macros: improve error massages #1420
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| return TokenStream::from(tokens); | ||
| let msg = "the main function cannot accept arguments"; | ||
| return syn::Error::new_spanned(&input.decl.inputs, msg) |
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Before:
error: the main function cannot accept arguments
--> tokio\examples\echo.rs:34:1
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34 | async fn main(foo: Foo) -> Result<(), Box<dyn Error>> {
| ^^^^^
After:
error: the main function cannot accept arguments
--> tokio\examples\echo.rs:34:15
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34 | async fn main(foo: Foo) -> Result<(), Box<dyn Error>> {
| ^^^^^^^^
| name => panic!("Unknown attribute {} is specified", name), | ||
| name => { | ||
| let msg = format!("Unknown attribute {} is specified", name); | ||
| return syn::Error::new_spanned(ident, msg) |
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Before
error: custom attribute panicked
--> tokio\examples\echo.rs:33:1
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33 | #[tokio::main(foo)]
| ^^^^^^^^^^^^^^^^^^^
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= help: message: Unknown attribute foo is specified
After:
error: Unknown attribute foo is specified
--> tokio\examples\echo.rs:33:15
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33 | #[tokio::main(foo)]
| ^^^
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| return TokenStream::from(tokens); | ||
| let msg = "the async keyword is missing from the function declaration"; | ||
| return syn::Error::new_spanned(input.decl.fn_token, msg) |
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There is no change (perhaps the clearest is to highlight fn.).
error: the async keyword is missing from the function declaration
--> tokio\examples\echo.rs:34:1
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34 | fn main() -> Result<(), Box<dyn Error>> {
| ^^
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Note that the original version highlights the entire function when procmacro2_semver_exempt is active.
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| return TokenStream::from(tokens); | ||
| let msg = "second test attribute is supplied"; | ||
| return syn::Error::new_spanned(&attr, msg) |
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There is no change (this should be fine.).
error: second test attribute is supplied
--> tokio\tests\buffered.rs:14:1
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14 | #[test]
| ^^^^^^^
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This looks great! This could maybe be added in a followup PR, but how do you feel about using https://github.com/dtolnay/trybuild/ to test the error messages? |
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Thanks 👍 I added a line item in #1257 to track adding tests for macros.
I think it's nice that the library that provides proc-macro does UI testing. |
Motivation
dtolnay/syn#575
Solution
Using
syn::Error::new_spanned.