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FP implicit_return, returns inserted into macros #9891
Description
Summary
.
Lint Name
implicit_return
Reproducer
I tried this code:
// Test that array subslice patterns are correctly handled in const evaluation.
// run-pass
#[derive(PartialEq, Debug, Clone)]
struct N(u8);
#[derive(PartialEq, Debug, Clone)]
struct Z;
macro_rules! n {
($($e:expr),* $(,)?) => {
[$(N($e)),*]
}
}
// This macro has an unused variable so that it can be repeated base on the
// number of times a repeated variable (`$e` in `z`) occurs.
macro_rules! zed {
($e:expr) => { Z }
}
macro_rules! z {
($($e:expr),* $(,)?) => {
[$(zed!($e)),*]
}
}
// Compare constant evaluation and runtime evaluation of a given expression.
macro_rules! compare_evaluation {
($e:expr, $t:ty $(,)?) => {{
const CONST_EVAL: $t = $e;
const fn const_eval() -> $t { $e }
static CONST_EVAL2: $t = const_eval();
let runtime_eval = $e;
assert_eq!(CONST_EVAL, runtime_eval);
assert_eq!(CONST_EVAL2, runtime_eval);
}}
}
// Repeat `$test`, substituting the given macro variables with the given
// identifiers.
//
// For example:
//
// repeat! {
// ($name); X; Y:
// struct $name;
// }
//
// Expands to:
//
// struct X; struct Y;
//
// This is used to repeat the tests using both the `N` and `Z`
// types.
macro_rules! repeat {
(($($dollar:tt $placeholder:ident)*); $($($values:ident),+);*: $($test:tt)*) => {
macro_rules! single {
($($dollar $placeholder:ident),*) => { $($test)* }
}
$(single!($($values),+);)*
}
}
fn main() {
repeat! {
($arr $Ty); n, N; z, Z:
compare_evaluation!({ let [_, x @ .., _] = $arr!(1, 2, 3, 4); x }, [$Ty; 2]);
compare_evaluation!({ let [_, ref x @ .., _] = $arr!(1, 2, 3, 4); x }, &'static [$Ty; 2]);
compare_evaluation!({ let [_, x @ .., _] = &$arr!(1, 2, 3, 4); x }, &'static [$Ty; 2]);
}
compare_evaluation!({ let [_, .., N(x)] = n!(1, 2, 3, 4); x }, u8);
compare_evaluation!({ let [_, .., N(ref x)] = n!(1, 2, 3, 4); x }, &'static u8);
compare_evaluation!({ let [_, .., N(x)] = &n!(1, 2, 3, 4); x }, &'static u8);
}I saw this happen:
cargo clippy --fix -- -Aclippy::all -Wclippy::implicit_return
Checking clpy v0.1.0 (/tmp/clpy)
warning: failed to automatically apply fixes suggested by rustc to crate `clpy`
after fixes were automatically applied the compiler reported errors within these files:
* /home/matthias/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/macros/mod.rs
* src/main.rs
This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag
The following errors were reported:
error[E0572]: return statement outside of function body
--> src/main.rs:74:25
|
74 | compare_evaluation!(return { let [_, .., N(x)] = n!(1, 2, 3, 4); x }, u8);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0572]: return statement outside of function body
--> src/main.rs:75:25
|
75 | compare_evaluation!(return { let [_, .., N(ref x)] = n!(1, 2, 3, 4); x }, &'static u8);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0572]: return statement outside of function body
--> src/main.rs:76:25
|
76 | compare_evaluation!(return { let [_, .., N(x)] = &n!(1, 2, 3, 4); x }, &'static u8);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error[E0308]: mismatched types
--> src/main.rs:74:70
|
74 | compare_evaluation!(return { let [_, .., N(x)] = n!(1, 2, 3, 4); x }, u8);
| ^ expected `()`, found `u8`
warning: unreachable statement
--> src/main.rs:74:5
|
74 | compare_evaluation!(return { let [_, .., N(x)] = n!(1, 2, 3, 4); x }, u8);
| ^^^^^^^^^^^^^^^^^^^^------------------------------------------------^^^^^
| | |
| | any code following this expression is unreachable
| unreachable statement
|
= note: `#[warn(unreachable_code)]` on by default
= note: this warning originates in the macro `assert_eq` which comes from the expansion of the macro `compare_evaluation` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0308]: mismatched types
--> src/main.rs:75:74
|
75 | compare_evaluation!(return { let [_, .., N(ref x)] = n!(1, 2, 3, 4); x }, &'static u8);
| ^ expected `()`, found `&u8`
warning: unreachable statement
--> src/main.rs:75:5
|
75 | compare_evaluation!(return { let [_, .., N(ref x)] = n!(1, 2, 3, 4); x }, &'static u8);
| ^^^^^^^^^^^^^^^^^^^^----------------------------------------------------^^^^^^^^^^^^^^
| | |
| | any code following this expression is unreachable
| unreachable statement
|
= note: this warning originates in the macro `assert_eq` which comes from the expansion of the macro `compare_evaluation` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0308]: mismatched types
--> src/main.rs:76:71
|
76 | compare_evaluation!(return { let [_, .., N(x)] = &n!(1, 2, 3, 4); x }, &'static u8);
| ^ expected `()`, found `&u8`
warning: unreachable statement
--> src/main.rs:76:5
|
76 | compare_evaluation!(return { let [_, .., N(x)] = &n!(1, 2, 3, 4); x }, &'static u8);
| ^^^^^^^^^^^^^^^^^^^^-------------------------------------------------^^^^^^^^^^^^^^
| | |
| | any code following this expression is unreachable
| unreachable statement
|
= note: this warning originates in the macro `assert_eq` which comes from the expansion of the macro `compare_evaluation` (in Nightly builds, run with -Z macro-backtrace for more info)
error: aborting due to 6 previous errors; 3 warnings emitted
Some errors have detailed explanations: E0308, E0572.
