Add rule annotations

Author: ehuss

src/attributes/coverage-instrumentation.md

@@ -4,13 +4,21 @@ The following [attributes] are used for controlling coverage instrumentation, wh
 
 ### The `coverage` attribute
 
-The *`coverage` [attribute]* indicates whether a function should instrument code coverage at all and show up in code coverage reports. It can only be controlled at the function level, but it can be applied to modules, `impl` blocks, or anything that can contain functions.
+r[attributes.coverage]
 
+r[attributes.coverage.intro]
+The *`coverage` [attribute]* indicates whether a function should instrument code coverage at all and show up in code coverage reports.
+
+r[attributes.coverage.allowed-positions]
+The `coverage` attribute can only be controlled at the function level, but it can be applied to modules, `impl` blocks, or anything that can contain functions.
+
+r[attributes.coverage.syntax]
 There are two ways to use the coverage attribute:
 
 * `#[coverage(off)]` indicates that all functions within an item, recursively, should not be instrumented, unless specified by another attribute.
 * `#[coverage(on)]` (the default) indicates that all functions within an item, recursively, *should* be instrumented, unless specified by another attribute.
 
+r[attributes.coverage.nesting]
 More-specific attributes always take priority over less-specific ones, e.g. if a crate is marked `#![coverage(off)]`, then functions inside that crate marked `#[coverage(on)]` will still have coverage.
 
 [attribute]: ../attributes.md