ci: bring back build tests (#1813)

This directory was deleted when `cargo hack` was introduced, however
there were some tests that were still useful (macro failure output).

Also, additional build tests will be added over time.

tests-build/tests/fail/macros_invalid_input.rs

@@ -0,0 +1,25 @@
+use tests_build::tokio;
+
+#[tokio::main]
+fn main_is_not_async() {}
+
+#[tokio::main(foo)]
+async fn main_attr_has_unknown_args() {}
+
+#[tokio::main(threadpool::bar)]
+async fn main_attr_has_path_args() {}
+
+#[tokio::test]
+fn test_is_not_async() {}
+
+#[tokio::test]
+async fn test_fn_has_args(_x: u8) {}
+
+#[tokio::test(foo)]
+async fn test_attr_has_args() {}
+
+#[tokio::test]
+#[test]
+async fn test_has_second_test_attr() {}
+
+fn main() {}

tests-build/tests/fail/macros_invalid_input.stderr

@@ -0,0 +1,41 @@
+error: the async keyword is missing from the function declaration
+ --> $DIR/macros_invalid_input.rs:4:1
+  |
+4 | fn main_is_not_async() {}
+  | ^^
+
+error: Unknown attribute foo is specified; expected `basic_scheduler` or `threaded_scheduler`
+ --> $DIR/macros_invalid_input.rs:6:15
+  |
+6 | #[tokio::main(foo)]
+  |               ^^^
+
+error: Must have specified ident
+ --> $DIR/macros_invalid_input.rs:9:15
+  |
+9 | #[tokio::main(threadpool::bar)]
+  |               ^^^^^^^^^^^^^^^
+
+error: the async keyword is missing from the function declaration
+  --> $DIR/macros_invalid_input.rs:13:1
+   |
+13 | fn test_is_not_async() {}
+   | ^^
+
+error: the test function cannot accept arguments
+  --> $DIR/macros_invalid_input.rs:16:27
+   |
+16 | async fn test_fn_has_args(_x: u8) {}
+   |                           ^^^^^^
+
+error: Unknown attribute foo is specified; expected `basic_scheduler` or `threaded_scheduler`
+  --> $DIR/macros_invalid_input.rs:18:15
+   |
+18 | #[tokio::test(foo)]
+   |               ^^^
+
+error: second test attribute is supplied
+  --> $DIR/macros_invalid_input.rs:22:1
+   |
+22 | #[test]
+   | ^^^^^^^

tests-build/tests/macros.rs

@@ -0,0 +1,9 @@
+#[test]
+fn compile_fail() {
+    let t = trybuild::TestCases::new();
+
+    #[cfg(feature = "full")]
+    t.compile_fail("tests/fail/macros_invalid_input.rs");
+
+    drop(t);
+}