Issue 21850. Fix for incremental resolving field formal parameters.

pkg/analyzer/test/generated/incremental_resolver_test.dart

Index: pkg/analyzer/test/generated/incremental_resolver_test.dart
diff --git a/pkg/analyzer/test/generated/incremental_resolver_test.dart b/pkg/analyzer/test/generated/incremental_resolver_test.dart
index 7aef61e75e07929e9260cc39c2641fb272db18d9..89b14119485a5a29a9ad13c95d711c8269e58d8f 100644
--- a/pkg/analyzer/test/generated/incremental_resolver_test.dart
+++ b/pkg/analyzer/test/generated/incremental_resolver_test.dart
@@ -1939,6 +1939,15 @@ class A {
     _resolve(_editString('+', '*'), _isFunctionBody);
   }
 
+  void test_constructor_fieldFormalParameter() {
+    _resolveUnit(r'''
+class A {
+  int xy;
+  A(this.x);
+}''');
+    _resolve(_editString('this.x', 'this.xy'), _isDeclaration);
+  }
+
   void test_constructor_fieldInitializer_add() {
     _resolveUnit(r'''
 class A {
@@ -4044,6 +4053,8 @@ class _SameResolutionValidator implements AstVisitor {
 
   void _verifyElement(Element a, Element b) {
     if (a != b) {
+      print(a.location);
+      print(b.location);
       fail('Expected: $b\n  Actual: $a');
     }
     if (a == null && b == null) {