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Dying young is a drag. Just ask those cancer kids from “The Fault in Our Stars.” But at least they were able to hear and edit their eulogies. In the new tearjerker “If I Stay,” based on Gayle Forman’s young adult novel, talented teenager Mia (Chloe Grace Moretz) may find herself as the fourth course in a buffet of funerals for her entire family, whose car spun out on Dead Man’s Curve. Her only hope is to pull out of the coma and start a cello-and-guitar ensemble with her rocker boyfriend, Adam (Jamie Blackley).

But Adam isn’t much help. Every time he barges into the Portland hospital and demands to strum his latest emo composition at Mia’s bedside, the nurses call security.

This looks like a job for Ghost Girl.

Like the classical musician she plays in the movie, Moretz is a rising star. If you don’t count the horror flick “Carrie,” this is her first lead in a love story. The settings and supporting roles suggest that “If I Stay” started out as someone’s passion project, but the final product only requires its star to sleepwalk through buckets of schlock.

In the timeless ugly-duckling tradition, nobody at her high school notices quiet Mia until Adam hears her soloing in the music room. With so many groupies to choose from, he picks Mia as his muse.

That thrills her still-young parents (Joshua Leonard and Mireille Enos), whose pad is a shrine to the alt-rock lifestyle. (The vintage T-shirts and grunge-era band references are the best thing in the movie.) But Mia’s main man is Beethoven, and as Adam’s band climbs the ladder of success, Mia struggles with her desire to study music in New York City.

But there’s nothing like a deadly car crash to reorient a girl’s priorities. A snowy-weekend drive with her family ends at the hospital, where the friends and relatives praying for a miracle have an unseen secret weapon: Mia’s disembodied spirit, which races around the emergency ward to keep tabs on her battered body.

We know from other movies that there’s no need to fear the reaper, but it seems like bad etiquette that ghost Mia spends so much time worrying about her interrupted relationship with Adam and so little time worrying about her dying parents and little brother. Yet “If I Stay” has enough signs of life at the fringes that we suspect it started out as something completely different, perhaps a comedy called “Smells Like Teen Spirit.”

What “If I Stay” • Two stars out of four • Rating PG-13 • Run time 1:46 • Content thematic elements and some sexual material

Joe Williams is the film critic for the St. Louis Post-Dispatch.