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Auto merge of #8885 - Serial-ATA:rc-clone-in-vec-init-weak, r=llogiq

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Support `Weak` in [`rc_clone_in_vec_init`]

changelog: Support `Weak` in [`rc_clone_in_vec_init`]
This commit is contained in:
bors 2022-05-27 04:02:53 +00:00
commit a5ece8132f
5 changed files with 327 additions and 45 deletions
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56
clippy_lints/src/rc_clone_in_vec_init.rs
View file

@ -2,7 +2,9 @@ use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::higher::VecArgs;
use clippy_utils::last_path_segment;
use clippy_utils::macros::root_macro_call_first_node;
use clippy_utils::paths;
use clippy_utils::source::{indent_of, snippet};
use clippy_utils::ty::match_type;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind, QPath, TyKind};
use rustc_lint::{LateContext, LateLintPass};
@ -11,10 +13,11 @@ use rustc_span::{sym, Span, Symbol};
declare_clippy_lint! {
/// ### What it does
/// Checks for `Arc::new` or `Rc::new` in `vec![elem; len]`
/// Checks for reference-counted pointers (`Arc`, `Rc`, `rc::Weak`, and `sync::Weak`)
/// in `vec![elem; len]`
///
/// ### Why is this bad?
/// This will create `elem` once and clone it `len` times - doing so with `Arc` or `Rc`
/// This will create `elem` once and clone it `len` times - doing so with `Arc`/`Rc`/`Weak`
/// is a bit misleading, as it will create references to the same pointer, rather
/// than different instances.
///
@ -26,7 +29,6 @@ declare_clippy_lint! {
/// ```
/// Use instead:
/// ```rust
///
/// // Initialize each value separately:
/// let mut data = Vec::with_capacity(100);
/// for _ in 0..100 {
@ -42,7 +44,7 @@ declare_clippy_lint! {
#[clippy::version = "1.62.0"]
pub RC_CLONE_IN_VEC_INIT,
suspicious,
"initializing `Arc` or `Rc` in `vec![elem; len]`"
"initializing reference-counted pointer in `vec![elem; len]`"
}
declare_lint_pass!(RcCloneInVecInit => [RC_CLONE_IN_VEC_INIT]);
@ -50,26 +52,12 @@ impl LateLintPass<'_> for RcCloneInVecInit {
fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
let Some(macro_call) = root_macro_call_first_node(cx, expr) else { return; };
let Some(VecArgs::Repeat(elem, len)) = VecArgs::hir(cx, expr) else { return; };
let Some(symbol) = new_reference_call(cx, elem) else { return; };
let Some((symbol, func_span)) = ref_init(cx, elem) else { return; };
emit_lint(cx, symbol, macro_call.span, elem, len);
emit_lint(cx, symbol, macro_call.span, elem, len, func_span);
}
}
fn elem_snippet(cx: &LateContext<'_>, elem: &Expr<'_>, symbol_name: &str) -> String {
let elem_snippet = snippet(cx, elem.span, "..").to_string();
if elem_snippet.contains('\n') {
// This string must be found in `elem_snippet`, otherwise we won't be constructing
// the snippet in the first place.
let reference_creation = format!("{symbol_name}::new");
let (code_until_reference_creation, _right) = elem_snippet.split_once(&reference_creation).unwrap();
return format!("{code_until_reference_creation}{reference_creation}(..)");
}
elem_snippet
}
fn loop_init_suggestion(elem: &str, len: &str, indent: &str) -> String {
format!(
r#"{{
@ -89,17 +77,17 @@ fn extract_suggestion(elem: &str, len: &str, indent: &str) -> String {
)
}
fn emit_lint(cx: &LateContext<'_>, symbol: Symbol, lint_span: Span, elem: &Expr<'_>, len: &Expr<'_>) {
fn emit_lint(cx: &LateContext<'_>, symbol: Symbol, lint_span: Span, elem: &Expr<'_>, len: &Expr<'_>, func_span: Span) {
let symbol_name = symbol.as_str();
span_lint_and_then(
cx,
RC_CLONE_IN_VEC_INIT,
lint_span,
&format!("calling `{symbol_name}::new` in `vec![elem; len]`"),
"initializing a reference-counted pointer in `vec![elem; len]`",
|diag| {
let len_snippet = snippet(cx, len.span, "..");
let elem_snippet = elem_snippet(cx, elem, symbol_name);
let elem_snippet = format!("{}(..)", snippet(cx, elem.span.with_hi(func_span.hi()), ".."));
let indentation = " ".repeat(indent_of(cx, lint_span).unwrap_or(0));
let loop_init_suggestion = loop_init_suggestion(&elem_snippet, len_snippet.as_ref(), &indentation);
let extract_suggestion = extract_suggestion(&elem_snippet, len_snippet.as_ref(), &indentation);
@ -109,7 +97,7 @@ fn emit_lint(cx: &LateContext<'_>, symbol: Symbol, lint_span: Span, elem: &Expr<
lint_span,
format!("consider initializing each `{symbol_name}` element individually"),
loop_init_suggestion,
Applicability::Unspecified,
Applicability::HasPlaceholders,
);
diag.span_suggestion(
lint_span,
@ -117,23 +105,33 @@ fn emit_lint(cx: &LateContext<'_>, symbol: Symbol, lint_span: Span, elem: &Expr<
"or if this is intentional, consider extracting the `{symbol_name}` initialization to a variable"
),
extract_suggestion,
Applicability::Unspecified,
Applicability::HasPlaceholders,
);
},
);
}
/// Checks whether the given `expr` is a call to `Arc::new` or `Rc::new`
fn new_reference_call(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<Symbol> {
/// Checks whether the given `expr` is a call to `Arc::new`, `Rc::new`, or evaluates to a `Weak`
fn ref_init(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<(Symbol, Span)> {
if_chain! {
if let ExprKind::Call(func, _args) = expr.kind;
if let ExprKind::Path(ref func_path @ QPath::TypeRelative(ty, _)) = func.kind;
if let TyKind::Path(ref ty_path) = ty.kind;
if let Some(def_id) = cx.qpath_res(ty_path, ty.hir_id).opt_def_id();
if last_path_segment(func_path).ident.name == sym::new;
then {
return cx.tcx.get_diagnostic_name(def_id).filter(|symbol| symbol == &sym::Arc || symbol == &sym::Rc);
if last_path_segment(func_path).ident.name == sym::new
&& let Some(symbol) = cx
.tcx
.get_diagnostic_name(def_id)
.filter(|symbol| symbol == &sym::Arc || symbol == &sym::Rc) {
return Some((symbol, func.span));
}
let ty_path = cx.typeck_results().expr_ty(expr);
if match_type(cx, ty_path, &paths::WEAK_RC) || match_type(cx, ty_path, &paths::WEAK_ARC) {
return Some((Symbol::intern("Weak"), func.span));
}
}
}

