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Auto merge of #12031 - y21:eager_transmute_more_binops, r=llogiq 

Lint nested binary operations and handle field projections in `eager_transmute`

This PR makes the lint a bit stronger. Previously it would only lint `(x < 4).then_some(transmute(x))` (that is, a single binary op in the condition). With this change, it understands:
- multiple, nested binary ops: `(x < 4 && x > 1).then_some(...)`
- local references with projections: `(x.field < 4 && x.field > 1).then_some(transmute(x.field))`

changelog: [`eager_transmute`]: lint nested binary operations and look through field/array accesses

r? llogiq (since you reviewed my initial PR #11981, I figured you have the most context here, sorry if you are too busy with other PRs, feel free to reassign to someone else then)
This commit is contained in:
bors 2024-01-03 21:43:01 +00:00
parent 17dcd0d2e4 6c28f0765e
commit ebf5c1a928
4 changed files with 225 additions and 15 deletions
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53
clippy_lints/src/transmute/eager_transmute.rs
View File

@ -1,6 +1,6 @@
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::ty::is_normalizable;
use clippy_utils::{path_to_local, path_to_local_id};
use clippy_utils::{eq_expr_value, path_to_local};
use rustc_abi::WrappingRange;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind, Node};
@ -25,6 +25,52 @@ fn range_fully_contained(from: WrappingRange, to: WrappingRange) -> bool {
to.contains(from.start) && to.contains(from.end)
}
/// Checks if a given expression is a binary operation involving a local variable or is made up of
/// other (nested) binary expressions involving the local. There must be at least one local
/// reference that is the same as `local_expr`.
///
/// This is used as a heuristic to detect if a variable
/// is checked to be within the valid range of a transmuted type.
/// All of these would return true:
/// * `x < 4`
/// * `x < 4 && x > 1`
/// * `x.field < 4 && x.field > 1` (given `x.field`)
/// * `x.field < 4 && unrelated()`
/// * `(1..=3).contains(&x)`
fn binops_with_local(cx: &LateContext<'_>, local_expr: &Expr<'_>, expr: &Expr<'_>) -> bool {
match expr.kind {
ExprKind::Binary(_, lhs, rhs) => {
binops_with_local(cx, local_expr, lhs) || binops_with_local(cx, local_expr, rhs)
},
ExprKind::MethodCall(path, receiver, [arg], _)
if path.ident.name == sym!(contains)
// ... `contains` called on some kind of range
&& let Some(receiver_adt) = cx.typeck_results().expr_ty(receiver).peel_refs().ty_adt_def()
&& let lang_items = cx.tcx.lang_items()
&& [
lang_items.range_from_struct(),
lang_items.range_inclusive_struct(),
lang_items.range_struct(),
lang_items.range_to_inclusive_struct(),
lang_items.range_to_struct()
].into_iter().any(|did| did == Some(receiver_adt.did())) =>
{
eq_expr_value(cx, local_expr, arg.peel_borrows())
},
_ => eq_expr_value(cx, local_expr, expr),
}
}
/// Checks if an expression is a path to a local variable (with optional projections), e.g.
/// `x.field[0].field2` would return true.
fn is_local_with_projections(expr: &Expr<'_>) -> bool {
match expr.kind {
ExprKind::Path(_) => path_to_local(expr).is_some(),
ExprKind::Field(expr, _) | ExprKind::Index(expr, ..) => is_local_with_projections(expr),
_ => false,
}
}
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'tcx>,
@ -36,9 +82,8 @@ pub(super) fn check<'tcx>(
&& let ExprKind::MethodCall(path, receiver, [arg], _) = then_some_call.kind
&& cx.typeck_results().expr_ty(receiver).is_bool()
&& path.ident.name == sym!(then_some)
&& let ExprKind::Binary(_, lhs, rhs) = receiver.kind
&& let Some(local_id) = path_to_local(transmutable)
&& (path_to_local_id(lhs, local_id) || path_to_local_id(rhs, local_id))
&& is_local_with_projections(transmutable)
&& binops_with_local(cx, transmutable, receiver)
&& is_normalizable(cx, cx.param_env, from_ty)
&& is_normalizable(cx, cx.param_env, to_ty)
// we only want to lint if the target type has a niche that is larger than the one of the source type

