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Rollup merge of #99696 - WaffleLapkin:uplift, r=fee1-dead

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Uplift `clippy::for_loops_over_fallibles` lint into rustc

This PR, as the title suggests, uplifts [`clippy::for_loops_over_fallibles`] lint into rustc. This lint warns for code like this:
```rust
for _ in Some(1) {}
for _ in Ok::<_, ()>(1) {}
```
i.e. directly iterating over `Option` and `Result` using `for` loop.

There are a number of suggestions that this PR adds (on top of what clippy suggested):
1. If the argument (? is there a better name for that expression) of a `for` loop is a `.next()` call, then we can suggest removing it (or rather replacing with `.by_ref()` to allow iterator being used later)
   ```rust
    for _ in iter.next() {}
    // turns into
    for _ in iter.by_ref() {}
    ```
2. (otherwise) We can suggest using `while let`, this is useful for non-iterator, iterator-like things like [async] channels
   ```rust
   for _ in rx.recv() {}
   // turns into
   while let Some(_) = rx.recv() {}
   ```
3. If the argument type is `Result<impl IntoIterator, _>` and the body has a `Result<_, _>` type, we can suggest using `?`
   ```rust
   for _ in f() {}
   // turns into
   for _ in f()? {}
   ```
4. To preserve the original behavior and clear intent, we can suggest using `if let`
   ```rust
   for _ in f() {}
   // turns into
   if let Some(_) = f() {}
   ```
(P.S. `Some` and `Ok` are interchangeable depending on the type)

I still feel that the lint wording/look is somewhat off, so I'll be happy to hear suggestions (on how to improve suggestions :D)!

Resolves #99272

[`clippy::for_loops_over_fallibles`]: https://rust-lang.github.io/rust-clippy/master/index.html#for_loops_over_fallibles
This commit is contained in:
Dylan DPC 2022-10-10 13:43:40 +05:30 • committed by GitHub
commit 7e16f9f1ea
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26 changed files with 381 additions and 366 deletions
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14
compiler/rustc_ast/src/visit.rs
View file

@ -244,14 +244,12 @@ pub trait Visitor<'ast>: Sized {
#[macro_export]
macro_rules! walk_list {
($visitor: expr, $method: ident, $list: expr) => {
for elem in $list {
$visitor.$method(elem)
}
};
($visitor: expr, $method: ident, $list: expr, $($extra_args: expr),*) => {
for elem in $list {
$visitor.$method(elem, $($extra_args,)*)
($visitor: expr, $method: ident, $list: expr $(, $($extra_args: expr),* )?) => {
{
#[cfg_attr(not(bootstrap), allow(for_loops_over_fallibles))]
for elem in $list {
$visitor.$method(elem $(, $($extra_args,)* )?)
}
}
}
}

183
compiler/rustc_lint/src/for_loops_over_fallibles.rs Normal file
View file

@ -0,0 +1,183 @@
use crate::{LateContext, LateLintPass, LintContext};
use hir::{Expr, Pat};
use rustc_errors::{Applicability, DelayDm};
use rustc_hir as hir;
use rustc_infer::traits::TraitEngine;
use rustc_infer::{infer::TyCtxtInferExt, traits::ObligationCause};
use rustc_middle::ty::{self, List};
use rustc_span::{sym, Span};
use rustc_trait_selection::traits::TraitEngineExt;
declare_lint! {
/// The `for_loops_over_fallibles` lint checks for `for` loops over `Option` or `Result` values.
///
/// ### Example
///
/// ```rust
/// let opt = Some(1);
/// for x in opt { /* ... */}
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// Both `Option` and `Result` implement `IntoIterator` trait, which allows using them in a `for` loop.
/// `for` loop over `Option` or `Result` will iterate either 0 (if the value is `None`/`Err(_)`)
/// or 1 time (if the value is `Some(_)`/`Ok(_)`). This is not very useful and is more clearly expressed
/// via `if let`.
///
/// `for` loop can also be accidentally written with the intention to call a function multiple times,
/// while the function returns `Some(_)`, in these cases `while let` loop should be used instead.
///
/// The "intended" use of `IntoIterator` implementations for `Option` and `Result` is passing them to
/// generic code that expects something implementing `IntoIterator`. For example using `.chain(option)`
/// to optionally add a value to an iterator.
