Also test that yes/no must be bare words

tests/ui/coverage-attr/subword.rs

@@ -0,0 +1,19 @@
+#![feature(coverage_attribute)]
+//@ edition: 2021
+
+// Check that yes/no in `#[coverage(yes)]` and `#[coverage(no)]` must be bare
+// words, not part of a more complicated substructure.
+
+#[coverage(yes(milord))] //~ ERROR expected `coverage(off)` or `coverage(on)`
+fn yes_list() {}
+
+#[coverage(no(milord))] //~ ERROR expected `coverage(off)` or `coverage(on)`
+fn no_list() {}
+
+#[coverage(yes = "milord")] //~ ERROR expected `coverage(off)` or `coverage(on)`
+fn yes_key() {}
+
+#[coverage(no = "milord")] //~ ERROR expected `coverage(off)` or `coverage(on)`
+fn no_key() {}
+
+fn main() {}

tests/ui/coverage-attr/subword.stderr

@@ -0,0 +1,26 @@
+error: expected `coverage(off)` or `coverage(on)`
+  --> $DIR/subword.rs:7:1
+   |
+LL | #[coverage(yes(milord))]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: expected `coverage(off)` or `coverage(on)`
+  --> $DIR/subword.rs:10:1
+   |
+LL | #[coverage(no(milord))]
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: expected `coverage(off)` or `coverage(on)`
+  --> $DIR/subword.rs:13:1
+   |
+LL | #[coverage(yes = "milord")]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: expected `coverage(off)` or `coverage(on)`
+  --> $DIR/subword.rs:16:1
+   |
+LL | #[coverage(no = "milord")]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 4 previous errors
+