Recast version: 0.20.5
Node version: 14.18.2
Mac OS X version: 12.0.1

Repro: https://github.com/lokshunhung/recast-definite-repro

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recast with recast/parser/typescript can remove definite assignment assertions for class properties by setting ClassProperty.definite = false (originally true)

// Before
class A {
  foo!: string;
}

// After
class A {
  foo: string;
}

but cannot add definite assignment assertions for class properties by setting ClassProperty.definite = true (originally undefined)

// Before
class A {
  foo: string;
}

// After
class A {
  foo: string;
}

// should be `foo!: string;`