Add support for struct auto-completion

[JesseHerrick]

#43

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Note

Medium Risk
Adds new BEAM CodeIntel protocol ops plus caching and completion-path logic, which can affect editor completion behavior and introduces concurrency/cache invalidation complexity. Failures are mostly handled gracefully, but incorrect inference or cache staleness could degrade completion accuracy/performance.

Overview
Adds Elixir struct field auto-completion to the LSP, covering both struct literals (%Module{...}) and variable.field access.

Extends the BEAM sidecar CodeIntel protocol with new ops to fetch compiled struct fields and to infer a function’s struct return type from the BEAM ExCk chunk, then wires this into server-side completion with a build-root scoped cache, background pre-warming on document open/change, and cache invalidation on reindex/delete/BEAM eviction.

Updates token-based parsing to detect struct key/value cursor contexts, %Module references, variable-to-struct bindings (pattern matches and @spec hints), and simple var = Module.func(...) assignments; completion trigger characters are expanded (including space) to support struct value-position variable suggestions, with extensive new unit/integration tests.

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[cursor]

Variable sort priority leaks into non-struct completions

Medium Severity

The addVariableCompletion helper unconditionally sets SortText: "000_" + varName, which forces variables to sort before all other completions. This was intended only for struct value positions (where variables are the likely target), but the same helper is used in the regular funcPrefix != "" path too. Previously, variable completions had no SortText and sorted naturally alongside functions. This changes the ordering behavior of all non-struct completions as a side effect.

 

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[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

There are 3 total unresolved issues (including 1 from previous review).

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[cursor]

Unused source parameter in countCallArity function

Low Severity

The countCallArity function accepts a source []byte parameter that is never used anywhere in the function body. This adds unnecessary noise to the API and every call site.

 

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[cursor]

Prewarming ExCk calls scoped to last function only

Low Severity

prewarmStructFieldsFromText passes lines (last line index) and len(text) (total byte count, not a column) to VariableFunctionCalls. This scopes the scan to only the last function definition in the file because VariableFunctionCalls finds the last def before the offset. Struct module refs from StructModuleRefs correctly scan the whole file, but ExCk-based prewarming misses calls in earlier functions.

 

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