test(formatjs): Add regression test for issue #532 string concatenation in defaultMessage (#594)

Fixes #532

Adds an explicit regression test reproducing the exact code from issue
#532, verifying that string concatenation like `'Hello ' + 'world'` in
`defaultMessage` is properly evaluated rather than producing an empty
array.

Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
Co-authored-by: Donny/강동윤 <kdy1@users.noreply.github.com>

Author: kdy1

packages/formatjs/__tests__/wasm.test.ts

@@ -111,6 +111,24 @@ describe("formatjs swc plugin", () => {
     expect(output).not.toMatch(/description/);
   });
 
+  // Regression test for https://github.com/swc-project/plugins/issues/532
+  it("should handle string concatenation in defaultMessage (issue #532)", async () => {
+    const input = `
+      import { defineMessage } from 'react-intl';
+
+      const message = defineMessage({
+        defaultMessage: 'Hello ' + 'world'
+      });
+    `;
+
+    const output = await transformCode(input);
+
+    expect(output).toMatch(/id: "[^"]+"/);
+    // Should concatenate strings, not produce an empty array
+    expect(output).toMatch(/defaultMessage: "Hello world"/);
+    expect(output).not.toMatch(/defaultMessage: \[\]/);
+  });
+
   it("should handle multiple string concatenations", async () => {
     const input = `
       import { defineMessage } from 'react-intl';