16
tests/ui/rc_clone_in_vec_init/arc.stderr
View file

@ -1,4 +1,4 @@
error: calling `Arc::new` in `vec![elem; len]`
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/arc.rs:7:13
|
LL | let v = vec![Arc::new("x".to_string()); 2];
@ -10,19 +10,19 @@ help: consider initializing each `Arc` element individually
|
LL ~ let v = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(Arc::new("x".to_string())));
LL + (0..2).for_each(|_| v.push(Arc::new(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Arc` initialization to a variable
|
LL ~ let v = {
LL + let data = Arc::new("x".to_string());
LL + let data = Arc::new(..);
LL + vec![data; 2]
LL ~ };
|
error: calling `Arc::new` in `vec![elem; len]`
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/arc.rs:15:21
|
LL | let v = vec![Arc::new("x".to_string()); 2];
@ -33,19 +33,19 @@ help: consider initializing each `Arc` element individually
|
LL ~ let v = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(Arc::new("x".to_string())));
LL + (0..2).for_each(|_| v.push(Arc::new(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Arc` initialization to a variable
|
LL ~ let v = {
LL + let data = Arc::new("x".to_string());
LL + let data = Arc::new(..);
LL + vec![data; 2]
LL ~ };
|
error: calling `Arc::new` in `vec![elem; len]`
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/arc.rs:21:13
|
LL | let v = vec![
@ -75,7 +75,7 @@ LL + vec![data; 2]
LL ~ };
|
error: calling `Arc::new` in `vec![elem; len]`
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/arc.rs:30:14
|
LL | let v1 = vec![

