Fix class extends t (#315)

packages/adl/compiler/checker.ts

@@ -385,15 +385,14 @@ export function createChecker(program: Program) {
         }
       }
 
-      const type: ModelType = createType({
+      return createType({
         kind: 'Model',
         name: node.kind === SyntaxKind.ModelStatement ? node.id.sv : '',
         node: node,
         properties,
         baseModels: baseModels
       });
-      
-      return type;
+
     } else {
       // model =
       // this will likely have to change, as right now `model =` is really just
@@ -416,9 +415,14 @@ export function createChecker(program: Program) {
   }
 
   function checkClassHeritage(heritage: ReferenceExpression[]): ModelType[] {
-    return heritage.map(heritageRef => {
+    return heritage.flatMap(heritageRef => {
       const heritageType = getTypeForNode(heritageRef);
 
+      if (heritageType.kind === "TemplateParameter") {
+        // don't need to track heritage for template parameters.
+        return [];
+      }
+
       if (heritageType.kind !== "Model") {
         throwDiagnostic("Models must extend other models.", heritageRef);
       }

packages/adl/compiler/parser.ts

@@ -689,6 +689,7 @@ export function visitChildren<T>(node: Types.Node, cb: NodeCb<T>): T | undefined
       return visitEach(cb, node.decorators) ||
         visitNode(cb, node.id) ||
         visitEach(cb, node.templateParameters) ||
+        visitEach(cb, node.heritage) ||
         visitNode(cb, node.assignment) ||
         visitEach(cb, node.properties);
     case Types.SyntaxKind.NamedImport: