Create AST structure for asserts in constructor initializers

pkg/analyzer/lib/src/generated/resolver.dart

Index: pkg/analyzer/lib/src/generated/resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/resolver.dart b/pkg/analyzer/lib/src/generated/resolver.dart
index a009cde3fe705736e4d5f691fb2a8546948df3d2..f0ffbdc5f38c7f4e1a0917d300aaae0d76c53b96 100644
--- a/pkg/analyzer/lib/src/generated/resolver.dart
+++ b/pkg/analyzer/lib/src/generated/resolver.dart
@@ -136,6 +136,12 @@ class BestPracticesVerifier extends RecursiveAstVisitor<Object> {
   }
 
   @override
+  Object visitAssertInitializer(AssertInitializer node) {
+    _checkForPossibleNullCondition(node.condition);
+    return super.visitAssertInitializer(node);
+  }
+
+  @override
   Object visitAssertStatement(AssertStatement node) {
     _checkForPossibleNullCondition(node.condition);
     return super.visitAssertStatement(node);
@@ -2799,6 +2805,9 @@ class ExitDetector extends GeneralizingAstVisitor<bool> {
   bool visitAsExpression(AsExpression node) => _nodeExits(node.expression);
 
   @override
+  bool visitAssertInitializer(AssertInitializer node) => false;
+
+  @override
   bool visitAssertStatement(AssertStatement node) => false;
 
   @override