Report better errors when multiple invalid constraints are combined

Instead of reporting that a constraint must come first, if there are multiple constraints that must come first, we now report that these constraints cannot be combined. We also suppress these errors if a previous error about inherited constraints was reported. Fixes #45141.
dotnet · Jun 13, 2020 · 7ca0c7e · 7ca0c7e
1 parent 18b41d0
commit 7ca0c7e
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Showing 20 changed files with 543 additions and 33 deletions.
diff --git a/src/Compilers/CSharp/Portable/Binder/Binder_Constraints.cs b/src/Compilers/CSharp/Portable/Binder/Binder_Constraints.cs
@@ -126,6 +126,7 @@ internal ImmutableArray<TypeParameterConstraintClause> BindTypeParameterConstrai
             Debug.Assert(!InExecutableBinder); // Cannot eagerly report diagnostics handled by LazyMissingNonNullTypesContextDiagnosticInfo 
             bool hasTypeLikeConstraint = false;
             bool reportedOverrideWithConstraints = false;
+            MessageID? firstTypeConstraintString = null;
 
             for (int i = 0, n = constraintsSyntax.Count; i < n; i++)
             {
@@ -137,14 +138,18 @@ internal ImmutableArray<TypeParameterConstraintClause> BindTypeParameterConstrai
 
                         if (i != 0)
                         {
-                            diagnostics.Add(ErrorCode.ERR_RefValBoundMustBeFirst, syntax.GetFirstToken().GetLocation());
+                            if (!reportedOverrideWithConstraints)
+                            {
+                                reportNotFirstOrCannotCombine(diagnostics, syntax.GetFirstToken().GetLocation(), ErrorCode.ERR_RefValBoundMustBeFirst, MessageID.IDS_Class, firstTypeConstraintString);
+                            }
 
                             if (isForOverride && (constraints & (TypeParameterConstraintKind.ValueType | TypeParameterConstraintKind.ReferenceType)) != 0)
                             {
                                 continue;
                             }
                         }
 
+                        firstTypeConstraintString ??= MessageID.IDS_Class;
                         var constraintSyntax = (ClassOrStructConstraintSyntax)syntax;
                         SyntaxToken questionToken = constraintSyntax.QuestionToken;
                         if (questionToken.IsKind(SyntaxKind.QuestionToken))
@@ -175,14 +180,18 @@ internal ImmutableArray<TypeParameterConstraintClause> BindTypeParameterConstrai
 
                         if (i != 0)
                         {
-                            diagnostics.Add(ErrorCode.ERR_RefValBoundMustBeFirst, syntax.GetFirstToken().GetLocation());
+                            if (!reportedOverrideWithConstraints)
+                            {
+                                reportNotFirstOrCannotCombine(diagnostics, syntax.GetFirstToken().GetLocation(), ErrorCode.ERR_RefValBoundMustBeFirst, MessageID.IDS_Struct, firstTypeConstraintString);
+                            }
 
                             if (isForOverride && (constraints & (TypeParameterConstraintKind.ValueType | TypeParameterConstraintKind.ReferenceType)) != 0)
                             {
                                 continue;
                             }
                         }
 
+                        firstTypeConstraintString ??= MessageID.IDS_Struct;
                         constraints |= TypeParameterConstraintKind.ValueType;
                         continue;
                     case SyntaxKind.ConstructorConstraint:
@@ -233,10 +242,12 @@ internal ImmutableArray<TypeParameterConstraintClause> BindTypeParameterConstrai
                                 case ConstraintContextualKeyword.Unmanaged:
                                     if (i != 0)
                                     {
-                                        diagnostics.Add(ErrorCode.ERR_UnmanagedConstraintMustBeFirst, typeSyntax.GetLocation());
+                                        reportNotFirstOrCannotCombine(diagnostics, typeSyntax.GetLocation(), ErrorCode.ERR_UnmanagedConstraintMustBeFirst, MessageID.IDS_Unmanaged, firstTypeConstraintString);
                                         continue;
                                     }
 
+                                    firstTypeConstraintString ??= MessageID.IDS_Unmanaged;
+
                                     // This should produce diagnostics if the types are missing
                                     GetWellKnownType(WellKnownType.System_Runtime_InteropServices_UnmanagedType, diagnostics, typeSyntax);
                                     GetSpecialType(SpecialType.System_ValueType, diagnostics, typeSyntax);
@@ -247,9 +258,10 @@ internal ImmutableArray<TypeParameterConstraintClause> BindTypeParameterConstrai
                                 case ConstraintContextualKeyword.NotNull:
                                     if (i != 0)
                                     {
-                                        diagnostics.Add(ErrorCode.ERR_NotNullConstraintMustBeFirst, typeSyntax.GetLocation());
+                                        reportNotFirstOrCannotCombine(diagnostics, typeSyntax.GetLocation(), ErrorCode.ERR_NotNullConstraintMustBeFirst, MessageID.IDS_Notnull, firstTypeConstraintString);
                                     }
 
