Function validate_enum_variable_values 

pub fn validate_enum_variable_values(
    schema: &CompiledSchema,
    operation_name: Option<&str>,
    variable_defs: &[VariableDefinition],
    values: Option<&Value>,
) -> Result<()>

Adjudicate enum membership for supplied variable values against their own declarations — § 6.1.2, for enums (#1362).

Kept separate from validate_variable_values rather than folded into it because that function answers a question about built-in scalars and needs no schema; this one cannot be asked without one. They are called together at every site, so the pair is the check.

Errors

Returns FraiseQLError::Validation naming the variable and the members its enum declares.