Make processing of entrypoints more efficient

tests-build/tests/fail/macros_core_no_default.stderr

@@ -1,5 +1,5 @@
-error: The default runtime flavor is `multi_thread`, but the `rt-multi-thread` feature is disabled.
- --> $DIR/macros_core_no_default.rs:3:1
+error: the default runtime flavor is `multi_thread`, but the `rt-multi-thread` feature is disabled
+ --> tests/fail/macros_core_no_default.rs:3:1
   |
 3 | #[tokio::main]
   | ^^^^^^^^^^^^^^

tests-build/tests/fail/macros_invalid_input.rs

@@ -1,3 +1,5 @@
+#![deny(duplicate_macro_attributes)]
+
 use tests_build::tokio;
 
 #[tokio::main]

tests-build/tests/fail/macros_invalid_input.stderr

@@ -1,79 +1,65 @@
-error: the `async` keyword is missing from the function declaration
- --> $DIR/macros_invalid_input.rs:4:1
+error: functions marked with `#[tokio::main]` must be `async`
+ --> tests/fail/macros_invalid_input.rs:6:1
   |
-4 | fn main_is_not_async() {}
+6 | fn main_is_not_async() {}
   | ^^
 
-error: Unknown attribute foo is specified; expected one of: `flavor`, `worker_threads`, `start_paused`
- --> $DIR/macros_invalid_input.rs:6:15
+error: unknown option `foo`, expected one of: `flavor`, `worker_threads`, `start_paused`
+ --> tests/fail/macros_invalid_input.rs:8:15
   |
-6 | #[tokio::main(foo)]
+8 | #[tokio::main(foo)]
   |               ^^^
 
-error: Must have specified ident
- --> $DIR/macros_invalid_input.rs:9:15
-  |
-9 | #[tokio::main(threadpool::bar)]
-  |               ^^^^^^^^^^^^^^^
+error: unknown option `threadpool`, expected one of: `flavor`, `worker_threads`, `start_paused`
+  --> tests/fail/macros_invalid_input.rs:11:15
+   |
+11 | #[tokio::main(threadpool::bar)]
+   |               ^^^^^^^^^^
 
-error: the `async` keyword is missing from the function declaration
-  --> $DIR/macros_invalid_input.rs:13:1
+error: functions marked with `#[tokio::test]` must be `async`
+  --> tests/fail/macros_invalid_input.rs:15:1
    |
-13 | fn test_is_not_async() {}
+15 | fn test_is_not_async() {}
    | ^^
 
-error: Unknown attribute foo is specified; expected one of: `flavor`, `worker_threads`, `start_paused`
-  --> $DIR/macros_invalid_input.rs:15:15
+error: unknown option `foo`, expected one of: `flavor`, `worker_threads`, `start_paused`
+  --> tests/fail/macros_invalid_input.rs:17:15
    |
-15 | #[tokio::test(foo)]
+17 | #[tokio::test(foo)]
    |               ^^^
 
-error: Unknown attribute foo is specified; expected one of: `flavor`, `worker_threads`, `start_paused`
-  --> $DIR/macros_invalid_input.rs:18:15
+error: unknown option `foo`, expected one of: `flavor`, `worker_threads`, `start_paused`
+  --> tests/fail/macros_invalid_input.rs:20:15
    |
-18 | #[tokio::test(foo = 123)]
-   |               ^^^^^^^^^
+20 | #[tokio::test(foo = 123)]
+   |               ^^^
 
-error: Failed to parse value of `flavor` as string.
-  --> $DIR/macros_invalid_input.rs:21:24
+error: no such runtime flavor, the runtime flavors are: "current_thread", "multi_thread"
+  --> tests/fail/macros_invalid_input.rs:23:24
    |
-21 | #[tokio::test(flavor = 123)]
+23 | #[tokio::test(flavor = 123)]
    |                        ^^^
 
-error: No such runtime flavor `foo`. The runtime flavors are `current_thread` and `multi_thread`.
-  --> $DIR/macros_invalid_input.rs:24:24
+error: no such runtime flavor, the runtime flavors are: "current_thread", "multi_thread"
+  --> tests/fail/macros_invalid_input.rs:26:24
    |
-24 | #[tokio::test(flavor = "foo")]
+26 | #[tokio::test(flavor = "foo")]
    |                        ^^^^^
 
