sysl 0.0.155 — a by-name parameter is a call inside a closure too

A parameter passed by name is now read the same way everywhere in its function: inside a closure, inside a nested function, and in the body after either one. Each read evaluates the argument. One spelling that 0.0.154 accepted is now refused (below).

Behaviour changes

Calling a by-name parameter inside a closure or nested function is now refused. In 0.0.154 that was the only way to read one there. Write the bare name instead, as the body always required.

f(x: -> int) -> int
    val g = () -> x() + 1      // 0.0.154: compiled. 0.0.155: refused.
    g()

error: type 'int' has no method 'call'

The fix is to drop the parentheses: val g = () -> x + 1. In the function's own body, x() was always refused with this message. A closure is now treated the same way.

What 0.0.154 refused and now compiles:

• A bare read inside a closure or nested function. val g = () -> x + 1 was refused with '+' needs '$F0: sysl.Add' and then '+' needs matching types, got a closure and int.
• A bare read in the function's own body, when it comes after any closure or nested function. val g = () -> 1 followed by x + g() was refused with '+' needs '$F0: sysl.Add[int]'. With the closure removed, the same line compiled.

Every other program compiles to the same thing as on 0.0.154. Nothing in the org wrote x() inside a closure. A grep of every repo under sysl-lang, and of slate-language, found no by-name parameter in any package or program. The only matches are parse-test strings in the self-hosted compiler. So nothing needed fixing for this release.

Fixes

A by-name parameter read in a closure or nested function is a call (020a727)

reference/types.md § A parameter passed by name says: "Each use is an evaluation, because each use is a call." Inside a closure or nested function in the body, the compiler did not follow that rule. A read there gave the thunk itself, not its value.

There were two causes, both in one mechanism. analyzeNested calls resetFunction, which cleared byNameLocals. Nothing marked the captured names as by-name again, so the closure's body read the thunk. Nothing restored the set afterwards either, so the function's own reads after a closure stopped being calls as well. Now the by-name mark follows a captured name into the closure's scope, and is restored when the closure ends (FunctionBodies.scala).

Building the closure's environment has to capture the callable itself, not call it. captureRead in Closures.scala does this for a closure's fields and for a nested group's addresses. So the argument is evaluated at each read inside the closure, and never at capture.

Tests

ByNameTests: 8 new cases. All of them failed before the fix.

• a closure of the body calls it
• a nested function of the body calls it
• a closure evaluates the argument at every call of it
• a nested function evaluates the argument at every read
• a closure that outlives the call evaluates the argument when it is called
• a closure inside a nested function reaches it through both
• the body still calls it after a closure is written
• calling it inside a closure is refused, as it is in the body

Documentation

reference/types.md § A parameter passed by name on sysl.sh has a new runnable block. In it, a closure reads a by-name parameter and is called twice, and the argument runs once per call, printing 11 and then 21. One sentence was also added: the rule holds inside a closure or nested function too. DocsTests runs the block, so the fixed behaviour stays pinned.

Install

brew install sysl-lang/tap/sysl      # or: brew upgrade sysl

The tarballs for macOS arm64, Linux x86_64 and Linux arm64 are attached to this release. The sh.sysl:sysl_3:0.0.155 jars are on GitHub Packages (https://maven.pkg.github.com/sysl-lang/sysl-bootstrap). sysl is not published to Maven Central.

Verification

• Native gate on the tagged tree (a34479b, which is 020a727 plus the version bump): GREEN, 12,290 succeeded and 0 failed. That is 416 suites in 46 chunks plus the groups that run alone. Nothing timed out and nothing was retried. The gate covers syslNative and syslDocNative. It took 57:04, after a cleaned warnings census. The fix had landed on a targeted gate, so this is its first full run.
• Warnings census, cleaned: JVM two, JS three, Native three, syslDocJVM one, syslDocNative two. That is the expected count, and every warning belongs to a dependency or is build infrastructure.
• Release tarball: extracted to a scratch prefix and run. sysl --version prints sysl 0.0.155, and sysl-doc is present. The 0.0.154 reproductions now behave as described above. val g = () -> x + 1 prints 42. x + g() after a closure prints 42. x() in a closure is refused with type 'int' has no method 'call'. The new sysl.sh block prints 11, 21, 2.
• GitHub Packages: all four artifacts (the pom, the jar, the sources jar and the javadoc jar) answer 302.
• brew: brew test sysl passes, and the installed sysl --version prints sysl 0.0.155. The Linux glibc floor, measured in the release run, is 2.34 on both architectures.
• sysl.sh on 0.0.155: 1,416 tests pass with 0 failures. Of those, 1,396 are DocsTests. The new block was checked by mutation: changing its expected output to 11 11 2, which is what evaluating the argument once at capture would print, turned DocsTests red on exactly that block (types.md program 26). Restoring it turned the suite green again.
• Org sweep with the release tarball's own binary: 77 builds, 71 green under the bare command.
  • 54 ran under sysl test ., 12 under sysl build . and 5 under sysl build-c <dir>.
  • Four repos fail the bare command by design and were run as their READMEs say. freertos against a freshly built FreeRTOS-Kernel POSIX port: 84 passed. libpq against a scratch PostgreSQL: 51 passed. quickjs-ng with its include path: 33 passed.
  • pico: build-lib --target thumbv6m-freestanding gets as far as the pico-sdk's generated cyw43_arch.h, which means the sysl type-check passed.
  • pico2 and zephyr refuse the bare command by design, through their requires { headers } clause.
  • Not swept, being kernel or board repos that need a toolchain or SDK this machine does not have: zephyr, picokit, ogol-pico, ogol-pico2, solder-pico2, zephyr-demo, pico-scratch. Also not swept, being infrastructure: sysl-bootstrap, sysl (the self-hosted compiler), sysl.sh, homebrew-tap, github-profile and svd.