Implement designator restrictions for C# 9.0 patterns (#40543)

Fixes #40533
Relates to dotnet/csharplang#2850
Relates to #40727 (test plan for C# 8 patterns)

src/Compilers/CSharp/Portable/Binder/SwitchBinder.cs

@@ -213,7 +213,7 @@ private void BuildSwitchLabels(SyntaxList<SwitchLabelSyntax> labelsSyntax, Binde
                         // bind the pattern, to cause its pattern variables to be inferred if necessary
                         var matchLabel = (CasePatternSwitchLabelSyntax)labelSyntax;
                         var pattern = sectionBinder.BindPattern(
-                            matchLabel.Pattern, SwitchGoverningType, SwitchGoverningValEscape, labelSyntax.HasErrors, tempDiagnosticBag);
+                            matchLabel.Pattern, SwitchGoverningType, SwitchGoverningValEscape, permitDesignations: true, labelSyntax.HasErrors, tempDiagnosticBag);
                         break;
 
                     default:

src/Compilers/CSharp/Portable/Binder/SwitchBinder_Patterns.cs

@@ -267,7 +267,7 @@ private BoundSwitchLabel BindSwitchSectionLabel(
                     {
                         var matchLabelSyntax = (CasePatternSwitchLabelSyntax)node;
                         BoundPattern pattern = sectionBinder.BindPattern(
-                            matchLabelSyntax.Pattern, SwitchGoverningType, SwitchGoverningValEscape, node.HasErrors, diagnostics);
+                            matchLabelSyntax.Pattern, SwitchGoverningType, SwitchGoverningValEscape, permitDesignations: true, node.HasErrors, diagnostics);
                         if (matchLabelSyntax.Pattern is ConstantPatternSyntax p)
                             reportIfConstantNamedUnderscore(pattern, p.Expression);
 

src/Compilers/CSharp/Portable/Binder/SwitchExpressionArmBinder.cs

@@ -36,7 +36,7 @@ internal override BoundSwitchExpressionArm BindSwitchExpressionArm(SwitchExpress
             Binder armBinder = this.GetBinder(node);
             bool hasErrors = _switchExpressionBinder.SwitchGoverningType.IsErrorType();
             ImmutableArray<LocalSymbol> locals = _armScopeBinder.Locals;
-            BoundPattern pattern = armBinder.BindPattern(node.Pattern, _switchExpressionBinder.SwitchGoverningType, _switchExpressionBinder.SwitchGoverningValEscape, hasErrors, diagnostics);
+            BoundPattern pattern = armBinder.BindPattern(node.Pattern, _switchExpressionBinder.SwitchGoverningType, _switchExpressionBinder.SwitchGoverningValEscape, permitDesignations: true, hasErrors, diagnostics);
             BoundExpression whenClause = node.WhenClause != null
                 ? armBinder.BindBooleanExpression(node.WhenClause.Condition, diagnostics)
                 : null;

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -5951,4 +5951,7 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_ImplicitRangeIndexerWithName" xml:space="preserve">
     <value>Invocation of implicit Range Indexer cannot name the argument.</value>
   </data>
+  <data name="ERR_DesignatorBeneathPatternCombinator" xml:space="preserve">
+    <value>A variable may not be declared within a 'not' or 'or' pattern.</value>
+  </data>
 </root>

src/Compilers/CSharp/Portable/Errors/ErrorCode.cs

@@ -1742,6 +1742,14 @@ internal enum ErrorCode
 
         ERR_ExternEventInitializer = 8760,
 
+        // available 8761-8779
+
+        #region diagnostics introduced for C# 9.0
+
+        ERR_DesignatorBeneathPatternCombinator = 8780,
+
+        #endregion diagnostics introduced for C# 9.0
+
         // Note: you will need to re-generate compiler code after adding warnings (eng\generate-compiler-code.cmd)
     }
 }

src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf

@@ -122,6 +122,11 @@
         <target state="translated">Výchozí literál default není platný jako vzor. Podle potřeby použijte jiný literál (například 0 nebo null). Pokud chcete, aby odpovídalo vše, použijte vzor discard „_“.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">Tento vzor discard není povolený jako návěstí příkazu case v příkazu switch. Použijte „case var _:“ pro vzor discard nebo „case @_:“ pro konstantu s názvem „_“.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf

@@ -122,6 +122,11 @@
         <target state="translated">Ein Standardliteral "default" ist als Muster ungültig. Verwenden Sie ggf. ein anderes Literal (z. B. 0 oder "null"). Verwenden Sie zum Abgleich aller Elemente ein discard-Muster "_".</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">Das discard-Muster ist als case-Bezeichnung in einer switch-Anweisung unzulässig. Verwenden Sie "case var _:" für ein discard-Muster oder "case @_:" für eine Konstante namens "_".</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf

@@ -122,6 +122,11 @@
         <target state="translated">Un literal predeterminado "default" no es válido como patrón. Use otro literal (por ejemplo, "0" o "null") según corresponda. Para hacer coincidir todo, use un patrón de descarte "_".</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">El patrón de descarte no se permite como etiqueta de caso en una instrucción switch. Use "case var _:" para un patrón de descarte o "case @_:" para una constante con el nombre '_'.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf

