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Improved error message for set_len() on empty Vec
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@Qwaz
Qwaz committed Oct 9, 2021
1 parent de0d2b1 commit 2181387
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Showing 2 changed files with 73 additions and 40 deletions.
101 changes: 70 additions & 31 deletions clippy_lints/src/uninit_vec.rs
View file
@@ -1,5 +1,5 @@
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::higher::get_vec_init_kind;
use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
use clippy_utils::higher::{get_vec_init_kind, VecInitKind};
use clippy_utils::ty::{is_type_diagnostic_item, is_uninit_value_valid_for_ty};
use clippy_utils::{is_lint_allowed, path_to_local_id, peel_hir_expr_while, SpanlessEq};
use rustc_hir::{Block, Expr, ExprKind, HirId, PatKind, PathSegment, Stmt, StmtKind};
Expand Down Expand Up @@ -83,69 +83,108 @@ fn handle_uninit_vec_pair(
if_chain! {
if let Some(vec) = extract_init_or_reserve_target(cx, maybe_init_or_reserve);
if let Some((set_len_self, call_span)) = extract_set_len_self(cx, maybe_set_len);
if vec.eq_expr(cx, set_len_self);
if vec.location.eq_expr(cx, set_len_self);
if let ty::Ref(_, vec_ty, _) = cx.typeck_results().expr_ty_adjusted(set_len_self).kind();
if let ty::Adt(_, substs) = vec_ty.kind();
// Check T of Vec<T>
if !is_uninit_value_valid_for_ty(cx, substs.type_at(0));
// `#[allow(...)]` attribute can be set on enclosing unsafe block of `set_len()`
if !is_lint_allowed(cx, UNINIT_VEC, maybe_set_len.hir_id);
then {
// FIXME: #7698, false positive of the internal lints
#[allow(clippy::collapsible_span_lint_calls)]
span_lint_and_then(
cx,
UNINIT_VEC,
vec![call_span, maybe_init_or_reserve.span],
"calling `set_len()` immediately after reserving a buffer creates uninitialized values",
|diag| {
diag.help("initialize the buffer or wrap the content in `MaybeUninit`");
},
);
if vec.has_capacity() {
// with_capacity / reserve -> set_len

// Check T of Vec<T>
if !is_uninit_value_valid_for_ty(cx, substs.type_at(0)) {
// FIXME: #7698, false positive of the internal lints
#[allow(clippy::collapsible_span_lint_calls)]
span_lint_and_then(
cx,
UNINIT_VEC,
vec![call_span, maybe_init_or_reserve.span],
"calling `set_len()` immediately after reserving a buffer creates uninitialized values",
|diag| {
diag.help("initialize the buffer or wrap the content in `MaybeUninit`");
},
);
}
} else {
// new / default -> set_len
span_lint(
cx,
UNINIT_VEC,
vec![call_span, maybe_init_or_reserve.span],
"calling `set_len()` on empty `Vec` creates out-of-bound values",
)
}
}
}
}

#[derive(Clone, Copy, Debug)]
enum LocalOrExpr<'tcx> {
/// The target `Vec` that is initialized or reserved
#[derive(Clone, Copy)]
struct TargetVec<'tcx> {
location: VecLocation<'tcx>,
/// `None` if `reserve()`
init_kind: Option<VecInitKind>,
}

impl TargetVec<'_> {
pub fn has_capacity(self) -> bool {
!matches!(self.init_kind, Some(VecInitKind::New | VecInitKind::Default))
}
}

#[derive(Clone, Copy)]
enum VecLocation<'tcx> {
Local(HirId),
Expr(&'tcx Expr<'tcx>),
}

impl<'tcx> LocalOrExpr<'tcx> {
fn eq_expr(self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
impl<'tcx> VecLocation<'tcx> {
pub fn eq_expr(self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
match self {
LocalOrExpr::Local(hir_id) => path_to_local_id(expr, hir_id),
LocalOrExpr::Expr(self_expr) => SpanlessEq::new(cx).eq_expr(self_expr, expr),
VecLocation::Local(hir_id) => path_to_local_id(expr, hir_id),
VecLocation::Expr(self_expr) => SpanlessEq::new(cx).eq_expr(self_expr, expr),
}
}
}

/// Finds the target location where the result of `Vec` initialization is stored
/// or `self` expression for `Vec::reserve()`.
fn extract_init_or_reserve_target<'tcx>(cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'tcx>) -> Option<LocalOrExpr<'tcx>> {
fn extract_init_or_reserve_target<'tcx>(cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'tcx>) -> Option<TargetVec<'tcx>> {
match stmt.kind {
StmtKind::Local(local) => {
if_chain! {
if let Some(init_expr) = local.init;
if let PatKind::Binding(_, hir_id, _, None) = local.pat.kind;
if get_vec_init_kind(cx, init_expr).is_some();
if let Some(init_kind) = get_vec_init_kind(cx, init_expr);
then {
Some(LocalOrExpr::Local(hir_id))
} else {
None
return Some(TargetVec {
location: VecLocation::Local(hir_id),
init_kind: Some(init_kind),
})
}
}
},
StmtKind::Expr(expr) | StmtKind::Semi(expr) => match expr.kind {
ExprKind::Assign(lhs, rhs, _span) if get_vec_init_kind(cx, rhs).is_some() => Some(LocalOrExpr::Expr(lhs)),
ExprKind::Assign(lhs, rhs, _span) => {
if let Some(init_kind) = get_vec_init_kind(cx, rhs) {
return Some(TargetVec {
location: VecLocation::Expr(lhs),
init_kind: Some(init_kind),
});
}
},
ExprKind::MethodCall(path, _, [self_expr, _], _) if is_reserve(cx, path, self_expr) => {
Some(LocalOrExpr::Expr(self_expr))
return Some(TargetVec {
location: VecLocation::Expr(self_expr),
init_kind: None,
});
},
_ => None,
_ => (),
},
StmtKind::Item(_) => None,
StmtKind::Item(_) => (),
}
None
}

fn is_reserve(cx: &LateContext<'_>, path: &PathSegment<'_>, self_expr: &Expr<'_>) -> bool {
Expand Down
12 changes: 3 additions & 9 deletions tests/ui/uninit_vec.stderr
View file
Expand Up @@ -21,38 +21,32 @@ LL | vec.set_len(200);
|
= help: initialize the buffer or wrap the content in `MaybeUninit`

error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
error: calling `set_len()` on empty `Vec` creates out-of-bound values
--> $DIR/uninit_vec.rs:24:5
|
LL | let mut vec: Vec<u8> = Vec::new();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LL | unsafe {
LL | vec.set_len(200);
| ^^^^^^^^^^^^^^^^
|
= help: initialize the buffer or wrap the content in `MaybeUninit`

error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
error: calling `set_len()` on empty `Vec` creates out-of-bound values
--> $DIR/uninit_vec.rs:30:5
|
LL | let mut vec: Vec<u8> = Default::default();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LL | unsafe {
LL | vec.set_len(200);
| ^^^^^^^^^^^^^^^^
|
= help: initialize the buffer or wrap the content in `MaybeUninit`

error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
error: calling `set_len()` on empty `Vec` creates out-of-bound values
--> $DIR/uninit_vec.rs:35:5
|
LL | let mut vec: Vec<u8> = Vec::default();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LL | unsafe {
LL | vec.set_len(200);
| ^^^^^^^^^^^^^^^^
|
= help: initialize the buffer or wrap the content in `MaybeUninit`

error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
--> $DIR/uninit_vec.rs:49:5
Expand Down

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