Fix duplicate inputs in function composition.
Fix duplicate inputs in function composition.

ihc/futhark,HIPERFIT/futhark,HIPERFIT/futhark,diku-dk/futhark,ihc/futhark,diku-dk/futhark,HIPERFIT/futhark,diku-dk/futhark,mrakgr/futhark,mrakgr/futhark,diku-dk/futhark,CulpaBS/wbBach,ihc/futhark,diku-dk/futhark,mrakgr/futhark