Disallow initializers for extern events (#40114)

RikkiGibson · web-flow · commit 6feed580730d · 2019-12-13T13:08:38.000-08:00
diff --git a/docs/compilers/CSharp/Compiler Breaking Changes - post VS2019.md b/docs/compilers/CSharp/Compiler Breaking Changes - post VS2019.md
@@ -78,3 +78,11 @@ could be different than the one that compiler used to find.
     ```
 
 11. Previously, the language version was not checked for `this ref` and `this in` orderings of parameter modifiers. In *Visual Studio 2019 version 16.4* these orderings produce an error with langversion below 7.2. See https://github.com/dotnet/roslyn/issues/38486
+
+12. https://github.com/dotnet/roslyn/issues/40092 Previously, the compiler allowed `extern event` declarations to have initializers, in violation of the C# language specification. In *Visual Studio 2019 version 16.5* such declarations produce compile errors.
+    ```C#
+    class C
+    {
+        extern event System.Action E = null; // error
+    }
+    ```
diff --git a/src/Compilers/CSharp/Portable/CSharpResources.Designer.cs b/src/Compilers/CSharp/Portable/CSharpResources.Designer.cs
diff --git a/src/Compilers/CSharp/Portable/CSharpResources.resx b/src/Compilers/CSharp/Portable/CSharpResources.resx
@@ -5924,4 +5924,7 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_VarianceInterfaceNesting" xml:space="preserve">
     <value>Enums, classes, and structures cannot be declared in an interface that has an 'in' or 'out' type parameter.</value>
   </data>
+  <data name="ERR_ExternEventInitializer" xml:space="preserve">
+    <value>'{0}': extern event cannot have initializer</value>
+  </data>
 </root>
diff --git a/src/Compilers/CSharp/Portable/Errors/ErrorCode.cs b/src/Compilers/CSharp/Portable/Errors/ErrorCode.cs
@@ -1737,6 +1737,8 @@ internal enum ErrorCode
 
         ERR_InternalError = 8751,
 
+        ERR_ExternEventInitializer = 8760,
+
         // Note: you will need to re-generate compiler code after adding warnings (eng\generate-compiler-code.cmd)
     }
 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceFieldLikeEventSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceFieldLikeEventSymbol.cs
@@ -68,6 +68,10 @@ internal SourceFieldLikeEventSymbol(SourceMemberContainerTypeSymbol containingTy
                 {
                     diagnostics.Add(ErrorCode.ERR_AbstractEventInitializer, this.Locations[0], this);
                 }
+                else if (this.IsExtern)
+                {
+                    diagnostics.Add(ErrorCode.ERR_ExternEventInitializer, this.Locations[0], this);
+                }
             }
 
