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Auto merge of #12116 - J-ZhengLi:issue12101, r=Alexendoo
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fix suggestion error in [`useless_vec`]

fixes: #12101

---

changelog: fix suggestion error in [`useless_vec`]

r+ `@matthiaskrgr` since they opened the issue?
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@bors
bors committed Feb 26, 2024
2 parents 1c50948 + 929f746 commit 8a35f20
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Showing 4 changed files with 120 additions and 107 deletions.
211 changes: 105 additions & 106 deletions clippy_lints/src/vec.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,12 +4,12 @@ use std::ops::ControlFlow;
use clippy_config::msrvs::{self, Msrv};
use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::span_lint_hir_and_then;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::source::snippet_opt;
use clippy_utils::ty::is_copy;
use clippy_utils::visitors::for_each_local_use_after_expr;
use clippy_utils::{get_parent_expr, higher, is_trait_method};
use rustc_errors::Applicability;
use rustc_hir::{BorrowKind, Expr, ExprKind, HirId, Mutability, Node, PatKind};
use rustc_hir::{BorrowKind, Expr, ExprKind, HirId, Local, Mutability, Node, Pat, PatKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_middle::ty::layout::LayoutOf;
Expand Down Expand Up @@ -52,35 +52,27 @@ declare_clippy_lint! {

impl_lint_pass!(UselessVec => [USELESS_VEC]);

fn adjusts_to_slice(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
matches!(cx.typeck_results().expr_ty_adjusted(e).kind(), ty::Ref(_, ty, _) if ty.is_slice())
}

/// Checks if the given expression is a method call to a `Vec` method
/// that also exists on slices. If this returns true, it means that
/// this expression does not actually require a `Vec` and could just work with an array.
pub fn is_allowed_vec_method(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
const ALLOWED_METHOD_NAMES: &[&str] = &["len", "as_ptr", "is_empty"];

if let ExprKind::MethodCall(path, ..) = e.kind {
ALLOWED_METHOD_NAMES.contains(&path.ident.name.as_str())
} else {
is_trait_method(cx, e, sym::IntoIterator)
}
}

impl<'tcx> LateLintPass<'tcx> for UselessVec {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if let Some(vec_args) = higher::VecArgs::hir(cx, expr.peel_borrows()) {
let Some(vec_args) = higher::VecArgs::hir(cx, expr.peel_borrows()) else {
return;
};
// the parent callsite of this `vec!` expression, or span to the borrowed one such as `&vec!`
let callsite = expr.span.parent_callsite().unwrap_or(expr.span);

match cx.tcx.parent_hir_node(expr.hir_id) {
// search for `let foo = vec![_]` expressions where all uses of `foo`
// adjust to slices or call a method that exist on slices (e.g. len)
if let Node::Local(local) = cx.tcx.parent_hir_node(expr.hir_id)
// for now ignore locals with type annotations.
// this is to avoid compile errors when doing the suggestion here: let _: Vec<_> = vec![..];
&& local.ty.is_none()
&& let PatKind::Binding(_, id, ..) = local.pat.kind
{
let only_slice_uses = for_each_local_use_after_expr(cx, id, expr.hir_id, |expr| {
Node::Local(Local {
ty: None,
pat:
Pat {
kind: PatKind::Binding(_, id, ..),
..
},
..
}) => {
let only_slice_uses = for_each_local_use_after_expr(cx, *id, expr.hir_id, |expr| {
// allow indexing into a vec and some set of allowed method calls that exist on slices, too
if let Some(parent) = get_parent_expr(cx, expr)
&& (adjusts_to_slice(cx, expr)
Expand All @@ -94,60 +86,40 @@ impl<'tcx> LateLintPass<'tcx> for UselessVec {
})
.is_continue();

