BE-581, BE-589: HashQL: Introduce pass::lower/pass::place pipeline facades and fix cached constructor closure bug

[indietyp]

🌟 What is the purpose of this PR?

This PR introduces two high-level pipeline functions, pass::lower and pass::place, that encapsulate the MIR lowering and execution placement pipelines respectively. Previously, callers had to manually orchestrate individual passes, manage scratch allocator resets, and collect diagnostics themselves. These new functions consolidate that logic into a single call site, making the pipeline easier to use correctly and harder to misuse.

Additionally, this PR fixes a bug in the MIR reifier where a cached constructor reference was emitted as a bare FnPtr on cache hit, while the calling convention requires a fat pointer (closure aggregate). The fix ensures both the first and subsequent uses of a constructor emit a closure(FnPtr, ()) aggregate. This resolves the previously failing access-struct-through-opaque interpreter test, which now passes.

The ReifyContext is also extended with a scratch allocator parameter so that the reifier can use scratch memory for temporary allocations (e.g., the Thunks vector), avoiding unnecessary heap allocations.

🔍 What does this change?

• Introduces pass::lower to run the pre-inline, inline, and post-inline transform passes as a single operation, handling scratch resets and diagnostic collection internally.
• Introduces pass::place to run size estimation and execution analysis as a single operation, returning the ExecutionAnalysisResidual on success.
• Adds LowerConfig as a configuration struct for the lowering pipeline, wrapping InlineConfig.
• Extends ReifyContext with a generic scratch allocator field (S: Allocator) so the reifier can allocate temporary structures (e.g., Thunks::defs) from scratch memory rather than the heap.
• Fixes the constructor caching bug in rvalue.rs where the cache-hit path returned a bare FnPtr instead of a closure aggregate, causing downstream interpreter failures.
• Updates mir_reify in the compiletest suite to return the Scratch allocator alongside the root and bodies, so callers that need scratch memory don't have to create a new one.
• Adds Debug implementations for LinkedGraph, IslandGraph, and ExecutionAnalysisResidual that do not require the allocator type parameter to implement Debug.
• Adds a regression test (ctor-cached-closure) covering the constructor caching fix.
• Updates the access-struct-through-opaque test from run: fail to run: pass now that the underlying bug is resolved.

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

This PR:

• does not modify any publishable blocks or libraries, or modifications do not need publishing

📜 Does this require a change to the docs?

The changes in this PR:

• are internal and do not require a docs change

🕸️ Does this require a change to the Turbo Graph?

The changes in this PR:

• do not affect the execution graph

🛡 What tests cover this?

• New ctor-cached-closure reify UI test covering the constructor caching regression.
• Updated access-struct-through-opaque interpreter UI test, now expected to pass with correct output.
• Existing MIR pass and reify UI tests continue to pass with the refactored pipeline.

❓ How to test this?

1. Run the MIR compiletest suite.
2. Confirm access-struct-through-opaque passes and produces the expected Opaque(Outer { x: A, y: A }) output.
3. Confirm ctor-cached-closure passes and produces the expected MIR with closure(FnPtr, ()) on both constructor uses.

[cursor]

PR Summary

Medium Risk
Changes MIR reification calling convention and centralizes the optimization/placement pipeline; the ctor fix is correctness-critical but covered by new and updated UI tests.

Overview
Adds pass::lower and pass::place in the MIR crate so lowering (pre-inline → inline → post-inline) and execution placement (size estimation → execution analysis) run as single calls with scratch resets and diagnostic handling, instead of each caller wiring passes by hand. The compiletest Pipeline now uses these facades for transform and prepare.

ReifyContext gains a scratch allocator; mir_reify creates it, passes it through reification, and returns it with the bodies so suites can reuse scratch memory. Reifier/thunk maps are parameterized over allocators where needed.

Fixes MIR reification when a type constructor is reused from cache: the cache-hit path now emits a closure(FnPtr, ()) aggregate like the miss path, instead of a bare FnPtr. That fixes interpreter struct projection on nested newtypes (access-struct-through-opaque now passes) and is covered by ctor-cached-closure.

Smaller follow-ons: custom Debug for LinkedGraph, IslandGraph, and ExecutionAnalysisResidual without requiring the allocator to implement Debug; eval_postgres passes heap into EvalContext; assorted #[inline] on hot paths.