pub FOR_LOOPS_OVER_FALLIBLES,
Warn,
"for-looping over an `Option` or a `Result`, which is more clearly expressed as an `if let`"
}
declare_lint_pass!(ForLoopsOverFallibles => [FOR_LOOPS_OVER_FALLIBLES]);
impl<'tcx> LateLintPass<'tcx> for ForLoopsOverFallibles {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
let Some((pat, arg)) = extract_for_loop(expr) else { return };
let ty = cx.typeck_results().expr_ty(arg);
let &ty::Adt(adt, substs) = ty.kind() else { return };
let (article, ty, var) = match adt.did() {
did if cx.tcx.is_diagnostic_item(sym::Option, did) => ("an", "Option", "Some"),
did if cx.tcx.is_diagnostic_item(sym::Result, did) => ("a", "Result", "Ok"),
_ => return,
};
let msg = DelayDm(|| {
format!(
"for loop over {article} `{ty}`. This is more readably written as an `if let` statement",
)
});
cx.struct_span_lint(FOR_LOOPS_OVER_FALLIBLES, arg.span, msg, |lint| {
if let Some(recv) = extract_iterator_next_call(cx, arg)
&& let Ok(recv_snip) = cx.sess().source_map().span_to_snippet(recv.span)
{
lint.span_suggestion(
recv.span.between(arg.span.shrink_to_hi()),
format!("to iterate over `{recv_snip}` remove the call to `next`"),
".by_ref()",
Applicability::MaybeIncorrect
);
} else {
lint.multipart_suggestion_verbose(
format!("to check pattern in a loop use `while let`"),
vec![
// NB can't use `until` here because `expr.span` and `pat.span` have different syntax contexts
(expr.span.with_hi(pat.span.lo()), format!("while let {var}(")),
(pat.span.between(arg.span), format!(") = ")),
],
Applicability::MaybeIncorrect
);
}
if suggest_question_mark(cx, adt, substs, expr.span) {
lint.span_suggestion(
arg.span.shrink_to_hi(),
"consider unwrapping the `Result` with `?` to iterate over its contents",
"?",
Applicability::MaybeIncorrect,
);
}
lint.multipart_suggestion_verbose(
"consider using `if let` to clear intent",
vec![
// NB can't use `until` here because `expr.span` and `pat.span` have different syntax contexts
(expr.span.with_hi(pat.span.lo()), format!("if let {var}(")),
(pat.span.between(arg.span), format!(") = ")),
],
Applicability::MaybeIncorrect,
)
})
}
}
fn extract_for_loop<'tcx>(expr: &Expr<'tcx>) -> Option<(&'tcx Pat<'tcx>, &'tcx Expr<'tcx>)> {
if let hir::ExprKind::DropTemps(e) = expr.kind
&& let hir::ExprKind::Match(iterexpr, [arm], hir::MatchSource::ForLoopDesugar) = e.kind
&& let hir::ExprKind::Call(_, [arg]) = iterexpr.kind
&& let hir::ExprKind::Loop(block, ..) = arm.body.kind
&& let [stmt] = block.stmts
&& let hir::StmtKind::Expr(e) = stmt.kind
&& let hir::ExprKind::Match(_, [_, some_arm], _) = e.kind
&& let hir::PatKind::Struct(_, [field], _) = some_arm.pat.kind
{
Some((field.pat, arg))
} else {
None
}
}
fn extract_iterator_next_call<'tcx>(
cx: &LateContext<'_>,
expr: &Expr<'tcx>,
) -> Option<&'tcx Expr<'tcx>> {
// This won't work for `Iterator::next(iter)`, is this an issue?
if let hir::ExprKind::MethodCall(_, recv, _, _) = expr.kind
&& cx.typeck_results().type_dependent_def_id(expr.hir_id) == cx.tcx.lang_items().next_fn()
{
Some(recv)
} else {
return None
}
}
fn suggest_question_mark<'tcx>(
cx: &LateContext<'tcx>,
adt: ty::AdtDef<'tcx>,
substs: &List<ty::GenericArg<'tcx>>,
span: Span,
) -> bool {
let Some(body_id) = cx.enclosing_body else { return false };
let Some(into_iterator_did) = cx.tcx.get_diagnostic_item(sym::IntoIterator) else { return false };
if !cx.tcx.is_diagnostic_item(sym::Result, adt.did()) {
return false;
}
// Check that the function/closure/constant we are in has a `Result` type.
// Otherwise suggesting using `?` may not be a good idea.
{
let ty = cx.typeck_results().expr_ty(&cx.tcx.hir().body(body_id).value);
let ty::Adt(ret_adt, ..) = ty.kind() else { return false };
if !cx.tcx.is_diagnostic_item(sym::Result, ret_adt.did()) {
return false;
}
}
let ty = substs.type_at(0);
let infcx = cx.tcx.infer_ctxt().build();
let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
let cause = ObligationCause::new(
span,
body_id.hir_id,
rustc_infer::traits::ObligationCauseCode::MiscObligation,
);
fulfill_cx.register_bound(
&infcx,
ty::ParamEnv::empty(),
// Erase any region vids from the type, which may not be resolved
infcx.tcx.erase_regions(ty),
into_iterator_did,
cause,
);
// Select all, including ambiguous predicates
let errors = fulfill_cx.select_all_or_error(&infcx);
errors.is_empty()
}

3
compiler/rustc_lint/src/lib.rs