16
tests/ui/rc_clone_in_vec_init/rc.stderr
View file

@ -1,4 +1,4 @@
error: calling `Rc::new` in `vec![elem; len]`
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/rc.rs:8:13
|
LL | let v = vec![Rc::new("x".to_string()); 2];
@ -10,19 +10,19 @@ help: consider initializing each `Rc` element individually
|
LL ~ let v = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(Rc::new("x".to_string())));
LL + (0..2).for_each(|_| v.push(Rc::new(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Rc` initialization to a variable
|
LL ~ let v = {
LL + let data = Rc::new("x".to_string());
LL + let data = Rc::new(..);
LL + vec![data; 2]
LL ~ };
|
error: calling `Rc::new` in `vec![elem; len]`
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/rc.rs:16:21
|
LL | let v = vec![Rc::new("x".to_string()); 2];
@ -33,19 +33,19 @@ help: consider initializing each `Rc` element individually
|
LL ~ let v = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(Rc::new("x".to_string())));
LL + (0..2).for_each(|_| v.push(Rc::new(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Rc` initialization to a variable
|
LL ~ let v = {
LL + let data = Rc::new("x".to_string());
LL + let data = Rc::new(..);
LL + vec![data; 2]
LL ~ };
|
error: calling `Rc::new` in `vec![elem; len]`
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/rc.rs:22:13
|
LL | let v = vec![
@ -75,7 +75,7 @@ LL + vec![data; 2]
LL ~ };
|
error: calling `Rc::new` in `vec![elem; len]`
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/rc.rs:31:14
|
LL | let v1 = vec![

83
tests/ui/rc_clone_in_vec_init/weak.rs Normal file
View file

@ -0,0 +1,83 @@
#![warn(clippy::rc_clone_in_vec_init)]
use std::rc::{Rc, Weak as UnSyncWeak};
use std::sync::{Arc, Mutex, Weak as SyncWeak};
fn main() {}
fn should_warn_simple_case() {
let v = vec![SyncWeak::<u32>::new(); 2];
let v2 = vec![UnSyncWeak::<u32>::new(); 2];
let v = vec![Rc::downgrade(&Rc::new("x".to_string())); 2];
let v = vec![Arc::downgrade(&Arc::new("x".to_string())); 2];
}
fn should_warn_simple_case_with_big_indentation() {
if true {
let k = 1;
dbg!(k);
if true {
let v = vec![Arc::downgrade(&Arc::new("x".to_string())); 2];
let v2 = vec![Rc::downgrade(&Rc::new("x".to_string())); 2];
}
}
}
fn should_warn_complex_case() {
let v = vec![
Arc::downgrade(&Arc::new(Mutex::new({
let x = 1;
dbg!(x);
x
})));
2
];
let v1 = vec![
Rc::downgrade(&Rc::new(Mutex::new({
let x = 1;
dbg!(x);
x
})));
2
];
}
fn should_not_warn_custom_weak() {
#[derive(Clone)]
struct Weak;
impl Weak {
fn new() -> Self {
Weak
}
}
let v = vec![Weak::new(); 2];
}
fn should_not_warn_vec_from_elem_but_not_weak() {
let v = vec![String::new(); 2];
let v1 = vec![1; 2];
let v2 = vec![
Box::new(Arc::downgrade(&Arc::new({
let y = 3;
dbg!(y);
y
})));
2
];
let v3 = vec![
Box::new(Rc::downgrade(&Rc::new({
let y = 3;
dbg!(y);
y
})));
2
];
}
fn should_not_warn_vec_macro_but_not_from_elem() {
let v = vec![Arc::downgrade(&Arc::new("x".to_string()))];
let v = vec![Rc::downgrade(&Rc::new("x".to_string()))];
}

