Anders Hejlsberg on Modern Compiler Construction (2016) [video] | Hacker News Reader

Anders Hejlsberg on Modern Compiler Construction (2016) [video]

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187 pointsehaskins40 comments

One take away for me was: Language designers & compiler writers today need to consider editor support as one of their goals.

On the top page there's another thread about rust-analyzer vs RLS. What Aleksey said[0] about RLS that "[RLS's] current architecture is not a good foundation for a perfect IDE long-term," feels similar to my coworker's conclusion in her effort to provide better editor support for PHP[1].

Parsers for compiling code into machine-executables vs parsers to serve LSP responses have different tradeoffs. For example, Anders mentioned TS parser need to have good error-recovery, can respond with completions/errors when one file changes inside a thousand-files-project. I vaguely remember TS had a goal to provide completions in < 50ms and errors in <150ms. Such goals are hard to achieve as after-thought. If your core compiler doesn't do error recovery, such as PHP, you need someone to write a new compiler from scratch for a language server implementation. If tools such as RLS rely on compiler to dump all JSON metadata and figure out LSP responses[0], it's too slow for editors.

TS's good editor support doesn't come free. I think one of the most under-appreciated achievement of TS is how it took editor support seriously and designed its compiler infrastructure to do it well. That's why I don't believe in those hot-new-web-languages that try to take over TS by designing a better type system. TS brought the average developer's expectation of a language to having fast completion, fast error reporting, editor autofix, F2 to rename and renaming-a-file-in-editor-to-update-all-references. It's 2020 and people aren't going back to write code like in Notepad.

[0]: https://ferrous-systems.com/blog/rust-analyzer-2019/

[1]: https://github.com/microsoft/tolerant-php-parser

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EDIT: grammar.

> One take away for me was: Language designers & compiler writers today need to consider editor support as one of their goals.

In a way this is very intuitive: a programming language is a kind of a UI for the language's runtime. The IDE is just another UI layer on top of that.

Turbo Pascal (which he authored) was quite the accomplishment back in the day - editor and compiler in 64K. Think about that for a minute.

The DOS TP compiler was still at the heart of Delphi 1 supported an inline assembler and reference-based class system, code generator, etc. in less than 43k lines of assembler (it was entirely written in assembler).

(32-bit Delphi 2 switched to a C-based compiler originally written by Peter Sollich. I maintained the front end on that compiler for 6 years; PS followed AH to MS.)

Cool. I love Delphi to this day. Nothing beats that for Windows native apps IMHO.

Any interesting stories to share? I read somewhere that now the compile is a million lines of undocumented code.

I got a lot of use out of that in my early career. Thank you.

To be clear, I was only involved in 2006-12 time period. I got a lot of use out of TP 6 and Delphi 2 when I was learning, which is a significant part of the reason I ended up at Borland.

That was my first language after BASIC - I loved it!

I may be remembering this wrong, but it seemed virtually free - it was about $100 when its competitors and most software was $500+. That was in about 1986. The only way to get a manual was to buy the software. Another world..

$99 was for Delphi up until version 5 for the cheapest version, which most likely explains why it was very popular among solo shareware developers.

Sadly that market was abandoned by Borland when they decided to go after enterprises and renamed themselves to Inprise and their prices skyrocketed after that.

You do remember wrong. It was $49.95. It changed my life.

Mine too.

Started with ZX BASIC then when we got a second hand PC I switched to TP - Pascal was and is an excellent first language, in that sense it met it's design goals well.

Ah yes, I think it was $70 here in Australia.

I got a copy of Delphi 3 on the cover CD of PC Plus magazine in ‘99. Changed my 15 year old life.

Huw Collingbourne shifted the needle on a lot of young UK & Ireland programmers, IMO.

Definitely. I owe him a lot. The late Wilf Hey also for his language columns, I remember following along with his Eiffel, Prolog and Smalltalk series as a youngster.

I paid 100 euros in today's money for Turbo Pascal for Windows 1.5, the last TP version before Delphi got released.

Likewise I paid 150 euros in today's money for Turbo C++ for Windows a couple of years later.

