Sprig stage-0 — implemented feature status

This table reflects what the compiler in this directory actually does, as verified by scripts/test.sh. The release validation record is on GitHub. The historical design kit in docs/history/design-kit/ describes target semantics rather than current capabilities.

Feature	Front end	Static semantics	Codegen + runtime	Tests
Expression match	one expression per branch	strict contextual/inferred results, shared exhaustive/binder rules	Java 17 switch/yield; no closures; scrutinee once	match expression runtime/generic/null/effect tests
Explicit export alias.Symbol	yes	original symbols, collisions, cycles and package boundaries	no wrapper/copy	reexport runtime/API/package suite
Canonical sprig fmt	trivia-preserving lexer	parse structure invariant	atomic file replacement, check/JSON modes	formatter fixtures + valid corpus
Foreign JVM conformance conform C to J	declaration form, one per relation	exact JVM witness matching, v1 restrictions, foreign conformance conversion	emitted implements; non-null entry guards (SPR-CONFORM-*)	tests/conform runtime and negative suite
Functions, typed parameters/returns, recursion	yes	yes	Java static methods	runtime 01/02, visitor
Indentation, blocks, if/elif/else, while, for, break/continue	yes	yes	Java control flow	runtime 03/13
let/var, local inference, assignment rules	yes	yes (SPR-NAME-LET-ASSIGN)	locals/static fields	runtime 16
Classes: named auto-ctor, per-instance defaults, implicit fields/methods	yes	yes	final Java classes	runtime 04/12
enum + exhaustive match	yes	yes	Java enum + if-chain	runtime 06
variant + typed case binders + exhaustive match	yes	yes	sealed interface + nested classes	runtime 05/14, visitor
Missing/duplicate/wrong-type cases, enum binder rejection	—	yes (SPR-MATCH-*)	—	semantics 11 cases
Nullability T?, null checks, narrowing	yes	yes (SPR-TYPE-NULL/NULLABLE)	boxed nullable locals	runtime 07
List/MutableList/Map/MutableMap, snapshots, indexing, in	yes	yes, distinct mutability	runtime wrappers	runtime 09/16
String positions: length, indexing, charAt, codeAt, substring, indexOf, iteration	yes	Unicode code-point indices; one-code-point String elements; no Char type	sprig.runtime.StringOps helpers and code-point iteration	runtime 20 + String semantics suite
Immutable collection mutation rejected	—	yes (SPR-COLLECTION-IMMUTABLE)	—	semantics
User generics: generic K, V: blocks (one or more parameters) for class/variant/function, explicitly applied as Entry[String, Int], erased and boxed in generated Java	yes	yes (SPR-TYPE-GENERIC-*)	raw Java classes + compiler-controlled boxing/unboxing	runtime 19, visitor generic_stack, semantics 8 cases, syntax 08
Generic variant expanded payloads + exhaustive match on instantiations	yes	yes	raw nested case classes	runtime 19
requires X: Equatable equality capability	yes	equality on the parameter allowed only with the clause; value equality in codegen	boxed Objects-style equality	visitor generic_stack, runtime 19
requires X: Comparable	parsed	rejected as not implemented (SPR-GENERIC-CONSTRAINT)	—	semantics
Project model: sprig.toml discovery, defaults, init, project --json, deps --json, explicit-file priority, run --bin	yes	validated (SPR-PROJECT-*)	default entry compiled with the normal pipeline	project model suite
Local and Git Sprig dependencies: recursive resolution, @alias/module.spr imports, exports enforcement, cycle detection, sprig.lock, stale/missing lock refusal	yes	yes (SPR-DEP-*, SPR-PROJECT-*)	dependency source modules compile through the normal pipeline	dependency resolver suite
Offline mode for local/Git dependencies (--offline, warm cache required)	yes	SPR-DEP-OFFLINE when the cache is incomplete	~/.sprig/git verified detached checkouts	dependency resolver
Maven/JVM dependency resolution	exact direct release coordinates	Apache Resolver effective POM + transitive mediation, schema-5 hashes/graph/locators and compiler identity	shared locked check/build/run/api/doctor classpath	Maven fixtures + real commons-text showcase
Source callable types fn(A) -> R, nullable (fn(A) -> R)?, invariant, arities 0–3	yes	signatures/fields/locals/collections/generics, no callable effects	existing Fn0..Fn3 representation	tests/callables
JVM callable ABI with concrete sprig.runtime.Fn0..Fn3 signatures	yes	boxed invariant parameters/results, non-null arguments	direct calls, nullable returned callable and runtime contract guards	tests/callables
Lambdas fn(...) => expr, arities 0–3, map/filter/forEach	yes	yes	Fn0..Fn3 anonymous classes	runtime 10, 18
throw/throws/try/catch/finally (typed errors)	yes	yes (SPR-FLOW-THROWS)	Java exceptions	runtime 08, interop 15
Flow: definite return, unreachable code	—	yes (SPR-FLOW-*)	—	semantics
Modules: file imports, alias access, init once, cycle detection	yes	yes	static $init() per module	runtime 12, semantics
JDK interop: imports, ctors, static/instance methods/fields, overloads	yes	reflection-based; reference results nullable and require narrowing	direct Java calls	runtime 15, correctness regressions
