Issue 23545. Replace unaccessible type parameters with 'dynamic'.

pkg/analysis_server/lib/src/services/correction/util.dart

Index: pkg/analysis_server/lib/src/services/correction/util.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/util.dart b/pkg/analysis_server/lib/src/services/correction/util.dart
index 9a2a8121b96761088939997cae3fb47825b826ca..c4082fa4765f599d1158f5dad493042ce6abf6ff 100644
--- a/pkg/analysis_server/lib/src/services/correction/util.dart
+++ b/pkg/analysis_server/lib/src/services/correction/util.dart
@@ -1030,6 +1030,10 @@ class CorrectionUtils {
    */
   String getTypeSource(DartType type, Set<LibraryElement> librariesToImport) {
     StringBuffer sb = new StringBuffer();
+    // type parameter
+    if (!_isTypeVisible(type)) {
+      return 'dynamic';
+    }
     // just a Function, not FunctionTypeAliasElement
     if (type is FunctionType && type.element is! FunctionTypeAliasElement) {
       return "Function";