BE-614: HashQL: Generate synthetic closure bodies for intrinsics used as first-class values

[indietyp]

🌟 What is the purpose of this PR?

Allows intrinsics to be used in value position (passed as arguments, bound to variables) by generating synthetic MIR wrapper bodies during reification. Previously, intrinsics like <= could only appear at call sites where specialization rewrites them. Now they can flow through higher-order functions:

let apply = fn (a, b, f) = (f a b) in
(apply 2 3 <=)

🔍 What does this change?

Synthetic body generation:

• Synthetics struct in CrossCompileState manages creation and caching of wrapper bodies
• SyntheticBuilder generates MIR bodies with fat closure ABI (unit env as first parameter)
• T! macro for matching qualified paths against ConstantSymbol arrays: &T![::core::cmp::gt] in slice patterns, sym::path::core::cmp::gt::CONST for the name
• Dispatch table covers all first-classable intrinsics (comparison, boolean, arithmetic, bitwise) with local binary!/unary! macros deriving path and name from the same segments

Thin-call specialization:

• rvalue_call_thin_specialize recognizes Call(Thin, Qualified(intrinsic), []) (the administrative thunk-force from the thunking phase) and produces the closure aggregate directly, skipping thunk body generation
• Type unwrapping handles the thunking phase's () -> ClosureType wrapper to extract the actual signature

Intrinsic classification:

• First-classable: comparison (gt, lt, gte, lte, eq, ne), boolean (and, or, not), arithmetic (add, sub), bitwise (and, or, not)
• Unconstructible MIR ops (BinOp variants with ! payload): mul, div, rem, mod, pow, xor, shl, shr
• No MIR ops: sqrt, cbrt, root
• Not first-classable (syntactic forms): graph::head::entities, graph::body::filter, graph::tail::collect produce a specific user-facing diagnostic

Diagnostics:

• intrinsic_not_first_class: user-facing error for graph intrinsics in value position
• synthetic_binary_arity_mismatch / synthetic_unary_arity_mismatch: ICE for monomorphized type invariant violations

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

⚠️ Known issues

• Bare intrinsic at module root ("<=" as the entire program) is not supported. The thunking phase does not wrap the root body when it is a variable, so it never reaches the synthetic machinery. Tracked with a run: skip test.

🐾 Next steps

• Untyped property access (the original motivation for this work)
• Module system support for root-level qualified paths (BE-67)

🛡 What tests cover this?

Compiletests (8 new):

• reify/synthetic-intrinsic-value: basic synthetic body generation and thin-call specialization
• reify/synthetic-intrinsic-reused: same intrinsic used twice shares one body (caching)
• reify/synthetic-intrinsic-multiple: different intrinsics get separate bodies
• reify/synthetic-graph-not-first-class: graph intrinsic in value position produces error
• reify/synthetic-intrinsic-bare: bare intrinsic at root (run: skip)
• interpret/synthetic-intrinsic-value: end-to-end correctness (evaluates to true)
• post_inline/synthetic-intrinsic-hof: full optimization cascade with constants (collapses to return true)
• post_inline/synthetic-intrinsic-hof-dynamic: HOF with dynamic inputs collapses to bare x <= y

❓ How to test this?

cargo run --package hashql-compiletest -- run --filter "test(synthetic)"

📹 Demo

The post_inline/synthetic-intrinsic-hof-dynamic test shows the full cascade. A higher-order function receiving <= as a value with dynamic inputs:

Initial:  construct closure for <=, pass to apply, call through fat pointer
Final:    %0 = input LOAD x
          %1 = input LOAD y
          %2 = %0 <= %1
          return %2

All indirection eliminated. Indistinguishable from writing ["<=", x, y] directly.

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[cursor]

PR Summary

Medium Risk
Touches core MIR reification and closure calling conventions for many intrinsics; behavior changes how qualified names compile but is guarded by extensive tests and leaves graph/syntactic forms explicitly rejected.

Overview
Enables intrinsics in value position (e.g. passing <= into a higher-order function) by generating cached synthetic MIR bodies during reification instead of treating qualified paths as unsupported modules.

Reification adds a Synthetics registry that maps known ::core::… paths to fat-closure bodies (cmp, bool, math add/sub, bits) and optional thunk wrappers; qualified operands resolve through this path to FnPtr thunks. Thin calls with no args on a qualified intrinsic are specialized to a closure aggregate directly, avoiding extra thunk indirection. Graph intrinsics (head::entities, body::filter, tail::collect) get a clear not first-class error; unknown paths still fall back to the existing external-module behavior.

Small supporting changes: From<ConstantSymbol> for Symbol, lhs/rhs symbols for synthetic locals, scratch.reset() after reify in the graph compile pipeline, and new reify diagnostics (arity ICEs, intrinsic_not_first_class). Compiletests cover caching, multiple intrinsics, HOF + optimization, interpretation, and graph errors.

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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-614: HashQL: Generate synthetic closure bodies for intrinsics used as first-class values #8895 👈 (View in Graphite)
• BE-615: HashQL: Introduce the concept of synthetic closures in the MIR #8894
• BE-607: HashQL: Refactor ModuleRegistry into builder/immutable split with allocator-generic stdlib construction #8887
• BE-538: HashQL: Permission system integration #8882
• BE-71: HashQL: Consolidate AST special-form expansion stages into one #8870
• BE-481: HashQL: Reify null and empty tuple as unit constants #8853
• BE-537, 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
• 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

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

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##             bm/be-615-hashql-introduce-synthetic-closures-and-trivial-closure    #8895   +/-   ##
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[codspeed-hq]

Merging this PR will improve performance by 38.94%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 3 improved benchmarks
❌ 1 regressed benchmark
✅ 52 untouched benchmarks
⏩ 24 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	pattern_match_constant	150.8 ns	180 ns	-16.2%
⚡	runtime	58.9 ns	29.7 ns	+98.13%
⚡	constant	58.9 ns	29.7 ns	+98.13%
⚡	type_checker_simulation	497.5 ns	439.2 ns	+13.28%

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-614-hashql-generate-synthetic-mir-bodies-for-intrinsics-in-value (7e692af) with bm/be-615-hashql-introduce-synthetic-closures-and-trivial-closure (944c357)}

Footnotes

1. 24 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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