I think it was Donald O’Connor who plays a sailor (WW2) being chased by the Shore Patrol in this scene. He runs into a dance contest and runs up at least 2 walls doing back-flips over the shore patrol who run into the walls. The contest judges are highly impressed! This may be part of the opening scene. This scene takes place in a major city, possibly New York or L.A. I think he was with a buddy when the Shore Patrol starts chasing them.
This film was most likely made somewhere between 1939 and 1950. It may have had Gene Kelly in it too. It is NOT Dancing’ in the Rain.