Add 2024 edition doctests to cover corner cases

Author: GuillaumeGomez

tests/rustdoc-ui/2024-doctests-checks.rs

@@ -0,0 +1,41 @@
+//@ check-pass
+//@ compile-flags: --test --test-args=--test-threads=1 -Zunstable-options --edition 2024
+//@ normalize-stdout-test: "tests/rustdoc-ui" -> "$$DIR"
+//@ normalize-stdout-test "finished in \d+\.\d+s" -> "finished in $$TIME"
+//@ normalize-stdout-test "wrong-ast.rs:\d+:\d+" -> "wrong-ast.rs:$$LINE:$$COL"
+
+/// This one should fail: crate attributes should remain crate attributes
+/// in standalone doctests.
+///
+/// ```compile_fail
+/// #![deny(missing_docs)]
+///
+/// pub struct Bar;
+/// ```
+///
+/// This one should not impact the other merged doctests.
+///
+/// ```
+/// #![deny(unused)]
+/// ```
+///
+/// ```
+/// let x = 12;
+/// ```
+///
+/// This one should not be a merged doctest (because of `$crate`):
+///
+/// ```
+/// macro_rules! bla {
+///     () => {{
+///         $crate::foo();
+///     }}
+/// }
+///
+/// fn foo() {}
+///
+/// fn main() {
+///     bla!();
+/// }
+/// ```
+pub struct Foo;

tests/rustdoc-ui/2024-doctests-checks.stdout

@@ -0,0 +1,14 @@
+
+running 2 tests
+test $DIR/2024-doctests-checks.rs - Foo (line 18) ... ok
+test $DIR/2024-doctests-checks.rs - Foo (line 22) ... ok
+
+test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+
+
+running 2 tests
+test $DIR/2024-doctests-checks.rs - Foo (line 10) - compile fail ... ok
+test $DIR/2024-doctests-checks.rs - Foo (line 28) ... ok
+
+test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+