{"slug": "i-can-barely-read-rust-but-i-m-building-a-compiler-in-rust", "title": "I Can Barely Read Rust, but I'm Building a Compiler in Rust", "summary": "Developer Kentaro Morishita is building the Seseragi programming language compiler in Rust, despite having limited Rust proficiency, by leveraging AI tools like Codex to write much of the implementation. Morishita focuses on architecture and semantics rather than writing every line, and the project now includes a Rust compiler, CLI, LSP, formatter, and WASM Playground.", "body_md": "The Seseragi compiler is currently written in Rust.\n\nI can barely read Rust.\n\nWritten as two sentences, this project sounds deeply questionable.\n\nIf you're building your own compiler, the obvious assumption is that you should understand the implementation language very well.\n\nThat is still an advantage. A huge one.\n\nBut in the Seseragi rewrite, Codex writes a large part of the Rust implementation.\n\nMy job is not to personally type every line.\n\nI spend much more time on questions like:\n\nAnd if the result feels wrong, I make it go back.\n\nAt first, part of me wondered whether AI implementation meant I could be more relaxed about internal structure.\n\nLocal implementation is astonishingly fast now.\n\nThat speed is exactly what makes careless architecture dangerous.\n\nIf you put a responsibility in the wrong place, **the wrong architecture can become fully implemented at incredible speed**.\n\nSometimes it even comes with tests.\n\nIt looks polished.\n\nIt is still wrong.\n\nThat is terrifying in a very modern way.\n\nBefore handing work to Codex, I now think much harder about the shape of the task.\n\nWhat is actually in scope?\n\nWhat is the source of truth?\n\nWhat should explicitly wait for a future Issue?\n\nDoes this change break an assumption needed by the next piece of work?\n\nAI made code production faster, so the human side of the loop moved further toward designing the entrance to the work.\n\nIt's strange, but I think I spend more time thinking about architecture now than I did when I personally wrote more of the implementation.\n\nI want to be clear about this.\n\nUnderstanding Rust would obviously make me stronger at this project.\n\nIt helps when debugging low-level behavior, looking at performance, reviewing ownership choices, or encountering `unsafe`\n\n.\n\nWhen I need to understand something, I read it.\n\nThe interesting part to me is not \"you don't need to know your tools anymore.\"\n\nIt's that **I can move a language implementation forward by holding onto the semantics and architecture even when I don't completely control the implementation language**.\n\nOnce AI enters the implementation loop this deeply, the question \"what does the author actually do?\" starts to change.\n\nCodex can produce a large Rust diff and I can review it fairly calmly.\n\nThen I look at a Seseragi sample and see:\n\n```\none character that feels unnecessary\n```\n\nor:\n\n```\nan ugly line break\n```\n\nand suddenly I become extremely opinionated.\n\nI think the reason is simple.\n\nI'm not primarily trying to create **a Rust compiler**.\n\nI'm trying to create **Seseragi as an interface that humans use**.\n\nThe compiler is the machinery that protects that meaning.\n\nSo I'm harsher on the surface than on implementation details I can delegate.\n\nThis seems logically consistent to me.\n\nCodex may have a different opinion.\n\n[https://github.com/KentaroMorishita/seseragi](https://github.com/KentaroMorishita/seseragi)\n\nThe project now has a Rust compiler, CLI, LSP, formatter, and WASM Playground sharing the same compiler-driver direction.\n\nI don't feel that the language stops being mine because I didn't personally write every line of Rust.\n\nI keep ownership of questions like:\n\nWhat does the language mean?\n\nWhat is allowed?\n\nWhat feels wrong enough to change?\n\nAn AI-assisted homemade programming language is a very strange kind of software project.\n\nI think we're only beginning to find out how strange.", "url": "https://wpnews.pro/news/i-can-barely-read-rust-but-i-m-building-a-compiler-in-rust", "canonical_source": "https://dev.to/kentaromorishita/i-can-barely-read-rust-but-im-building-a-compiler-in-rust-1d59", "published_at": "2026-08-16 13:55:02+00:00", "updated_at": "2026-08-16 14:12:58.166048+00:00", "lang": "en", "topics": ["developer-tools", "artificial-intelligence", "ai-tools"], "entities": ["Kentaro Morishita", "Seseragi", "Codex", "Rust"], "alternates": {"html": "https://wpnews.pro/news/i-can-barely-read-rust-but-i-m-building-a-compiler-in-rust", "markdown": "https://wpnews.pro/news/i-can-barely-read-rust-but-i-m-building-a-compiler-in-rust.md", "text": "https://wpnews.pro/news/i-can-barely-read-rust-but-i-m-building-a-compiler-in-rust.txt", "jsonld": "https://wpnews.pro/news/i-can-barely-read-rust-but-i-m-building-a-compiler-in-rust.jsonld"}}