diff options
| -rw-r--r-- | clippy_lints/src/drop_forget_ref.rs | 2 | ||||
| -rw-r--r-- | tests/ui/drop_ref.rs | 23 | ||||
| -rw-r--r-- | tests/ui/drop_ref.stderr | 38 |
3 files changed, 61 insertions, 2 deletions
diff --git a/clippy_lints/src/drop_forget_ref.rs b/clippy_lints/src/drop_forget_ref.rs index 4721a7b3705..11e1bcdf12d 100644 --- a/clippy_lints/src/drop_forget_ref.rs +++ b/clippy_lints/src/drop_forget_ref.rs @@ -206,7 +206,7 @@ impl<'tcx> LateLintPass<'tcx> for DropForgetRef { let is_copy = is_copy(cx, arg_ty); let drop_is_single_call_in_arm = is_single_call_in_arm(cx, arg, expr); let (lint, msg) = match fn_name { - sym::mem_drop if arg_ty.is_ref() => (DROP_REF, DROP_REF_SUMMARY), + sym::mem_drop if arg_ty.is_ref() && !drop_is_single_call_in_arm => (DROP_REF, DROP_REF_SUMMARY), sym::mem_forget if arg_ty.is_ref() => (FORGET_REF, FORGET_REF_SUMMARY), sym::mem_drop if is_copy && !drop_is_single_call_in_arm => (DROP_COPY, DROP_COPY_SUMMARY), sym::mem_forget if is_copy => (FORGET_COPY, FORGET_COPY_SUMMARY), diff --git a/tests/ui/drop_ref.rs b/tests/ui/drop_ref.rs index 7de0b0bbdf9..10044e65f11 100644 --- a/tests/ui/drop_ref.rs +++ b/tests/ui/drop_ref.rs @@ -72,3 +72,26 @@ fn test_owl_result_2() -> Result<u8, ()> { produce_half_owl_ok().map(drop)?; Ok(1) } + +#[allow(unused)] +#[allow(clippy::unit_cmp)] +fn issue10122(x: u8) { + // This is a function which returns a reference and has a side-effect, which means + // that calling drop() on the function is considered an idiomatic way of achieving the side-effect + // in a match arm. + fn println_and<T>(t: &T) -> &T { + println!("foo"); + t + } + + match x { + 0 => drop(println_and(&12)), // Don't lint (copy type), we only care about side-effects + 1 => drop(println_and(&String::new())), // Don't lint (no copy type), we only care about side-effects + 2 => { + drop(println_and(&13)); // Lint, even if we only care about the side-effect, it's already in a block + }, + 3 if drop(println_and(&14)) == () => (), // Lint, idiomatic use is only in body of `Arm` + 4 => drop(&2), // Lint, not a fn/method call + _ => (), + } +} diff --git a/tests/ui/drop_ref.stderr b/tests/ui/drop_ref.stderr index 4743cf79b5d..293b9f6de83 100644 --- a/tests/ui/drop_ref.stderr +++ b/tests/ui/drop_ref.stderr @@ -107,5 +107,41 @@ note: argument has type `&SomeStruct` LL | std::mem::drop(&SomeStruct); | ^^^^^^^^^^^ -error: aborting due to 9 previous errors +error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing + --> $DIR/drop_ref.rs:91:13 + | +LL | drop(println_and(&13)); // Lint, even if we only care about the side-effect, it's already in a block + | ^^^^^^^^^^^^^^^^^^^^^^ + | +note: argument has type `&i32` + --> $DIR/drop_ref.rs:91:18 + | +LL | drop(println_and(&13)); // Lint, even if we only care about the side-effect, it's already in a block + | ^^^^^^^^^^^^^^^^ + +error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing + --> $DIR/drop_ref.rs:93:14 + | +LL | 3 if drop(println_and(&14)) == () => (), // Lint, idiomatic use is only in body of `Arm` + | ^^^^^^^^^^^^^^^^^^^^^^ + | +note: argument has type `&i32` + --> $DIR/drop_ref.rs:93:19 + | +LL | 3 if drop(println_and(&14)) == () => (), // Lint, idiomatic use is only in body of `Arm` + | ^^^^^^^^^^^^^^^^ + +error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing + --> $DIR/drop_ref.rs:94:14 + | +LL | 4 => drop(&2), // Lint, not a fn/method call + | ^^^^^^^^ + | +note: argument has type `&i32` + --> $DIR/drop_ref.rs:94:19 + | +LL | 4 => drop(&2), // Lint, not a fn/method call + | ^^ + +error: aborting due to 12 previous errors |