Checked Int/Int32, explicit integer quotient, numeric literal ranges	yes	SPR-NUM-* checks	NumericOps checked JVM operations	numeric acceptance suite
IEEE Float/Float32, explicit exact/lossy conversion	yes	mixed-type and narrowing checks	Java double/float	numeric acceptance suite
BigInt and Decimal	yes	distinct native types	BigInteger/BigDecimal wrappers	numeric acceptance suite
Java checked exceptions + typed catch + error.message	yes	yes	Java try/catch	runtime 15
sprig check/run/build/explain/codes/help/capabilities/api/doctor, --json, --syntax-only	—	—	—	scripts/test.sh, agent tooling suite
Explicit local --classpath on check/build/run/api	—	shared class loader + javac/JVM path	locked JVM JARs precede explicit entries; compiler libraries isolated	agent tooling suite
Bounded JVM interop: opaque arrays, concrete generics, explicit collection adapters	explicit Type[Arg] application; @std/jvm.spr; sprig.runtime.jvm.HostBytes	structured interopLevel/interopReasonCodes; wildcards, inference, recursive bounds and varargs rejected before javac	arrays keep exact JVM classes; snapshots/copies are independent; no implicit conversion	JVM interop suite
javac error → Sprig span translation	—	—	line map	by design
Checked effects from omitted class defaults	—	checked at each constructor call; explicit field values skip unused defaults	defaults still evaluate per instance, in declaration order	correctness regressions
Unit value positions and unsupported type arguments	rejected before codegen	SPR-TYPE-UNIT / SPR-TYPE-MISMATCH	no invalid Java emitted	correctness regressions
Match on statically inferred variant case	yes	singleton exhaustiveness; impossible other branches rejected	concrete case instanceof dispatch	correctness regressions
JSON CLI results	—	includes command/status and structured diagnostics	run output carried as programOutput	correctness regressions
sprig test project runner	ordinary .spr files under tests/	compile-fail .expect.toml matches stable error codes using normal project/dependency checking	isolated child JVM per runtime test, 30-second timeout, per-test temp directory, deterministic JSON rows and @std/test.spr process helper	test runner integration suite + five-case dogfood project
Managed Linux/macOS SDK install and upgrade	release ZIP + checksum workflow	managed-install metadata and layout validation	staged installation and atomic current pointer switch; older versions retained	installer, upgrade and installed-SDK dogfood suites
SQLite migrations (@sqlite/migrations.spr)	Sprig package module	validated NNN_description.sql names, sorted ledger and idempotent apply	trusted multi-statement SQL and ledger row share a SQLite batch transaction	migration apply/restart/failure-retry suite
CLI parsing (@cli/cli.spr)	Sprig package module	typed option specs, duplicate/unknown/missing checks	deterministic usage, flags/values/aliases/positionals	CLI library and installed json-select dogfood
Sprig module API (sprig api module.spr|@pkg/module.spr)	resolved checked AST	declaration/field/method/throws/generic metadata; --member Type.member	compiler-owned JSON; never executes code	Sprig API suite
Java-to-Sprig wrapper generator (sprig wrap)	shared JvmMetadata.Support classification; canonical formatting; generated source is checked before writing	plain editable .spr, deterministic, --force overwrite, structured skip report	no runtime reflection or generator dependency; Optional/adapters/throws mappings; unsupported members keep their reason codes	wrap suite
Project API inventory (sprig api .)	project + lockfile validation	source modules plus each dependency's exported modules	no application execution; stale/unexported targets refused	Sprig API suite and installed SDK dogfood
Structured diagnostic metadata	optional relatedHelp and repair fields	machineApplicable false unless semantics-preserving and unambiguous	stable fields unchanged	agent tooling suite
Capability feature guidance	featureGuidance per unsupported feature	alternatives and help topic reflect current compiler only	additive to features booleans	agent tooling and Sprig API suites
Operational explain	whyMatters, confusedWith, causes/fixes/examples, repair, relatedHelp	conservative, compact	same data in text and --json	agent tooling suite
Sprig-written agent tools	examples/agent_tools (api-report, diag-summary, api-diff)	plain Sprig JSON/file/CLI policy	consume saved compiler JSON	agent tools suite
Agent task pack	deterministic fixtures and runner under tests/agent_eval	acceptance is mechanical; no model run claimed	initial states fail, known solutions pass	task-pack gate

Not implemented (honest status): generic type inference, variance, Comparable and user-defined capabilities, inheritance or interfaces, nested/positional patterns, %=, tuples/destructuring, varargs and source array syntax/annotations in interop, wildcard typing or Java generic inference, LSP, publishing/registry, incremental checking, self-hosting. See KNOWN_LIMITATIONS.md for boundaries.