BoundaryML/baml · error · ConvertError

Unknown class: {0}

Error message

Unknown class: {0}

What it means

ConvertError::UnknownClass(DefKey) is declared in the SAP model conversion error enum. It represents a type reference to a class name that cannot be found among the registered class definitions when resolving SAP model types.

Source

Thrown at baml_language/crates/bex_sap/src/sap_model/convert.rs:32

    self, AnnotatedEnumVariant, AnnotatedField, AnnotatedTy, ArrayTy, AttrLiteral, BigintLiteralTy,
    BigintTy, BoolLiteralTy, BoolTy, ClassTy, EnumTy, EnumVariantTy, FloatTy, IntLiteralTy, IntTy,
    MapTy, MediaTy, NullTy, StringLiteralTy, StringTy, TyResolved, TyWithMeta, TypeAnnotations,
    TypeRefDb, UnionTy,
};

impl crate::sap_model::TypeIdent for DefKey {}

#[derive(thiserror::Error, Debug)]
pub enum ConvertError {
    #[error("Failed to parse float: {0}")]
    ParseFloat(#[from] std::num::ParseFloatError),
    #[error("Unknown media kind")]
    UnknownMediaKind,
    #[error("Float literals cannot be parsed")]
    FloatLiteral,
    #[error("Non-parsable type: {0:?}")]
    NonParsableType(Box<SapTy>),
    #[error("Unknown class: {0}")]
    UnknownClass(DefKey),
    #[error("Unknown enum: {0}")]
    UnknownEnum(DefKey),
    #[error("Unknown type alias: {0}")]
    UnknownTypeAlias(DefKey),
    #[error("Unknown name (could not determine if it was a class, enum, or type alias): {0}")]
    UnknownName(DefKey),
    #[error("Could not add a type to the database as the name `{0}` is already present")]
    AlreadyPresent(DefKey),
    #[error("Recursion depth exceeded for {0}")]
    RecursionDepthExceeded(&'static str),
    #[error("Unions must be flattened")]
    UnflattenedUnion,
    /// Something like `type A = B; type B = A;` is invalid.
    #[error("Recursive type alias without indirection: {0}")]
    DirectRecursiveTypeAlias(DefKey),
    #[error("Internal error (please report): {0}")]
    InternalError(&'static str),

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Verify the class name in the error is declared and spelled correctly in your BAML sources.
2. Ensure the module/file containing the class is included in the compilation context passed to TypeCtx (SysOpContext.class_definitions).
3. Rebuild/regenerate the SAP model after adding the missing class definition.

Example fix

// before
function Extract() -> MissingClass
// after
class MissingClass { name: string }
function Extract() -> MissingClass

// Verify every referenced class name exists before conversion
fn class_exists(ctx: &TypeCtx, key: &DefKey) -> bool {
    ctx.class_definitions.contains_key(key)
}

match result {
    Err(ConvertError::UnknownClass(key)) => eprintln!("declare class {key:?} or fix its spelling"),
    other => other,
}

When it happens

Trigger: Resolving a class-typed reference whose DefKey has no entry in TypeCtx::class_definitions — i.e. the referenced class was never declared or was pruned from the context before build_db.

Common situations: A BAML file references a class defined in another module that was not loaded; a typo in a class name; a class removed in a refactor while aliases or fields still reference it.

Related errors

• Unknown enum: {0}
• Unknown type alias: {0}
• Unknown name (could not determine if it was a class, enum, o
• Non-parsable type: {0:?}
• Could not add a type to the database as the name `{0}` is al

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/5df1530c1fee5985. Report an issue: GitHub.