makeCatchBlock() {
    const context = this.tryContext;
    const forkContext = this.forkContext;
    const thrown = context.thrownForkContext;

    // Update state.
    context.position = 'catch';
    context.thrownForkContext = ForkContext.newEmpty(forkContext);
    context.lastOfTryIsReachable = forkContext.reachable;

    // Merge thrown paths.
    thrown.add(forkContext.head);
    const thrownSegments = thrown.makeNext(0, -1);

    // Fork to a bypass and the merged thrown path.
    this.pushForkContext();
    this.forkBypassPath();
    this.forkContext.add(thrownSegments);
  }
Makes a code path segment for a `catch` block.
@returns {void}