Function lower

compiler/packages/babel-plugin-react-compiler/src/HIR/BuildHIR.ts:72–264

(
  func: NodePath<t.Function>,
  env: Environment,
  // Bindings captured from the outer function, in case lower() is called recursively (for lambdas)
  bindings: Bindings | null = null,
  capturedRefs: Map<t.Identifier, SourceLocation> = new Map(),
)

 * the runtime, ie by invalidating memoization.
 */
export function lower(
  func: NodePath<t.Function>,
  env: Environment,
  // Bindings captured from the outer function, in case lower() is called recursively (for lambdas)
  bindings: Bindings | null = null,
  capturedRefs: Map<t.Identifier, SourceLocation> = new Map(),
): Result<HIRFunction, CompilerError> {
  const builder = new HIRBuilder(env, {
    bindings,
    context: capturedRefs,
  });
  const context: HIRFunction['context'] = [];

  for (const [ref, loc] of capturedRefs ?? []) {
    context.push({
      kind: 'Identifier',
      identifier: builder.resolveBinding(ref),
      effect: Effect.Unknown,
      reactive: false,
      loc,
    });
  }

  let id: string | null = null;
  if (func.isFunctionDeclaration() || func.isFunctionExpression()) {
    const idNode = (
      func as NodePath<t.FunctionDeclaration | t.FunctionExpression>
    ).get('id');
    if (hasNode(idNode)) {
      id = idNode.node.name;
    }
  }
  const params: Array<Place | SpreadPattern> = [];
  func.get('params').forEach(param => {
    if (param.isIdentifier()) {
      const binding = builder.resolveIdentifier(param);
      if (binding.kind !== 'Identifier') {
        builder.errors.pushDiagnostic(
          CompilerDiagnostic.create({
            category: ErrorCategory.Invariant,
            reason: 'Could not find binding',
            description: `[BuildHIR] Could not find binding for param \`${param.node.name}\``,
          }).withDetails({
            kind: 'error',
            loc: param.node.loc ?? null,
            message: 'Could not find binding',
          }),
        );
        return;
      }
      const place: Place = {
        kind: 'Identifier',
        identifier: binding.identifier,
        effect: Effect.Unknown,
        reactive: false,
        loc: param.node.loc ?? GeneratedSource,
      };
      params.push(place);