Add additional LLDB plugin example

src/doc/rustc-dev-guide/src/debuginfo/lldb-internals.md

@@ -15,6 +15,9 @@ Here are some existing implementations of LLDB's plugin API:
 * [Apple's fork with support for Swift](https://github.com/swiftlang/llvm-project)
 * [CodeLLDB's former fork with support for Rust](https://archive.softwareheritage.org/browse/origin/directory/?branch=refs/heads/codelldb/16.x&origin_url=https://github.com/vadimcn/llvm-project&path=lldb/source/Plugins/TypeSystem/Rust&timestamp=2023-09-11T04:55:10Z)
 * [A work in progress reimplementation of Rust support](https://github.com/Walnut356/llvm-project/tree/lldbrust/19.x)
+* [A Rust expression parser plugin](https://github.com/tromey/lldb/tree/a0fc10ce0dacb3038b7302fff9f6cb8cb34b37c6/source/Plugins/ExpressionParser/Rust).
+This was written before the `TypeSystem` API was created. Due to the freeform nature of expression parsing, the
+underlyng lexing, parsing, function calling, etc. should still offer valuable insights.
 
 ## Rust Support and TypeSystemClang
 

src/doc/rustc-dev-guide/src/debuginfo/rust-codegen.md

@@ -56,7 +56,7 @@ Using the `const` qualifier to denote non-`mut` poses potential issues due to LL
 optimizations. In short, LLDB attempts to cache the child-values of variables (e.g. struct fields,
 array elements) when stepping through code. A heuristic is used to determine which values are safely
 cache-able, and `const` is part of that heuristic. Research has not been done into how this would
-interact with things like Rust's interrior mutability constructs.
+interact with things like Rust's interior mutability constructs.
 
 ### DWARF vs PDB