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Terse diagnostic "unexpected end of macro invocation" when misusing assert_eq! #103238
Description
Given the following code (playground):
fn main() {
assert_eq!(1 + 2 == 3);
}Current output: terse
error: unexpected end of macro invocation
--> src/main.rs:2:26
|
2 | assert_eq!(1 + 2 == 3);
| ^ missing tokens in macro arguments
Better output: show macro correspondence
note: This expression was treated as the $left argument to assert_eq!
|
2 | assert_eq!(1 + 2 == 3);
| ^^^^^^^^^^
note: Following $left, assert_eq! expects ","
(See also #97108, which also asks for more verbose "missing tokens in macro arguments" errors.)
Ideal output: fix my mistake
help: To assert equality, separate the two expressions with a comma:
|
2 | assert_eq!(1 + 2, 3);
| ^
(See also #57507, which asks for specific diagnostics when making a similar mistake with the assert! macro.)
Activity
lyming2007 commentedon Oct 19, 2022
@rustbot claim
lyming2007 commentedon Oct 19, 2022
I'm afraid we can't suggest some thing like:
Because
1 + 2 == 3is a legal expression for RUST so we don't know if the programmer really wanted to write code like:assert_eq!(1+2 == 3, true);orassert_eq!(1+2 , 3)jruderman commentedon Oct 19, 2022
I think it would be okay to suggest the more likely intended code.
Otoh, Clippy has disabled lints suggesting to replace assert with assert_eq in anticipation of Rust changes. Perhaps it would be better to hold off for now on suggestions that commit to preferring a particular assert syntax.
jruderman commentedon Oct 24, 2022
#103439 will improve diagnostics for macro use by showing what token or ast node was expected :)
Noratrieb commentedon Oct 30, 2022
With that PR, the new error is
which is better but still not great
estebank commentedon Mar 20, 2026
Current output: