From c59d431f47960436034ee5c9f0490c9575d86b17 Mon Sep 17 00:00:00 2001
From: CyrusNajmabadi <cyrusn@microsoft.com>
Date: Mon, 20 Feb 2017 13:52:11 -0800
Subject: [PATCH] Update Coalesce-for-nullables as well.

---
 .../UseCoalesceExpressionForNullableTests.cs  | 27 +++++++++++++++++++
 .../UseCoalesceExpressionTests.vb             |  4 +--
 ...sceExpressionForNullableCodeFixProvider.cs | 19 ++++++++++---
 3 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/src/EditorFeatures/CSharpTest/UseCoalesceExpression/UseCoalesceExpressionForNullableTests.cs b/src/EditorFeatures/CSharpTest/UseCoalesceExpression/UseCoalesceExpressionForNullableTests.cs
index 2dc12ff6e87..73931184fce 100644
--- a/src/EditorFeatures/CSharpTest/UseCoalesceExpression/UseCoalesceExpressionForNullableTests.cs
+++ b/src/EditorFeatures/CSharpTest/UseCoalesceExpression/UseCoalesceExpressionForNullableTests.cs
@@ -184,6 +184,33 @@ void M(int? x, int? y, int? z)
     {
         var w = x ?? y ?? z;
     }
+}");
+        }
+
+        [WorkItem(17028, "https://github.com/dotnet/roslyn/issues/17028")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCoalesceExpression)]
+        public async Task TestInExpressionOfT()
+        {
+            await TestAsync(
+@"using System;
+using System.Linq.Expressions;
+
+class C
+{
+    void M(int? x, int? y)
+    {
+        Expression<Func<int>> e = () => [||]!x.HasValue ? y : x.Value;
+    }
+}",
+@"using System;
+using System.Linq.Expressions;
+
+class C
+{
+    void M(int? x, int? y)
+    {
+        Expression<Func<int>> e = () => {|Warning:x ?? y|};
+    }
 }");
         }
     }
diff --git a/src/EditorFeatures/VisualBasicTest/UseCoalesceExpression/UseCoalesceExpressionTests.vb b/src/EditorFeatures/VisualBasicTest/UseCoalesceExpression/UseCoalesceExpressionTests.vb
index 8bd8c55f33f..a955f5ca3b6 100644
--- a/src/EditorFeatures/VisualBasicTest/UseCoalesceExpression/UseCoalesceExpressionTests.vb
+++ b/src/EditorFeatures/VisualBasicTest/UseCoalesceExpression/UseCoalesceExpressionTests.vb
@@ -247,7 +247,7 @@ Imports System.Linq.Expressions
 
 Class C
     Sub M(x as string, y as string)
-        dim e as Expression(of Func(of string)) = [||]If (x isnot Nothing, x, y)
+        dim e as Expression(of Func(of string)) = func() [||]If (x isnot Nothing, x, y)
     End Sub
 End Class",
 "Imports System
@@ -255,7 +255,7 @@ Imports System.Linq.Expressions
 
 Class C
     Sub M(x as string, y as string, z as string)
-        dim e as Expression(of Func(of string)) = If (x, y)
+        dim e as Expression(of Func(of string)) = func () If (x, y)
     End Sub
 End Class")
         End Function
diff --git a/src/Features/Core/Portable/UseCoalesceExpression/UseCoalesceExpressionForNullableCodeFixProvider.cs b/src/Features/Core/Portable/UseCoalesceExpression/UseCoalesceExpressionForNullableCodeFixProvider.cs
index 6f73ad2c463..0a8a3d471c0 100644
--- a/src/Features/Core/Portable/UseCoalesceExpression/UseCoalesceExpressionForNullableCodeFixProvider.cs
+++ b/src/Features/Core/Portable/UseCoalesceExpression/UseCoalesceExpressionForNullableCodeFixProvider.cs
@@ -33,11 +33,15 @@ public override Task RegisterCodeFixesAsync(CodeFixContext context)
             return SpecializedTasks.EmptyTask;
         }
 
-        protected override Task FixAllAsync(
+        protected override async Task FixAllAsync(
             Document document, ImmutableArray<Diagnostic> diagnostics,
             SyntaxEditor editor, CancellationToken cancellationToken)
         {
+            var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
+            var expressionTypeOpt = semanticModel.Compilation.GetTypeByMetadataName("System.Linq.Expressions.Expression`1");
+
             var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
+            var semanticFacts = document.GetLanguageService<ISemanticFactsService>();
             var generator = editor.Generator;
             var root = editor.OriginalRoot;
 
@@ -54,13 +58,20 @@ public override Task RegisterCodeFixesAsync(CodeFixContext context)
                         syntaxFacts.GetPartsOfConditionalExpression(
                             c, out var currentCondition, out var currentWhenTrue, out var currentWhenFalse);
 
-                        return whenPart == whenTrue
+                        var coalesceExpression = whenPart == whenTrue
                             ? g.CoalesceExpression(conditionExpression, syntaxFacts.WalkDownParentheses(currentWhenTrue))
                             : g.CoalesceExpression(conditionExpression, syntaxFacts.WalkDownParentheses(currentWhenFalse));
+
+                        if (semanticFacts.IsInExpressionTree(
+                                semanticModel, conditionalExpression, expressionTypeOpt, cancellationToken))
+                        {
+                            coalesceExpression = coalesceExpression.WithAdditionalAnnotations(
+                                WarningAnnotation.Create(FeaturesResources.Changes_to_expression_trees_may_result_in_behavior_changes_at_runtime));
+                        }
+
+                        return coalesceExpression;
                     });
             }
-
-            return SpecializedTasks.EmptyTask;
         }
 
         private class MyCodeAction : CodeAction.DocumentChangeAction
-- 
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