Method getNullableType

internal/checker/checker.go:18563–18574

Add undefined or null or both to a type if they are missing.

(t *Type, flags TypeFlags)

// Add undefined or null or both to a type if they are missing.
func (c *Checker) getNullableType(t *Type, flags TypeFlags) *Type {
	missing := (flags & ^t.flags) & (TypeFlagsUndefined | TypeFlagsNull)
	switch {
	case missing == 0:
		return t
	case missing == TypeFlagsUndefined:
		return c.getUnionType([]*Type{t, c.undefinedType})
	case missing == TypeFlagsNull:
		return c.getUnionType([]*Type{t, c.nullType})
	}
	return c.getUnionType([]*Type{t, c.undefinedType, c.nullType})
}

func (c *Checker) GetNonNullableType(t *Type) *Type {
	if c.strictNullChecks {