Borland products were king for small business, but then they decided to switch focus to corporate users, and the rest is history.

As side note, Delphi and C++ Builder are still quite loved in Germany, several companies keep using them, and there is at least an yearly conference.

turbo pascal went straight from source to machine code. no ast!

^and it was awesome.

This is a great talk, I was struck by how similar some of the high level design goals are to LLVM https://www.aosabook.org/en/llvm.html

I kind of hope Anders moves on from TypeScript soon, he’s done a fantastic job there considering the constraints of JavaScript, but I’d love to see him tackle something new.

Between Delphi, C#, and TypeScript the man has already had a storied and impactful career.

Yes, he’s fantastically accomplished and capable, and I think he could do amazing things in a new area.

I’d love to see him take lessons learned from C# for a language designed for WASM from the get go.

But wasm is an architecture. Like x86. The more interesting question is: what language is optimal for the use cases wasm serves. Games come into mind.

WASM is just yet another bytecode format.

AssemblyScript is already quite ahead regarding WASM support.

Unfortunately, he is quite adamantly not a fan of WASM.

Why is he not?

Only thing I could find of him mentioning WebAssembly was here at 19:45: https://youtu.be/MxB0ldQfvT4?t=1185

In that video he says that it’s not a suitable target for TypeScript to compile to because WebAssembly doesn’t have a garbage collector. They’d have to basically implement an entire JavaScript engine in WebAssembly which would be pointless.

He gives some examples of things it could be good for, which are all CPU intensive things like image processing and video games, but he doesn’t seem to think it’s really suitable for making normal web apps.

My three favourite languages ever (with Turbo Pascal as my first proper programming language) - The man has quite simply defined my career.

You forgot about the previous 10 year's of the man's career with Turbo Pascal.

Also his first work in Microsoft: Windows Foundation Classes (WFC) and Visual J++ development system.

He says he doesn’t think he’ll make another language. Which is a shame... I’d particularly like to see an actually good language for Azure(/cloud in general) resource management. There have been a bunch of attempts, but typically they’re just config files are their core.

Anyone know a declarative interface for describing services and their interactions that “compiles” to a complete cloud resource manager.

Very basic stuff. Actually only the fact that for a syntax aware editor you need other data structures than for a compiler and that edits only affect parts of that structure.

A thread from 2018: https://news.ycombinator.com/item?id=17280589

Discussed at the time: https://news.ycombinator.com/item?id=11685317

It sounds like that content-addressed code as in the Unison language https://www.unisonweb.org/ could end up facilitating the design of a very effective IDE since the language can naturally generate an immutable structure by default.

I don't know enough to know if this hunch is correct, I'm wondering if anyone better informed can chime in.

Yes this is correct. We use content addressable code, inspired by Unison for yazz Pilot, and it makes so many things in the ide really simple, including dependency management and stuff like that

Very interesting, even though we don’t have a compiler in the traditional sense for yazz Pilot as a container image is our output format, many of the points are still valid.

Also very interesting how rosalyn had the idea of compiler as an API, we went in the opposite direction and did not have any extensibility, instead we made the Code editor an API

Something I’ve observed with languages he designs are that they end up with a ui form builder. I wonder if that will happen with typescript. It’s harder, because they’d either need to pick a framework, or design it for at least react, vue, angular.

At that time I wanted to read about compiler building. Missed that I'm University. That video made me skipping that. The standard books do not exist for this level of evolvement.

This is kinda how the compiler-stuff in Dark is written.

Everything - the editor, semantic analysis, version control, execution engine, everything - all use the same data structures (the same abstract syntax tree).

We use functional data structure everywhere and we do functional updates within the AST all the time; that's even how text entry in the editor updates the program.

> Everything - the editor, semantic analysis, version control, execution engine, everything - all use the same data structures (the same abstract syntax tree).

Is that data structure suitable for all those purposes though?

How do you do optimisations like GVN on an AS->T<-?

It's not suitable for all purposes, but it's suitable for all editor purposes (including an in-editor execution engine). We don't do GVN, or any optimizations really, right now - I'm sure when we have a compiler of sorts we'll have other structures, SSA, etc.

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