View file

@ -52,6 +52,7 @@ mod early;
mod enum_intrinsics_non_enums;
mod errors;
mod expect;
mod for_loops_over_fallibles;
pub mod hidden_unicode_codepoints;
mod internal;
mod late;
@ -86,6 +87,7 @@ use rustc_span::Span;
use array_into_iter::ArrayIntoIter;
use builtin::*;
use enum_intrinsics_non_enums::EnumIntrinsicsNonEnums;
use for_loops_over_fallibles::*;
use hidden_unicode_codepoints::*;
use internal::*;
use let_underscore::*;
@ -188,6 +190,7 @@ macro_rules! late_lint_mod_passes {
$macro!(
$args,
[
ForLoopsOverFallibles: ForLoopsOverFallibles,
HardwiredLints: HardwiredLints,
ImproperCTypesDeclarations: ImproperCTypesDeclarations,
ImproperCTypesDefinitions: ImproperCTypesDefinitions,

1
library/core/tests/option.rs
View file

@ -57,6 +57,7 @@ fn test_get_resource() {
}
#[test]
#[cfg_attr(not(bootstrap), allow(for_loops_over_fallibles))]
fn test_option_dance() {
let x = Some(());
let mut y = Some(5);

14
src/test/ui/drop/dropck_legal_cycles.rs
View file

@ -1017,7 +1017,7 @@ impl<'a> Children<'a> for HM<'a> {
where C: Context + PrePost<Self>, Self: Sized
{
if let Some(ref hm) = self.contents.get() {
for (k, v) in hm.iter().nth(index / 2) {
if let Some((k, v)) = hm.iter().nth(index / 2) {
[k, v][index % 2].descend_into_self(context);
}
}
@ -1032,7 +1032,7 @@ impl<'a> Children<'a> for VD<'a> {
where C: Context + PrePost<Self>, Self: Sized
{
if let Some(ref vd) = self.contents.get() {
for r in vd.iter().nth(index) {
if let Some(r) = vd.iter().nth(index) {
r.descend_into_self(context);
}
}
@ -1047,7 +1047,7 @@ impl<'a> Children<'a> for VM<'a> {
where C: Context + PrePost<VM<'a>>
{
if let Some(ref vd) = self.contents.get() {
for (_idx, r) in vd.iter().nth(index) {
if let Some((_idx, r)) = vd.iter().nth(index) {
r.descend_into_self(context);
}
}
@ -1062,7 +1062,7 @@ impl<'a> Children<'a> for LL<'a> {
where C: Context + PrePost<LL<'a>>
{
if let Some(ref ll) = self.contents.get() {
for r in ll.iter().nth(index) {
if let Some(r) = ll.iter().nth(index) {
r.descend_into_self(context);
}
}
@ -1077,7 +1077,7 @@ impl<'a> Children<'a> for BH<'a> {
where C: Context + PrePost<BH<'a>>
{
if let Some(ref bh) = self.contents.get() {
for r in bh.iter().nth(index) {
if let Some(r) = bh.iter().nth(index) {
r.descend_into_self(context);
}
}
@ -1092,7 +1092,7 @@ impl<'a> Children<'a> for BTM<'a> {
where C: Context + PrePost<BTM<'a>>
{
if let Some(ref bh) = self.contents.get() {
for (k, v) in bh.iter().nth(index / 2) {
if let Some((k, v)) = bh.iter().nth(index / 2) {
[k, v][index % 2].descend_into_self(context);
}
}
@ -1107,7 +1107,7 @@ impl<'a> Children<'a> for BTS<'a> {
where C: Context + PrePost<BTS<'a>>
{
if let Some(ref bh) = self.contents.get() {
for r in bh.iter().nth(index) {
if let Some(r) = bh.iter().nth(index) {
r.descend_into_self(context);
}
}

1
src/test/ui/issues/issue-30371.rs
View file

@ -1,5 +1,6 @@
// run-pass
#![allow(unreachable_code)]
#![allow(for_loops_over_fallibles)]
#![deny(unused_variables)]
fn main() {

43
src/test/ui/lint/for_loop_over_fallibles.rs Normal file
View file

@ -0,0 +1,43 @@
// check-pass
fn main() {
// Common
for _ in Some(1) {}
//~^ WARN for loop over an `Option`. This is more readably written as an `if let` statement
//~| HELP to check pattern in a loop use `while let`
//~| HELP consider using `if let` to clear intent
for _ in Ok::<_, ()>(1) {}
//~^ WARN for loop over a `Result`. This is more readably written as an `if let` statement
//~| HELP to check pattern in a loop use `while let`
//~| HELP consider using `if let` to clear intent
// `Iterator::next` specific
for _ in [0; 0].iter().next() {}
//~^ WARN for loop over an `Option`. This is more readably written as an `if let` statement
//~| HELP to iterate over `[0; 0].iter()` remove the call to `next`
//~| HELP consider using `if let` to clear intent
// `Result<impl Iterator, _>`, but function doesn't return `Result`
for _ in Ok::<_, ()>([0; 0].iter()) {}
//~^ WARN for loop over a `Result`. This is more readably written as an `if let` statement
//~| HELP to check pattern in a loop use `while let`
//~| HELP consider using `if let` to clear intent
}
fn _returns_result() -> Result<(), ()> {
// `Result<impl Iterator, _>`
for _ in Ok::<_, ()>([0; 0].iter()) {}
//~^ WARN for loop over a `Result`. This is more readably written as an `if let` statement
//~| HELP to check pattern in a loop use `while let`
