dotnet · gafter · Apr 6, 2019 · Apr 2, 2019
diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_Patterns.cs b/src/Compilers/CSharp/Portable/Binder/Binder_Patterns.cs
@@ -185,8 +185,7 @@ internal BoundExpression ConvertPatternExpression(
 
             // If we are pattern-matching against an open type, we do not convert the constant to the type of the input.
             // This permits us to match a value of type `IComparable<T>` with a pattern of type `int`.
-            bool inputContainsTypeParameter = inputType.ContainsTypeParameter();
-            if (inputContainsTypeParameter)
+            if (inputType.ContainsTypeParameter())
             {
                 convertedExpression = expression;
                 if (!hasErrors)
@@ -198,11 +197,25 @@ internal BoundExpression ConvertPatternExpression(
                         {
                             // We do not permit matching null against a struct type.
                             diagnostics.Add(ErrorCode.ERR_ValueCantBeNull, expression.Syntax.Location, inputType);
+                            hasErrors = true;
                         }
                     }
                     else if (ExpressionOfTypeMatchesPatternType(Conversions, inputType, expression.Type, ref useSiteDiagnostics, out _, operandConstantValue: null) == false)
                     {
                         diagnostics.Add(ErrorCode.ERR_PatternWrongType, expression.Syntax.Location, inputType, expression.Display);
+                        hasErrors = true;
+                    }
+
+                    if (!hasErrors)
+                    {
+                        var requiredVersion = MessageID.IDS_FeatureRecursivePatterns.RequiredVersion();
+                        if (Compilation.LanguageVersion < requiredVersion &&
+                            // A null pattern can be tested against a type that can be assigned null, even in C# 7.3
+                            !(expression.ConstantValue == ConstantValue.Null && inputType.CanBeAssignedNull()))
+                        {
+                            diagnostics.Add(ErrorCode.ERR_ConstantPatternVsOpenType,
+                                expression.Syntax.Location, inputType, expression.Display, new CSharpRequiredLanguageVersion(requiredVersion));
+                        }
                     }
 
                     diagnostics.Add(node, useSiteDiagnostics);
@@ -222,7 +235,7 @@ internal BoundExpression ConvertPatternExpression(
                     if (inputType.IsNullableType() && (convertedExpression.ConstantValue == null || !convertedExpression.ConstantValue.IsNull))
                     {
                         // Null is a special case here because we want to compare null to the Nullable<T> itself, not to the underlying type.
-                        var discardedDiagnostics = DiagnosticBag.GetInstance(); // We are not intested in the diagnostic that get created here
+                        var discardedDiagnostics = DiagnosticBag.GetInstance(); // We are not interested in the diagnostic that get created here
                         convertedExpression = CreateConversion(operand, inputType.GetNullableUnderlyingType(), discardedDiagnostics);
                         discardedDiagnostics.Free();
                     }

diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_Symbols.cs b/src/Compilers/CSharp/Portable/Binder/Binder_Symbols.cs
@@ -786,7 +786,7 @@ protected NamespaceOrTypeOrAliasSymbolWithAnnotations BindNonGenericSimpleNamesp
                  SyntaxFacts.IsInTypeOnlyContext(node)) &&
                 node.Identifier.ValueText == "dynamic" &&
                 !IsViableType(result) &&
-                ((CSharpParseOptions)node.SyntaxTree.Options).LanguageVersion >= MessageID.IDS_FeatureDynamic.RequiredVersion())
+                Compilation.LanguageVersion >= MessageID.IDS_FeatureDynamic.RequiredVersion())
             {
                 bindingResult = Compilation.DynamicType;
                 ReportUseSiteDiagnosticForDynamic(diagnostics, node);

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
@@ -5076,6 +5076,9 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_PatternWrongType" xml:space="preserve">
     <value>An expression of type '{0}' cannot be handled by a pattern of type '{1}'.</value>
   </data>
+  <data name="ERR_ConstantPatternVsOpenType" xml:space="preserve">
+    <value>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</value>
+  </data>
   <data name="WRN_AttributeIgnoredWhenPublicSigning" xml:space="preserve">
     <value>Attribute '{0}' is ignored when public signing is specified.</value>
   </data>

diff --git a/src/Compilers/CSharp/Portable/Errors/ErrorCode.cs b/src/Compilers/CSharp/Portable/Errors/ErrorCode.cs
@@ -1610,7 +1610,7 @@ internal enum ErrorCode
         ERR_VarMayNotBindToType = 8508,
         WRN_SwitchExpressionNotExhaustive = 8509,
         ERR_SwitchArmSubsumed = 8510,
-        // 8511, // available
+        ERR_ConstantPatternVsOpenType = 8511,
         WRN_CaseConstantNamedUnderscore = 8512,
         WRN_IsTypeNamedUnderscore = 8513,
         ERR_ExpressionTreeContainsSwitchExpression = 8514,

diff --git a/src/Compilers/CSharp/Portable/FlowAnalysis/AbstractFlowPass_Switch.cs b/src/Compilers/CSharp/Portable/FlowAnalysis/AbstractFlowPass_Switch.cs
@@ -88,7 +88,7 @@ private bool IsTraditionalSwitch(BoundSwitchStatement node)
 
