Aether 30.0 — comprehensions grow up: pattern generators, let-qualifiers & range literals

[kkd16]

Improves the existing aether-lang-c3d8 project (a from-scratch ML-family language toolchain that runs entirely in the browser). This is a single-project PR — every changed file lives under projects/aether-lang-c3d8/.

What changed

Aether had list comprehensions, but only the thinnest slice: a generator bound a plain name and a qualifier was a boolean guard — and there were no range literals at all. 30.0 closes that gap the way the language is proud of — as pure front-end sugar, desugared in the parser into the existing core (concat/map/if/let/match). The type checker, the optimizing middle-end and all three backends (bytecode VM · JavaScript · WebAssembly) never see a comprehension or a range, so the release is strictly additive — an old program takes the exact pre-30.0 path.

• Range literals — [a .. b] (inclusive) and [a, s .. b] (stepped, ascending or descending; a zero step terminates as []). Backed by two new prelude functions enumFromTo / enumFromThenTo, written in Aether itself. A new .. lexer token uses longest-match, so 1..10 splits cleanly while r.field field access and floats like 1.5 are untouched.
• Pattern generators — a generator's binder can be any pattern: (a, b) <- ps, Som x <- opts, h :: _ <- rows. An irrefutable binder keeps the clean bare-map desugaring; any other pattern maps a match … | _ -> [] whose wildcard arm drops the non-matching elements (the list-monad fail).
• let-qualifiers — [ e | x <- xs, let y = f x, y > 0 ], scoped over the qualifiers to their right.

Verification

• New 200-program differential fuzzer (comprehensionFuzz.ts): each random comprehension — nested generators, inclusive/stepped ranges, guards, let-qualifiers and tuple/Som/cons pattern generators — is proved sound two ways: the compiled program's VM result equals an independent TypeScript reference (the comprehension re-evaluated by nested iteration, never touching the desugaring) and that value re-appears on the JavaScript backend (VM ≡ JS). Holds at 200/200, and across 7 seeds × 300 runs (2,100 programs) with zero failures. Stable badge on the Tests page.
• New 19-case in-app comprehensions battery (VM + JS ≡ VM): suite grows 147 → 166, all green; the headless harness also re-runs each on WASM (150/150).
• No regression: existing in-app suite 166/166, WASM ≡ VM 150/150, semantics 19/19, and the optimizer / SpecConstr / SROA fuzzers all still pass.
• Full CI gate (scripts/verify-project.mjs: scope + conformance + lint + tsc + build) is green locally.

Four new gallery examples: a comprehensions tour, two-line quicksort, a prime sieve, and a turtle "comprehension garden" driven by a stepped range. JOURNAL.md carries the plan and a session-log entry.

🤖 Generated with Claude Code

https://claude.ai/code/session_01BSXUJbL86qsEW8zJqvUppq

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✅ Scope + lint + build passed.