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Backlog

Open compiler work that is not derivable from the code or the issue tracker. Keep it short: when an item lands, delete it here and let the commit and PR carry the history. Durable lessons go under Notes; finished-work narrative does not.

The Lua backend performance items live in LUA_HOT_PATH_SPEC.md, which carries their root causes, required changes and acceptance criteria. Task 2 of that spec is done (#1284); Tasks 1, 3, 4 and 5 are open.

Open

  • A dead dispatch slot survives for overloads inside a specialised class. Two overloads of one source method share a declared name, so a specialised class holding only overloads still composes one shared slot and binds it to whichever is reached first. Nothing calls it. A fix needs an identity which treats a chain's differing type variables as the same signature while still separating real parameter differences; the dispatch group key cannot be used because it embeds each class's type variable (void|T192,real against void|T636,real). Worth doing only if this stops being dead weight.

  • CompilerFuzzTestsSC writes one fixed output filename for every generated program. All programs go to test-output/CompilerFuzzTestsSC_assertCompilesForBothBackends_*.j, so concurrent writers tear the file and pjass reports a truncated keyword. Seen once in a full run on 2026-09-03, passes when the class runs alone. Give each generated program its own output name.

Blocked on a decision

  • Eliminating the remaining castTo int. The motivating case is timer data attachment (ClosureTimers.wurst) and the containers behind it: Table, HashList, HashSet, HashMap. None can adopt type class bounds as things stand, because an instance is declared one type at a time and these accept any type. It needs a way to give an instance for a whole family, every class type or every handle type, which is a language design question: syntax, where such an instance may be declared under the orphan rule, and whether a specific instance beats a family one. Do not start this autonomously.

Notes

  • % is real modulo in Wurst; mod is integer modulo. int % 8 types as real. div and mod return the left operand's type, so real r = 7 div 2 compiles and is meant to (ExpressionTests.integerDivisionOfLiteralsIsStillAssignableToReal).
  • Emitted Lua must be byte-identical for identical input (AGENTS.md §8), and emitted Jass can be diffed across runs too. LuaTranslationTests.luaOutputIsDeterministicForGenericOverrideSlots failed once on Windows CI and never again in 250 local compiles; the test now writes both scripts and names the first differing lines, so the next occurrence will say what differed. Do not weaken it.
  • A name that looks redundant is usually carrying a distinction. The mangled method name separates overloads; leftType on div keeps a literal assignable to a real. Check what a name distinguishes before replacing it with a tidier one.
  • The suite is the specification. Before changing what the type checker accepts, grep the tests for the shape being rejected.
  • A test that hangs looks exactly like a test that is slow. If the suite stops making progress, take a thread dump of the forked worker (jstack <pid>) before killing it.
  • Method names are not what the frontend called them. LuaDispatchPreparation.normalizeMethodNames renames a whole dispatch group to one name, records the slot segment on ImTranslator, and only then does the backend run. A question about which Lua slot something lands in is a question about that pass, not about LuaTranslator.
  • Tests run five Jass configurations plus the interpreter, then the Lua target separately. testAssertOkLines(true, ...) covers both the pre-transform interpreter and full monomorphisation.
  • @Test functions are interpreter unit tests by design; StdLibOwnTests and grill test run them there. The only Lua-target execution the suite has is test().testLua(true).executeProg(), which runs the emitted script in a real Lua 5.3 against the shim in src/test/resources/luaruntime/. Its reach is bounded by how much of the roughly one thousand natives the shim models, so those tests stay small and targeted. There is no Wurst-level end-to-end feature; correctness in a real map on the Lua target is asserted in the agent workflow.
  • Test forks: eight forks won on eight cores (7m03s wall against 13m11s serial) even though each test runs 2.6 times slower there. Wall time cannot go below the slowest class, ExportToWurstTest at 108s, until it is split.
  • The stdlib copy under de.peeeq.wurstscript/temp/WurstStdlib2 is a fetched artefact for tests. Real stdlib changes belong in the WurstStdlib2 repo.
  • WURST_LANGUAGE.md ships as a compiler resource at de.peeeq.wurstscript/src/main/resources/agent-docs/WURST_LANGUAGE.md, not at the repository root. Keep it and CHANGELOG.md current in the PR that changes the behaviour.