test evaluating default values parameters in `@generated` functions

test-generated.jl

const U = Union{Type{Val{true}}, Type{Val{false}}}

f1(p::U = Val{false}) = p isa Type{Val{true}}
f2(p::U = Val{false}) = p isa      Val{true}   # false
f3(p::U = Val{false}) = p <:  Type{Val{true}}  # false
f4(p::U = Val{false}) = p <:       Val{true}
f5(p::U = Val{false}) = p === Type{Val{true}}  # false
f6(p::U = Val{false}) = p ===      Val{true}
f7(p::U = Val{false}) = p ==  Type{Val{true}}  # false
f8(p::U = Val{false}) = p ==       Val{true}

@generated g1(p::U = Val{false}) = :($(p isa Type{Val{true}})) # false
@generated g2(p::U = Val{false}) = :($(p isa      Val{true}))  # false
@generated g3(p::U = Val{false}) = :($(p <:  Type{Val{true}}))
@generated g4(p::U = Val{false}) = :($(p <:       Val{true}))  # false
@generated g5(p::U = Val{false}) = :($(p === Type{Val{true}}))
@generated g6(p::U = Val{false}) = :($(p ===      Val{true}))  # false
@generated g7(p::U = Val{false}) = :($(p ==  Type{Val{true}}))
@generated g8(p::U = Val{false}) = :($(p ==       Val{true}))  # false

for f in (f1,f2,f3,f4,f5,f6,f7,f8,g1,g2,g3,g4,g5,g6,g7,g8)
    print("$f(Val{true})  : $(f(Val{true}) == true)\n")
    print("$f(Val{false}) : $(f(Val{false}) == false)\n")
    print("$f()           : $(f() == false)\n\n")
end