# `BB.Dsl.ValidateChildSpecBehavioursTransformer`
[🔗](https://github.com/beam-bots/bb/blob/main/lib/bb/dsl/validate_child_spec_behaviours_transformer.ex#L5)

Enforces that every module wired into a component slot in the topology DSL
implements the matching BB component behaviour.

Spark's built-in `{:behaviour, X}` schema type only validates that the
value is an atom — it does not check behaviour conformance — so a bare
`use GenServer` module could otherwise be wired in as e.g. an actuator,
passing DSL compilation only to crash at runtime when the server expects
callbacks (`options_schema/0`, `init/1`, etc.) that aren't defined.

This check lives in a transformer (rather than a verifier) so it raises
at compile time. Verifiers run in `@after_verify` where Elixir does not
tolerate errors, so they can only warn.

# `after_compile?`

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*Consult [api-reference.md](api-reference.md) for complete listing*