PruneHoistedContexts.ts — react Source File

Source Code

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import {CompilerError} from '..';
import {
  convertHoistedLValueKind,
  IdentifierId,
  InstructionId,
  InstructionKind,
  Place,
  ReactiveFunction,
  ReactiveInstruction,
  ReactiveScopeBlock,
  ReactiveStatement,
} from '../HIR';
import {empty, Stack} from '../Utils/Stack';
import {
  ReactiveFunctionTransform,
  Transformed,
  visitReactiveFunction,
} from './visitors';

/*
 * Prunes DeclareContexts lowered for HoistedConsts, and transforms any references back to its
 * original instruction kind.
 *
 * Also detects and bails out on context variables which are:
 * - function declarations, which are hoisted by JS engines to the nearest block scope
 * - referenced before they are defined (i.e. having a `DeclareContext HoistedConst`)
 * - declared
 *
 * This is because React Compiler converts a `function foo()` function declaration to
 * 1. a `let foo;` declaration before reactive memo blocks
 * 2. a `foo = function foo() {}` assignment within the block
 *
 * This means references before the assignment are invalid (see fixture
 * error.todo-functiondecl-hoisting)
 */
export function pruneHoistedContexts(fn: ReactiveFunction): void {
  visitReactiveFunction(fn, new Visitor(), {
    activeScopes: empty(),
    uninitialized: new Map(),
  });
}

type VisitorState = {
  activeScopes: Stack<Set<IdentifierId>>;
  uninitialized: Map<
    IdentifierId,
    | {
        kind: 'unknown-kind';
      }
    | {
        kind: 'func';
        definition: Place | null;
      }
// ... (111 more lines)