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P-003-lifetime-visualization.md

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P-003 — Lifetime visualization (RustOwl-style)

  • Status: draft (horizon)
  • Depends on: spec/OwnCore.md, spec/Lifetimes.md

Motivation

The most compelling existing ownership tools for Rust are visual: RustOwl (in-editor ownership/loan highlighting), RustViz (timeline of ownership and borrow events), BORIS (borrow visualizer). For .NET there is no equivalent. A "who holds whom, who must release, and why this object doesn't die" picture is exactly the killer demo for the business-lifetime story — far more persuasive than a code listing.

Scope

  • A lifetime graph per function: owners, their loans (shared/mut) as spans, and subscribe edges, with the region-escape (OWN014) path highlighted ("expected: Window — actual: App — path: bus → self").
  • A timeline per owned resource: acquire → borrows → move/release/escape.
  • Output as text/ASCII first (cheap, CI-friendly), then SVG/DOT; IDE integration much later.

Non-goals

A full IDE extension or LSP server in v0. Runtime heap-graph visualization (that is a separate runtime-diagnostics track). Anything requiring a GUI toolkit.

Sketch

All the data already exists: the CFG carries instructions with symbols, states, and loans; the lifetime analysis carries regions and subscribe edges. A visualizer is a consumer of these facts — no new analysis. Start by emitting DOT from the CFG + lifetime facts.

CFG + lifetime facts  --[graph/timeline emitter]-->  *.dot / ASCII timeline

Open questions

  1. ASCII-only (CI-renderable, in-repo) vs SVG/DOT (needs Graphviz) for v0.
  2. Per-function graph vs whole-module lifetime graph.
  3. Does this belong before or after P-001? (A visualization of hand-written .own is less compelling than one of real extracted C#, so likely after.)