macros: Improve IDE support

tests-build/tests/fail/macros_invalid_input.stderr

@@ -112,10 +112,28 @@ error: second test attribute is supplied, consider removing or changing the orde
 64 | #[std::prelude::rust_2021::test]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: second test attribute is supplied, consider removing or changing the order of your test attributes
-  --> tests/fail/macros_invalid_input.rs:67:1
+error: duplicated attribute
+  --> tests/fail/macros_invalid_input.rs:48:1
+   |
+48 | #[test]
+   | ^^^^^^^
    |
-67 | #[tokio::test]
-   | ^^^^^^^^^^^^^^
+note: the lint level is defined here
+  --> tests/fail/macros_invalid_input.rs:1:9
    |
-   = note: this error originates in the attribute macro `tokio::test` (in Nightly builds, run with -Z macro-backtrace for more info)
+1  | #![deny(duplicate_macro_attributes)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0277]: `()` is not a future
+ --> tests/fail/macros_invalid_input.rs:5:1
+  |
+5 | #[tokio::main]
+  | ^^^^^^^^^^^^^^ `()` is not a future
+  |
+  = help: the trait `Future` is not implemented for `()`
+note: required by a bound in `tests_build::tokio::runtime::Runtime::block_on`
+ --> $WORKSPACE/tokio/src/runtime/runtime.rs
+  |
+  |     pub fn block_on<F: Future>(&self, future: F) -> F::Output {
+  |                        ^^^^^^ required by this bound in `Runtime::block_on`
+  = note: this error originates in the attribute macro `tokio::main` (in Nightly builds, run with -Z macro-backtrace for more info)

tests-build/tests/fail/macros_type_mismatch.rs

@@ -12,14 +12,6 @@ async fn missing_return_type() {
 
 #[tokio::main]
 async fn extra_semicolon() -> Result<(), ()> {
-    /* TODO(taiki-e): help message still wrong
-    help: try using a variant of the expected enum
-       |
-    23 |     Ok(Ok(());)
-       |
-    23 |     Err(Ok(());)
-       |
-    */
     Ok(());
 }
 

tests-build/tests/fail/macros_type_mismatch.stderr

@@ -6,54 +6,33 @@ error[E0308]: mismatched types
   |
   = note: expected unit type `()`
                   found enum `Result<(), _>`
-help: a return type might be missing here
-  |
-4 | async fn missing_semicolon_or_return_type() -> _ {
-  |                                             ++++
-help: consider using `Result::expect` to unwrap the `Result<(), _>` value, panicking if the value is a `Result::Err`
-  |
-5 |     Ok(()).expect("REASON")
-  |           +++++++++++++++++
 
 error[E0308]: mismatched types
-  --> tests/fail/macros_type_mismatch.rs:10:5
+  --> tests/fail/macros_type_mismatch.rs:10:12
    |
 10 |     return Ok(());
-   |     ^^^^^^^^^^^^^^ expected `()`, found `Result<(), _>`
+   |            ^^^^^^ expected `()`, found `Result<(), _>`
    |
    = note: expected unit type `()`
                    found enum `Result<(), _>`
-help: a return type might be missing here
-   |
-9  | async fn missing_return_type() -> _ {
-   |                                ++++
-help: consider using `Result::expect` to unwrap the `Result<(), _>` value, panicking if the value is a `Result::Err`
-   |
-10 |     return Ok(());.expect("REASON")
-   |                   +++++++++++++++++
 
 error[E0308]: mismatched types
-  --> tests/fail/macros_type_mismatch.rs:23:5
+  --> tests/fail/macros_type_mismatch.rs:14:46
    |
-14 | async fn extra_semicolon() -> Result<(), ()> {
-   |                               -------------- expected `Result<(), ()>` because of return type
-...
-23 |     Ok(());
-   |     ^^^^^^^ expected `Result<(), ()>`, found `()`
+14 |   async fn extra_semicolon() -> Result<(), ()> {
+   |  ______________________________________________^
+15 | |     Ok(());
+   | |           - help: remove this semicolon to return this value
+16 | | }
+   | |_^ expected `Result<(), ()>`, found `()`
    |
    = note:   expected enum `Result<(), ()>`
            found unit type `()`
-help: try adding an expression at the end of the block
-   |
-23 ~     Ok(());;
-24 +     Ok(())
-   |
 
 error[E0308]: mismatched types
-  --> tests/fail/macros_type_mismatch.rs:32:5
+  --> tests/fail/macros_type_mismatch.rs:23:12
    |
-30 | async fn issue_4635() {
+22 | async fn issue_4635() {
    |                      - help: try adding a return type: `-> i32`
-31 |     return 1;
-32 |     ;
-   |     ^ expected `()`, found integer
+23 |     return 1;
+   |            ^ expected `()`, found integer

tests-build/tests/macros.rs

@@ -13,10 +13,10 @@ fn compile_fail_full() {
     t.pass("tests/pass/macros_main_loop.rs");
 
     #[cfg(feature = "full")]
-    t.compile_fail("tests/fail/macros_invalid_input.rs");
+    t.pass("tests/fail/macros_dead_code.rs");
 
     #[cfg(feature = "full")]
-    t.compile_fail("tests/fail/macros_dead_code.rs");
+    t.compile_fail("tests/fail/macros_invalid_input.rs");
 
     #[cfg(feature = "full")]
     t.compile_fail("tests/fail/macros_type_mismatch.rs");