^{Reviewed by Cursor Bugbot for commit ce89d48. Bugbot is set up for automated code reviews on this repo. Configure here.}

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[indietyp]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• BE-481: HashQL: Reify null and empty tuple as unit constants #8853
• BE-537: hgraph: REST /hashql endpoint with E2E tests #8827
• BE-592: HashQL: Remove old eval graph path and core value types #8841
• BE-590: hgraph: Refactor entity query handlers into entity/query submodule #8840
• BE-587, BE-588: HashQL: Introduce CodeGenerationContext/CodeExecutionContext split and eval-stage Interner #8839
• BE-581, BE-589: HashQL: Introduce pass::lower/pass::place pipeline facades and fix cached constructor closure bug #8838 👈 (View in Graphite)
• BE-585, BE-591: HashQL: Add MIR interpreter test suite and refactor diagnostic categories #8837
• BE-583, BE-584, BE-586: HashQL: Add HeapPool, improve spans, and propagate Critical severity through diagnostics #8836
• BE-582: HashQL: Change opaque types from invariant to covariant #8835
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[codecov]

Codecov Report

❌ Patch coverage is 16.00000% with 63 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.52%. Comparing base (ee4ae89) to head (ce89d48).

Files with missing lines	Patch %	Lines
libs/@local/hashql/mir/src/pass/mod.rs	0.00%	44 Missing ⚠️
.../hashql/mir/src/pass/execution/island/graph/mod.rs	0.00%	7 Missing ⚠️
libs/@local/hashql/core/src/graph/linked.rs	0.00%	6 Missing ⚠️
libs/@local/hashql/mir/src/pass/execution/mod.rs	0.00%	6 Missing ⚠️

Additional details and impacted files

@@                                   Coverage Diff                                   @@
##           bm/be-585-hashql-split-mir-interpret-diagnostic-api    #8838      +/-   ##
=======================================================================================
+ Coverage                                                59.50%   59.52%   +0.02%     
=======================================================================================
  Files                                                     1347     1347              
  Lines                                                   130804   130990     +186     
  Branches                                                  5879     5883       +4     
=======================================================================================
+ Hits                                                     77838    77978     +140     
- Misses                                                   52063    52105      +42     
- Partials                                                   903      907       +4     

Flag	Coverage Δ
rust.hash-graph-api	2.52% <ø> (ø)
rust.hashql-core	79.77% <0.00%> (+0.18%)	⬆️
rust.hashql-eval	75.20% <ø> (ø)
rust.hashql-mir	88.04% <17.39%> (-0.41%)	⬇️
rust.hashql-syntax-jexpr	94.04% <ø> (ø)

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[Copilot]

Pull request overview

This PR refactors HashQL’s MIR pipeline API by introducing facade functions for lowering and execution placement, while also fixing a MIR reification bug where cached constructor references were emitted with the wrong calling convention representation (thin FnPtr vs closure aggregate fat pointer). It updates the compiletest harness and UI tests to cover the regression and to reflect the corrected interpreter behavior.

Changes:

• Add pass::lower and pass::place pipeline facades (plus LowerConfig) to centralize scratch resets and diagnostic draining.
• Fix constructor caching in MIR reification so both first-use and cache-hit paths emit closure(FnPtr, ()) aggregates.
• Thread scratch allocator support through reification/compiletest utilities and add/adjust UI regression tests.

