findTemporariesUsedOutsideDeclaringScope() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/HIR/PropagateScopeDependenciesHIR.ts lines 120–180

export function findTemporariesUsedOutsideDeclaringScope(
  fn: HIRFunction,
): ReadonlySet<DeclarationId> {
  /*
   * tracks all relevant LoadLocal and PropertyLoad lvalues
   * and the scope where they are defined
   */
  const declarations = new Map<DeclarationId, ScopeId>();
  const prunedScopes = new Set<ScopeId>();
  const scopeTraversal = new ScopeBlockTraversal();
  const usedOutsideDeclaringScope = new Set<DeclarationId>();

  function handlePlace(place: Place): void {
    const declaringScope = declarations.get(place.identifier.declarationId);
    if (
      declaringScope != null &&
      !scopeTraversal.isScopeActive(declaringScope) &&
      !prunedScopes.has(declaringScope)
    ) {
      // Declaring scope is not active === used outside declaring scope
      usedOutsideDeclaringScope.add(place.identifier.declarationId);
    }
  }

  function handleInstruction(instr: Instruction): void {
    const scope = scopeTraversal.currentScope;
    if (scope == null || prunedScopes.has(scope)) {
      return;
    }
    switch (instr.value.kind) {
      case 'LoadLocal':
      case 'LoadContext':
      case 'PropertyLoad': {
        declarations.set(instr.lvalue.identifier.declarationId, scope);
        break;
      }
      default: {
        break;
      }
    }
  }

  for (const [blockId, block] of fn.body.blocks) {
    scopeTraversal.recordScopes(block);
    const scopeStartInfo = scopeTraversal.blockInfos.get(blockId);
    if (scopeStartInfo?.kind === 'begin' && scopeStartInfo.pruned) {
      prunedScopes.add(scopeStartInfo.scope.id);
    }
    for (const instr of block.instructions) {
      for (const place of eachInstructionOperand(instr)) {
        handlePlace(place);
      }
      handleInstruction(instr);
    }

    for (const place of eachTerminalOperand(block.terminal)) {
      handlePlace(place);
    }
  }
  return usedOutsideDeclaringScope;
}