sysl 0.0.160 — __VERSION__, and defaults read at the type each call settles

__VERSION__, and defaults read at the type each call settles

Five items. A program's version now lives in one place: __VERSION__ reads the version in the package.hocon of the code that uses it. A generic parameter's default no longer steers the call's solve, and a default may now name its declaration's own type parameters. Two capability fixes, from the same freeze exception as 0.0.157–0.0.159, close the last holes in what a board program may link.

Behaviour changes

Two of the five can refuse, or stop compiling, something that compiled before. Both are listed here first.

• A dependency's @tests file is no longer read by its consumer's build (a87760a, d04dbb7). A dependency's @tests files, and its @test functions and hooks, are now taken out before analysis in every build of a consumer — build, run, build-c, emit-llvm, emit-typed, prove, and the consumer's own sysl test — whether the dependency arrives through --lib or as a fetched coordinate. Before, they were name-resolved and type-checked against the consumer's target and dropped only afterwards, so a library whose tests made a scratch directory could not be linked by a board program at all ("'sysl.fs' declares no 'make_temp_dir'", pointing into a file no build of that program keeps). What reference/modules.md § A @tests file states its own capabilities promised now holds.
  • Behaviour change: a consumer's @test that called a helper declared in a dependency's @tests file used to compile; the helper is no longer there to call. A test helper meant for other packages belongs in an ordinary file, or in a package of its own.
  • A mistake in a dependency's tests — a type error, or an import of its own dev_dependencies — is now reported by that package's sysl test and nowhere else.
  • Unchanged: a package's own sysl test compiles and runs its @tests files as before, and a program's own scaffolding is still analyzed by its build and then dropped.
• An alias of an applied Drop type dies as that type does (45ed551). type M = Option[&Handle], held by a @no_os program, was charged nothing although its value runs Handle's destructor; it is now refused with "a 'sys.M' can die here, and its destructor reaches 'sys'", exactly as Option[&Handle] written out is. A bare alias (type H = Handle) was already followed.
  • Behaviour change: code that compiled only through this hole is refused.

Features

__VERSION__ (47bec55, a92f403, d29ecfe)

__VERSION__ reads the version in the package.hocon of the code that uses it, so a program's version lives in one place; it is refused in a file that is not part of a package.

print("mytool ", __VERSION__)      // "mytool 1.4.0" under a manifest saying version = "1.4.0"

• A seventh built-in beside __FILE__ and __LINE__: a string literal, folded where it is written, so it may initialize a const or a module-level val.
• It is per package as __FILE__ is per file: a library's __VERSION__ is the library's own.
• As a default argument it takes the CALLER's package version, as __FILE__ does. A library's stamp(v: string = __VERSION__) answers the version of whichever package the call sits in — which is what lets a library offer a --version helper that reports the program using it.
• Refused, in the self-hosted compiler's wording, in a file with no package.hocon at its project root ("'VERSION' is the 'version' in package.hocon, and this file is not part of a package — no package.hocon stands at the root of its tree") and under a manifest with no version ("… and declares none").
• The manifest travels on each source through AstCodec, so an importer re-analyzing a generic body still knows its package. AstCodec.Version 60 → 61: every cached .syslib is rebuilt on first use.

Tests: VersionBuiltinTests.

A default may name its declaration's own type parameters (1742280, cd9342f)

offset[T: Zero + Add](x: T, step: T = T.zero()) -> T = x + step
tuned[F: Float](f: F, a4: F = F(440.0)) -> F = f + a4

print(offset(2.5), offset(7), tuned(0.5))      // 2.5 7 440.5

A type parameter is part of the signature rather than local to it, so a default may name one in value or type position, and it is read at each call at the type that call solved — never the caller's. The default takes no part in the solve: a T only the default could settle is refused as uninferable. At the declaration it is held to the bounds as a generic body is (T.zero() with no Zero bound is refused there); a conversion at T is checked at each instantiation. Other parameters and locals are still undefined in a default.

The same holds on a trait member, including one whose signature names Self through an arrow — over[N: Zero + Add](self, f: Self::Item -> N, base: N = N.zero()) reads N's bounds with Self spelled as the receiver's type, exactly as a call already does. A member with no default never builds the defaults' type parameters at all, so a trait member taking f: Self::Item -> N and no default is untouched by this feature.

Tests: ArgumentTests, TraitCallableTests.

Fixes

A default no longer steers a generic call's solve (f68fedb, fcaf050)

f[T](lo: T, step: T = 1) called with a real lo solves T = real, and the error now says the default cannot be read at the parameter's type at this call. The omitted 1 used to be analyzed bare, as an int, while the call was still solving T — so f(x) with a real x was refused ("'step' of 'f' is real, but int was given"). It now waits like any other literal, is consulted only after everything the call wrote, and is read at the solved type. A default that type cannot hold is refused at the call:

'step' of 'f' was left to its default, which cannot be read at int — the type this call settles it to

Verification

• Full Native gate on cd9342f6 (./run-gate.sh): GATE: GREEN, 12391 succeeded, 0 failed, no retries; full JVM run 12357 / 0. The release is that sha plus the version bump.
• TraitCallableTests on the release tree: 20 succeeded, 0 failed (syslJVM/testOnly sh.sysl.TraitCallableTests).
• Warnings census clean (JVM / JS / Native / syslDocJVM / syslDocNative): after clean, two / three / three / one / two — every warning named and none in this repository (Reader.scala:26:6 from scala-parser-combinators, Set.scala:62:15 from the Scala.js scaladoc, and the build-infra -Xplugin lines).
• Documented on sysl.sh: reference/lexical.md § __VERSION__ is the package's version (the lone-file refusal, as a checked error block) and reference/declarations.md § Default parameters and named arguments (the type-parameter default, as a runnable block printing 2.5 7 440.5).