Alain Resnais's Coeurs (aka Private Fears in Public Places) finds Resnais in full operetta mode - although there aren't any musical numbers, with the pleasantly artificial sets and carefully-designed interactions and transactions between the different characters and sets, it certainly wouldn't be out of place for someone to burst into song. The film is light-hearted enough that an indoor snowstorm works quite nicely as metaphorical punctuation for the understated climax.
Because Resnais is working in what feels like such familiar territory, when the film strays from classical romantic formula there's something of a shock effect. As in Hollywood's grandest romantic tradition, characters are paired off from the very beginning of the film - obliquely at first, more directly later. Resnais understands perfectly well how invested the viewer becomes in an ending that is not just "happy," but the sort of happy ending in which romantic pairings are all finalized by the end of the film - and so the departures from this formula take the audience out of its comfort zone, and made me, for one, feel a little uneasy leaving the theater.
I think the play with conventions (which I'm assuming - and please correct me if I'm wrong - comes from the original theater piece from which the film is adapted) is pointed, in that it serves what appears to be a very specific purpose. Nobody ends up together, romantically-speaking, but the ending isn't really a sad one. The romantic loneliness spread among (most of) the characters does give the ending a melancholy feel, but my impression is that the ending offers an intervention that's not exactly cheerful but is nonetheless necessary. That is, Resnais's characters lean on the possibility of romantic fulfillment (and, more than that, on the potential of a relationship that hasn't yet begun) as the sole object and outlet for their own happiness. As a relationship falls apart, one partner finds a replacement without pausing for breath. A woman spends every night answering personal ads. An older man pines after a co-worker who has inadvertently left him naked footage of herself on a borrowed video. Romance (or rather, the possibility of romance) serves a different specific function for each, but in each case it's an all-purpose solution, an escape from whatever problems they have in their daily lives. The resolution forces the characters to return to the lives they're running away from, and signals that they need to be secure in their own lives before they start chasing fairy tales. As cynical as that sounds, the film is strong in both optimism and humanism - Resnais isn't condemning his characters to loneliness, but forcing them to start over. It should be noted that the proposed pairings would make for terrible relationships, the kind born out of convenience, proximity and desperation. What makes it truly optimistic is the sense all the characters will be okay, that they'll learn to exist in their own situations before seeking to enter someone else's (or that they'll stay single, and that might be fine as well). Coeurs is an extraordinarily mature, humane film. It's also a lot of fun.