Fix completion after null-coalescing assignment (#34348)

src/EditorFeatures/CSharpTest/Diagnostics/GenerateMethod/GenerateMethodTests.cs

@@ -44,6 +44,60 @@ private void Goo()
 }");
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsGenerateMethod)]
+        public async Task TestOnRightOfNullCoalescingAssignment_NullableBool()
+        {
+            await TestInRegularAndScriptAsync(
+@"class Class
+{
+    void Method(bool? b)
+    {
+        b ??= [|Goo|]();
+    }
+}",
+@"using System;
+
+class Class
+{
+    void Method(bool? b)
+    {
+        b ??= Goo();
+    }
+
+    private bool? Goo()
+    {
+        throw new NotImplementedException();
+    }
+}");
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsGenerateMethod)]
+        public async Task TestOnRightOfNullCoalescingAssignment_String()
+        {
+            await TestInRegularAndScriptAsync(
+@"class Class
+{
+    void Method(string s)
+    {
+        s ??= [|Goo|]();
+    }
+}",
+@"using System;
+
+class Class
+{
+    void Method(string s)
+    {
+        s ??= Goo();
+    }
+
+    private string Goo()
+    {
+        throw new NotImplementedException();
+    }
+}");
+        }
+
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsGenerateMethod)]
         public async Task TestSimpleInvocationIntoSameType_CodeStyle1()
         {

src/EditorFeatures/CSharpTest2/Recommendations/NewKeywordRecommenderTests.cs

@@ -117,6 +117,14 @@ public async Task TestStartOfExpression()
 @"var q = $$"));
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.KeywordRecommending)]
+        [WorkItem(34324, "https://github.com/dotnet/roslyn/issues/34324")]
+        public async Task TestAfterNullCoalescingAssignment()
+        {
+            await VerifyKeywordAsync(AddInsideMethod(
+@"q ??= $$"));
+        }
+
         [Fact, Trait(Traits.Feature, Traits.Features.KeywordRecommending)]
         public async Task TestInParenthesizedExpression()
         {

src/Workspaces/CSharp/Portable/Extensions/ContextQuery/SyntaxTreeExtensions.cs

@@ -2023,6 +2023,7 @@ public static bool IsLabelContext(this SyntaxTree syntaxTree, int position, Canc
             // q |= |
             // q <<= |
             // q >>= |
+            // q ??= |
             if (token.IsKind(SyntaxKind.EqualsToken) ||
                 token.IsKind(SyntaxKind.MinusEqualsToken) ||
                 token.IsKind(SyntaxKind.AsteriskEqualsToken) ||
@@ -2034,7 +2035,8 @@ public static bool IsLabelContext(this SyntaxTree syntaxTree, int position, Canc
                 token.IsKind(SyntaxKind.BarEqualsToken) ||
                 token.IsKind(SyntaxKind.PercentEqualsToken) ||
                 token.IsKind(SyntaxKind.LessThanLessThanEqualsToken) ||
-                token.IsKind(SyntaxKind.GreaterThanGreaterThanEqualsToken))
+                token.IsKind(SyntaxKind.GreaterThanGreaterThanEqualsToken) ||
+                token.IsKind(SyntaxKind.QuestionQuestionEqualsToken))
             {
                 return true;
             }