sysl

The sysl compiler, written in sysl.

This is the compiler that ships as sysl. It builds itself; the Scala bootstrap compiler (sysl-lang/sysl-bootstrap) is retired and archived. The language is specified by the pages in docs/content/, which sysl.sh publishes from a release tag.

The layout

directory	what it holds
compiler/	the compiler: its package.hocon, sysl.sum and the module sh.sysl.compiler
library/	the standard library, the tree whose root module is sysl
docs/	the documentation site: juicer's site.toml, the themes, the static files, the grammar, and under docs/content/ the pages — the reference, the library, the tour — every sysl block of which the compiler's suite builds and runs (tests_docs.sysl, with SYSL_DOCS=1)
scripts/	the censuses that compare this compiler with the reference

The compiler is a project of its own in compiler/ because a compiler reads every .sysl file under a project's root as part of that project, and the library's modules are not the compiler's.

The site at sysl.sh is built by juicer from docs/. .github/workflows/docs.yml builds it on every push to dev and deploys it to GitHub Pages only from a release tag, so the published site documents a release. Building it needs juicer and nothing else — no sysl compiler or library. A local preview is sbt 'juicerJVM/run serve -s <this repository>/docs -L', run from a juicer checkout.

Building

cd compiler
SYSL_LIB=../library sysl build .
SYSL_LIB=../library sysl test .

Both commands are the bootstrap compiler's, installed with brew install sysl-lang/tap/sysl. The first produces compiler/sysl; the second runs every @test in the tree. SYSL_LIB names the library the compiler under test compiles programs against; the standard library's own suite is SYSL_LIB=../library ./sysl test ../library --std.

The road to self-hosting

1. A conformance suite: programs with the output and the diagnostics they owe, in a form either compiler can be run against. It is green against the bootstrap before anything else is written.
2. A scanner and a parser for sysl's grammar, written by hand, producing the same tree the bootstrap does. Both are written. lex.sysl turns bytes into tokens and turns the shape of a file into Newline, Indent and Dedent, so that nothing above it ever looks at a column; parse.sysl and the files beside it read a whole file — every expression, type and pattern, every statement, every declaration, the header, the annotations, and a literate .lsysl document. It is checked against every file of this compiler's own source, of the standard library, and of the parsing package it is built on.
3. Analysis, then LLVM emission, phase by phase against the suite.
4. This compiler builds itself, and the compiler it builds builds the same thing again.

License

ISC. See LICENSE.