Type Inference

What it does

This skill provides access to Biome's type inference system, which automatically determines data types within code snippets. It leverages a module graph and specialized data structures like TypeReference and TypeData to enable fast, IDE-focused updates and performance. The system handles various TypeScript type constructs including primitives, functions, objects, unions, intersections, tuples, and more, represented by distinct variants of the TypeData enum.

When to use it

• When working with Biome's code editor for improved developer productivity.
• To understand how Biome infers types in local expressions (e.g., a + b).
• For debugging or analyzing type inference results within a Biome project.
• When needing to examine the module-level ("thin") type inference process, which resolves references within a single module's scope.

Key capabilities

• Type Inference: Automatically determines data types from code.
• Module Graph Integration: Operates within Biome’s module graph architecture.
• TypeReference Usage: Utilizes TypeReference for type referencing instead of direct references to avoid stale data.
• TypeData Enum Representation: Provides access to the TypeData enum, which represents various TypeScript types (e.g., Unknown, Boolean, Function, Object).
• Local Inference: Performs type inference based on expressions without surrounding context.
• Module-Level Inference: Resolves references within a module's scope.

Example prompts

• "What is the inferred type of 'a + b' in this Biome project?"
• "Show me the TypeData representation for the inferred type of this function."
• "Explain how Biome resolves type references during module-level inference."

Tips & gotchas

• This skill requires familiarity with TypeScript type system concepts and Biome's architecture.
• Refer to crates/biome_js_type_info/CONTRIBUTING.md for detailed architectural information.
• Biome prioritizes IDE support and instant updates, so data copying between modules is prohibited; instead, use TypeReference.