//~| HELP consider unwrapping the `Result` with `?` to iterate over its contents
//~| HELP consider using `if let` to clear intent
// `Result<impl IntoIterator>`
for _ in Ok::<_, ()>([0; 0]) {}
//~^ WARN for loop over a `Result`. This is more readably written as an `if let` statement
//~| HELP to check pattern in a loop use `while let`
//~| HELP consider unwrapping the `Result` with `?` to iterate over its contents
//~| HELP consider using `if let` to clear intent
Ok(())
}

101
src/test/ui/lint/for_loop_over_fallibles.stderr Normal file
View file

@ -0,0 +1,101 @@
warning: for loop over an `Option`. This is more readably written as an `if let` statement
--> $DIR/for_loop_over_fallibles.rs:5:14
|
LL | for _ in Some(1) {}
| ^^^^^^^
|
= note: `#[warn(for_loops_over_fallibles)]` on by default
help: to check pattern in a loop use `while let`
|
LL | while let Some(_) = Some(1) {}
| ~~~~~~~~~~~~~~~ ~~~
help: consider using `if let` to clear intent
|
LL | if let Some(_) = Some(1) {}
| ~~~~~~~~~~~~ ~~~
warning: for loop over a `Result`. This is more readably written as an `if let` statement
--> $DIR/for_loop_over_fallibles.rs:9:14
|
LL | for _ in Ok::<_, ()>(1) {}
| ^^^^^^^^^^^^^^
|
help: to check pattern in a loop use `while let`
|
LL | while let Ok(_) = Ok::<_, ()>(1) {}
| ~~~~~~~~~~~~~ ~~~
help: consider using `if let` to clear intent
|
LL | if let Ok(_) = Ok::<_, ()>(1) {}
| ~~~~~~~~~~ ~~~
warning: for loop over an `Option`. This is more readably written as an `if let` statement
--> $DIR/for_loop_over_fallibles.rs:15:14
|
LL | for _ in [0; 0].iter().next() {}
| ^^^^^^^^^^^^^^^^^^^^
|
help: to iterate over `[0; 0].iter()` remove the call to `next`
|
LL | for _ in [0; 0].iter().by_ref() {}
| ~~~~~~~~~
help: consider using `if let` to clear intent
|
LL | if let Some(_) = [0; 0].iter().next() {}
| ~~~~~~~~~~~~ ~~~
warning: for loop over a `Result`. This is more readably written as an `if let` statement
--> $DIR/for_loop_over_fallibles.rs:21:14
|
LL | for _ in Ok::<_, ()>([0; 0].iter()) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
help: to check pattern in a loop use `while let`
|
LL | while let Ok(_) = Ok::<_, ()>([0; 0].iter()) {}
| ~~~~~~~~~~~~~ ~~~
help: consider using `if let` to clear intent
|
LL | if let Ok(_) = Ok::<_, ()>([0; 0].iter()) {}
| ~~~~~~~~~~ ~~~
warning: for loop over a `Result`. This is more readably written as an `if let` statement
--> $DIR/for_loop_over_fallibles.rs:29:14
|
LL | for _ in Ok::<_, ()>([0; 0].iter()) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
help: to check pattern in a loop use `while let`
|
LL | while let Ok(_) = Ok::<_, ()>([0; 0].iter()) {}
| ~~~~~~~~~~~~~ ~~~
help: consider unwrapping the `Result` with `?` to iterate over its contents
|
LL | for _ in Ok::<_, ()>([0; 0].iter())? {}
| +
help: consider using `if let` to clear intent
|
LL | if let Ok(_) = Ok::<_, ()>([0; 0].iter()) {}
| ~~~~~~~~~~ ~~~
warning: for loop over a `Result`. This is more readably written as an `if let` statement
--> $DIR/for_loop_over_fallibles.rs:36:14
|
LL | for _ in Ok::<_, ()>([0; 0]) {}
| ^^^^^^^^^^^^^^^^^^^
|
help: to check pattern in a loop use `while let`
|
LL | while let Ok(_) = Ok::<_, ()>([0; 0]) {}
| ~~~~~~~~~~~~~ ~~~
help: consider unwrapping the `Result` with `?` to iterate over its contents
|
LL | for _ in Ok::<_, ()>([0; 0])? {}
| +
help: consider using `if let` to clear intent
|
LL | if let Ok(_) = Ok::<_, ()>([0; 0]) {}
| ~~~~~~~~~~ ~~~
warning: 6 warnings emitted

1
src/tools/clippy/clippy_lints/src/lib.register_all.rs
View file

@ -109,7 +109,6 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
LintId::of(loops::EMPTY_LOOP),
LintId::of(loops::EXPLICIT_COUNTER_LOOP),
LintId::of(loops::FOR_KV_MAP),
LintId::of(loops::FOR_LOOPS_OVER_FALLIBLES),
LintId::of(loops::ITER_NEXT_LOOP),
LintId::of(loops::MANUAL_FIND),
LintId::of(loops::MANUAL_FLATTEN),

1
src/tools/clippy/clippy_lints/src/lib.register_lints.rs
View file

@ -227,7 +227,6 @@ store.register_lints(&[
loops::EXPLICIT_INTO_ITER_LOOP,
loops::EXPLICIT_ITER_LOOP,
loops::FOR_KV_MAP,
loops::FOR_LOOPS_OVER_FALLIBLES,
loops::ITER_NEXT_LOOP,
loops::MANUAL_FIND,
loops::MANUAL_FLATTEN,

1
src/tools/clippy/clippy_lints/src/lib.register_suspicious.rs
View file

@ -21,7 +21,6 @@ store.register_group(true, "clippy::suspicious", Some("clippy_suspicious"), vec!
