feat(ivy): add getBaseClassIdentifier() to ReflectionHost (#31544)

This method will be useful for writing ngcc `Migrations` that
need to be able to find base classes.

PR Close #31544

packages/compiler-cli/ngcc/src/host/esm2015_host.ts

@@ -190,9 +190,21 @@ export class Esm2015ReflectionHost extends TypeScriptReflectionHost implements N
       return false;
     }
 
-    return innerClassDeclaration.heritageClauses !== undefined &&
-        innerClassDeclaration.heritageClauses.some(
-            clause => clause.token === ts.SyntaxKind.ExtendsKeyword);
+    return super.hasBaseClass(innerClassDeclaration);
+  }
+
+  getBaseClassExpression(clazz: ClassDeclaration): ts.Expression|null {
+    // First try getting the base class from the "outer" declaration
+    const superBaseClassIdentifier = super.getBaseClassExpression(clazz);
+    if (superBaseClassIdentifier) {
+      return superBaseClassIdentifier;
+    }
+    // That didn't work so now try getting it from the "inner" declaration.
+    const innerClassDeclaration = getInnerClassDeclaration(clazz);
+    if (innerClassDeclaration === null) {
+      return null;
+    }
+    return super.getBaseClassExpression(innerClassDeclaration);
   }
 
   /**

packages/compiler-cli/ngcc/src/host/esm5_host.ts

@@ -56,6 +56,32 @@ export class Esm5ReflectionHost extends Esm2015ReflectionHost {
     return iife.parameters.length === 1 && isSuperIdentifier(iife.parameters[0].name);
   }
 
+  getBaseClassExpression(clazz: ClassDeclaration): ts.Expression|null {
+    const superBaseClassIdentifier = super.getBaseClassExpression(clazz);
+    if (superBaseClassIdentifier) {
+      return superBaseClassIdentifier;
+    }
+
+    const classDeclaration = this.getClassDeclaration(clazz);
+    if (!classDeclaration) return null;
+
+    const iifeBody = getIifeBody(classDeclaration);
+    if (!iifeBody) return null;
+
+    const iife = iifeBody.parent;
+    if (!iife || !ts.isFunctionExpression(iife)) return null;
+
+    if (iife.parameters.length !== 1 || !isSuperIdentifier(iife.parameters[0].name)) {
+      return null;
+    }
+
+    if (!ts.isCallExpression(iife.parent)) {
+      return null;
+    }
+
+    return iife.parent.arguments[0];
+  }
+
   /**
    * Find the declaration of a class given a node that we think represents the class.
    *