Three flags. Eight combinations.Four real states.

boolean soup

loading:Ferror:Fdata:–idle

loading:Terror:Fdata:–loading

loading:Ferror:Tdata:–error

loading:Ferror:Fdata:✓loaded

loading:Terror:Tdata:–impossible — compiles

loading:Terror:Tdata:✓impossible — compiles

loading:Terror:Fdata:✓impossible — compiles

loading:Ferror:Tdata:✓impossible — compiles

discriminated union

{ kind: 'idle' }

{ kind: 'loading' }

{ kind: 'error'; error: string }

{ kind: 'loaded'; data: T }

nothing else is constructible

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