35
tests/ui/eager_transmute.fixed
View File

@ -12,16 +12,49 @@ enum Opcode {
Div = 3,
}
struct Data {
foo: &'static [u8],
bar: &'static [u8],
}
fn int_to_opcode(op: u8) -> Option<Opcode> {
(op < 4).then(|| unsafe { std::mem::transmute(op) })
}
fn f(op: u8, unrelated: u8) {
fn f(op: u8, op2: Data, unrelated: u8) {
true.then_some(unsafe { std::mem::transmute::<_, Opcode>(op) });
(unrelated < 4).then_some(unsafe { std::mem::transmute::<_, Opcode>(op) });
(op < 4).then(|| unsafe { std::mem::transmute::<_, Opcode>(op) });
(op > 4).then(|| unsafe { std::mem::transmute::<_, Opcode>(op) });
(op == 0).then(|| unsafe { std::mem::transmute::<_, Opcode>(op) });
let _: Option<Opcode> = (op > 0 && op < 10).then(|| unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = (op > 0 && op < 10 && unrelated == 0).then(|| unsafe { std::mem::transmute(op) });
// lint even when the transmutable goes through field/array accesses
let _: Option<Opcode> = (op2.foo[0] > 0 && op2.foo[0] < 10).then(|| unsafe { std::mem::transmute(op2.foo[0]) });
// don't lint: wrong index used in the transmute
let _: Option<Opcode> = (op2.foo[0] > 0 && op2.foo[0] < 10).then_some(unsafe { std::mem::transmute(op2.foo[1]) });
// don't lint: no check for the transmutable in the condition
let _: Option<Opcode> = (op2.foo[0] > 0 && op2.bar[1] < 10).then_some(unsafe { std::mem::transmute(op2.bar[0]) });
// don't lint: wrong variable
let _: Option<Opcode> = (op2.foo[0] > 0 && op2.bar[1] < 10).then_some(unsafe { std::mem::transmute(op) });
// range contains checks
let _: Option<Opcode> = (1..=3).contains(&op).then(|| unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = ((1..=3).contains(&op) || op == 4).then(|| unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = (1..3).contains(&op).then(|| unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = (1..).contains(&op).then(|| unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = (..3).contains(&op).then(|| unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = (..=3).contains(&op).then(|| unsafe { std::mem::transmute(op) });
// unrelated binding in contains
let _: Option<Opcode> = (1..=3)
.contains(&unrelated)
.then_some(unsafe { std::mem::transmute(op) });
}
unsafe fn f2(op: u8) {

35
tests/ui/eager_transmute.rs
View File

@ -12,16 +12,49 @@ enum Opcode {
Div = 3,
}
struct Data {
foo: &'static [u8],
bar: &'static [u8],
}
fn int_to_opcode(op: u8) -> Option<Opcode> {
(op < 4).then_some(unsafe { std::mem::transmute(op) })
}
fn f(op: u8, unrelated: u8) {
fn f(op: u8, op2: Data, unrelated: u8) {
true.then_some(unsafe { std::mem::transmute::<_, Opcode>(op) });
(unrelated < 4).then_some(unsafe { std::mem::transmute::<_, Opcode>(op) });
(op < 4).then_some(unsafe { std::mem::transmute::<_, Opcode>(op) });
(op > 4).then_some(unsafe { std::mem::transmute::<_, Opcode>(op) });
(op == 0).then_some(unsafe { std::mem::transmute::<_, Opcode>(op) });
let _: Option<Opcode> = (op > 0 && op < 10).then_some(unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = (op > 0 && op < 10 && unrelated == 0).then_some(unsafe { std::mem::transmute(op) });
// lint even when the transmutable goes through field/array accesses
let _: Option<Opcode> = (op2.foo[0] > 0 && op2.foo[0] < 10).then_some(unsafe { std::mem::transmute(op2.foo[0]) });
// don't lint: wrong index used in the transmute
let _: Option<Opcode> = (op2.foo[0] > 0 && op2.foo[0] < 10).then_some(unsafe { std::mem::transmute(op2.foo[1]) });
// don't lint: no check for the transmutable in the condition
let _: Option<Opcode> = (op2.foo[0] > 0 && op2.bar[1] < 10).then_some(unsafe { std::mem::transmute(op2.bar[0]) });
// don't lint: wrong variable
let _: Option<Opcode> = (op2.foo[0] > 0 && op2.bar[1] < 10).then_some(unsafe { std::mem::transmute(op) });
// range contains checks
let _: Option<Opcode> = (1..=3).contains(&op).then_some(unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = ((1..=3).contains(&op) || op == 4).then_some(unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = (1..3).contains(&op).then_some(unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = (1..).contains(&op).then_some(unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = (..3).contains(&op).then_some(unsafe { std::mem::transmute(op) });
let _: Option<Opcode> = (..=3).contains(&op).then_some(unsafe { std::mem::transmute(op) });
// unrelated binding in contains
let _: Option<Opcode> = (1..=3)
.contains(&unrelated)
.then_some(unsafe { std::mem::transmute(op) });
}
unsafe fn f2(op: u8) {

