig::Sig(cx.tcx.fn_sig(id), Some(id)))
} else {
ty_sig(cx, cx.typeck_results().expr_ty_adjusted(expr).peel_refs())
}
@ -575,9 +579,9 @@ fn ty_sig<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<ExprFnSig<'tcx>>
.and_then(|id| cx.tcx.hir().fn_decl_by_hir_id(cx.tcx.hir().local_def_id_to_hir_id(id)));
Some(ExprFnSig::Closure(decl, subs.as_closure().sig()))
},
ty::FnDef(id, subs) => Some(ExprFnSig::Sig(cx.tcx.bound_fn_sig(id).subst(cx.tcx, subs))),
ty::FnDef(id, subs) => Some(ExprFnSig::Sig(cx.tcx.bound_fn_sig(id).subst(cx.tcx, subs), Some(id))),
ty::Opaque(id, _) => ty_sig(cx, cx.tcx.type_of(id)),
ty::FnPtr(sig) => Some(ExprFnSig::Sig(sig)),
ty::FnPtr(sig) => Some(ExprFnSig::Sig(sig, None)),
ty::Dynamic(bounds, _) => {
let lang_items = cx.tcx.lang_items();
match bounds.principal() {
@ -793,3 +797,33 @@ pub fn variant_of_res<'tcx>(cx: &LateContext<'tcx>, res: Res) -> Option<&'tcx Va
_ => None,
}
}
/// Checks if the type is a type parameter implementing `FnOnce`, but not `FnMut`.
pub fn ty_is_fn_once_param<'tcx>(tcx: TyCtxt<'_>, ty: Ty<'tcx>, predicates: &'tcx [Predicate<'_>]) -> bool {
let ty::Param(ty) = *ty.kind() else {
return false;
};
let lang = tcx.lang_items();
let (Some(fn_once_id), Some(fn_mut_id), Some(fn_id))
= (lang.fn_once_trait(), lang.fn_mut_trait(), lang.fn_trait())
else {
return false;
};
predicates
.iter()
.try_fold(false, |found, p| {
if let PredicateKind::Trait(p) = p.kind().skip_binder()
&& let ty::Param(self_ty) = p.trait_ref.self_ty().kind()
&& ty.index == self_ty.index
{
// This should use `super_traits_of`, but that's a private function.
if p.trait_ref.def_id == fn_once_id {
return Some(true);
} else if p.trait_ref.def_id == fn_mut_id || p.trait_ref.def_id == fn_id {
return None;
}
}
Some(found)
})
.unwrap_or(false)
}

46
tests/ui/while_let_on_iterator.fixed
View file

@ -7,7 +7,8 @@
unused_mut,
dead_code,
clippy::equatable_if_let,
clippy::manual_find
clippy::manual_find,
clippy::redundant_closure_call
)]
fn base() {
@ -259,7 +260,7 @@ fn issue1924() {
fn f(&mut self) -> Option<u32> {
// Used as a field.
for i in self.0.by_ref() {
if !(3..=7).contains(&i) {
if !(3..8).contains(&i) {
return Some(i);
}
}
@ -403,6 +404,47 @@ fn issue_8113() {
}
}
fn fn_once_closure() {
let mut it = 0..10;
(|| {
for x in it {
if x % 2 == 0 {
break;
}
}
})();
fn f(_: impl FnOnce()) {}
let mut it = 0..10;
f(|| {
for x in it {
if x % 2 == 0 {
break;
}
}
});
fn f2(_: impl FnMut()) {}
let mut it = 0..10;
f2(|| {
for x in it.by_ref() {
if x % 2 == 0 {
break;
}
}
});
fn f3(_: fn()) {}
f3(|| {
let mut it = 0..10;
for x in it {
if x % 2 == 0 {
break;
}
}
})
}
fn main() {
let mut it = 0..20;
for _ in it {

