Kotlin Context Parameters

Kotlin Context Parameters

Quick start

• Declare dependencies with context(name: Type) before a function or property.
• Introduce values at boundaries with context(value) { ... } or from an existing implicit receiver such as with(value) { ... }.
• Use named context parameters for services you call directly; use _ for marker/scope capabilities used only for resolution.
• Prefer small, explicit contexts. Avoid having multiple same-typed values available at the same scope level.
• Read references/context-parameters.md before writing examples or migration advice.

Workflow

1. Identify the contextual capability: service dependency, DSL/scope marker, typeclass-like evidence, or migration from context receivers.
2. Decide names: named parameter when code needs the value; _ plus bridge functions when the context should only unlock operations.
3. Add a boundary that supplies the context (context(...) {} or a wrapper accepting a context(Type) () -> A block).
4. Check restrictions: no constructor/class contexts, no context-property initializers/backing fields/delegation.
5. Compile-test syntax with the target Kotlin version.

Rules of thumb

• Context resolution is by type at the call site, not by parameter name.
• Context values come from in-scope context parameters and implicit receivers.
• If two compatible values are available at the same scope level, expect ambiguity.
• Do not present proposal-only features as available unless verified with the user's Kotlin version.
• For contextual function references and explicit context arguments, use lambdas or compile-test first; support has lagged the proposal in tested Kotlin builds.

Output expectations

• Show call sites, not just declarations.
• Prefer examples that compile on the target Kotlin version, or clearly mark untested/proposal-only behavior.

References

• Load references/context-parameters.md for examples, restrictions, migration notes, and test prompts.