117
tests/ui/eager_transmute.stderr
View File

@ -1,5 +1,5 @@
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:16:33
--> $DIR/eager_transmute.rs:21:33
|
LL | (op < 4).then_some(unsafe { std::mem::transmute(op) })
| ^^^^^^^^^^^^^^^^^^^^^^^
@ -12,7 +12,7 @@ LL | (op < 4).then(|| unsafe { std::mem::transmute(op) })
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:22:33
--> $DIR/eager_transmute.rs:27:33
|
LL | (op < 4).then_some(unsafe { std::mem::transmute::<_, Opcode>(op) });
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -23,7 +23,7 @@ LL | (op < 4).then(|| unsafe { std::mem::transmute::<_, Opcode>(op) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:23:33
--> $DIR/eager_transmute.rs:28:33
|
LL | (op > 4).then_some(unsafe { std::mem::transmute::<_, Opcode>(op) });
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -34,7 +34,7 @@ LL | (op > 4).then(|| unsafe { std::mem::transmute::<_, Opcode>(op) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:24:34
--> $DIR/eager_transmute.rs:29:34
|
LL | (op == 0).then_some(unsafe { std::mem::transmute::<_, Opcode>(op) });
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -45,7 +45,106 @@ LL | (op == 0).then(|| unsafe { std::mem::transmute::<_, Opcode>(op) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:28:24
--> $DIR/eager_transmute.rs:31:68
|
LL | let _: Option<Opcode> = (op > 0 && op < 10).then_some(unsafe { std::mem::transmute(op) });
| ^^^^^^^^^^^^^^^^^^^^^^^
|
help: consider using `bool::then` to only transmute if the condition holds
|
LL | let _: Option<Opcode> = (op > 0 && op < 10).then(|| unsafe { std::mem::transmute(op) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:32:86
|
LL | let _: Option<Opcode> = (op > 0 && op < 10 && unrelated == 0).then_some(unsafe { std::mem::transmute(op) });
| ^^^^^^^^^^^^^^^^^^^^^^^
|
help: consider using `bool::then` to only transmute if the condition holds
|
LL | let _: Option<Opcode> = (op > 0 && op < 10 && unrelated == 0).then(|| unsafe { std::mem::transmute(op) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:35:84
|
LL | let _: Option<Opcode> = (op2.foo[0] > 0 && op2.foo[0] < 10).then_some(unsafe { std::mem::transmute(op2.foo[0]) });
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
help: consider using `bool::then` to only transmute if the condition holds
|
LL | let _: Option<Opcode> = (op2.foo[0] > 0 && op2.foo[0] < 10).then(|| unsafe { std::mem::transmute(op2.foo[0]) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:47:70
|
LL | let _: Option<Opcode> = (1..=3).contains(&op).then_some(unsafe { std::mem::transmute(op) });
| ^^^^^^^^^^^^^^^^^^^^^^^
|
help: consider using `bool::then` to only transmute if the condition holds
|
LL | let _: Option<Opcode> = (1..=3).contains(&op).then(|| unsafe { std::mem::transmute(op) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:48:83
|
LL | let _: Option<Opcode> = ((1..=3).contains(&op) || op == 4).then_some(unsafe { std::mem::transmute(op) });
| ^^^^^^^^^^^^^^^^^^^^^^^
|
help: consider using `bool::then` to only transmute if the condition holds
