Unconditional recursion in a const fn produces a massive diagnostic #92796
Description
Given the following code (playground):
#![allow(unused)]
const fn f<T>(x: T) {
f(x);
}
const X: () = f(1);The current output is:
Massive diagnostic
warning: function cannot return without recursing
--> src/lib.rs:3:1
|
3 | const fn f<T>(x: T) {
| ^^^^^^^^^^^^^^^^^^^ cannot return without recursing
4 | f(x);
| ---- recursive call site
|
= note: `#[warn(unconditional_recursion)]` on by default
= help: a `loop` may express intention better if this is on purpose
error: any use of this value will cause an error
--> src/lib.rs:4:5
|
4 | f(x);
| ^^^^
| |
| reached the configured maximum number of stack frames
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `f::<i32>` at src/lib.rs:4:5
| inside `X` at src/lib.rs:7:15
...
7 | const X: () = f(1);
| -------------------
|
= note: `#[deny(const_err)]` on by default
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
Ideally, the duplicate lines should be hidden:
warning: function cannot return without recursing
--> src/lib.rs:3:1
|
3 | const fn f<T>(x: T) {
| ^^^^^^^^^^^^^^^^^^^ cannot return without recursing
4 | f(x);
| ---- recursive call site
|
= note: `#[warn(unconditional_recursion)]` on by default
= help: a `loop` may express intention better if this is on purpose
error: any use of this value will cause an error
--> src/lib.rs:4:5
|
4 | f(x);
| ^^^^
| |
| reached the configured maximum number of stack frames
| inside `f::<i32>` at src/lib.rs:4:5
| [... inside N additional calls to `f::<i32>` ...]
| inside `X` at src/lib.rs:7:15
...
7 | const X: () = f(1);
| -------------------
|
= note: `#[deny(const_err)]` on by default
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
@rustbot modify labels: +A-const-fn +D-verbose