let span = expr.span.ctxt().outer_expn_data().call_site;
if only_slice_uses {
self.check_vec_macro(cx, &vec_args, span, expr.hir_id, SuggestedType::Array);
self.check_vec_macro(cx, &vec_args, callsite, expr.hir_id, SuggestedType::Array);
} else {
self.span_to_lint_map.insert(span, None);
self.span_to_lint_map.insert(callsite, None);
}
}
},
// if the local pattern has a specified type, do not lint.
else if let Some(_) = higher::VecArgs::hir(cx, expr)
&& let Node::Local(local) = cx.tcx.parent_hir_node(expr.hir_id)
&& local.ty.is_some()
{
let span = expr.span.ctxt().outer_expn_data().call_site;
self.span_to_lint_map.insert(span, None);
}
Node::Local(Local { ty: Some(_), .. }) if higher::VecArgs::hir(cx, expr).is_some() => {
self.span_to_lint_map.insert(callsite, None);
},
// search for `for _ in vec![...]`
else if let Some(parent) = get_parent_expr(cx, expr)
&& parent.span.is_desugaring(DesugaringKind::ForLoop)
&& self.msrv.meets(msrvs::ARRAY_INTO_ITERATOR)
Node::Expr(Expr { span, .. })
if span.is_desugaring(DesugaringKind::ForLoop) && self.msrv.meets(msrvs::ARRAY_INTO_ITERATOR) =>
{
// report the error around the `vec!` not inside `<std macros>:`
let span = expr.span.ctxt().outer_expn_data().call_site;
self.check_vec_macro(cx, &vec_args, span, expr.hir_id, SuggestedType::Array);
}
let suggest_slice = suggest_type(expr);
self.check_vec_macro(cx, &vec_args, callsite, expr.hir_id, suggest_slice);
},
// search for `&vec![_]` or `vec![_]` expressions where the adjusted type is `&[_]`
else {
let (suggest_slice, span) = if let ExprKind::AddrOf(BorrowKind::Ref, mutability, _) = expr.kind {
// `expr` is `&vec![_]`, so suggest `&[_]` (or `&mut[_]` resp.)
(SuggestedType::SliceRef(mutability), expr.span)
} else {
// `expr` is the `vec![_]` expansion, so suggest `[_]`
// and also use the span of the actual `vec![_]` expression
(SuggestedType::Array, expr.span.ctxt().outer_expn_data().call_site)
};
_ => {
let suggest_slice = suggest_type(expr);

if adjusts_to_slice(cx, expr) {
self.check_vec_macro(cx, &vec_args, span, expr.hir_id, suggest_slice);
self.check_vec_macro(cx, &vec_args, callsite, expr.hir_id, suggest_slice);
} else {
self.span_to_lint_map.insert(span, None);
self.span_to_lint_map.insert(callsite, None);
}
}
},
}
}

fn check_crate_post(&mut self, cx: &LateContext<'tcx>) {
for (span, lint_opt) in &self.span_to_lint_map {
if let Some((hir_id, suggest_slice, snippet, applicability)) = lint_opt {
let help_msg = format!(
"you can use {} directly",
match suggest_slice {
SuggestedType::SliceRef(_) => "a slice",
SuggestedType::Array => "an array",
}
);
let help_msg = format!("you can use {} directly", suggest_slice.desc(),);
span_lint_hir_and_then(cx, USELESS_VEC, *hir_id, *span, "useless use of `vec!`", |diag| {
diag.span_suggestion(*span, help_msg, snippet, *applicability);
});
Expand All @@ -158,14 +130,6 @@ impl<'tcx> LateLintPass<'tcx> for UselessVec {
extract_msrv_attr!(LateContext);
}

#[derive(Copy, Clone)]
pub(crate) enum SuggestedType {
/// Suggest using a slice `&[..]` / `&mut [..]`
SliceRef(Mutability),
/// Suggest using an array: `[..]`
Array,
}

impl UselessVec {
fn check_vec_macro<'tcx>(
&mut self,
Expand All @@ -179,8 +143,6 @@ impl UselessVec {
return;
}

let mut applicability = Applicability::MachineApplicable;

let snippet = match *vec_args {
higher::VecArgs::Repeat(elem, len) => {
if let Some(Constant::Int(len_constant)) = constant(cx, cx.typeck_results(), len) {
Expand All @@ -194,54 +156,91 @@ impl UselessVec {
return;
}

let elem = snippet_with_applicability(cx, elem.span, "elem", &mut applicability);
let len = snippet_with_applicability(cx, len.span, "len", &mut applicability);

match suggest_slice {
SuggestedType::SliceRef(Mutability::Mut) => format!("&mut [{elem}; {len}]"),
SuggestedType::SliceRef(Mutability::Not) => format!("&[{elem}; {len}]"),
SuggestedType::Array => format!("[{elem}; {len}]"),
}
suggest_slice.snippet(cx, Some(elem.span), Some(len.span))
} else {
return;
}
},
higher::VecArgs::Vec(args) => {
if let Some(last) = args.iter().last() {
let args_span = if let Some(last) = args.iter().last() {
if args.len() as u64 * size_of(cx, last) > self.too_large_for_stack {
return;
}
let span = args[0].span.source_callsite().to(last.span.source_callsite());
let args = snippet_with_applicability(cx, span, "..", &mut applicability);