|
LL | let _: Option<Opcode> = ((1..=3).contains(&op) || op == 4).then(|| unsafe { std::mem::transmute(op) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:49:69
|
LL | let _: Option<Opcode> = (1..3).contains(&op).then_some(unsafe { std::mem::transmute(op) });
| ^^^^^^^^^^^^^^^^^^^^^^^
|
help: consider using `bool::then` to only transmute if the condition holds
|
LL | let _: Option<Opcode> = (1..3).contains(&op).then(|| unsafe { std::mem::transmute(op) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:50:68
|
LL | let _: Option<Opcode> = (1..).contains(&op).then_some(unsafe { std::mem::transmute(op) });
| ^^^^^^^^^^^^^^^^^^^^^^^
|
help: consider using `bool::then` to only transmute if the condition holds
|
LL | let _: Option<Opcode> = (1..).contains(&op).then(|| unsafe { std::mem::transmute(op) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:51:68
|
LL | let _: Option<Opcode> = (..3).contains(&op).then_some(unsafe { std::mem::transmute(op) });
| ^^^^^^^^^^^^^^^^^^^^^^^
|
help: consider using `bool::then` to only transmute if the condition holds
|
LL | let _: Option<Opcode> = (..3).contains(&op).then(|| unsafe { std::mem::transmute(op) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:52:69
|
LL | let _: Option<Opcode> = (..=3).contains(&op).then_some(unsafe { std::mem::transmute(op) });
| ^^^^^^^^^^^^^^^^^^^^^^^
|
help: consider using `bool::then` to only transmute if the condition holds
|
LL | let _: Option<Opcode> = (..=3).contains(&op).then(|| unsafe { std::mem::transmute(op) });
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:61:24
|
LL | (op < 4).then_some(std::mem::transmute::<_, Opcode>(op));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -56,7 +155,7 @@ LL | (op < 4).then(|| std::mem::transmute::<_, Opcode>(op));
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:57:60
--> $DIR/eager_transmute.rs:90:60
|
LL | let _: Option<NonZeroU8> = (v1 > 0).then_some(unsafe { std::mem::transmute(v1) });
| ^^^^^^^^^^^^^^^^^^^^^^^
@ -67,7 +166,7 @@ LL | let _: Option<NonZeroU8> = (v1 > 0).then(|| unsafe { std::mem::transmut
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:63:86
--> $DIR/eager_transmute.rs:96:86
|
LL | let _: Option<NonMaxU8> = (v2 < NonZeroU8::new(255).unwrap()).then_some(unsafe { std::mem::transmute(v2) });
| ^^^^^^^^^^^^^^^^^^^^^^^
@ -78,7 +177,7 @@ LL | let _: Option<NonMaxU8> = (v2 < NonZeroU8::new(255).unwrap()).then(|| u
| ~~~~ ++
error: this transmute is always evaluated eagerly, even if the condition is false
--> $DIR/eager_transmute.rs:69:93
--> $DIR/eager_transmute.rs:102:93
|
LL | let _: Option<NonZeroNonMaxU8> = (v2 < NonZeroU8::new(255).unwrap()).then_some(unsafe { std::mem::transmute(v2) });
| ^^^^^^^^^^^^^^^^^^^^^^^
@ -88,5 +187,5 @@ help: consider using `bool::then` to only transmute if the condition holds
LL | let _: Option<NonZeroNonMaxU8> = (v2 < NonZeroU8::new(255).unwrap()).then(|| unsafe { std::mem::transmute(v2) });
| ~~~~ ++
error: aborting due to 8 previous errors
error: aborting due to 17 previous errors