-error: The `start_paused` option requires the `current_thread` runtime flavor. Use `#[tokio::test(flavor = "current_thread")]`
-  --> $DIR/macros_invalid_input.rs:27:55
+error: the `worker_threads` option requires the "multi_thread" runtime flavor. Use `#[tokio::test(flavor = "multi_thread")]`
+  --> tests/fail/macros_invalid_input.rs:35:59
    |
-27 | #[tokio::test(flavor = "multi_thread", start_paused = false)]
-   |                                                       ^^^^^
-
-error: Failed to parse value of `worker_threads` as integer.
-  --> $DIR/macros_invalid_input.rs:30:57
-   |
-30 | #[tokio::test(flavor = "multi_thread", worker_threads = "foo")]
-   |                                                         ^^^^^
-
-error: The `worker_threads` option requires the `multi_thread` runtime flavor. Use `#[tokio::test(flavor = "multi_thread")]`
-  --> $DIR/macros_invalid_input.rs:33:59
-   |
-33 | #[tokio::test(flavor = "current_thread", worker_threads = 4)]
+35 | #[tokio::test(flavor = "current_thread", worker_threads = 4)]
    |                                                           ^
 
-error: second test attribute is supplied
-  --> $DIR/macros_invalid_input.rs:37:1
-   |
-37 | #[test]
-   | ^^^^^^^
-
 error: duplicated attribute
-  --> $DIR/macros_invalid_input.rs:37:1
+  --> tests/fail/macros_invalid_input.rs:39:1
    |
-37 | #[test]
+39 | #[test]
    | ^^^^^^^
    |
-   = note: `-D duplicate-macro-attributes` implied by `-D warnings`
+note: the lint level is defined here
+  --> tests/fail/macros_invalid_input.rs:1:9
+   |
+1  | #![deny(duplicate_macro_attributes)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^

tests-build/tests/fail/macros_main_generics.rs

@@ -0,0 +1,11 @@
+use tests_build::tokio;
+
+// This should parse but fail since default values for const generic parameters
+// are experimental.
+//
+// TODO(udoprog): might want to version constrain this check with `rustversion`
+// since this won't always be experimental moving forward (!).
+#[tokio::main]
+async fn where_clause_const_generics<const T: usize = { 1 + 1 }>() {}
+
+fn main() {}

tests-build/tests/fail/macros_main_generics.stderr

@@ -0,0 +1,5 @@
+error: defaults for const parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+ --> tests/fail/macros_main_generics.rs:9:44
+  |
+9 | async fn where_clause_const_generics<const T: usize = { 1 + 1 }>() {}
+  |                                            ^

tests-build/tests/fail/macros_main_missing_async.rs

@@ -0,0 +1,6 @@
+use tests_build::tokio;
+
+#[tokio::main]
+fn test_missing_async() {}
+
+fn main() {}

tests-build/tests/fail/macros_main_missing_async.stderr

@@ -0,0 +1,5 @@
+error: functions marked with `#[tokio::main]` must be `async`
+ --> tests/fail/macros_main_missing_async.rs:4:1
+  |
+4 | fn test_missing_async() {}
+  | ^^

tests-build/tests/fail/macros_type_mismatch.rs

@@ -23,4 +23,13 @@ async fn extra_semicolon() -> Result<(), ()> {
     Ok(());
 }
 
+/// Intentionally try and make return heuristics misfire by introducing a generic return.
+#[tokio::main]
+async fn extra_semicolon_generic<T>() -> Result<(), ()>
+where
+    T: Fn() -> (),
+{
+    Ok(());
+}
+
 fn main() {}

tests-build/tests/fail/macros_type_mismatch.stderr

@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
- --> $DIR/macros_type_mismatch.rs:5:5
+ --> tests/fail/macros_type_mismatch.rs:5:5
   |
 4 | async fn missing_semicolon_or_return_type() {
   |                                             - possibly return type missing here?
@@ -12,7 +12,7 @@ error[E0308]: mismatched types
                   found enum `Result<(), _>`
 
 error[E0308]: mismatched types
-  --> $DIR/macros_type_mismatch.rs:10:5
+  --> tests/fail/macros_type_mismatch.rs:10:5
    |
 9  | async fn missing_return_type() {
    |                                - possibly return type missing here?
@@ -23,7 +23,7 @@ error[E0308]: mismatched types
                    found enum `Result<(), _>`
 