201
tests/ui/rc_clone_in_vec_init/weak.stderr Normal file
View file

@ -0,0 +1,201 @@
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/weak.rs:8:13
|
LL | let v = vec![SyncWeak::<u32>::new(); 2];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `-D clippy::rc-clone-in-vec-init` implied by `-D warnings`
= note: each element will point to the same `Weak` instance
help: consider initializing each `Weak` element individually
|
LL ~ let v = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(SyncWeak::<u32>::new(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Weak` initialization to a variable
|
LL ~ let v = {
LL + let data = SyncWeak::<u32>::new(..);
LL + vec![data; 2]
LL ~ };
|
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/weak.rs:9:14
|
LL | let v2 = vec![UnSyncWeak::<u32>::new(); 2];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: each element will point to the same `Weak` instance
help: consider initializing each `Weak` element individually
|
LL ~ let v2 = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(UnSyncWeak::<u32>::new(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Weak` initialization to a variable
|
LL ~ let v2 = {
LL + let data = UnSyncWeak::<u32>::new(..);
LL + vec![data; 2]
LL ~ };
|
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/weak.rs:11:13
|
LL | let v = vec![Rc::downgrade(&Rc::new("x".to_string())); 2];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: each element will point to the same `Weak` instance
help: consider initializing each `Weak` element individually
|
LL ~ let v = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(Rc::downgrade(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Weak` initialization to a variable
|
LL ~ let v = {
LL + let data = Rc::downgrade(..);
LL + vec![data; 2]
LL ~ };
|
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/weak.rs:12:13
|
LL | let v = vec![Arc::downgrade(&Arc::new("x".to_string())); 2];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: each element will point to the same `Weak` instance
help: consider initializing each `Weak` element individually
|
LL ~ let v = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(Arc::downgrade(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Weak` initialization to a variable
|
LL ~ let v = {
LL + let data = Arc::downgrade(..);
LL + vec![data; 2]
LL ~ };
|
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/weak.rs:20:21
|
LL | let v = vec![Arc::downgrade(&Arc::new("x".to_string())); 2];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: each element will point to the same `Weak` instance
help: consider initializing each `Weak` element individually
|
LL ~ let v = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(Arc::downgrade(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Weak` initialization to a variable
|
LL ~ let v = {
LL + let data = Arc::downgrade(..);
LL + vec![data; 2]
LL ~ };
|
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/weak.rs:21:22
|
LL | let v2 = vec![Rc::downgrade(&Rc::new("x".to_string())); 2];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: each element will point to the same `Weak` instance
help: consider initializing each `Weak` element individually
|
LL ~ let v2 = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(Rc::downgrade(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Weak` initialization to a variable
|
LL ~ let v2 = {
LL + let data = Rc::downgrade(..);
LL + vec![data; 2]
LL ~ };
|
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/weak.rs:27:13
|
LL | let v = vec![
| _____________^
LL | | Arc::downgrade(&Arc::new(Mutex::new({
LL | | let x = 1;
LL | | dbg!(x);
... |
LL | | 2
LL | | ];
| |_____^
|
= note: each element will point to the same `Weak` instance
help: consider initializing each `Weak` element individually
|
LL ~ let v = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(Arc::downgrade(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Weak` initialization to a variable
|
LL ~ let v = {
LL + let data = Arc::downgrade(..);
LL + vec![data; 2]
LL ~ };
|
error: initializing a reference-counted pointer in `vec![elem; len]`
--> $DIR/weak.rs:36:14
|
LL | let v1 = vec![
| ______________^
LL | | Rc::downgrade(&Rc::new(Mutex::new({
LL | | let x = 1;
LL | | dbg!(x);
... |
LL | | 2
LL | | ];
| |_____^
|
= note: each element will point to the same `Weak` instance
help: consider initializing each `Weak` element individually
|
LL ~ let v1 = {
LL + let mut v = Vec::with_capacity(2);
LL + (0..2).for_each(|_| v.push(Rc::downgrade(..)));
LL + v
LL ~ };
|
help: or if this is intentional, consider extracting the `Weak` initialization to a variable
|
LL ~ let v1 = {
LL + let data = Rc::downgrade(..);
LL + vec![data; 2]
LL ~ };
|
error: aborting due to 8 previous errors