Use when working on C/C++ ABI interop — passing values/structs to/from external C/C++ DLLs (import[cpp-dll]/import[cpp-lib]), C ABI type annotations (int8/int32/float32/...), InstanceData raw-block layout, zero-copy vs. shadow-conversion struct passing, or write-back for mutable pointer arguments. This is a design spec + implementation-phase log (P0–P7, all marked done) referenced from many src/ comments.
Use when debugging or testing the VS Code extension's type-inference/analysis code (inlay hints, hover, diagnostics) via the standalone debug runner (node run_debug.js), without launching VS Code itself. Also use after changing analysis.ts, type_infer.ts, or native_module.ts to know which npm script to recompile. For adding/modifying an extension feature itself or packaging the VSIX, use the vscode-extension-dev skill instead.
Use when adding or modifying a feature of the Arrow VS Code extension itself (vscode-extension/) — syntax highlighting, hover, inlay hints, completions, go-to-definition, diagnostics, commands/keybindings, settings, or the built-in function stub. Covers the source-file map, build commands, and the mandatory VSIX packaging step. For just exercising existing analysis code against a .ar file, use the vscode-debug-runner skill instead.
Use before modifying the lexer, parser, static type checker, interpreter, or VS Code extension — gives a compact map of what each subsystem already supports (keywords, control flow, type-guard narrowing, value types, closures, exceptions, async, native modules) and which dedicated skill to open for the full implementation reference.
Use when you need to know where a file, module, or subsystem lives in the Arrow repository (Rust src/, Python impl_python/, examples/, vscode-extension/), or what a given file is responsible for. Read this before navigating an unfamiliar part of the tree instead of globbing blindly.
Use when writing, reading, or extending Arrow (.ar) import statements — `import[lang] module.path as alias` / `from module import[lang] Name` — including .py, .dll/.lib (C), .rs, C#, or Node.js interop. Explains what each `[lang]` tag loads and how src/parser/imports.rs and src/interpreter/exec.rs implement it, down to key line numbers.
Use when modifying src/interpreter/ — the tree-walk interpreter (statement exec, expression eval, function/closure calls, class instantiation, operators, exceptions, async task threads, or the native ABI handle arena). Gives the module map, Interpreter/Value struct layout, exec/eval dispatch tables, closure capture rules, and the native ABI handle table.
Use when modifying src/parser/ — the recursive-descent parser (statement/expression precedence chain, class/trait parsing, type/param parsing, or import/module loading during parsing). Gives the module map, Parser struct fields, parse_stmt dispatch table, expression precedence chain, and the full list of parse-time validations.