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macros: improve error massages #1420

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merged 2 commits into from
Aug 9, 2019
Merged

macros: improve error massages #1420

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23d6281
macro: improve error massages
taiki-e Aug 9, 2019
93f44b1
fix
taiki-e Aug 9, 2019
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55 changes: 27 additions & 28 deletions tokio-macros/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,8 +7,7 @@
extern crate proc_macro;

use proc_macro::TokenStream;
use quote::{quote, quote_spanned};
use syn::spanned::Spanned;
use quote::quote;

/// Marks async function to be executed by selected runtime.
///
Expand Down Expand Up @@ -56,17 +55,15 @@ pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
let attrs = &input.attrs;

if input.asyncness.is_none() {
let tokens = quote_spanned! { input.span() =>
compile_error!("the async keyword is missing from the function declaration");
};

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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@taiki-e taiki-e Aug 9, 2019 •
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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
   |
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.

.to_compile_error()
.into();
} else if !input.decl.inputs.is_empty() {
let tokens = quote_spanned! { input.span() =>
compile_error!("the main function cannot accept arguments");
};

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
   |
34 | async fn main(foo: Foo) -> Result<(), Box<dyn Error>> {
   | ^^^^^

After:

error: the main function cannot accept arguments
  --> tokio\examples\echo.rs:34:15
   |
34 | async fn main(foo: Foo) -> Result<(), Box<dyn Error>> {
   |               ^^^^^^^^

.to_compile_error()
.into();
}

let mut runtime = RuntimeType::Multi;
Expand All @@ -76,7 +73,12 @@ pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
match ident.to_string().to_lowercase().as_str() {
"multi_thread" => runtime = RuntimeType::Multi,
"single_thread" => runtime = RuntimeType::Single,
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
   |
33 | #[tokio::main(foo)]
   | ^^^^^^^^^^^^^^^^^^^
   |
   = help: message: Unknown attribute foo is specified

After:

error: Unknown attribute foo is specified
  --> tokio\examples\echo.rs:33:15
   |
33 | #[tokio::main(foo)]
   |               ^^^

.to_compile_error()
.into();
}
}
}
}
Expand Down Expand Up @@ -126,26 +128,23 @@ pub fn test(_attr: TokenStream, item: TokenStream) -> TokenStream {

for attr in attrs {
if attr.path.is_ident("test") {
let tokens = quote_spanned! { input.span() =>
compile_error!("second test attribute is supplied");
};

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
   |
14 | #[test]
   | ^^^^^^^

.to_compile_error()
.into();
}
}

if input.asyncness.is_none() {
let tokens = quote_spanned! { input.span() =>
compile_error!("the async keyword is missing from the function declaration");
};

return TokenStream::from(tokens);
let msg = "the async keyword is missing from the function declaration";
return syn::Error::new_spanned(&input, msg)
.to_compile_error()
.into();
} else if !input.decl.inputs.is_empty() {
let tokens = quote_spanned! { input.span() =>
compile_error!("the test function cannot accept arguments");
};

return TokenStream::from(tokens);
let msg = "the test function cannot accept arguments";
return syn::Error::new_spanned(&input.decl.inputs, msg)
.to_compile_error()
.into();
}

let result = quote! {
Expand Down