Initial analysis and test case for document highlight crash

Co-authored-by: jakebailey <[email protected]>

Author: Copilot

internal/fourslash/tests/gen/documentHighlightImportPath_test.go

@@ -0,0 +1,23 @@
+package fourslash_test
+
+import (
+	"testing"
+
+	"github.com/microsoft/typescript-go/internal/fourslash"
+	"github.com/microsoft/typescript-go/internal/testutil"
+)
+
+func TestDocumentHighlightImportPath(t *testing.T) {
+	t.Parallel()
+
+	defer testutil.RecoverAndFail(t, "Panic on fourslash test")
+	const content = `// @Filename: /a.d.ts
+declare module "my-module" {
+    export const foo: number;
+}
+
+// @Filename: /b.ts
+import { foo } from "[|my-module|]";`
+	f := fourslash.NewFourslash(t, nil /*capabilities*/, content)
+	f.VerifyBaselineDocumentHighlights(t, nil /*preferences*/, f.Ranges()[0])
+}