All 10 diagnostics in this file are the `strictNullChecks: false` narrowing
limitation: a boolean-literal discriminant narrows the positive branch but
leaves the negative one as the full union, so `if (!resolved.ok)` and the code
after `if (outcome.success)` could not see `status`/`error`.
Three unions, all module-private and untouched by any test, so per the rule
recorded on #8499 these are retagged rather than fixed with predicates —
predicates are for exported unions whose shape callers depend on:
resolveDesignerWebRequest ok: true|false -> state: "resolved"|"invalid"
DesignerWebStepResult done + success -> state: "pending"|"ready"|"failed"
The step union collapsed two booleans into one discriminant; `done`/`success`
encoded three states across two flags, which is also why the pending arm had no
`success` property for `outcome.success` to read.
Also narrowed runDesignerWebPollLoop's declared return from
`DesignerWebStepResult | {…504…}` to a new DesignerWebOutcome (ready | failed).
The loop returns a step only after confirming it is terminal, and otherwise
synthesizes a 504 — it can never return a pending step, and the old signature
claiming it could is what made `.success` unreadable on the union at all.
280 -> 270, zero new, on a line-number-agnostic diff of the full tsc error set.
Tests: unlike the previous slices this rewrote real control flow (three
conditionals), so the existing suite is doing actual work here —
microsoft-designer-web-6672.test.ts drives the handler end-to-end through 400,
401, immediate-ready, poll-then-ready, non-OK upstream and 504-timeout, i.e.
every arm but one. The "empty" arm (unrecognized 200 body -> terminal 502) was
tested only at the parser level, never through the handler, so the 502 itself
was unasserted. Added designer-web-empty-response-502.test.ts (2 tests) pinning
that it is terminal (exactly one fetch, no polling) and distinct from the 504
deadline path. Both suites pass against the parent commit too — the tests are
black-box through the exported handler, so they are agnostic to the discriminant
rename and prove the retag is behavior-preserving. 61/61 across the 3 suites.
Co-authored-by: backryun <busan011@ormbiz.co.kr>