For more information about an error, try `rustc --explain E0308`.
Original diagnostics will follow.
warning: missing `return` statement
--> src/main.rs:69:29
|
69 | compare_evaluation!({ let [_, x @ .., _] = $arr!(1, 2, 3, 4); x }, [$Ty; 2]);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: add `return` as shown: `return { let [_, x @ .., _] = $arr!(1, 2, 3, 4); x }`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#implicit_return
= note: requested on the command line with `-W clippy::implicit-return`
= note: this warning originates in the macro `single` which comes from the expansion of the macro `repeat` (in Nightly builds, run with -Z macro-backtrace for more info)
warning: missing `return` statement
--> src/main.rs:70:29
|
70 | compare_evaluation!({ let [_, ref x @ .., _] = $arr!(1, 2, 3, 4); x }, &'static [$Ty; 2]);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: add `return` as shown: `return { let [_, ref x @ .., _] = $arr!(1, 2, 3, 4); x }`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#implicit_return
= note: this warning originates in the macro `single` which comes from the expansion of the macro `repeat` (in Nightly builds, run with -Z macro-backtrace for more info)
warning: missing `return` statement
--> src/main.rs:71:29
|
71 | compare_evaluation!({ let [_, x @ .., _] = &$arr!(1, 2, 3, 4); x }, &'static [$Ty; 2]);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: add `return` as shown: `return { let [_, x @ .., _] = &$arr!(1, 2, 3, 4); x }`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#implicit_return
= note: this warning originates in the macro `single` which comes from the expansion of the macro `repeat` (in Nightly builds, run with -Z macro-backtrace for more info)
warning: missing `return` statement
--> src/main.rs:69:29
|
69 | compare_evaluation!({ let [_, x @ .., _] = $arr!(1, 2, 3, 4); x }, [$Ty; 2]);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: add `return` as shown: `return { let [_, x @ .., _] = $arr!(1, 2, 3, 4); x }`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#implicit_return
= note: this warning originates in the macro `single` which comes from the expansion of the macro `repeat` (in Nightly builds, run with -Z macro-backtrace for more info)
warning: missing `return` statement
--> src/main.rs:74:25
|
74 | compare_evaluation!({ let [_, .., N(x)] = n!(1, 2, 3, 4); x }, u8);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: add `return` as shown: `return { let [_, .., N(x)] = n!(1, 2, 3, 4); x }`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#implicit_return
warning: missing `return` statement
--> src/main.rs:75:25
|
75 | compare_evaluation!({ let [_, .., N(ref x)] = n!(1, 2, 3, 4); x }, &'static u8);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: add `return` as shown: `return { let [_, .., N(ref x)] = n!(1, 2, 3, 4); x }`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#implicit_return
warning: missing `return` statement
--> src/main.rs:76:25
|
76 | compare_evaluation!({ let [_, .., N(x)] = &n!(1, 2, 3, 4); x }, &'static u8);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: add `return` as shown: `return { let [_, .., N(x)] = &n!(1, 2, 3, 4); x }`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#implicit_return
warning: `clpy` (bin "clpy") generated 9 warnings (2 duplicates) (run `cargo fix --bin "clpy"` to apply 3 suggestions)
warning: `clpy` (bin "clpy" test) generated 9 warnings (9 duplicates)
Finished dev [unoptimized + debuginfo] target(s) in 0.32s
I expected to see this happen:
Version
rustc 1.67.0-nightly (c5d82ed7a 2022-11-19)
binary: rustc
commit-hash: c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b
commit-date: 2022-11-19
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4
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