Fix QRY037: CTE chains with captured inner and outer parameters (#305)

[DJGosnell]

Summary

• Closes QRY037: CTE chain with captured inner and outer parameters fails to build — outer carrier param field never assigned (valid SQL) #305
• Fixes the QRY037 build failure for CTE chains that combine a captured parameter inside the With<T>(...) lambda with a captured parameter in an outer clause (Where after FromCte<T>()).

Reason for Change

The inner+outer parameterized CTE shape — valid SQL on all four dialects — was unbuildable: the generated carrier declared the outer parameter's field (P1) but no clause interceptor assigned it, tripping the generator's QRY037 self-check.

Root cause (differs from the issue's suspicion): ChainAnalyzer's parameter rebasing and SqlAssembler's placeholder rebasing are both correct. The defect was in AssembledPlan.BuildSiteParamsMap / BuildParamConditionalMap: both walk clause entries accumulating the global parameter offset each emitter uses to route __c.P{n} assignments, but a CteDefinition entry (whose Clause is null — it is not clause-bearing) advanced the offset by 0 despite owning InnerParameters.Count slots in the chain's parameter list. Every param-bearing clause after a param-bearing With() therefore resolved its carrier P-fields short by the inner-param count: the outer Where wrote P0 (the CTE's slot) and P1 was never assigned. With zero inner params the skew is zero — exactly why inner-only, two-inner, and outer-only chains all worked.

Fix: advance the offset by the matching CteDef.InnerParameters.Count, matched by CTE short name via CteNameHelpers.ExtractShortName (the same first-match rule as TransitionBodyEmitter.EmitCteDefinition; duplicate names are already QRY082 errors, failed-analysis CTEs already QRY080). All emitter paths funnel through this one map, so the single fix point covers every consumer.

Impact

• Inner+outer parameterized CTE chains (single- and multi-CTE) now build and bind correctly on all four dialects.
• No behavior change for any previously-buildable chain: the new branch fires only for CteDefinition entries, and every shape whose offsets would differ was a hard QRY037 build error before.
• Also closes the MySQL positional ? binding misalignment in DistinctOrderBy wrap (and audit other surfaces) #303 audit gap: the inner+outer combination was the one parameterized-CTE shape whose MySQL inner-before-outer positional bind order could not be execution-verified.

Plan items implemented as specified

1. AssembledPlan offset-walk fix + generation guard (CteInnerAndOuterCapturedParams_NoQRY037_AssignsBothPFields) — verified to fail without the fix.
2. Cross-dialect SQL + execution test (Cte_FromCte_InnerAndOuterCapturedParams) — exact WITH rendering and row verification on all four backends.
3. MySQL bind-order execution pin (ParameterizedCteInnerAndOuterParams_OnMySQL_BindsInnerBeforeOuter), exactly as specified in QRY037: CTE chain with captured inner and outer parameters fails to build — outer carrier param field never assigned (valid SQL) #305, plus retirement of the QRY037 caveats in the sibling ParameterizedCte* pins.

Deviations from plan implemented

• The planned "inline branch" in both walks was refined into a shared GetCteInnerParamCount helper called from an inline branch in each walk (review F1, dismissed as benign — behavior identical, duplication reduced).

Gaps in original plan implemented

Review findings addressed post-implementation:

• F2 (M): ConditionalOuterClause_AfterParameterizedCte_MySQL_NoQRY048 — the only shape that observes the BuildParamConditionalMap half of the fix (a conditional outer clause after a parameterized CTE on MySQL, newly reachable). Verified to fail when only that branch is removed.
• F3 (L): Cte_TwoChainedWiths_CapturedParams_AndOuterCapturedParam — cumulative offset accumulation across two param-bearing CTEs plus an outer captured param, on all four dialects.
• F4 (L): generation guard tightened to exact-count P0/P1 assertions (the pre-fix stomp signature was two P0 assignments and zero P1).

Deferred (review F5, class C, pending confirmation): consolidating the CteDef-by-short-name first-match lookup (now present in AssembledPlan, CarrierAnalyzer, and twice in TransitionBodyEmitter) into a single shared helper — a cleanup, not a defect.

Performance Considerations

The added lookup is a short linear scan over Plan.CteDefinitions (almost always 0–3 entries) inside two already-cached map builders — no measurable generator cost.

Breaking Changes

• Consumer-facing: none (previously-failing shapes now build; no existing SQL or binding changes — manifest goldens show additions only).
• Internal: none (private helpers only; no signature changes).