With NNBD null-shorting is performed.

scheglov · commit-bot@chromium.org · commit 68ba13e4e8b6 · 2019-09-05T16:44:13.000Z
So, the type of `a?.b.c` is nullable, but the type of `c` is not. Everything after `a?` is just not executed if `a` is null. R=brianwilkerson@google.com Change-Id: I705051080b8cc2bb5014355688561b0f3dccc0d8 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/115660 Reviewed-by: Brian Wilkerson <brianwilkerson@google.com> Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
diff --git a/pkg/analyzer/lib/src/generated/error_verifier.dart b/pkg/analyzer/lib/src/generated/error_verifier.dart
@@ -4364,13 +4364,7 @@ class ErrorVerifier extends RecursiveAstVisitor<void> {
     StaticWarningCode code = expression.staticType == _typeProvider.nullType
         ? StaticWarningCode.INVALID_USE_OF_NULL_VALUE
         : StaticWarningCode.UNCHECKED_USE_OF_NULLABLE_VALUE;
-
-    if (expression is MethodInvocation) {
-      SimpleIdentifier methodName = expression.methodName;
-      _errorReporter.reportErrorForNode(code, methodName, []);
-    } else {
-      _errorReporter.reportErrorForNode(code, expression, []);
-    }
+    _errorReporter.reportErrorForNode(code, expression, []);
 
     return true;
   }
diff --git a/pkg/analyzer/lib/src/generated/static_type_analyzer.dart b/pkg/analyzer/lib/src/generated/static_type_analyzer.dart
@@ -332,6 +332,7 @@ class StaticTypeAnalyzer extends SimpleAstVisitor<void> {
           _featureSet);
       _recordStaticType(node, staticType);
     }
+    _nullShortingTermination(node);
   }
 
   /**
@@ -967,15 +968,12 @@ class StaticTypeAnalyzer extends SimpleAstVisitor<void> {
       // TODO(brianwilkerson) Report this internal error.
     }
 
-    if (node.operator.type == TokenType.QUESTION_PERIOD &&
-        _nonNullableEnabled) {
-      staticType = _typeSystem.makeNullable(staticType);
-    }
     staticType = _inferTearOff(node, node.propertyName, staticType);
 
     if (!_inferObjectAccess(node, staticType, propertyName)) {
       _recordStaticType(propertyName, staticType);
       _recordStaticType(node, staticType);
+      _nullShortingTermination(node);
     }
   }
 
@@ -2006,6 +2004,25 @@ class StaticTypeAnalyzer extends SimpleAstVisitor<void> {
     return type;
   }
 
+  /// If we reached a null-shorting termination, and the [node] has null
+  /// shorting, make the type of the [node] nullable.
+  void _nullShortingTermination(Expression node) {
+    if (!_nonNullableEnabled) return;
+
+    var parent = node.parent;
+    if (parent is AssignmentExpression && parent.leftHandSide == node) {
+      return;
+    }
+    if (parent is PropertyAccess) {
+      return;
+    }
+
+    if (_hasNullShorting(node)) {
+      var type = node.staticType;
+      node.staticType = _typeSystem.makeNullable(type);
+    }
+  }
+
   /**
    * Record that the static type of the given node is the given type.
    *
@@ -2120,6 +2137,18 @@ class StaticTypeAnalyzer extends SimpleAstVisitor<void> {
       return type;
     }
   }
+
+  /// Return `true` if the [node] has null-aware shorting, e.g. `foo?.bar`.
+  static bool _hasNullShorting(Expression node) {
+    if (node is AssignmentExpression) {
+      return _hasNullShorting(node.leftHandSide);
+    }
+    if (node is PropertyAccess) {
+      return node.operator.type == TokenType.QUESTION_PERIOD ||
+          _hasNullShorting(node.target);
+    }
+    return false;
+  }
 }
 
 class _InferredCollectionElementTypeInformation {
diff --git a/pkg/analyzer/test/src/diagnostics/unchecked_use_of_nullable_value_test.dart b/pkg/analyzer/test/src/diagnostics/unchecked_use_of_nullable_value_test.dart
