Second iteration of the kernel-extension-mechanics milestone. The
plan ships the `new` Form-A keyword + Term::New AST variant + NewArg
enum + checker elaboration + two diagnostics, plus the schema-drift
pin and the data-model.md / form_a.md anchor additions.
Decomposition:
- Task 1 (large mechanical): AST variant declaration + workspace-wide
compile-forced arms across 24 files (44+ exhaustive Term-match
sites). Six arm patterns inlined; per-site table assigns one
pattern per site. Includes the prep.1 pre-pass partner — the
`qualify_workspace_term` arm that rewrites bare Term::New.type_name
to qualified form, mirroring the existing Term::Ctor arm. Synth
gets a Pattern-E stub here; Task 3 replaces with real logic.
- Task 2: Form-A lex/parse/print + round-trip fixture. New
`parse_new` method with Type-vs-Term arg disambiguation by
syntactic form (head keyword = Type-production heads
`con`/`fn-type`/`borrow`/`own` → NewArg::Type; else NewArg::Value).
- Task 3: Checker synth real-logic + 2 new CheckError variants
(NewTypeNotConstructible, NewArgKindMismatch) + 3 RED-first
in-source tests covering the spec's worked example, the missing-
`new`-def case, and the kind-mismatch case.
- Task 4: Schema-drift pin (term_new_round_trips +
term_new_type_arg_round_trips) + spec_drift exemplar + form_a.md
keyword cheatsheet + design/contracts/0002-data-model.md JSON-tag
block.
Spec is already correct on prep.2 scope; the recon surfaced one
design decision the plan resolves inline: NewArg uses
`#[serde(tag = "kind", content = "value", rename_all = "lowercase")]`
to land the spec's exact JSON byte shape. Codegen remains explicitly
out of scope per the milestone spec; Task 1's codegen sites get
Pattern-D error-arms ("Term::New requires desugar first; codegen
support lands in the raw-buf milestone").
Forward-reference: Task 1's Pattern-C arm in `qualify_workspace_term`
extends prep.1's workspace-wide normalisation pre-pass — Term::New
joins Term::Ctor and Type::Con as a type_name-bearing site that
gets bare→qualified normalised before the checker sees it.
Brummel
70e6fcd5c0