LintId::of(formatting::SUSPICIOUS_ELSE_FORMATTING),
LintId::of(formatting::SUSPICIOUS_UNARY_OP_FORMATTING),
LintId::of(loops::EMPTY_LOOP),
LintId::of(loops::FOR_LOOPS_OVER_FALLIBLES),
LintId::of(loops::MUT_RANGE_BOUND),
LintId::of(methods::NO_EFFECT_REPLACE),
LintId::of(methods::SUSPICIOUS_MAP),

65
src/tools/clippy/clippy_lints/src/loops/for_loops_over_fallibles.rs
View file

@ -1,65 +0,0 @@
use super::FOR_LOOPS_OVER_FALLIBLES;
use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::source::snippet;
use clippy_utils::ty::is_type_diagnostic_item;
use rustc_hir::{Expr, Pat};
use rustc_lint::LateContext;
use rustc_span::symbol::sym;
/// Checks for `for` loops over `Option`s and `Result`s.
pub(super) fn check(cx: &LateContext<'_>, pat: &Pat<'_>, arg: &Expr<'_>, method_name: Option<&str>) {
let ty = cx.typeck_results().expr_ty(arg);
if is_type_diagnostic_item(cx, ty, sym::Option) {
let help_string = if let Some(method_name) = method_name {
format!(
"consider replacing `for {0} in {1}.{method_name}()` with `if let Some({0}) = {1}`",
snippet(cx, pat.span, "_"),
snippet(cx, arg.span, "_")
)
} else {
format!(
"consider replacing `for {0} in {1}` with `if let Some({0}) = {1}`",
snippet(cx, pat.span, "_"),
snippet(cx, arg.span, "_")
)
};
span_lint_and_help(
cx,
FOR_LOOPS_OVER_FALLIBLES,
arg.span,
&format!(
"for loop over `{0}`, which is an `Option`. This is more readably written as an \
`if let` statement",
snippet(cx, arg.span, "_")
),
None,
&help_string,
);
} else if is_type_diagnostic_item(cx, ty, sym::Result) {
let help_string = if let Some(method_name) = method_name {
format!(
"consider replacing `for {0} in {1}.{method_name}()` with `if let Ok({0}) = {1}`",
snippet(cx, pat.span, "_"),
snippet(cx, arg.span, "_")
)
} else {
format!(
"consider replacing `for {0} in {1}` with `if let Ok({0}) = {1}`",
snippet(cx, pat.span, "_"),
snippet(cx, arg.span, "_")
)
};
span_lint_and_help(
cx,
FOR_LOOPS_OVER_FALLIBLES,
arg.span,
&format!(
"for loop over `{0}`, which is a `Result`. This is more readably written as an \
`if let` statement",
snippet(cx, arg.span, "_")
),
None,
&help_string,
);
}
}

5
src/tools/clippy/clippy_lints/src/loops/iter_next_loop.rs
View file

@ -5,7 +5,7 @@ use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_span::sym;
pub(super) fn check(cx: &LateContext<'_>, arg: &Expr<'_>) -> bool {
pub(super) fn check(cx: &LateContext<'_>, arg: &Expr<'_>) {
if is_trait_method(cx, arg, sym::Iterator) {
span_lint(
cx,
@ -14,8 +14,5 @@ pub(super) fn check(cx: &LateContext<'_>, arg: &Expr<'_>) -> bool {
"you are iterating over `Iterator::next()` which is an Option; this will compile but is \
probably not what you want",
);
true
} else {
false
}
}

57
src/tools/clippy/clippy_lints/src/loops/mod.rs
View file

@ -3,7 +3,6 @@ mod explicit_counter_loop;
mod explicit_into_iter_loop;
mod explicit_iter_loop;
mod for_kv_map;
mod for_loops_over_fallibles;
mod iter_next_loop;
mod manual_find;
mod manual_flatten;
@ -173,49 +172,6 @@ declare_clippy_lint! {
"for-looping over `_.next()` which is probably not intended"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `for` loops over `Option` or `Result` values.
///
/// ### Why is this bad?
/// Readability. This is more clearly expressed as an `if
/// let`.
///
/// ### Example
/// ```rust
/// # let opt = Some(1);
/// # let res: Result<i32, std::io::Error> = Ok(1);
/// for x in opt {
/// // ..
/// }
///
/// for x in &res {
/// // ..
/// }
///
/// for x in res.iter() {
/// // ..
/// }
/// ```
///
/// Use instead:
/// ```rust
/// # let opt = Some(1);
/// # let res: Result<i32, std::io::Error> = Ok(1);
/// if let Some(x) = opt {
/// // ..
/// }
///
/// if let Ok(x) = res {
/// // ..
