Function validate 

pub fn validate(
    api: &Api,
    identity: &Identity,
    source: Option<(&str, &str)>,
) -> Result<Model, ValidationDiagnostics>

Validate an Api document against the library’s identity, reporting every rule violation found, and build its Model.

This is the one checked way to obtain the Model every generator consumes, and it builds the model exactly once. The C symbol table is checked with the real identity, in the same pass. The optional source is (filename, contents) of the IDL file and is used to attach spans to the returned diagnostics, each located within its enclosing declaration. Pass None when the API is constructed in memory and there is no on-disk source.

Errors

Returns ValidationDiagnostics carrying one ValidationDiagnostic per violation: an unsupported schema version, a duplicate or invalid name, an unknown, qualified, or misplaced type, an empty struct or enum, a throws without an error domain, a C symbol collision, or any other rule violation in the catalog above.