Fix fusion type environment.
Fix fusion type environment.

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