fix: copy non-hidden bases when erasing hidden interfaces (#392)

When a type inherits (extends/implements) from a hidden (private/internal)
interface, and that interface extends a non-hidden interface, we need to 
copy the non-hidden interface to the consuming type so that it can be polymorphically
used.

Follow up on #390

Co-authored-by: RomainMuller <rmuller@amazon.com>

Author: Elad Ben-Israel

packages/jsii-calc/lib/compliance.ts

@@ -1424,3 +1424,55 @@ export class ImplementsPrivateInterface implements IPrivateInterface {
 export interface ExtendsPrivateInterface extends IPrivateInterface {
     moreThings: string[];
 }
+
+//
+// hidden (private/internal) base interface erasure will copy non-hidden bases from
+// hidden to consuming type.
+//
+
+export interface IAnotherPublicInterface {
+    a: string;
+
+}
+
+/** @internal */
+export interface IAnotherInternalInterface extends IAnotherPublicInterface {
+    b: string;
+}
+
+export interface INonInternalInterface extends IAnotherInternalInterface {
+    c: string;
+}
+
+/** @internal */
+export interface IInternalInterfaceThatExtendsTheNonInternalOne extends INonInternalInterface {
+    d: string;
+}
+
+interface IPrivateInterfaceThatExtendsTheNonInternalOne extends INonInternalInterface {
+    e: string;
+}
+
+export class ClassThatImplementsTheInternalInterface implements IInternalInterfaceThatExtendsTheNonInternalOne, INonInternalInterface {
+    public a = 'a';
+    public b = 'b';
+    public c = 'c';
+    public d = 'd';
+}
+
+export class ClassThatImplementsThePrivateInterface implements IPrivateInterfaceThatExtendsTheNonInternalOne {
+    public a = 'a';
+    public b = 'b';
+    public c = 'c';
+    public e = 'e';
+}
+
+export class ConsumersOfThisCrazyTypeSystem {
+    public consumeAnotherPublicInterface(obj: IAnotherPublicInterface) {
+        return obj.a;
+    }
+
+    public consumeNonInternalInterface(obj: INonInternalInterface): any {
+        return { a: obj.a, b: obj.b, c: obj.c };
+    }
+}

