Running with -XNoAlternativeLayoutRule

layout006.hs:12:4: warning: [-Woverlapping-patterns (in -Wdefault)]
    Pattern match is redundant
    In an equation for ‘f’: f | True = ...
Running with -XAlternativeLayoutRule

layout006.hs:12:2: error: parse error on input ‘|’
Running with -XAlternativeLayoutRule -XAlternativeLayoutRuleTransitional

layout006.hs:12:2: warning: [-Walternative-layout-rule-transitional (in -Wdefault)]
    transitional layout will not be accepted in the future:
    `|' at the same depth as implicit layout block

layout006.hs:12:4: warning: [-Woverlapping-patterns (in -Wdefault)]
    Pattern match is redundant
    In an equation for ‘f’: f | True = ...