match suggest_slice {
SuggestedType::SliceRef(Mutability::Mut) => {
format!("&mut [{args}]")
},
SuggestedType::SliceRef(Mutability::Not) => {
format!("&[{args}]")
},
SuggestedType::Array => {
format!("[{args}]")
},
}
Some(args[0].span.source_callsite().to(last.span.source_callsite()))
} else {
match suggest_slice {
SuggestedType::SliceRef(Mutability::Mut) => "&mut []".to_owned(),
SuggestedType::SliceRef(Mutability::Not) => "&[]".to_owned(),
SuggestedType::Array => "[]".to_owned(),
}
}
None
};
suggest_slice.snippet(cx, args_span, None)
},
};

self.span_to_lint_map
.entry(span)
.or_insert(Some((hir_id, suggest_slice, snippet, applicability)));
self.span_to_lint_map.entry(span).or_insert(Some((
hir_id,
suggest_slice,
snippet,
Applicability::MachineApplicable,
)));
}
}

#[derive(Copy, Clone)]
pub(crate) enum SuggestedType {
/// Suggest using a slice `&[..]` / `&mut [..]`
SliceRef(Mutability),
/// Suggest using an array: `[..]`
Array,
}

impl SuggestedType {
fn desc(self) -> &'static str {
match self {
Self::SliceRef(_) => "a slice",
Self::Array => "an array",
}
}

fn snippet(self, cx: &LateContext<'_>, args_span: Option<Span>, len_span: Option<Span>) -> String {
let maybe_args = args_span.and_then(|sp| snippet_opt(cx, sp)).unwrap_or_default();
let maybe_len = len_span
.and_then(|sp| snippet_opt(cx, sp).map(|s| format!("; {s}")))
.unwrap_or_default();

match self {
Self::SliceRef(Mutability::Mut) => format!("&mut [{maybe_args}{maybe_len}]"),
Self::SliceRef(Mutability::Not) => format!("&[{maybe_args}{maybe_len}]"),
Self::Array => format!("[{maybe_args}{maybe_len}]"),
}
}
}

fn size_of(cx: &LateContext<'_>, expr: &Expr<'_>) -> u64 {
let ty = cx.typeck_results().expr_ty_adjusted(expr);
cx.layout_of(ty).map_or(0, |l| l.size.bytes())
}

fn adjusts_to_slice(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
matches!(cx.typeck_results().expr_ty_adjusted(e).kind(), ty::Ref(_, ty, _) if ty.is_slice())
}

/// Checks if the given expression is a method call to a `Vec` method
/// that also exists on slices. If this returns true, it means that
/// this expression does not actually require a `Vec` and could just work with an array.
pub fn is_allowed_vec_method(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
const ALLOWED_METHOD_NAMES: &[&str] = &["len", "as_ptr", "is_empty"];

if let ExprKind::MethodCall(path, ..) = e.kind {
ALLOWED_METHOD_NAMES.contains(&path.ident.name.as_str())
} else {
is_trait_method(cx, e, sym::IntoIterator)
}
}

fn suggest_type(expr: &Expr<'_>) -> SuggestedType {
if let ExprKind::AddrOf(BorrowKind::Ref, mutability, _) = expr.kind {
// `expr` is `&vec![_]`, so suggest `&[_]` (or `&mut[_]` resp.)
SuggestedType::SliceRef(mutability)
} else {
// `expr` is the `vec![_]` expansion, so suggest `[_]`
SuggestedType::Array
}
}
4 changes: 4 additions & 0 deletions tests/ui/vec.fixed
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Original file line number Diff line number Diff line change
Expand Up @@ -217,3 +217,7 @@ fn issue_11958() {
// should not lint, `String` is not `Copy`
f(&vec!["test".to_owned(); 2]);
}

fn issue_12101() {
for a in &[1, 2] {}
}
4 changes: 4 additions & 0 deletions tests/ui/vec.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -217,3 +217,7 @@ fn issue_11958() {
// should not lint, `String` is not `Copy`
f(&vec!["test".to_owned(); 2]);
}

fn issue_12101() {
for a in &(vec![1, 2]) {}
}
8 changes: 7 additions & 1 deletion tests/ui/vec.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -121,5 +121,11 @@ error: useless use of `vec!`
LL | this_macro_doesnt_need_vec!(vec![1]);
| ^^^^^^^ help: you can use an array directly: `[1]`

error: aborting due to 20 previous errors
error: useless use of `vec!`
--> tests/ui/vec.rs:222:14
|
LL | for a in &(vec![1, 2]) {}
| ^^^^^^^^^^^^^ help: you can use a slice directly: `&[1, 2]`

error: aborting due to 21 previous errors

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