@@ -122,6 +122,11 @@
         <target state="translated">Un littéral par défaut 'default' est non valide en tant que modèle. Utilisez un autre littéral (par exemple, '0' ou 'null') selon le cas. Pour correspondre à tout, utilisez un modèle d'abandon '_'.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">Le modèle d'abandon n'est pas autorisé en tant qu'étiquette case dans une instruction switch. Utilisez 'case var _:' pour un modèle d'abandon, ou 'case @_:' pour une constante nommée '_'.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf

@@ -122,6 +122,11 @@
         <target state="translated">Non è possibile usare un valore letterale predefinito 'default' come criterio. Usare un altro valore letterale, ad esempio '0' o 'null'. Per abbinare tutto, usare un criterio di rimozione '_'.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">Il criterio di rimozione non è consentito come etichetta case in un'istruzione switch. Usare 'case var _:' per un criterio di rimozione oppure 'case @_:' per una costante denominata '_'.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf

@@ -122,6 +122,11 @@
         <target state="translated">既定のリテラル 'default' はパターンとして無効です。必要に応じて別のリテラル (例: '0' または 'null') をご使用ください。すべてと一致させるには、破棄パターン '_' をご使用ください。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">この破棄パターンは switch ステートメントの case ラベルとして許可されていません。破棄パターンに 'case var _:' を使用するか、'_' という定数に'case @_:' をご使用ください。</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf

@@ -122,6 +122,11 @@
         <target state="translated">기본 리터럴 'default'가 패턴으로 유효하지 않습니다. 다른 리터럴(예: '0' 또는 'null')을 적절하게 사용하세요. 모두 일치시키려면 무시 패턴 '_'을 사용하세요.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">무시 패턴은 switch 문의 case 레이블로 사용할 수 없습니다. 무시 패턴에 대해 'case var _:'을 사용하거나 이름이 '_'인 상수에 대해 'case @_:'을 사용하세요.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf

@@ -122,6 +122,11 @@
         <target state="translated">Domyślny literał „default” nie jest prawidłowy jako wzorzec. Użyj innego odpowiedniego literału (np. „0” lub „null”). Aby dopasować wszystko, użyj wzorca odrzucania „_”.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">Wzorzec odrzucania nie jest dozwolony jako etykieta instrukcji case w instrukcji switch. Użyj instrukcji „case var _:” w przypadku wzorca odrzucania lub użyj instrukcji „case @_:” w przypadku stałej o nazwie „_”.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf

@@ -122,6 +122,11 @@
         <target state="translated">Um literal padrão 'default' não é válido como um padrão. Use outro literal (por exemplo, '0' ou 'null') conforme o necessário. Para corresponder a tudo, use um padrão de descarte '_'.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">O padrão de descarte não é permitido como um rótulo de caso em uma instrução switch. Use 'case var _:' para um padrão de descarte ou 'case @_:' para uma constante chamada '_'.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf

@@ -122,6 +122,11 @@
         <target state="translated">Литерал по умолчанию "default" недопустимо использовать в качестве шаблона. Используйте другой литерал (например, "0" или "null") по мере необходимости. Чтобы задать полное совпадение, используйте шаблон отмены "_".</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">Шаблон отмены запрещено использовать как метку case в операторе switch. Используйте "case var _:" в качестве шаблона отмены или "case @_:" в качестве константы "_".</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf

@@ -122,6 +122,11 @@
         <target state="translated">'default' varsayılan sabit değeri bir desen olarak geçerli değil. Uygun olan başka bir sabit değeri (ör. '0' veya 'null') kullanın. Tüm öğeleri eşleştirmek için '_' atma desenini kullanın.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">Bir switch deyiminde case etiketi olarak atma desenine izin verilmez. Atma deseni için 'case var _:' veya '_' adlı bir sabit için 'case @_:' seçeneğini kullanın.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf

@@ -122,6 +122,11 @@
         <target state="new">There is no target type for the default literal.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">在 switch 语句中，不允许将放弃模式作为大小写标签。对于放弃模式，使用 "case var _:"；对于名为 "_" 的常量，使用 "case @_:"。</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf

@@ -122,6 +122,11 @@
         <target state="translated">預設常值 'default' 作為模式無效。請使用另一個適當的常值 (例如 '0' 或 'null')。若要比對所有項目，請使用捨棄模式 '_'。</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_DesignatorBeneathPatternCombinator">
+        <source>A variable may not be declared within a 'not' or 'or' pattern.</source>
+        <target state="new">A variable may not be declared within a 'not' or 'or' pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DiscardPatternInSwitchStatement">
         <source>The discard pattern is not permitted as a case label in a switch statement. Use 'case var _:' for a discard pattern, or 'case @_:' for a constant named '_'.</source>
         <target state="translated">捨棄模式不可為 switch 陳述式中的 case 標籤。針對捨棄模式，請使用 'case var _:'，針對名為 '_' 的常數，則請使用 'case @_:'。</target>