Rename to unstable_ir, add docs

Author: Heesoo Yang

docs.md

@@ -94,9 +94,18 @@ cbindgen = "0.24.0"
 
 If you'd like to use a `build.rs` script with a `cbindgen.toml`, consider using [`cbindgen::generate()`](https://docs.rs/cbindgen/*/cbindgen/fn.generate.html) instead.
 
+## Internal Representation
 
+Some users may find it useful to access the **unstable** internal representation (IR) that cbindgen uses to parse and generate code. By default, the IR is private, but you can access it by enabling the `"unstable_ir"` feature flag like so:
 
+```
+[build-dependencies]
+cbindgen = { version = "0.27.0", features = ["unstable_ir"] }
+```
+
+This opens up the `cbindgen::bindgen::ir` module.
 
+Please remember that the IR is **not stable**, so if you use this feature, you will need to pin cbindgen to avoid breakages.
 
 # Writing Your C API
 

src/bindgen/mod.rs

@@ -45,9 +45,9 @@ mod config;
 mod declarationtyperesolver;
 mod dependencies;
 mod error;
-#[cfg(feature = "ir")]
+#[cfg(feature = "unstable_ir")]
 pub mod ir;
-#[cfg(not(feature = "ir"))]
+#[cfg(not(feature = "unstable_ir"))]
 mod ir;
 mod language_backend;
 mod library;

src/lib.rs

@@ -14,9 +14,9 @@ extern crate quote;
 extern crate syn;
 extern crate toml;
 
-#[cfg(feature = "ir")]
+#[cfg(feature = "unstable_ir")]
 pub mod bindgen;
-#[cfg(not(feature = "ir"))]
+#[cfg(not(feature = "unstable_ir"))]
 mod bindgen;
 
 pub use crate::bindgen::*;