packages/jsii-calc/test/assembly.jsii

@@ -1040,6 +1040,98 @@
         }
       ]
     },
+    "jsii-calc.ClassThatImplementsTheInternalInterface": {
+      "assembly": "jsii-calc",
+      "fqn": "jsii-calc.ClassThatImplementsTheInternalInterface",
+      "initializer": {
+        "initializer": true
+      },
+      "interfaces": [
+        {
+          "fqn": "jsii-calc.INonInternalInterface"
+        }
+      ],
+      "kind": "class",
+      "name": "ClassThatImplementsTheInternalInterface",
+      "properties": [
+        {
+          "name": "a",
+          "overrides": {
+            "fqn": "jsii-calc.IAnotherPublicInterface"
+          },
+          "type": {
+            "primitive": "string"
+          }
+        },
+        {
+          "name": "b",
+          "type": {
+            "primitive": "string"
+          }
+        },
+        {
+          "name": "c",
+          "overrides": {
+            "fqn": "jsii-calc.INonInternalInterface"
+          },
+          "type": {
+            "primitive": "string"
+          }
+        },
+        {
+          "name": "d",
+          "type": {
+            "primitive": "string"
+          }
+        }
+      ]
+    },
+    "jsii-calc.ClassThatImplementsThePrivateInterface": {
+      "assembly": "jsii-calc",
+      "fqn": "jsii-calc.ClassThatImplementsThePrivateInterface",
+      "initializer": {
+        "initializer": true
+      },
+      "interfaces": [
+        {
+          "fqn": "jsii-calc.INonInternalInterface"
+        }
+      ],
+      "kind": "class",
+      "name": "ClassThatImplementsThePrivateInterface",
+      "properties": [
+        {
+          "name": "a",
+          "overrides": {
+            "fqn": "jsii-calc.IAnotherPublicInterface"
+          },
+          "type": {
+            "primitive": "string"
+          }
+        },
+        {
+          "name": "b",
+          "type": {
+            "primitive": "string"
+          }
+        },
+        {
+          "name": "c",
+          "overrides": {
+            "fqn": "jsii-calc.INonInternalInterface"
+          },
+          "type": {
+            "primitive": "string"
+          }
+        },
+        {
+          "name": "e",
+          "type": {
+            "primitive": "string"
+          }
+        }
+      ]
+    },
     "jsii-calc.ClassWithMutableObjectLiteralProperty": {
       "assembly": "jsii-calc",
       "fqn": "jsii-calc.ClassWithMutableObjectLiteralProperty",
@@ -1140,6 +1232,45 @@
       ],
       "name": "Constructors"
     },
+    "jsii-calc.ConsumersOfThisCrazyTypeSystem": {
+      "assembly": "jsii-calc",
+      "fqn": "jsii-calc.ConsumersOfThisCrazyTypeSystem",
+      "initializer": {
+        "initializer": true
+      },
+      "kind": "class",
+      "methods": [
+        {
+          "name": "consumeAnotherPublicInterface",
+          "parameters": [
+            {
+              "name": "obj",
+              "type": {
+                "fqn": "jsii-calc.IAnotherPublicInterface"
+              }
+            }
+          ],
+          "returns": {
+            "primitive": "string"
+          }
+        },
+        {
+          "name": "consumeNonInternalInterface",
+          "parameters": [
+            {
+              "name": "obj",
+              "type": {
+                "fqn": "jsii-calc.INonInternalInterface"
+              }
+            }
+          ],
+          "returns": {
+            "primitive": "any"
+          }
+        }
+      ],
+      "name": "ConsumersOfThisCrazyTypeSystem"
+    },
     "jsii-calc.DefaultedConstructorArgument": {
       "assembly": "jsii-calc",
       "fqn": "jsii-calc.DefaultedConstructorArgument",
@@ -1611,6 +1742,21 @@
       ],
       "name": "GreetingAugmenter"
     },
+    "jsii-calc.IAnotherPublicInterface": {
+      "assembly": "jsii-calc",
+      "fqn": "jsii-calc.IAnotherPublicInterface",
+      "kind": "interface",
+      "name": "IAnotherPublicInterface",
+      "properties": [
+        {
+          "abstract": true,
+          "name": "a",
+          "type": {
+            "primitive": "string"
+          }
+        }
+      ]
+    },
     "jsii-calc.IFriendlier": {
       "assembly": "jsii-calc",
       "docs": {
@@ -1750,6 +1896,26 @@
       ],
       "name": "IInterfaceWithOptionalMethodArguments"
     },
+    "jsii-calc.INonInternalInterface": {
+      "assembly": "jsii-calc",
+      "fqn": "jsii-calc.INonInternalInterface",
+      "interfaces": [
+        {
+          "fqn": "jsii-calc.IAnotherPublicInterface"
+        }
+      ],
+      "kind": "interface",
+      "name": "INonInternalInterface",
+      "properties": [
+        {
+          "abstract": true,
+          "name": "c",
+          "type": {
+            "primitive": "string"
+          }
+        }
+      ]
+    },
     "jsii-calc.IPrivatelyImplemented": {
       "assembly": "jsii-calc",
       "fqn": "jsii-calc.IPrivatelyImplemented",
@@ -4083,5 +4249,5 @@
     }
   },
   "version": "0.7.15",
-  "fingerprint": "iMxRj3lsHKNzSiBrjCyBH6Pp7Uvo+1Sxh/jN3hW+3nA="
+  "fingerprint": "y7h6OQBzbQrvU43LHTizXl12OUAEOpXhqD02OJfmhWQ="
 }