 error[E0308]: mismatched types
-  --> $DIR/macros_type_mismatch.rs:23:5
+  --> tests/fail/macros_type_mismatch.rs:23:5
    |
 14 | async fn extra_semicolon() -> Result<(), ()> {
    |                               -------------- expected `Result<(), ()>` because of return type
@@ -38,3 +38,20 @@ 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
+   |
+28 | async fn extra_semicolon_generic<T>() -> Result<(), ()>
+   |                                          -------------- expected `Result<(), ()>` because of return type
+...
+32 |     Ok(());
+   |     ^^^^^^^ expected enum `Result`, found `()`
+   |
+   = note:   expected enum `Result<(), ()>`
+           found unit type `()`
+help: try adding an expression at the end of the block
+   |
+32 ~     Ok(());;
+33 +     Ok(())
+   |

tests-build/tests/macros.rs

@@ -5,12 +5,18 @@ fn compile_fail_full() {
     #[cfg(feature = "full")]
     t.pass("tests/pass/forward_args_and_output.rs");
 
+    #[cfg(feature = "full")]
+    t.pass("tests/pass/macros_main.rs");
+
     #[cfg(feature = "full")]
     t.pass("tests/pass/macros_main_return.rs");
 
     #[cfg(feature = "full")]
     t.pass("tests/pass/macros_main_loop.rs");
 
+    #[cfg(feature = "full")]
+    t.pass("tests/pass/macros_main_generics.rs");
+
     #[cfg(feature = "full")]
     t.compile_fail("tests/fail/macros_invalid_input.rs");
 
@@ -20,6 +26,12 @@ fn compile_fail_full() {
     #[cfg(feature = "full")]
     t.compile_fail("tests/fail/macros_type_mismatch.rs");
 
+    #[cfg(feature = "full")]
+    t.compile_fail("tests/fail/macros_main_generics.rs");
+
+    #[cfg(feature = "full")]
+    t.compile_fail("tests/fail/macros_main_missing_async.rs");
+
     #[cfg(all(feature = "rt", not(feature = "full")))]
     t.compile_fail("tests/fail/macros_core_no_default.rs");
 

tests-build/tests/pass/macros_main.rs

@@ -0,0 +1,10 @@
+use tests_build::tokio;
+
+// This ensures that `'static>>` is not being incorrectly consumed as one
+// sequence of joint tokens while parsing the angle bracket group.
+#[tokio::main]
+async fn ensure_proper_continuation() -> Result<(), Box<dyn std::error::Error + 'static>> {
+    todo!()
+}
+
+fn main() {}

tests-build/tests/pass/macros_main_generics.rs

@@ -0,0 +1,36 @@
+use tests_build::tokio;
+
+use std::fmt::Debug;
+
+#[tokio::main]
+async fn single_parameter<T>() {}
+
+// This should parse since we treat angle brackets as groups during parsing and
+// simply skip over them.
+#[tokio::main]
+async fn where_clause<T>()
+where
+    T: Iterator,
+    <T as Iterator>::Item: Debug,
+{
+}
+
+#[tokio::main]
+async fn join_bracket_in_return() -> Option<fn() -> ()> {
+    todo!()
+}
+
+#[tokio::main]
+async fn joint_bracket_in_generic<T: Iterator<Item = Option<fn() -> ()>>>(_: T) {}
+
+struct GroupsInReturnPosition<const N: usize, const U: usize>;
+
+// Tests both bracket groups `<{inner}>` and braces `{<inner>}` in the return
+// position. The latter which should already be skipped over as part of the
+// angle bracket processing.
+#[tokio::main]
+async fn groups_in_return_position() -> GroupsInReturnPosition<1, { 2 + 1 }> {
+    todo!()
+}
+
+fn main() {}

tokio-macros/Cargo.toml

@@ -19,13 +19,6 @@ categories = ["asynchronous"]
 [lib]
 proc-macro = true
 
-[features]
-
-[dependencies]
-proc-macro2 = "1.0.7"
-quote = "1"
-syn = { version = "1.0.56", features = ["full"] }
-
 [dev-dependencies]
 tokio = { version = "1.0.0", path = "../tokio", features = ["full"] }