Fix versioning validation regression (#9454)

#9444 introduced a regression in reporting things that are valid

Typespec azure check PR with integration tests runnign
Azure/typespec-azure#3832

Author: timotheeguerin

.chronus/changes/fix-versioning-validation-regression-2026-0-23-18-52-52.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: internal
+packages:
+  - "@typespec/versioning"
+---
+
+Fix versioning validation regression

packages/versioning/src/validate.ts

@@ -535,12 +535,13 @@ function validateReference(program: Program, source: Type | Type[], target: Type
     }
   }
 
+  const sources = Array.isArray(source) ? source : [source];
   switch (target.kind) {
     case "Model":
       // For anonymous model expressions (inline models), validate their properties
       if (!target.name) {
         for (const prop of target.properties.values()) {
-          validateReference(program, source, prop.type);
+          validateReference(program, [prop, ...sources], prop.type);
         }
       }
       break;

packages/versioning/test/incompatible-versioning.test.ts

@@ -68,8 +68,7 @@ describe("versioning: validate incompatible references", () => {
   });
 
   describe("operation", () => {
-    // TODO See: https://github.com/microsoft/typespec/issues/2695
-    it.skip("emit diagnostic when unversioned op has a versioned model as a parameter", async () => {
+    it("emit diagnostic when unversioned op has a versioned model as a parameter", async () => {
       const diagnostics = await runner.diagnose(`
         @added(Versions.v2)
         model Foo {}
@@ -111,8 +110,7 @@ describe("versioning: validate incompatible references", () => {
       });
     });
 
-    // TODO See: https://github.com/microsoft/typespec/issues/2695
-    it.skip("emit diagnostic when unversioned op based on a template has a versioned model as a parameter", async () => {
+    it("emit diagnostic when unversioned op based on a template has a versioned model as a parameter", async () => {
       const diagnostics = await runner.diagnose(`
         @added(Versions.v2)
         model Foo {}
@@ -1095,6 +1093,17 @@ describe("versioning: validate incompatible references", () => {
       });
     });
 
+    describe("succeed when annotations are correctly defined", () => {
+      it("on property inside model expression", async () => {
+        const diagnostics = await runner.diagnose(`
+          @added(Versions.v3)
+          model A {}
+          model B { prop: { @added(Versions.v3) a: A }}
+        `);
+        expectDiagnosticEmpty(diagnostics);
+      });
+    });
+
     describe("report issues inside model expression under model", () => {
       it("when base model is added before", async () => {
         const diagnostics = await runner.diagnose(