/// }
/// ```
#[clippy::version = "1.45.0"]
pub FOR_LOOPS_OVER_FALLIBLES,
suspicious,
"for-looping over an `Option` or a `Result`, which is more clearly expressed as an `if let`"
}
declare_clippy_lint! {
/// ### What it does
/// Detects `loop + match` combinations that are easier
@ -648,7 +604,6 @@ declare_lint_pass!(Loops => [
EXPLICIT_ITER_LOOP,
EXPLICIT_INTO_ITER_LOOP,
ITER_NEXT_LOOP,
FOR_LOOPS_OVER_FALLIBLES,
WHILE_LET_LOOP,
NEEDLESS_COLLECT,
EXPLICIT_COUNTER_LOOP,
@ -739,30 +694,22 @@ fn check_for_loop<'tcx>(
manual_find::check(cx, pat, arg, body, span, expr);
}
fn check_for_loop_arg(cx: &LateContext<'_>, pat: &Pat<'_>, arg: &Expr<'_>) {
let mut next_loop_linted = false; // whether or not ITER_NEXT_LOOP lint was used
fn check_for_loop_arg(cx: &LateContext<'_>, _: &Pat<'_>, arg: &Expr<'_>) {
if let ExprKind::MethodCall(method, self_arg, [], _) = arg.kind {
let method_name = method.ident.as_str();
// check for looping over x.iter() or x.iter_mut(), could use &x or &mut x
match method_name {
"iter" | "iter_mut" => {
explicit_iter_loop::check(cx, self_arg, arg, method_name);
for_loops_over_fallibles::check(cx, pat, self_arg, Some(method_name));
},
"into_iter" => {
explicit_iter_loop::check(cx, self_arg, arg, method_name);
explicit_into_iter_loop::check(cx, self_arg, arg);
for_loops_over_fallibles::check(cx, pat, self_arg, Some(method_name));
},
"next" => {
next_loop_linted = iter_next_loop::check(cx, arg);
iter_next_loop::check(cx, arg);
},
_ => {},
}
}
if !next_loop_linted {
for_loops_over_fallibles::check(cx, pat, arg, None);
}
}

5
src/tools/clippy/clippy_lints/src/renamed_lints.rs
View file

@ -11,8 +11,8 @@ pub static RENAMED_LINTS: &[(&str, &str)] = &[
("clippy::disallowed_method", "clippy::disallowed_methods"),
("clippy::disallowed_type", "clippy::disallowed_types"),
("clippy::eval_order_dependence", "clippy::mixed_read_write_in_expression"),
("clippy::for_loop_over_option", "clippy::for_loops_over_fallibles"),
("clippy::for_loop_over_result", "clippy::for_loops_over_fallibles"),
("clippy::for_loop_over_option", "for_loops_over_fallibles"),
("clippy::for_loop_over_result", "for_loops_over_fallibles"),
("clippy::identity_conversion", "clippy::useless_conversion"),
("clippy::if_let_some_result", "clippy::match_result_ok"),
("clippy::logic_bug", "clippy::overly_complex_bool_expr"),
@ -31,6 +31,7 @@ pub static RENAMED_LINTS: &[(&str, &str)] = &[
("clippy::to_string_in_display", "clippy::recursive_format_impl"),
("clippy::zero_width_space", "clippy::invisible_characters"),
("clippy::drop_bounds", "drop_bounds"),
("clippy::for_loops_over_fallibles", "for_loops_over_fallibles"),
("clippy::into_iter_on_array", "array_into_iter"),
("clippy::invalid_atomic_ordering", "invalid_atomic_ordering"),
("clippy::invalid_ref", "invalid_value"),

1
src/tools/clippy/src/docs.rs
View file

@ -170,7 +170,6 @@ docs! {
"fn_to_numeric_cast_any",
"fn_to_numeric_cast_with_truncation",
"for_kv_map",
"for_loops_over_fallibles",
"forget_copy",
"forget_non_drop",
"forget_ref",

32
src/tools/clippy/src/docs/for_loops_over_fallibles.txt
View file

@ -1,32 +0,0 @@
### What it does
Checks for `for` loops over `Option` or `Result` values.
### Why is this bad?
Readability. This is more clearly expressed as an `if
let`.
### Example
```
for x in opt {
// ..
}
for x in &res {
// ..
}
for x in res.iter() {
// ..
}
```
Use instead:
```
if let Some(x) = opt {
// ..
}
if let Ok(x) = res {
// ..
}
```

1
src/tools/clippy/tests/ui/for_loop_unfixable.rs
View file

@ -8,6 +8,7 @@
clippy::for_kv_map
)]
#[allow(clippy::linkedlist, clippy::unnecessary_mut_passed, clippy::similar_names)]
#[allow(for_loops_over_fallibles)]
fn main() {
let vec = vec![1, 2, 3, 4];

2
src/tools/clippy/tests/ui/for_loop_unfixable.stderr
View file

@ -1,5 +1,5 @@
error: you are iterating over `Iterator::next()` which is an Option; this will compile but is probably not what you want
--> $DIR/for_loop_unfixable.rs:14:15
--> $DIR/for_loop_unfixable.rs:15:15
|
LL | for _v in vec.iter().next() {}
| ^^^^^^^^^^^^^^^^^

73
src/tools/clippy/tests/ui/for_loops_over_fallibles.rs
View file

@ -1,73 +0,0 @@
#![warn(clippy::for_loops_over_fallibles)]
#![allow(clippy::uninlined_format_args)]
fn for_loops_over_fallibles() {
let option = Some(1);
let mut result = option.ok_or("x not found");
let v = vec![0, 1, 2];
// check over an `Option`
for x in option {
println!("{}", x);
}
// check over an `Option`
for x in option.iter() {
println!("{}", x);
}
// check over a `Result`
for x in result {
println!("{}", x);
}
// check over a `Result`
for x in result.iter_mut() {
println!("{}", x);
}
// check over a `Result`
for x in result.into_iter() {
println!("{}", x);
}
for x in option.ok_or("x not found") {
println!("{}", x);
}
// make sure LOOP_OVER_NEXT lint takes clippy::precedence when next() is the last call
// in the chain
for x in v.iter().next() {
println!("{}", x);
}
// make sure we lint when next() is not the last call in the chain
for x in v.iter().next().and(Some(0)) {
println!("{}", x);
}
