Running with -XNoAlternativeLayoutRule
Running with -XAlternativeLayoutRule

layout001.hs:6:3: error: [GHC-58481] parse error on input ‘where’
Running with -XAlternativeLayoutRule -XAlternativeLayoutRuleTransitional

layout001.hs:6:3: warning: [GHC-93617] [-Walternative-layout-rule-transitional (in -Wdefault)]
    transitional layout will not be accepted in the future:
    `where' clause at the same depth as implicit layout block