46
tests/ui/while_let_on_iterator.rs
View file

@ -7,7 +7,8 @@
unused_mut,
dead_code,
clippy::equatable_if_let,
clippy::manual_find
clippy::manual_find,
clippy::redundant_closure_call
)]
fn base() {
@ -259,7 +260,7 @@ fn issue1924() {
fn f(&mut self) -> Option<u32> {
// Used as a field.
while let Some(i) = self.0.next() {
if i < 3 || i > 7 {
if !(3..8).contains(&i) {
return Some(i);
}
}
@ -403,6 +404,47 @@ fn issue_8113() {
}
}
fn fn_once_closure() {
let mut it = 0..10;
(|| {
while let Some(x) = it.next() {
if x % 2 == 0 {
break;
}
}
})();
fn f(_: impl FnOnce()) {}
let mut it = 0..10;
f(|| {
while let Some(x) = it.next() {
if x % 2 == 0 {
break;
}
}
});
fn f2(_: impl FnMut()) {}
let mut it = 0..10;
f2(|| {
while let Some(x) = it.next() {
if x % 2 == 0 {
break;
}
}
});
fn f3(_: fn()) {}
f3(|| {
let mut it = 0..10;
while let Some(x) = it.next() {
if x % 2 == 0 {
break;
}
}
})
}
fn main() {
let mut it = 0..20;
while let Some(..) = it.next() {

78
tests/ui/while_let_on_iterator.stderr
View file

@ -1,5 +1,5 @@
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:15:5
--> $DIR/while_let_on_iterator.rs:16:5
|
LL | while let Option::Some(x) = iter.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in iter`
@ -7,138 +7,154 @@ LL | while let Option::Some(x) = iter.next() {
= note: `-D clippy::while-let-on-iterator` implied by `-D warnings`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:20:5
--> $DIR/while_let_on_iterator.rs:21:5
|
LL | while let Some(x) = iter.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in iter`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:25:5
--> $DIR/while_let_on_iterator.rs:26:5
|
LL | while let Some(_) = iter.next() {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for _ in iter`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:101:9
--> $DIR/while_let_on_iterator.rs:102:9
|
LL | while let Some([..]) = it.next() {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for [..] in it`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:108:9
--> $DIR/while_let_on_iterator.rs:109:9
|
LL | while let Some([_x]) = it.next() {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for [_x] in it`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:121:9
--> $DIR/while_let_on_iterator.rs:122:9
|
LL | while let Some(x @ [_]) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x @ [_] in it`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:141:9
--> $DIR/while_let_on_iterator.rs:142:9
|
LL | while let Some(_) = y.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for _ in y`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:198:9
--> $DIR/while_let_on_iterator.rs:199:9
|
LL | while let Some(m) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:209:5
--> $DIR/while_let_on_iterator.rs:210:5
|
LL | while let Some(n) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for n in it`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:211:9
--> $DIR/while_let_on_iterator.rs:212:9
|
LL | while let Some(m) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:220:9
--> $DIR/while_let_on_iterator.rs:221:9
|
LL | while let Some(m) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:229:9
--> $DIR/while_let_on_iterator.rs:230:9
|
LL | while let Some(m) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:246:9
--> $DIR/while_let_on_iterator.rs:247:9
|
LL | while let Some(m) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:261:13
--> $DIR/while_let_on_iterator.rs:262:13
|
LL | while let Some(i) = self.0.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for i in self.0.by_ref()`
error: manual `!RangeInclusive::contains` implementation
--> $DIR/while_let_on_iterator.rs:262:20
|
LL | if i < 3 || i > 7 {
| ^^^^^^^^^^^^^^ help: use: `!(3..=7).contains(&i)`
|
= note: `-D clippy::manual-range-contains` implied by `-D warnings`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:293:13
--> $DIR/while_let_on_iterator.rs:294:13
|
LL | while let Some(i) = self.0.0.0.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for i in self.0.0.0.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:322:5
--> $DIR/while_let_on_iterator.rs:323:5
|
LL | while let Some(n) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for n in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:334:9
--> $DIR/while_let_on_iterator.rs:335:9
|
LL | while let Some(x) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:348:5
--> $DIR/while_let_on_iterator.rs:349:5
|
LL | while let Some(x) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:359:5
--> $DIR/while_let_on_iterator.rs:360:5
|
LL | while let Some(x) = it.0.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it.0.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:394:5
--> $DIR/while_let_on_iterator.rs:395:5
|
LL | while let Some(x) = s.x.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in s.x.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:401:5
--> $DIR/while_let_on_iterator.rs:402:5
|
LL | while let Some(x) = x[0].next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in x[0].by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:408:5
--> $DIR/while_let_on_iterator.rs:410:9
|
LL | while let Some(x) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:420:9
|
LL | while let Some(x) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:430:9
|
LL | while let Some(x) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:440:9
|
LL | while let Some(x) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:450:5
|
LL | while let Some(..) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for _ in it`
error: aborting due to 23 previous errors
error: aborting due to 26 previous errors