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Missing "interpreted as a constant pattern" note for raw identifiers in local bindings #162949
Description
Code
#[allow(non_upper_case_globals)]
const x: u8 = 0;
fn main() {
let r#x = 0;
}Current output
error[E0005]: refutable pattern in local binding
--> src/main.rs:5:7
|
5 | let r#x = 0;
| ^^^ pattern `1_u8..=u8::MAX` not covered
|
= note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
= note: for more information, visit https://doc.rust-lang.org/book/ch19-02-refutability.html
= note: the matched value is of type `u8`
help: you might want to use `if let` to ignore the variant that isn't matched
|
5 | if let r#x = 0 { todo!() };
| ++ +++++++++++
For more information about this error, try `rustc --explain E0005`.Desired output
error[E0005]: refutable pattern in local binding
--> src/main.rs:5:7
|
2 | const x: u8 = 0;
| ----------- missing patterns are not covered because `x` is interpreted as a constant pattern, not a new variable
...
5 | let r#x = 0;
| ^ pattern `1_u8..=u8::MAX` not covered
|
= note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
= note: for more information, visit https://doc.rust-lang.org/book/ch19-02-refutability.html
= note: the matched value is of type `u8`
help: introduce a variable instead
|
5 | let r#x_var = 0;
| ++++
For more information about this error, try `rustc --explain E0005`.Rationale and extra context
First related issue I could find: #112269 which was fixed by #112272 adding the note
#113989 was made after and perhaps the fix was not stable at the time
- Whether the suggestion to "introduce a variable instead" should keep the the
r#or not should be decided to be consistent with other diagnostics
Other cases
Rust Version
rustc 1.98.1 (48a229cea 2026-09-01)
binary: rustc
commit-hash: 48a229ceaefd4985c50990b14116b6d856af0985
commit-date: 2026-09-01
host: x86_64-unknown-linux-gnu
release: 1.98.1
LLVM version: 22.1.8Anything else?
I am not familiar with compiler internals but I assume that there may be other things that behave differently when using raw identifiers. For example I was able to come up with this discrepancy based on the observation the author of #112269 made about statics:
#[allow(non_upper_case_globals)]
const y: i32 = 4;
fn main() {
static y: i32 = 3;
let y = 0;
}error[E0530]: let bindings cannot shadow statics
--> src/main.rs:5:7
|
4 | static y: i32 = 3;
| ------------------ the static `y` is defined here
5 | let y = 0;
| ^ cannot be named the same as a static
warning: unused variable: `y`
--> src/main.rs:5:7
|
5 | let y = 0;
| ^
|
= note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default
help: if this is intentional, prefix it with an underscore
|
5 | let _y = 0;
| +
For more information about this error, try `rustc --explain E0530`.
#[allow(non_upper_case_globals)]
const y: i32 = 4;
fn main() {
static y: i32 = 3;
let r#y = 0;
}error[E0530]: let bindings cannot shadow statics
--> src/main.rs:5:7
|
4 | static y: i32 = 3;
| ------------------ the static `y` is defined here
5 | let r#y = 0;
| ^^^ cannot be named the same as a static
warning: unused variable: `y`
--> src/main.rs:5:7
|
5 | let r#y = 0;
| ^^^
|
= note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default
help: you might have meant to pattern match on the similarly named constant `y`
|
5 - let r#y = 0;
5 + let y = 0;
|
help: if this is intentional, prefix it with an underscore
|
5 - let r#y = 0;
5 + let _y = 0;
|
For more information about this error, try `rustc --explain E0530`.
Activity
emit the constant pattern note for raw identifier bindings
Rollup merge of rust-lang#163106 - Albab-Hasan:const-pattern-note-raw…
Rollup merge of rust-lang#163106 - Albab-Hasan:const-pattern-note-raw…
Rollup merge of rust-lang#163106 - Albab-Hasan:const-pattern-note-raw…
Unrolled build for #163106 in rollup 163157