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Auto merge of rust-lang#11395 - c410-f3r:let-chain, r=Manishearth
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[`arithmetic_side_effects`] Fix rust-lang#11393

Fix rust-lang#11393

```
changelog: [`arithmetic_side_effects`]: Detect division by zero for `Wrapping` and `Saturating`
```
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bors committed Aug 25, 2023
2 parents 19eaafb + d802ab2 commit 706c48b
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Showing 3 changed files with 90 additions and 9 deletions.
55 changes: 48 additions & 7 deletions clippy_lints/src/operators/arithmetic_side_effects.rs
Original file line number Diff line number Diff line change
@@ -1,22 +1,18 @@
use super::ARITHMETIC_SIDE_EFFECTS;
use clippy_utils::consts::{constant, constant_simple, Constant};
use clippy_utils::diagnostics::span_lint;
use clippy_utils::ty::{match_type, type_diagnostic_name};
use clippy_utils::{expr_or_init, is_from_proc_macro, is_lint_allowed, peel_hir_expr_refs, peel_hir_expr_unary};
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty::Ty;
use rustc_session::impl_lint_pass;
use rustc_span::source_map::{Span, Spanned};
use rustc_span::symbol::sym;
use rustc_span::Symbol;
use {rustc_ast as ast, rustc_hir as hir};

const HARD_CODED_ALLOWED_BINARY: &[[&str; 2]] = &[
["f32", "f32"],
["f64", "f64"],
["std::num::Saturating", "*"],
["std::num::Wrapping", "*"],
["std::string::String", "str"],
];
const HARD_CODED_ALLOWED_BINARY: &[[&str; 2]] = &[["f32", "f32"], ["f64", "f64"], ["std::string::String", "str"]];
const HARD_CODED_ALLOWED_UNARY: &[&str] = &["f32", "f64", "std::num::Saturating", "std::num::Wrapping"];
const INTEGER_METHODS: &[&str] = &["saturating_div", "wrapping_div", "wrapping_rem", "wrapping_rem_euclid"];

Expand Down Expand Up @@ -86,6 +82,48 @@ impl ArithmeticSideEffects {
self.allowed_unary.contains(ty_string_elem)
}

/// Verifies built-in types that have specific allowed operations
fn has_specific_allowed_type_and_operation(
cx: &LateContext<'_>,
lhs_ty: Ty<'_>,
op: &Spanned<hir::BinOpKind>,
rhs_ty: Ty<'_>,
) -> bool {
const SATURATING: &[&str] = &["core", "num", "saturating", "Saturating"];
const WRAPPING: &[&str] = &["core", "num", "wrapping", "Wrapping"];
let is_non_zero = |symbol: Option<Symbol>| {
matches!(
symbol,
Some(
sym::NonZeroI128
| sym::NonZeroI16
| sym::NonZeroI32
| sym::NonZeroI64
| sym::NonZeroI8
| sym::NonZeroU128
| sym::NonZeroU16
| sym::NonZeroU32
| sym::NonZeroU64
| sym::NonZeroU8
)
)
};
// If the RHS is NonZero*, then division or module by zero will never occur
if is_non_zero(type_diagnostic_name(cx, rhs_ty)) && let hir::BinOpKind::Div | hir::BinOpKind::Rem = op.node {
return true;
}
// For `Saturation` or `Wrapping` (RHS), all but division and module are allowed.
let is_div_or_rem = matches!(op.node, hir::BinOpKind::Div | hir::BinOpKind::Rem);
if (match_type(cx, rhs_ty, SATURATING) || match_type(cx, rhs_ty, WRAPPING)) && !is_div_or_rem {
return true;
}
// For `Saturation` or `Wrapping` (LHS), everything is allowed
if match_type(cx, lhs_ty, SATURATING) || match_type(cx, lhs_ty, WRAPPING) {
return true;
}
false
}

// For example, 8i32 or &i64::MAX.
fn is_integral(ty: Ty<'_>) -> bool {
ty.peel_refs().is_integral()
Expand Down Expand Up @@ -147,6 +185,9 @@ impl ArithmeticSideEffects {
if self.has_allowed_binary(lhs_ty, rhs_ty) {
return;
}
if Self::has_specific_allowed_type_and_operation(cx, lhs_ty, op, rhs_ty) {
return;
}
let has_valid_op = if Self::is_integral(lhs_ty) && Self::is_integral(rhs_ty) {
if let hir::BinOpKind::Shl | hir::BinOpKind::Shr = op.node {
// At least for integers, shifts are already handled by the CTFE
Expand Down
30 changes: 29 additions & 1 deletion tests/ui/arithmetic_side_effects.rs
Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@

extern crate proc_macro_derive;

use core::num::{Saturating, Wrapping};
use core::num::{NonZeroUsize, Saturating, Wrapping};

const ONE: i32 = 1;
const ZERO: i32 = 0;
Expand Down Expand Up @@ -493,4 +493,32 @@ pub fn issue_11262() {
let _ = 2 / zero;
}

pub fn issue_11392() {
fn example_div(unsigned: usize, nonzero_unsigned: NonZeroUsize) -> usize {
unsigned / nonzero_unsigned
}

fn example_rem(unsigned: usize, nonzero_unsigned: NonZeroUsize) -> usize {
unsigned % nonzero_unsigned
}

let (unsigned, nonzero_unsigned) = (0, NonZeroUsize::new(1).unwrap());
example_div(unsigned, nonzero_unsigned);
example_rem(unsigned, nonzero_unsigned);
}

pub fn issue_11393() {
fn example_div(x: Wrapping<i32>, maybe_zero: Wrapping<i32>) -> Wrapping<i32> {
x / maybe_zero
}

fn example_rem(x: Wrapping<i32>, maybe_zero: Wrapping<i32>) -> Wrapping<i32> {
x % maybe_zero
}

let [x, maybe_zero] = [1, 0].map(Wrapping);
example_div(x, maybe_zero);
example_rem(x, maybe_zero);
}

fn main() {}
14 changes: 13 additions & 1 deletion tests/ui/arithmetic_side_effects.stderr
Original file line number Diff line number Diff line change
Expand Up @@ -702,5 +702,17 @@ error: arithmetic operation that can potentially result in unexpected side-effec
LL | 10 / a
| ^^^^^^

error: aborting due to 117 previous errors
error: arithmetic operation that can potentially result in unexpected side-effects
--> $DIR/arithmetic_side_effects.rs:498:9
|
LL | unsigned / nonzero_unsigned
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: arithmetic operation that can potentially result in unexpected side-effects
--> $DIR/arithmetic_side_effects.rs:502:9
|
LL | unsigned % nonzero_unsigned
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 119 previous errors

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