BoundaryML/baml · error

undefined enum: {name}

Error message

undefined enum: {name}

What it means

Panic when compiling an enum member access `EnumName.Variant`: the variant itself resolved (it exists in `self.enums`), but the enum's name is missing from the globals table, so codegen cannot emit the `LoadGlobal` needed to materialize the enum type at runtime. This indicates enum registration and the globals table are inconsistent across compiler phases.

Source

Thrown at engine/baml-compiler/src/codegen.rs:1158

                self.emit(
                    match base.meta().1.as_ref().expect("must have a resolved type") {
                        TypeIR::List(_, _) => Instruction::LoadArrayElement,
                        TypeIR::Map(_, _, _) => Instruction::LoadMapElement,
                        _ => panic!("array access should be either map or array."),
                    },
                );
            }

            thir::Expr::FieldAccess { base, field, .. } => {
                // Direct enum access: Share.Rectangle
                if let thir::Expr::Var(name, _) = base.as_ref() {
                    if let Some(enm) = self.enums.get(name) {
                        let Some(variant_index) = enm.get(field) else {
                            panic!("undefined enum variant: {name}.{field}");
                        };

                        let Some(enum_index) = self.globals.get(name) else {
                            panic!("undefined enum: {name}");
                        };

                        let const_index = self.add_constant(Value::Int(*variant_index as i64));
                        self.emit(Instruction::LoadConst(const_index));

                        let allocation_instruction =
                            self.emit(Instruction::AllocVariant(ObjectIndex::from_raw(usize::MAX)));

                        // TODO: Confusing name because of class alloc reuse.
                        self.class_alloc_patch_list.push(AllocInstancePatch {
                            location: allocation_instruction,
                            global: *enum_index,
                        });

                        return;
                    }
                }

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Verify the enum is declared/imported in the same compilation unit so it gets registered as a global
2. Reorder or re-register declarations so the enum is registered before expressions referencing it are compiled
3. Check for duplicate definitions or shadowing that suppress global registration
4. If the enum is plainly declared, report a compiler bug: globals registration missed the enum

Example fix

// before
// enum Share { ... } defined in another file, not imported
let s = Share.Rectangle
// after
import "./share.baml"  // brings enum Share into the unit
let s = Share.Rectangle

// Ensure enums referenced via member access are registered in the compile unit
fn ensure_enum_registered(unit: &Unit, enum_name: &str) -> Result<(), String> {
    if unit.enums.contains_key(enum_name) && unit.globals.contains_key(enum_name) { Ok(()) }
    else { Err(format!("enum `{enum_name}` is not registered in this compilation unit")) }
}

When it happens

Trigger: Compiling `Expr::FieldAccess` on a base `Var(name)` where `self.enums` contains `name` but `self.globals.get(name)` is None — the enum was collected during resolution but never registered as a global before codegen.

Common situations: Enums defined dynamically or in files not added to the global registry; partial compilation where some declarations were skipped; compiler bugs where enum collection and global registration use different visibility rules.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• undefined enum variant: {name}.{field}
• undefined enum: {enum_name}
• undefined variant: {enum_name}.{variant}
• Field access on non-class type
• undefined class: {class_name}

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/8e51e9965c1a699b. Report an issue: GitHub.