Example condition that does not work on Bicep

subnet.bicep

resource natGateway 'Microsoft.Network/natGateways@2023-11-01' = if (hasNatGateway) {
  name: natGatewayName
  location: location
  sku: {
    name: 'Standard'
  }
}

resource subnets 'Microsoft.Network/virtualNetworks/subnets@2022-11-01' = {
  name: name
  parent: virtualNetwork
  properties: {
    addressPrefix: addressPrefix
    natGateway: hasNatGateway
      ? {
          id: natGateway.id
        }
      : null
  }
}

The solution is duplicating subnet resource with condition on each

resource subnets 'Microsoft.Network/virtualNetworks/subnets@2022-11-01' = if (hasNatGateway) {