for x in v.iter().next().ok_or("x not found") {
println!("{}", x);
}
// check for false positives
// for loop false positive
for x in v {
println!("{}", x);
}
// while let false positive for Option
while let Some(x) = option {
println!("{}", x);
break;
}
// while let false positive for Result
while let Ok(x) = result {
println!("{}", x);
break;
}
}
fn main() {}

95
src/tools/clippy/tests/ui/for_loops_over_fallibles.stderr
View file

@ -1,95 +0,0 @@
error: for loop over `option`, which is an `Option`. This is more readably written as an `if let` statement
--> $DIR/for_loops_over_fallibles.rs:10:14
|
LL | for x in option {
| ^^^^^^
|
= help: consider replacing `for x in option` with `if let Some(x) = option`
= note: `-D clippy::for-loops-over-fallibles` implied by `-D warnings`
error: for loop over `option`, which is an `Option`. This is more readably written as an `if let` statement
--> $DIR/for_loops_over_fallibles.rs:15:14
|
LL | for x in option.iter() {
| ^^^^^^
|
= help: consider replacing `for x in option.iter()` with `if let Some(x) = option`
error: for loop over `result`, which is a `Result`. This is more readably written as an `if let` statement
--> $DIR/for_loops_over_fallibles.rs:20:14
|
LL | for x in result {
| ^^^^^^
|
= help: consider replacing `for x in result` with `if let Ok(x) = result`
error: for loop over `result`, which is a `Result`. This is more readably written as an `if let` statement
--> $DIR/for_loops_over_fallibles.rs:25:14
|
LL | for x in result.iter_mut() {
| ^^^^^^
|
= help: consider replacing `for x in result.iter_mut()` with `if let Ok(x) = result`
error: for loop over `result`, which is a `Result`. This is more readably written as an `if let` statement
--> $DIR/for_loops_over_fallibles.rs:30:14
|
LL | for x in result.into_iter() {
| ^^^^^^
|
= help: consider replacing `for x in result.into_iter()` with `if let Ok(x) = result`
error: for loop over `option.ok_or("x not found")`, which is a `Result`. This is more readably written as an `if let` statement
--> $DIR/for_loops_over_fallibles.rs:34:14
|
LL | for x in option.ok_or("x not found") {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: consider replacing `for x in option.ok_or("x not found")` with `if let Ok(x) = option.ok_or("x not found")`
error: you are iterating over `Iterator::next()` which is an Option; this will compile but is probably not what you want
--> $DIR/for_loops_over_fallibles.rs:40:14
|
LL | for x in v.iter().next() {
| ^^^^^^^^^^^^^^^
|
= note: `#[deny(clippy::iter_next_loop)]` on by default
error: for loop over `v.iter().next().and(Some(0))`, which is an `Option`. This is more readably written as an `if let` statement
--> $DIR/for_loops_over_fallibles.rs:45:14
|
LL | for x in v.iter().next().and(Some(0)) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: consider replacing `for x in v.iter().next().and(Some(0))` with `if let Some(x) = v.iter().next().and(Some(0))`
error: for loop over `v.iter().next().ok_or("x not found")`, which is a `Result`. This is more readably written as an `if let` statement
--> $DIR/for_loops_over_fallibles.rs:49:14
|
LL | for x in v.iter().next().ok_or("x not found") {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: consider replacing `for x in v.iter().next().ok_or("x not found")` with `if let Ok(x) = v.iter().next().ok_or("x not found")`
error: this loop never actually loops
--> $DIR/for_loops_over_fallibles.rs:61:5
|
LL | / while let Some(x) = option {
LL | | println!("{}", x);
LL | | break;
LL | | }
| |_____^
|
= note: `#[deny(clippy::never_loop)]` on by default
error: this loop never actually loops
--> $DIR/for_loops_over_fallibles.rs:67:5
|
LL | / while let Ok(x) = result {
LL | | println!("{}", x);
LL | | break;
LL | | }
| |_____^
error: aborting due to 11 previous errors

2
src/tools/clippy/tests/ui/manual_map_option.fixed
View file

@ -7,7 +7,7 @@
clippy::unit_arg,
clippy::match_ref_pats,
clippy::redundant_pattern_matching,
clippy::for_loops_over_fallibles,
for_loops_over_fallibles,
dead_code
)]

2
src/tools/clippy/tests/ui/manual_map_option.rs
View file

@ -7,7 +7,7 @@
clippy::unit_arg,
clippy::match_ref_pats,
clippy::redundant_pattern_matching,
clippy::for_loops_over_fallibles,
for_loops_over_fallibles,
dead_code
)]

7
src/tools/clippy/tests/ui/rename.fixed
View file

@ -12,7 +12,7 @@
#![allow(clippy::disallowed_methods)]
#![allow(clippy::disallowed_types)]
#![allow(clippy::mixed_read_write_in_expression)]
#![allow(clippy::for_loops_over_fallibles)]
#![allow(for_loops_over_fallibles)]
#![allow(clippy::useless_conversion)]
#![allow(clippy::match_result_ok)]
#![allow(clippy::overly_complex_bool_expr)]
@ -45,8 +45,8 @@
#![warn(clippy::disallowed_methods)]
#![warn(clippy::disallowed_types)]
#![warn(clippy::mixed_read_write_in_expression)]
#![warn(clippy::for_loops_over_fallibles)]
#![warn(clippy::for_loops_over_fallibles)]
#![warn(for_loops_over_fallibles)]
#![warn(for_loops_over_fallibles)]
#![warn(clippy::useless_conversion)]
#![warn(clippy::match_result_ok)]
