facebook/flow · error

Records cannot have getters

Error message

Records cannot have getters

What it means

In Flow record declarations, the typing pass panics on MethodKind::Get: records have no accessor semantics, so a getter in a record body crashes the statement typer rather than producing a diagnostic. Like the constructor case, this is an intentional hard boundary — records only model data plus plain methods.

Source

Thrown at rust_port/crates/flow_typing_statement/src/statement.rs:18860

                                                }),
                                            ),
                                            value: (func_loc_c, typed_func),
                                            kind: kind_c,
                                            static_: static_c,
                                            override_: false,
                                            ts_accessibility: None,
                                            decorators: vec![].into(),
                                            comments: method_comments_c,
                                        },
                                    ))
                                };

                                match kind {
                                    ast::class::MethodKind::Constructor => {
                                        panic!("Records cannot have constructors")
                                    }
                                    ast::class::MethodKind::Get => {
                                        panic!("Records cannot have getters")
                                    }
                                    ast::class::MethodKind::Set => {
                                        panic!("Records cannot have setters")
                                    }
                                    ast::class::MethodKind::Method => {
                                        check_duplicate_name(
                                            &mut public_seen_names,
                                            method_id_loc.dupe(),
                                            &Name::new(name.dupe()),
                                            static_,
                                            false,
                                            ClassMemberKind::ClassMemberMethod,
                                        );
                                        class_sig::add_method(
                                            static_,
                                            false,
                                            false,
                                            Name::new(name),

View on GitHub (pinned to 5c86586199)

Solutions

1. Remove the getter from the record body.
2. Replace derived values with a plain function taking the record: function getName(c: Config): string.
3. Keep accessors by using a class instead of a record.
4. Add a lint rule that rejects accessor members inside record bodies.

Example fix

// before
record Config {
  name_: string;
  get name(): string { return this.name_; }
}

// after: compute via a function
record Config { name: string; }
function getName(c: Config): string { return c.name; }

// lint before typechecking: records must not contain getters
function recordHasAccessor(node) {
  return node.body.some(
    (el) => el.type === 'Method' && (el.kind === 'get' || el.kind === 'set')
  );
}
if (recordHasAccessor(recordNode)) reportError(recordNode, 'records cannot have accessors');

function recordMemberAllowed(el) {
  if (el.type === 'Property') return true;
  if (el.type !== 'Method') return false;
  return el.kind === 'method' && el.key.type === 'Identifier';
}

When it happens

Trigger: Typechecking a record whose body contains a getter — record Config { get name(): string { ... } } — where the parser accepted the accessor and typing reaches the member lowering.

Common situations: Class-to-record conversions that keep accessors; developers assuming record getters behave like class getters; codemods and code generators emitting accessors into record bodies.

Related errors

• Records cannot have constructors
• Records cannot have setters
• Records cannot have private methods
• Records can only have identifier method keys
• Unexpected function parameter ${param.type}

AI-assisted analysis of facebook/flow@5c86586199 (2026-08-20). Data as JSON: /api/errors/8fac7f5d09deafdb. Report an issue: GitHub.