Validates that a value is equal to a given expected value using an Eq comparator.

Equal enforces an equality constraint of the form: "value must equal X".

Equality is defined by an Eq instance, not by structural equality.

Options

• :value (required) The expected value to compare against.

• :eq (optional) An equality comparator. Defaults to Funx.Eq.Protocol.

• :message (optional) A custom error message callback (value -> String.t()) used to override the default error message on failure.

Semantics

• If the value equals the expected value under the given Eq, validation succeeds.
• If the expected value is a module and the value is a struct, validation succeeds when value.__struct__ == expected.
• If the value does not equal the expected value, validation fails.
• Nothing values are preserved and treated as not applicable.
• Just values are unwrapped before comparison.