#![warn(clippy::overly_complex_bool_expr)]
@ -65,6 +65,7 @@
#![warn(clippy::recursive_format_impl)]
#![warn(clippy::invisible_characters)]
#![warn(drop_bounds)]
#![warn(for_loops_over_fallibles)]
#![warn(array_into_iter)]
#![warn(invalid_atomic_ordering)]
#![warn(invalid_value)]

3
src/tools/clippy/tests/ui/rename.rs
View file

@ -12,7 +12,7 @@
#![allow(clippy::disallowed_methods)]
#![allow(clippy::disallowed_types)]
#![allow(clippy::mixed_read_write_in_expression)]
#![allow(clippy::for_loops_over_fallibles)]
#![allow(for_loops_over_fallibles)]
#![allow(clippy::useless_conversion)]
#![allow(clippy::match_result_ok)]
#![allow(clippy::overly_complex_bool_expr)]
@ -65,6 +65,7 @@
#![warn(clippy::to_string_in_display)]
#![warn(clippy::zero_width_space)]
#![warn(clippy::drop_bounds)]
#![warn(clippy::for_loops_over_fallibles)]
#![warn(clippy::into_iter_on_array)]
#![warn(clippy::invalid_atomic_ordering)]
#![warn(clippy::invalid_ref)]

34
src/tools/clippy/tests/ui/rename.stderr
View file

@ -54,17 +54,17 @@ error: lint `clippy::eval_order_dependence` has been renamed to `clippy::mixed_r
LL | #![warn(clippy::eval_order_dependence)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `clippy::mixed_read_write_in_expression`
error: lint `clippy::for_loop_over_option` has been renamed to `clippy::for_loops_over_fallibles`
error: lint `clippy::for_loop_over_option` has been renamed to `for_loops_over_fallibles`
--> $DIR/rename.rs:48:9
|
LL | #![warn(clippy::for_loop_over_option)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `clippy::for_loops_over_fallibles`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `for_loops_over_fallibles`
error: lint `clippy::for_loop_over_result` has been renamed to `clippy::for_loops_over_fallibles`
error: lint `clippy::for_loop_over_result` has been renamed to `for_loops_over_fallibles`
--> $DIR/rename.rs:49:9
|
LL | #![warn(clippy::for_loop_over_result)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `clippy::for_loops_over_fallibles`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `for_loops_over_fallibles`
error: lint `clippy::identity_conversion` has been renamed to `clippy::useless_conversion`
--> $DIR/rename.rs:50:9
@ -174,59 +174,65 @@ error: lint `clippy::drop_bounds` has been renamed to `drop_bounds`
LL | #![warn(clippy::drop_bounds)]
| ^^^^^^^^^^^^^^^^^^^ help: use the new name: `drop_bounds`
error: lint `clippy::into_iter_on_array` has been renamed to `array_into_iter`
error: lint `clippy::for_loops_over_fallibles` has been renamed to `for_loops_over_fallibles`
--> $DIR/rename.rs:68:9
|
LL | #![warn(clippy::for_loops_over_fallibles)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `for_loops_over_fallibles`
error: lint `clippy::into_iter_on_array` has been renamed to `array_into_iter`
--> $DIR/rename.rs:69:9
|
LL | #![warn(clippy::into_iter_on_array)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `array_into_iter`
error: lint `clippy::invalid_atomic_ordering` has been renamed to `invalid_atomic_ordering`
--> $DIR/rename.rs:69:9
--> $DIR/rename.rs:70:9
|
LL | #![warn(clippy::invalid_atomic_ordering)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `invalid_atomic_ordering`
error: lint `clippy::invalid_ref` has been renamed to `invalid_value`
--> $DIR/rename.rs:70:9
--> $DIR/rename.rs:71:9
|
LL | #![warn(clippy::invalid_ref)]
| ^^^^^^^^^^^^^^^^^^^ help: use the new name: `invalid_value`
error: lint `clippy::mem_discriminant_non_enum` has been renamed to `enum_intrinsics_non_enums`
--> $DIR/rename.rs:71:9
--> $DIR/rename.rs:72:9
|
LL | #![warn(clippy::mem_discriminant_non_enum)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `enum_intrinsics_non_enums`
error: lint `clippy::panic_params` has been renamed to `non_fmt_panics`
--> $DIR/rename.rs:72:9
--> $DIR/rename.rs:73:9
|
LL | #![warn(clippy::panic_params)]
| ^^^^^^^^^^^^^^^^^^^^ help: use the new name: `non_fmt_panics`
error: lint `clippy::positional_named_format_parameters` has been renamed to `named_arguments_used_positionally`
--> $DIR/rename.rs:73:9
--> $DIR/rename.rs:74:9
|
LL | #![warn(clippy::positional_named_format_parameters)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `named_arguments_used_positionally`
error: lint `clippy::temporary_cstring_as_ptr` has been renamed to `temporary_cstring_as_ptr`
--> $DIR/rename.rs:74:9
--> $DIR/rename.rs:75:9
|
LL | #![warn(clippy::temporary_cstring_as_ptr)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `temporary_cstring_as_ptr`
error: lint `clippy::unknown_clippy_lints` has been renamed to `unknown_lints`
--> $DIR/rename.rs:75:9
--> $DIR/rename.rs:76:9
|
LL | #![warn(clippy::unknown_clippy_lints)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `unknown_lints`
error: lint `clippy::unused_label` has been renamed to `unused_labels`
--> $DIR/rename.rs:76:9
--> $DIR/rename.rs:77:9
|
LL | #![warn(clippy::unused_label)]
| ^^^^^^^^^^^^^^^^^^^^ help: use the new name: `unused_labels`
error: aborting due to 38 previous errors
error: aborting due to 39 previous errors