Merge pull request #2734 from reddevilmidzy/eRFC

Document experimental RFC process in walkthrough

Author: tshepang

src/walkthrough.md

@@ -97,7 +97,7 @@ If that sounds like a lot of work, it's because it is.
 But no fear!
 Even if you're not a compiler hacker, you can get great feedback by doing a _pre-RFC_.
 This is an _informal_ discussion of the idea.
-The best place to do this is internals.rust-lang.org.
+The best place to do this is [internals.rust-lang.org](https://internals.rust-lang.org).
 Your post doesn't have to follow any particular structure.
 It doesn't even need to be a cohesive idea.
 Generally, you will get tons of feedback that you can integrate back to produce a good RFC.
@@ -159,6 +159,19 @@ Here is the tracking issue on for our [`?` macro feature][tracking].
 
 [tracking]: https://github.com/rust-lang/rust/issues/48075
 
+## Experimental RFC (eRFC)
+
+An eRFC is a variant of the RFC process used for complex features where the high-level need
+is clear, but the design space is too large to settle on a detailed specification upfront.
+Instead of providing a final design, an eRFC outlines a high-level strategy to authorize
+a period of active experimentation. This allows the team to implement the feature behind
+a feature gate and gather practical data, which then informs a subsequent formal RFC for stabilization.
+While this process was used for major features like coroutines ([see RFC 2033][rfc2033]),
+the explicit "eRFC" label is rarely used today. The project now generally prefers approving a standard
+RFC for an initial version and iterating on it through the nightly channel before final stabilization.
+
+[rfc2033]: https://github.com/rust-lang/rfcs/pull/2033#issuecomment-309057591
+
 <a id="impl"></a>
 
 ## Implementation