transformInstruction() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/PruneNonEscapingScopes.ts lines 1067–1122

  override transformInstruction(
    instruction: ReactiveInstruction,
    state: Set<DeclarationId>,
  ): Transformed<ReactiveStatement> {
    this.traverseInstruction(instruction, state);

    const value = instruction.value;
    if (value.kind === 'StoreLocal' && value.lvalue.kind === 'Reassign') {
      // Complex cases of useMemo inlining result in a temporary that is reassigned
      const ids = getOrInsertDefault(
        this.reassignments,
        value.lvalue.place.identifier.declarationId,
        new Set(),
      );
      ids.add(value.value.identifier);
    } else if (
      value.kind === 'LoadLocal' &&
      value.place.identifier.scope != null &&
      instruction.lvalue != null &&
      instruction.lvalue.identifier.scope == null
    ) {
      /*
       * Simpler cases result in a direct assignment to the original lvalue, with a
       * LoadLocal
       */
      const ids = getOrInsertDefault(
        this.reassignments,
        instruction.lvalue.identifier.declarationId,
        new Set(),
      );
      ids.add(value.place.identifier);
    } else if (value.kind === 'FinishMemoize') {
      let decls;
      if (value.decl.identifier.scope == null) {
        /**
         * If the manual memo was a useMemo that got inlined, iterate through
         * all reassignments to the iife temporary to ensure they're memoized.
         */
        decls = this.reassignments.get(value.decl.identifier.declarationId) ?? [
          value.decl.identifier,
        ];
      } else {
        decls = [value.decl.identifier];
      }

      if (
        [...decls].every(
          decl => decl.scope == null || this.prunedScopes.has(decl.scope.id),
        )
      ) {
        value.pruned = true;
      }
    }

    return {kind: 'keep'};
  }