T21119 test output is not invariant between validate / perf flavours
See https://gitlab.haskell.org/ghc/ghc/-/jobs/984016
T21119.$trModule:
T21119.get: <1!P(S!P(L),S!P(L))><1!P(L)><1L>
T21119.getIO: <1P(SL,L)><1L><ML><L>
-T21119.indexError: <S!P(SCS(C1(L)),1C1(L),B)><1!S><S!S><1!S>b
-T21119.throwIndexError: <LP(LCL(C1(L)),MCM(L),A)><ML><L><ML><L>x
+T21119.indexError: <1!P(SCS(C1(C1(L))),1C1(L),B)><1!S><S!S><1!S>b
+T21119.throwIndexError: <MP(LCL(C1(C1(L))),MCM(L),A)><ML><L><ML><L>x
Can you advise about how to normalise the output @sgraf812 ?