move ResourceTracker from heap to vm

[davidhewitt]

This PR moves the resource tracker from the Heap to the HeapReader, and makes it & shared. This should be a step towards enabling StringBuilder to access the tracker inside py_repr_fmt (which needs the vm).

---

Summary by cubic

Moved ResourceTracker from Heap to VM and threaded a shared tracker through HeapReader. This reduces borrow conflicts, enables StringBuilder in py_repr_fmt, and clarifies when resource-sensitive operations are allowed. Also reworked external function identity and added captured comprehension support.

• Refactors

  • Heap is no longer generic; HeapReader<'h> carries the branded heap + shared tracker.
  • ContainsHeap now provides heap() and dec_ref(..) (removed heap_mut()); drop sites use dec_ref.
  • Allocation/refcount paths take &HeapReader (e.g., allocate_string, allocate_tuple); read-only paths use &Heap.
  • External functions are heap-backed ExtFunction values cached by name; Value::ExtFunction(StringId) removed. LoadGlobalCallName now pushes an external function for undefined names.
  • Added Opcode::BuildCell; parser/compiler track captured comprehension slots and VM allocates undefined cells for inlined comprehensions so closures capture targets correctly. Serialization preserves captured cells.
  • REPL/executor store heap and ResourceTracker separately; snapshots expose snapshot.tracker; VM uses heap.tracker()/tracker_mut() where needed.
  • Added indexmap for deterministic capture/name handling; compiler/prepare updated.

• Migration

  • Implement ContainsHeap with fn heap(&self) -> &Heap and fn dec_ref(&mut self, HeapId).
  • Change params from &Heap/&mut Heap to &HeapReader<'_> where allocating, refcounting, or tracking resources.
  • Replace inline external-function handling with heap-allocated ExtFunction (Value::Ref to HeapData::ExtFunction).
  • Construct heaps with Heap::new(0) and pass a tracker from the VM; update REPL/executor/snapshot code to access tracker directly.

^{Written for commit faddf6c. Summary will update on new commits.}

[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 16 skipped benchmarks¹

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_{Comparing dh/hoist-globals-tracker (f7f9d9b) with main (4aa972b)}

Footnotes

1. 16 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. ↩

[github-actions]

Codecov Results 📊

✅ Patch coverage is 100.00%. Project has 8954 uncovered lines.
✅ Project coverage is 82.34%. Comparing base (base) to head (head).

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    82.34%    82.34%        —%
==========================================
  Files          218       218         —
  Lines        50709     50709         —
  Branches    107202    107202         —
==========================================
+ Hits         41755     41755         —
- Misses        8954      8954         —
- Partials      3254      3254         —

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Generated by Codecov Action

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[cubic-dev-ai]

1 issue found across 55 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="crates/monty/src/types/tuple.rs">

<violation number="1" location="crates/monty/src/types/tuple.rs:35">
P3: Rustdoc now has an unresolved `Heap::check_time` link in this module, so documentation builds can emit a warning or fail under `-D warnings`. Updating that link to `HeapReader::check_time` keeps the API documentation valid after this import change.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P3: Rustdoc now has an unresolved Heap::check_time link in this module, so documentation builds can emit a warning or fail under -D warnings. Updating that link to HeapReader::check_time keeps the API documentation valid after this import change.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At crates/monty/src/types/tuple.rs, line 35:

<comment>Rustdoc now has an unresolved `Heap::check_time` link in this module, so documentation builds can emit a warning or fail under `-D warnings`. Updating that link to `HeapReader::check_time` keeps the API documentation valid after this import change.</comment>

<file context>
@@ -32,7 +32,7 @@ use crate::{
     exception_private::{ExcType, RunResult},
     hash::HashValue,
-    heap::{DropWithContext, Heap, HeapData, HeapId, HeapItem, HeapRead, HeapReadOutput},
+    heap::{DropWithContext, HeapData, HeapId, HeapItem, HeapRead, HeapReadOutput, HeapReader},
     intern::StaticStrings,
     resource::{ResourceError, ResourceTracker},
</file context>

[macroscopeapp]

Approvability

Verdict: Needs human review

Unable to check for correctness in faddf6c. This PR introduces significant runtime behavior changes beyond the title's scope: new comprehension closure capture semantics with a new opcode (BuildCell), restructured external function identity (now heap-based with weak caching), and ResourceTracker architectural changes. These core VM semantic changes warrant careful review.

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[macroscopeapp]

Macroscope skipped reviewing this pull request. Per-review cost limit exceeded (workspace setting).

This review would cost an estimated $9.97, which exceeds your per-review limit of $5.00.

The top 3 files driving up this estimate:

File	Size	Estimate
crates/monty/src/heap.rs	37.89KB	$1.89
crates/monty/src/prepare.rs	21.65KB	$1.08
crates/monty/src/bytecode/compiler.rs	19.56KB	$0.98

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