When generating a .y file with the --glr flag enabled, the .y header gets a -- module name filled in by Happy line written. This makes happy (I'm using version 1.19.9) spit out a file with incorrect syntax:

$ ghc TestTestProlg.hs

ParTestProlg.hs:5:8: error: parse error on input ‘name’

This can be quick-fixed by editing the .y file manually before running happy, but it looks like bnfc can actually do something about this. At source/src/BNFC/Backend/Haskell/CFtoHappy.hs line 77, the string output by the case of GLR can simply be set to the same as Standard.