facebook/flow · error · InvalidRemovalError

Tried to remove ${node.type} from parent of type ${node.pare

Error message

Tried to remove ${node.type} from parent of type ${node.parent.type}.
However ${node.type} can only be safely removed from parent of type ArrowFunctionExpression | FunctionDeclaration | FunctionExpression | ArrayExpression | ArrayPattern.

What it means

removeNodeMutation supports removing an Identifier only from array positions it knows how to patch: params of function-like nodes and elements of ArrayExpression/ArrayPattern. Any other parent (a reference in a MemberExpression, a VariableDeclarator id, a Property key) hits the default case and throws InvalidRemovalError listing the allowed parents. Removing a binding identifier from other positions would leave an invalid AST, so it is rejected up front.

Source

Thrown at packages/flow-transform/src/transform/mutations/RemoveNode.js:192

      case 'Property':
        assertParent(VALID_PROPERTY_PARENTS);
        return 'properties';

      // Identifier can be the child of a number of usecases
      case 'Identifier':
        switch (node.parent.type) {
          case 'ArrowFunctionExpression':
          case 'FunctionDeclaration':
          case 'FunctionExpression':
            return 'params';

          case 'ArrayExpression':
          case 'ArrayPattern':
            return 'elements';

          default:
            throw new InvalidRemovalError(
              getErrorMessage([
                'ArrowFunctionExpression',
                'FunctionDeclaration',
                'FunctionExpression',
                'ArrayExpression',
                'ArrayPattern',
              ]),
            );
        }

      // RestElement can be the child of a number of usecases
      case 'RestElement':
        switch (node.parent.type) {
          case 'ArrowFunctionExpression':
          case 'FunctionDeclaration':
          case 'FunctionExpression':
          case 'ComponentDeclaration':
            return 'params';

View on GitHub (pinned to d1341dac89)

Solutions

Narrow the visitor to Identifiers whose parent is a function-like node's params array or an ArrayPattern
For binding removal, remove the enclosing VariableDeclarator or Property instead of the Identifier
Use replaceNodeMutation for positions removal does not support

Example fix

// before
if (node.type === 'Identifier') mutations.push(removeNode(node)); // throws for references

// after
const P = node.parent;
if (node.type === 'Identifier' &&
    (P.type === 'ArrowFunctionExpression' || P.type === 'FunctionDeclaration' || P.type === 'FunctionExpression')) {
  mutations.push(removeNode(node)); // params only
}

Defensive patterns

Strategy: type-guard

Validate before calling

const IDENTIFIER_REMOVE_PARENTS = new Set(['ArrowFunctionExpression', 'FunctionDeclaration', 'FunctionExpression', 'ArrayExpression', 'ArrayPattern']);
function canRemoveIdentifier(node) {
  return node.type === 'Identifier' && IDENTIFIER_REMOVE_PARENTS.has(node.parent.type);
}

Type guard

const isRemovableIdentifier = (node) =>
  node.type === 'Identifier' && ['ArrowFunctionExpression', 'FunctionDeclaration', 'FunctionExpression', 'ArrayExpression', 'ArrayPattern'].includes(node.parent && node.parent.type);

Prevention

Match Identifiers by parent context (params or elements), never by type alone
To remove a binding, remove the VariableDeclarator or Property that owns it
Read the allowlist out of the error message and encode it as a guard set in your codemod

When it happens

Trigger: removeNodeMutation(identifier) where identifier.parent is a MemberExpression, VariableDeclarator, Property, or CallExpression callee: anything other than ArrowFunctionExpression, FunctionDeclaration, or FunctionExpression (params) or ArrayExpression or ArrayPattern (elements).

Common situations: Unused-parameter cleanup codemods that match Identifier nodes too broadly and try to remove references, not just parameters; destructuring-aware cleanup assuming every Identifier sits in a pattern.

Related errors

AI-assisted analysis of facebook/flow@d1341dac89 (2026-08-17). Data as JSON: /api/errors/d19ee4758534aa21. Report an issue: GitHub.