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Typescript union types are not correctly resolved in Java

See original GitHub issue

In Typescript CloudFormationStackArtifact#getAssets returns AssetMetadataEntry[], where AssetMetadataEntry = FileAssetMetadataEntry | ContainerImageAssetMetadataEntry. In Java this method returns a List<Object>, which is, actually, a list of JSII objects. The JSII objects are supposed to reference FileAssetMetadataEntry and ContainerImageAssetMetadataEntry objects from JSII runtime, however the reference type is always FileAssetMetadataEntry:

final Object asset = stackArtifact.getAssets().get(0);
// the reference interface will always be FileAssetMetadataEntry even though it's actually ContainerImageAssetMetadataEntry
JsiiEngine.getInstance().nativeToObjRef(asset).getInterfaces()

The issue is also actual for software.amazon.awscdk.cloudassembly.schema.MissingContext#getProps. It is supposed to return ContextQueryProperties which is a union type in Typescript, however, the JSII object reference is always of type AmiContextQuery (looks like it always takes the first type in the union type definition as both FileAssetMetadataEntry and AmiContextQuery are defined first.

Reproduction Steps

Define a container image asset in your stack
Synthesize the templates
Try to access repositoryName of the asset:

Object asset = stackArtifact.getAssets().get(0);
JsiiEngine jsiiEngine = JsiiEngine.getInstance();
JsiiObjectRef objectRef = jsiiEngine.nativeToObjRef(asset);
JsiiClient client = jsiiEngine.getClient();
String packaging = client.getPropertyValue(objectRef, "packaging").asText();
assert packaging.equals("container-image");
String repositoryName = client.getPropertyValue(objectRef, "repositoryName").asText(); //causes an exception

Error Log

Error: Type Object or interface(s) @aws-cdk/cloud-assembly-schema.FileAssetMetadataEntry doesn't have a property 'repositoryName'
    at Kernel._typeInfoForProperty (/private/var/folders/g6/wh2_ynfn4nb9wcpv5vjfphww0000gn/T/jsii-java-runtime14150496997154827187/jsii-runtime.js:8205:19)
    at Kernel.get (/private/var/folders/g6/wh2_ynfn4nb9wcpv5vjfphww0000gn/T/jsii-java-runtime14150496997154827187/jsii-runtime.js:7642:25)
    at KernelHost.processRequest (/private/var/folders/g6/wh2_ynfn4nb9wcpv5vjfphww0000gn/T/jsii-java-runtime14150496997154827187/jsii-runtime.js:7388:28)
    at KernelHost.run (/private/var/folders/g6/wh2_ynfn4nb9wcpv5vjfphww0000gn/T/jsii-java-runtime14150496997154827187/jsii-runtime.js:7328:14)
    at Immediate._onImmediate (/private/var/folders/g6/wh2_ynfn4nb9wcpv5vjfphww0000gn/T/jsii-java-runtime14150496997154827187/jsii-runtime.js:7331:37)
    at processImmediate (internal/timers.js:456:21)