Fix enum in union example

.chronus/changes/fix-enum-in-union-example-2024-8-17-18-25-2.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: fix
+packages:
+  - "@typespec/compiler"
+---
+
+Fix examples with enums inside of unions

packages/compiler/src/lib/examples.ts

@@ -74,11 +74,10 @@ function resolveUnions(program: Program, value: ObjectValue, type: Type): Type |
   }
   for (const variant of type.variants.values()) {
     if (
-      variant.type.kind === "Model" &&
       ignoreDiagnostics(
         program.checker.isTypeAssignableTo(
-          value,
-          { entityKind: "MixedParameterConstraint", valueType: variant.type },
+          value.type.projectionBase ?? value.type,
+          variant.type.projectionBase ?? variant.type,
           value,
         ),
       )

packages/openapi3/test/examples.test.ts

@@ -31,6 +31,25 @@ describe("schema examples", () => {
     );
     expect(res.components.schemas.Test.example).toEqual({ dob: "2021-01-01" });
   });
+
+  it("enum in union", async () => {
+    const res = await openApiFor(
+      `
+      enum Types {a, b}
+
+      model A { type: Types;}
+
+      union Un { A }
+
+      @example(#{ prop: #{ type: Types.a } })
+      model Test {
+        prop: Un;
+      }
+
+      `,
+    );
+    expect(res.components.schemas.Test.example).toEqual({ prop: { type: "a" } });
+  });
 });
 
 describe("operation examples", () => {