Do null-aware shorting for IndexExpression.

scheglov · commit-bot@chromium.org · commit 35f45f0ee410 · 2019-09-05T23:52:39.000Z
R=brianwilkerson@google.com Change-Id: I72e6aabb4fd2f79201ee1146e6ea83aa54ceb7a6 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/115763 Reviewed-by: Brian Wilkerson <brianwilkerson@google.com> Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
diff --git a/pkg/analyzer/lib/src/generated/static_type_analyzer.dart b/pkg/analyzer/lib/src/generated/static_type_analyzer.dart
@@ -616,14 +616,9 @@ class StaticTypeAnalyzer extends SimpleAstVisitor<void> {
     }
 
     type ??= _dynamicType;
-    if (_nonNullableEnabled) {
-      if (node.leftBracket.type ==
-          TokenType.QUESTION_PERIOD_OPEN_SQUARE_BRACKET) {
-        type = _typeSystem.makeNullable(type);
-      }
-    }
 
     _recordStaticType(node, type);
+    _nullShortingTermination(node);
   }
 
   /**
@@ -2154,6 +2149,11 @@ class StaticTypeAnalyzer extends SimpleAstVisitor<void> {
     if (node is AssignmentExpression) {
       return _hasNullShorting(node.leftHandSide);
     }
+    if (node is IndexExpression) {
+      return node.leftBracket.type ==
+              TokenType.QUESTION_PERIOD_OPEN_SQUARE_BRACKET ||
+          _hasNullShorting(node.target);
+    }
     if (node is PropertyAccess) {
       return node.operator.type == TokenType.QUESTION_PERIOD ||
           _hasNullShorting(node.target);
diff --git a/pkg/analyzer/test/src/dart/resolution/index_expression_test.dart b/pkg/analyzer/test/src/dart/resolution/index_expression_test.dart
@@ -218,7 +218,6 @@ main(A? a) {
     assertType(indexExpression, 'bool?');
   }
 
-  @failingTest
   test_readWrite_nullable() async {
     await assertNoErrorsInCode(r'''
 class A {
@@ -242,7 +241,7 @@ main(A? a) {
       indexExpression.index,
       indexEqElement.parameters[0],
     );
-    assertType(indexExpression, 'num?');
+    assertType(indexExpression, 'num');
 
     var assignment = indexExpression.parent as AssignmentExpression;
     assertElement(assignment, numPlusElement);
@@ -253,7 +252,6 @@ main(A? a) {
     );
   }
 
-  @failingTest
   test_write_nullable() async {
     await assertNoErrorsInCode(r'''
 class A {
@@ -274,7 +272,7 @@ main(A? a) {
       indexExpression.index,
       indexEqElement.parameters[0],
     );
-    assertType(indexExpression, 'num?');
+    assertType(indexExpression, 'num');
 
     var assignment = indexExpression.parent as AssignmentExpression;
     assertElement(assignment, null);
diff --git a/tests/language_2/nnbd/resolution/question_dot_index_produces_nullable_type_test.dart b/tests/language_2/nnbd/resolution/question_dot_index_produces_nullable_type_test.dart
@@ -8,18 +8,26 @@ void main() {}
 
 void f1(NotGeneric x) {
   x[0] + 1; //# 01: ok
+  x[0] = 1; //# 02: ok
+  useNonNullable(x[0] = 1); //# 03: ok
+  x[0] += 1; //# 04: ok
+  useNonNullable(x[0] += 1); //# 05: ok
 }
 
 void f2(NotGeneric? x) {
-  x?.[0] + 1; //# 02: compile-time error
+  x?.[0] + 1; //# 06: compile-time error
+  x?.[0] = 1; //# 07: ok
+  useNonNullable(x?.[0] = 1); //# 08: compile-time error
+  x?.[0] += 1; //# 09: ok
+  useNonNullable(x?.[0] += 1); //# 10: compile-time error
 }
 
 void f3<T extends num>(Generic<T>? x) {
-  x?.[0] + 1; //# 03: compile-time error
+  x?.[0] + 1; //# 11: compile-time error
 }
 
 void f4<T extends num>(Generic<T?> x) {
-  x[0] + 1; //# 04: compile-time error
+  x[0] + 1; //# 12: compile-time error
 }
 
 class NotGeneric {
@@ -31,3 +39,5 @@ class Generic<T> {
   T operator[](int index) => throw 'unreachable';
   void operator[]=(int index, T value) => throw 'unreachable';
 }
+
+void useNonNullable(int a) {}