Reviewed changes

Copilot reviewed 38 out of 38 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
libs/@local/hashql/mir/tests/ui/reify/ctor-cached-closure.stdout	New expected MIR output asserting cached ctor uses emit closure(FnPtr, ()).
libs/@local/hashql/mir/tests/ui/reify/ctor-cached-closure.jsonc	New UI test input for cached-constructor closure aggregate regression.
libs/@local/hashql/mir/tests/ui/interpret/access-struct-through-opaque.stdout	New passing interpreter output snapshot for opaque struct access.
libs/@local/hashql/mir/tests/ui/interpret/access-struct-through-opaque.stderr	Removes prior ICE stderr expectations now that the bug is fixed.
libs/@local/hashql/mir/tests/ui/interpret/access-struct-through-opaque.jsonc	Flips the test directive from run: fail to run: pass.
libs/@local/hashql/mir/tests/ui/interpret/access-struct-through-opaque.aux.mir	Updates auxiliary MIR to reflect closure aggregate emission and downstream simplifications.
libs/@local/hashql/mir/src/reify/transform.rs	Updates Reifier impl generics to support allocator-parametrized context.
libs/@local/hashql/mir/src/reify/terminator.rs	Updates Reifier impl generics to match new allocator parameters.
libs/@local/hashql/mir/src/reify/rvalue.rs	Fixes ctor caching path to always build a closure aggregate (fat pointer).
libs/@local/hashql/mir/src/reify/mod.rs	Extends ReifyContext with scratch allocator and threads allocator generics through reifier state.
libs/@local/hashql/mir/src/reify/current.rs	Adds #[inline] on small From impls.
libs/@local/hashql/mir/src/reify/atom.rs	Updates Reifier impl generics to match new allocator parameters.
libs/@local/hashql/mir/src/pass/transform/ssa_repair/mod.rs	Adds #[inline] on Default impl.
libs/@local/hashql/mir/src/pass/transform/inst_simplify/mod.rs	Adds #[inline] on Default impl.
libs/@local/hashql/mir/src/pass/transform/forward_substitution.rs	Adds #[inline] on Default impl.
libs/@local/hashql/mir/src/pass/transform/dse/mod.rs	Adds #[inline] on Default impl.
libs/@local/hashql/mir/src/pass/transform/copy_propagation/mod.rs	Adds #[inline] on Default impl.
libs/@local/hashql/mir/src/pass/transform/cfg_simplify/mod.rs	Adds #[inline] on Default impl.
libs/@local/hashql/mir/src/pass/transform/canonicalization.rs	Adds #[inline] on Default impl for config.
libs/@local/hashql/mir/src/pass/mod.rs	Introduces LowerConfig, pass::lower, and pass::place facade functions.
libs/@local/hashql/mir/src/pass/execution/traversal/mod.rs	Adds #[inline] on From impl.
libs/@local/hashql/mir/src/pass/execution/terminator_placement/mod.rs	Adds #[inline] on Default impl.
libs/@local/hashql/mir/src/pass/execution/splitting/mod.rs	Adds #[inline] on Default impl.
libs/@local/hashql/mir/src/pass/execution/mod.rs	Adds allocator-agnostic Debug for ExecutionAnalysisResidual.
libs/@local/hashql/mir/src/pass/execution/island/mod.rs	Adds #[inline] and Default-related tweaks.
libs/@local/hashql/mir/src/pass/execution/island/graph/mod.rs	Adds allocator-agnostic Debug for IslandGraph.
libs/@local/hashql/mir/src/pass/execution/cost/mod.rs	Adds #[inline] on From impl.
libs/@local/hashql/mir/src/pass/analysis/data_dependency/mod.rs	Adds #[inline] on Default impl.
libs/@local/hashql/mir/src/interpret/error.rs	Updates diagnostic alias documentation to match Critical default.
libs/@local/hashql/mir/src/body/operand.rs	Adds #[inline] on small From impls.
libs/@local/hashql/eval/src/orchestrator/error.rs	Updates diagnostic alias documentation to match Critical default.
libs/@local/hashql/core/src/graph/linked.rs	Adds allocator-agnostic Debug for LinkedGraph (removes derived Debug).
libs/@local/hashql/compiletest/src/suite/mir_reify.rs	Returns Scratch from mir_reify and passes scratch into ReifyContext.
libs/@local/hashql/compiletest/src/suite/mir_pass_transform_pre_inline.rs	Updates for new mir_reify return shape.
libs/@local/hashql/compiletest/src/suite/mir_pass_transform_cfg_simplify.rs	Reuses Scratch returned by mir_reify instead of creating a new one.
libs/@local/hashql/compiletest/src/suite/mir_pass_analysis_data_dependency.rs	Updates for new mir_reify return shape.
libs/@local/hashql/compiletest/src/suite/eval_postgres.rs	Minor fix to use heap consistently when passing allocator to eval context.
libs/@local/hashql/compiletest/src/pipeline.rs	Switches orchestration to use pass::lower / pass::place facades and threads scratch into reify.

---

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[codspeed-hq]

Merging this PR will not alter performance

⚡ 2 improved benchmarks
❌ 3 regressed benchmarks
✅ 75 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	linear	6.8 µs	7.8 µs	-12.67%
❌	diamond	10.9 µs	12.3 µs	-11.76%
❌	complex	16.2 µs	18.2 µs	-10.6%
⚡	bit_matrix/dense/iter_row[64]	170 ns	140.8 ns	+20.71%
⚡	bit_matrix/dense/iter_row[200]	215 ns	185.8 ns	+15.7%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing bm/be-581-hashql-cached-constructor-produces-bare-fnptr-instead-of (ce89d48) with bm/be-585-hashql-split-mir-interpret-diagnostic-api (ee4ae89)}

[Copilot]

Pull request overview

Copilot reviewed 36 out of 36 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

libs/@local/hashql/compiletest/src/suite/mir_pass_transform_pre_inline.rs:175

• This suite ignores the Scratch returned by mir_reify and then allocates a new Scratch for PreInline. Since mir_reify now returns a resettable scratch allocator specifically to avoid extra scratch construction, this is doing redundant allocation/work here.

    let (root, mut bodies, _) = mir_reify(heap, expr, interner, environment, diagnostics)?;

    render.render(
        &mut RenderContext {
            heap,

[Copilot]

Pull request overview

Copilot reviewed 36 out of 36 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 36 out of 36 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

libs/@local/hashql/compiletest/src/pipeline.rs:191

• ReifyContext now uses scratch for temporary allocations during reify::from_hir (e.g. Thunks::defs). In this staged pipeline, Pipeline::lower doesn’t reset self.scratch after reification, so repeated calls to lower() without subsequently calling transform()/prepare() can cause scratch memory to grow unnecessarily.

Resetting the scratch allocator immediately after from_hir keeps the stage self-contained and matches the intent of scratch allocations being temporary.

        let entry = tri!(hashql_mir::reify::from_hir(node, &mut reify_context));