@ctxo/lang-go

Go language plugin for Ctxo. Ships two analysis tiers selected at runtime:

| Tier | Engine | Activated when | |---|---|---| | Full | ctxo-go-analyzer binary (Go stdlib + x/tools SSA + CHA) | Go ≥ 1.22 on PATH and the bundled analyzer source builds successfully | | Syntax | tree-sitter-go | Go toolchain absent; binary build fails; or analyzer cannot locate go.mod / go.work |

The composite picks at initialize() and forwards every extractSymbols / extractEdges call to the active layer. extractComplexity is always served by tree-sitter — the analyzer intentionally emits empty complexity arrays so the two layers compose cleanly.

What full-tier adds over tree-sitter

• Cross-package symbol-id resolution. pkg/a calling pkg/b.Do() produces an edge whose target is pkg/b/file.go::Do::function, not a synthetic placeholder. Every get_blast_radius, find_importers, and get_logic_slice query that crosses a package boundary now returns real results.
• implements edges. Go's structural typing means interface satisfaction is invisible to a syntactic parser; the analyzer pairs every concrete type against every interface and emits an edge when types.Implements(T, I) or types.Implements(*T, I) is true.
• extends edges for embedding. Anonymous fields (struct embedding) and embedded interface members produce explicit hierarchy edges so get_class_hierarchy works on Go.
• Generics with typeArgs metadata. List[int] and List[string] both produce a uses edge to the unconstructed List symbol; the type arguments are preserved on edge metadata for future query precision. See ADR-013 §4 Q4.
• Dead-code detection via CHA reachability. Unreachable functions and methods are emitted in a single dead record. A reflect-safe pass marks methods of any type touched by reflect.TypeOf / reflect.ValueOf / reflect.New or json.Marshal / Unmarshal / NewDecoder / NewEncoder as live to prevent false positives.

How the binary is built

On first use, GoAnalyzerAdapter.initialize() hashes the analyzer source + go version and runs go build -trimpath -o ~/.cache/ctxo/lang-go-analyzer/<hash-goVersion>/ctxo-go-analyzer[.exe]. Subsequent runs reuse the cached binary. No build happens during npm install to keep package installs sandbox-safe (ADR-013 §4 Q2).

If go is not on PATH, build fails, or no go.mod/go.work is found, the plugin transparently falls back to tree-sitter and ctxo doctor surfaces the missing toolchain.

Limitations (v0.8.0-alpha.0)

• Library mode is approximate. Without a main.main to anchor RTA-style reachability, every exported function/method becomes a root. This over-approximates liveness — fewer false dead-code reports, but symbols that nothing actually consumes still look live.
• Generic types skipped from implements / extends enumeration. Pairing generic named types is unstable in current go/types; we revisit when the upstream API stabilizes.
• Closures and reflective construction. Functions passed to stdlib callbacks (sort.Slice(..., func(i,j) bool {...})) follow a CHA edge so they ARE reachable; constructed-via-reflection types are kept alive only for the explicit reflect/json call sites listed above.

Architecture and rationale

See ADR-013 for the full decision record (alternative options considered, library choices, open question resolutions). Mirrors the C# pattern from ADR-007.