             // NOTE: if there's an initializer in source, we'd better create a backing field, regardless of
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf
@@ -177,6 +177,11 @@
         <target state="translated">Strom výrazů nesmí obsahovat operátor řazené kolekce členů == nebo !=.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">Funkce {0} je aktuálně ve verzi Preview a je *nepodporovaná*. Pokud chcete používat funkce Preview, použijte jazykovou verzi preview.</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf
@@ -177,6 +177,11 @@
         <target state="translated">Eine Ausdrucksbaumstruktur darf keinen ==- oder !=-Tupeloperator enthalten.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">Das Feature "{0}" befindet sich zurzeit in der Vorschau und wird *nicht unterstützt*. Um Previewfunktionen zu nutzen, verwenden Sie die Sprachversion "Preview".</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf
@@ -177,6 +177,11 @@
         <target state="translated">Un árbol de expresión no puede contener un operador de tupla == o !=.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">La característica "{0}" se encuentra actualmente en vista previa y *no se admite*. Para usar características en vista previa, utilice la versión de idioma "vista previa".</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf
@@ -177,6 +177,11 @@
         <target state="translated">Une arborescence de l'expression ne peut pas contenir un opérateur de tuple == ou !=</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">La fonctionnalité '{0}' est actuellement en préversion et *n'est pas prise en charge*. Pour utiliser les fonctionnalités en préversion, utilisez la version de langage 'preview'.</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf
@@ -177,6 +177,11 @@
         <target state="translated">Un albero delle espressioni non può contenere un operatore == o != di tupla</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">La funzionalità '{0}' è attualmente disponibile in anteprima e *non è supportata*. Per usare funzionalità in anteprima, scegliere la versione del linguaggio 'preview'.</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf
@@ -177,6 +177,11 @@
         <target state="translated">式ツリーにタプルの == または != 演算子を含めることはできません</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">機能 '{0}' は現在、プレビュー段階であり、*サポートされていません*。プレビュー機能を使用するには、'preview' 言語バージョンを使用してください。</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf
@@ -177,6 +177,11 @@
         <target state="translated">식 트리에는 튜플 == 또는 != 연산자를 사용할 수 없습니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">'{0}' 기능은 현재 미리 보기로 제공되며 *지원되지 않습니다*. 미리 보기 기능을 사용하려면 '미리 보기' 언어 버전을 사용하세요.</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf
@@ -177,6 +177,11 @@
         <target state="translated">Drzewo wyrażenia nie może zawierać operatora == ani != krotki.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">Funkcja „{0}” jest obecnie w wersji zapoznawczej i jest *nieobsługiwana*. Aby używać funkcji w wersji zapoznawczej, skorzystaj z wersji języka w wersji zapoznawczej.</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf
@@ -177,6 +177,11 @@
         <target state="translated">Uma árvore de expressão não pode conter um operador == ou != de tupla</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">O recurso '{0}' está atualmente na Versão Prévia e *sem suporte*. Para usar os recursos da Versão Prévia, use a versão de linguagem da "versão prévia".</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf
@@ -177,6 +177,11 @@
         <target state="translated">Дерево выражений не может содержать оператор == или != кортежа.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">Функция "{0}" сейчас находится на этапе предварительной версии и *является неподдерживаемой*. Для работы с предварительными версиями функций используйте версию языка "preview".</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf
@@ -177,6 +177,11 @@
         <target state="translated">İfade ağacı, demetin == veya != işlecini içeremez.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">'{0}' özelliği şu anda Önizleme aşamasındadır ve *desteklenmemektedir*. Önizleme özelliklerini kullanmak için 'önizleme' dil sürümünü kullanın.</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf
@@ -177,6 +177,11 @@
         <target state="translated">表达式树不能包含元组 == 或 != 运算符</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">功能“{0}”当前为预览版且*不受支持*。要使用预览版功能，请使用“预览”语言版本。</target>
diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf
@@ -177,6 +177,11 @@
         <target state="translated">運算式樹狀架構不得包含元組 == 或 != 運算子。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ExternEventInitializer">
+        <source>'{0}': extern event cannot have initializer</source>
+        <target state="new">'{0}': extern event cannot have initializer</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_FeatureInPreview">
         <source>The feature '{0}' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.</source>
         <target state="translated">功能 '{0}' 目前處於預覽階段，且*不受支援*。若要使用預覽功能，請使用「預覽語言」版本。</target>
diff --git a/src/Compilers/CSharp/Test/Symbol/Symbols/Source/EventTests.cs b/src/Compilers/CSharp/Test/Symbol/Symbols/Source/EventTests.cs
@@ -2453,6 +2453,24 @@ static void Main()
                 );
         }
 
+        [Fact, WorkItem(40092, "https://github.com/dotnet/roslyn/issues/40092")]
+        public void ExternEventInitializer()
+        {
+            var text = @"
+delegate void D();
+
+class Test
+{
+#pragma warning disable 414 // The field '{0}' is assigned but its value is never used
+    public extern event D e = null; // 1
+}
+";
+            CreateCompilation(text).VerifyDiagnostics(
+                // (7,27): error CS8760: 'Test.e': extern event cannot have initializer
+                //     public extern event D e = null; // 1
+                Diagnostic(ErrorCode.ERR_ExternEventInitializer, "e").WithArguments("Test.e").WithLocation(7, 27));
+        }
+
         #endregion
     }
 }

Original file line number	Diff line number	Diff line change
`@@ -1737,6 +1737,8 @@ internal enum ErrorCode`
`1737`	`1737`
`1738`	`1738`	`ERR_InternalError = 8751,`
`1739`	`1739`
	`1740`	`+ ERR_ExternEventInitializer = 8760,`
	`1741`	`+`
`1740`	`1742`	`// Note: you will need to re-generate compiler code after adding warnings (eng\generate-compiler-code.cmd)`
`1741`	`1743`	`}`
`1742`	`1744`	`}`
Original file line number	Diff line number	Diff line change
`@@ -68,6 +68,10 @@ internal SourceFieldLikeEventSymbol(SourceMemberContainerTypeSymbol containingTy`
`68`	`68`	`{`
`69`	`69`	`diagnostics.Add(ErrorCode.ERR_AbstractEventInitializer, this.Locations[0], this);`
`70`	`70`	`}`
	`71`	`+ else if (this.IsExtern)`
	`72`	`+ {`
	`73`	`+ diagnostics.Add(ErrorCode.ERR_ExternEventInitializer, this.Locations[0], this);`
	`74`	`+ }`
`71`	`75`	`}`
`72`	`76`
`73`	`77`	`// NOTE: if there's an initializer in source, we'd better create a backing field, regardless of`