Thanks for the write-up.

Neil Jones' (free) book about partial evaluation deserves a mention here, since it explains how/why it works in some detail.

Query languages are a very cool application of this stuff. I was planning to use wasm for Mangle implementation (a language extending datalog, with its implementation a library for deductive database), following Tiark Rompf and Nada Amin's "a SQL to C compiler in 500 lines of code"... but of course I only have the interpreter for now and started a Rust rewrite instead.