             // If we are in a recent enough language version, we treat the switch as a fully pattern-based switch
             // for the purposes of flow analysis.
-            if (((CSharpParseOptions)node.Syntax.SyntaxTree.Options).LanguageVersion >= MessageID.IDS_FeatureRecursivePatterns.RequiredVersion())
+            if (compilation.LanguageVersion >= MessageID.IDS_FeatureRecursivePatterns.RequiredVersion())
             {
                 return false;
             }

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf
@@ -67,6 +67,11 @@
         <target state="translated">Parametr typu {1} má omezení unmanaged, takže není možné používat {1} jako omezení pro {0}.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">Název {0} neodpovídá příslušnému parametru Deconstruct {1}.</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf
@@ -67,6 +67,11 @@
         <target state="translated">Der {1}-Typparameter enthält die Einschränkung "unmanaged". "{1}" kann daher nicht als Einschränkung für "{0}" verwendet werden.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">Der Name "{0}" stimmt nicht mit dem entsprechenden Deconstruct-Parameter "{1}" überein.</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf
@@ -67,6 +67,11 @@
         <target state="translated">El parámetro de tipo "{1}" tiene la restricción "unmanaged"; por tanto, "{1}" no se puede usar como restricción para "{0}"</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">El nombre "{0}" no coincide con el parámetro de "Deconstruct" correspondiente, "{1}".</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf
@@ -67,6 +67,11 @@
         <target state="translated">Le paramètre de type '{1}' a la contrainte 'unmanaged'. '{1}' ne peut donc pas être utilisé comme contrainte pour '{0}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">Le nom '{0}' ne correspond pas au paramètre 'Deconstruct' correspondant '{1}'.</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf
@@ -67,6 +67,11 @@
         <target state="translated">Il parametro di tipo '{1}' ha il vincolo 'managed'. Non è quindi possibile usare '{1}' come vincolo per '{0}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">Il nome '{0}' non corrisponde al parametro '{1}' di 'Deconstruct' corrispondente.</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf
@@ -67,6 +67,11 @@
         <target state="translated">型パラメーター '{1}' は 'unmanaged' 制約を含むので、'{0}' の制約として '{1}' を使用することはできません</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">名前 '{0}' は対応する 'Deconstruct' パラメーター '{1}' と一致しません。</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf
@@ -67,6 +67,11 @@
         <target state="translated">형식 매개 변수 '{1}'에 'unmanaged' 제약 조건이 있으므로 '{1}'은(는) '{0}'에 대한 제약 조건으로 사용할 수 없습니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">'{0}' 이름이 해당 'Deconstruct' 매개 변수 '{1}'과(와) 일치하지 않습니다.</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf
@@ -67,6 +67,11 @@
         <target state="translated">Parametr typu „{1}” ma ograniczenie „unmanaged”, dlatego elementu „{1}” nie można użyć jako ograniczenia dla elementu „{0}”</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">Nazwa „{0}” nie jest zgodna z odpowiednim parametrem „Deconstruct” „{1}”.</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf
@@ -67,6 +67,11 @@
         <target state="translated">O parâmetro de tipo '{1}' tem a restrição 'unmanaged' e, por isso, '{1}' não pode ser usado como uma restrição de '{0}'</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">O nome '{0}' não corresponde ao parâmetro 'Deconstruct' '{1}'.</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf
@@ -67,6 +67,11 @@
         <target state="translated">Параметр типа "{1}" имеет ограничение "unmanaged", поэтому "{1}" не может использоваться в качестве ограничения для "{0}".</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">Имя "{0}" не соответствует указанному параметру "Deconstruct" "{1}".</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf
@@ -67,6 +67,11 @@
         <target state="translated">'{1}' tür parametresinde 'unmanaged' kısıtlaması olduğundan '{1}', '{0}' için kısıtlama olarak kullanılamaz</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">'{0}' adı ilgili '{1}' 'Deconstruct' parametresiyle eşleşmiyor.</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf
@@ -67,6 +67,11 @@
         <target state="translated">类型参数“{1}”具有 "unmanaged" 约束，因此“{1}”不能用作“{0}”的约束</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">名称“{0}”与相应 "Deconstruct" 参数“{1}”不匹配。</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf
@@ -67,6 +67,11 @@
         <target state="translated">類型參數 '{1}' 有 'unmanaged' 條件約束，因此 '{1}' 不可作為 '{0}' 的條件約束</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_ConstantPatternVsOpenType">
+        <source>An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</source>
+        <target state="new">An expression of type '{0}' cannot be handled by a pattern of type '{1}'. Please use language version '{2}' or greater to match an open type with a constant pattern.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_DeconstructParameterNameMismatch">
         <source>The name '{0}' does not match the corresponding 'Deconstruct' parameter '{1}'.</source>
         <target state="translated">名稱 '{0}' 與對應的 'Deconstruct' 參數 '{1}' 不相符。</target>