[Rust] Add code-graph extractor

[Yashasvi2229]

Target branch: code-graph-preview

Goal

Add a Rust extractor against the frozen LanguageExtractor interface. The initial implementation should model common modules and type declarations while treating macro-expanded behavior conservatively.

Scope

• Detect .rs files as rust.
• Vendor and register a compatible Tree-sitter Rust WASM grammar.
• Emit a file node and containment tree.
• Extract functions, structs, enums and members, traits, implementations, methods, modules, constants, and static variables.
• Capture signatures, visibility, documentation comments, return types, and generic parameters when explicit.
• Emit use/module imports, calls, containment, trait implementation, type, and instantiation references where syntax is explicit.
• Leave cross-file and module targets unresolved through targetName.

Required changes

• Add src/graph/extraction/languages/rust.ts.
• Register the extractor in src/graph/extraction/languages/index.ts.
• Register .rs and the grammar filename in src/graph/extraction/grammars.ts.
• Add the grammar WASM under src/graph/wasm/ and document its source, version, and license.
• Add a representative Rust fixture and focused extractor tests.

Acceptance criteria

• The extractor implements the frozen LanguageExtractor interface without changing it.
• Extraction is pure, deterministic, and limited to one file.
• Tests cover modules, functions, structs, enums, traits, impl methods, qualified names, containment, imports, calls, and explicit trait implementations.
• Macro invocations and unsupported constructs degrade conservatively without invented edges.
• Cross-file references remain unresolved for the engine to bind.
• npm run typecheck, npm test, and npm run build pass.
• The packed build contains the Rust grammar WASM.

Out of scope

• Macro expansion or procedural macro execution.
• Cargo metadata execution or dependency downloading.
• Type inference and borrow-checker semantics.
• Changes to identity, reconciliation, schema, or grounding semantics.

Contributor references

• Extending the code graph
• src/graph/extraction/languages/typescript.ts
• src/graph/__tests__/extractor.test.ts

Contributor workflow

git switch code-graph-preview
git pull
git switch -c feat/rust-code-graph-extractor

Open the pull request with base branch code-graph-preview.

[abhinav-phi]

Hi @Yashasvi2229,

I'd like to work on this issue. If it's still available, could you please assign it to me?

Thanks!

[Yashasvi2229]

Hi @abhinav-phi , yes it's available, assigned it to you. Good to go!