+                                    firstTypeConstraintString ??= MessageID.IDS_Notnull;
                                     constraints |= TypeParameterConstraintKind.NotNull;
                                     continue;
 
@@ -286,6 +298,18 @@ static void reportOverrideWithConstraints(ref bool reportedOverrideWithConstrain
                     reportedOverrideWithConstraints = true;
                 }
             }
+
+            static void reportNotFirstOrCannotCombine(DiagnosticBag diagnostics, Location constraintLocation, ErrorCode notFirstDiagnostic, MessageID currentConstraintString, MessageID? firstConstraintString)
+            {
+                if (firstConstraintString is MessageID firstConstraint)
+                {
+                    diagnostics.Add(ErrorCode.ERR_CannotCombineTypeConstraints, constraintLocation, currentConstraintString.Localize(), firstConstraint.Localize());
+                }
+                else
+                {
+                    diagnostics.Add(notFirstDiagnostic, constraintLocation);
+                }
+            }
         }
 
         internal ImmutableArray<TypeParameterConstraintClause> GetDefaultTypeParameterConstraintClauses(TypeParameterListSyntax typeParameterList)

diff --git a/src/Compilers/CSharp/Portable/CSharpResources.resx b/src/Compilers/CSharp/Portable/CSharpResources.resx
@@ -6262,4 +6262,19 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_CopyConstructorMustInvokeBaseCopyConstructor" xml:space="preserve">
     <value>A copy constructor in a record must call a copy constructor of the base, or a parameterless object constructor if the record inherits from object.</value>
   </data>
+  <data name="IDS_Class" xml:space="preserve">
+    <value>class</value>
+  </data>
+  <data name="IDS_Struct" xml:space="preserve">
+    <value>struct</value>
+  </data>
+  <data name="IDS_Unmanaged" xml:space="preserve">
+    <value>unmanaged</value>
+  </data>
+  <data name="IDS_Notnull" xml:space="preserve">
+    <value>notnull</value>
+  </data>
+  <data name="ERR_CannotCombineTypeConstraints" xml:space="preserve">
+    <value>The '{0}' constraint cannot be combined with the '{1}' constraint</value>
+  </data>
 </root>
diff --git a/src/Compilers/CSharp/Portable/Errors/ErrorCode.cs b/src/Compilers/CSharp/Portable/Errors/ErrorCode.cs
@@ -1835,6 +1835,7 @@ internal enum ErrorCode
         ERR_BadRecordMemberForPositionalParameter = 8866,
         ERR_NoCopyConstructorInBaseType = 8867,
         ERR_CopyConstructorMustInvokeBaseCopyConstructor = 8868,
+        ERR_CannotCombineTypeConstraints = 8869,
 
         #endregion
 

diff --git a/src/Compilers/CSharp/Portable/Errors/MessageID.cs b/src/Compilers/CSharp/Portable/Errors/MessageID.cs
@@ -206,6 +206,10 @@ internal enum MessageID
         IDS_FeatureInitOnlySetters = MessageBase + 12781,
         IDS_FeatureRecords = MessageBase + 12782,
         IDS_FeatureNullPointerConstantPattern = MessageBase + 12783,
+        IDS_Class = MessageBase + 12784,
+        IDS_Struct = MessageBase + 12785,
+        IDS_Unmanaged = MessageBase + 12786,
+        IDS_Notnull = MessageBase + 12787,
     }
 
     // Message IDs may refer to strings that need to be localized.

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf
@@ -152,6 +152,11 @@
         <target state="translated">Chyba syntaxe příkazového řádku: {0} není platná hodnota možnosti {1}. Hodnota musí mít tvar {2}.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_CannotCombineTypeConstraints">
+        <source>The '{0}' constraint cannot be combined with the '{1}' constraint</source>
+        <target state="new">The '{0}' constraint cannot be combined with the '{1}' constraint</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -1114,6 +1119,11 @@
 </target>
         <note>Visual C# Compiler Options</note>
       </trans-unit>
+      <trans-unit id="IDS_Class">
+        <source>class</source>
+        <target state="new">class</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_DefaultInterfaceImplementation">
         <source>default interface implementation</source>
         <target state="translated">implementace výchozího rozhraní</target>
@@ -1364,11 +1374,21 @@
         <target state="translated">&lt;null&gt;</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Notnull">
+        <source>notnull</source>
+        <target state="new">notnull</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_OverrideWithConstraints">
         <source>constraints for override and explicit interface implementation methods</source>
         <target state="translated">omezení pro metody přepsání a explicitní implementace rozhraní</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Struct">
+        <source>struct</source>
+        <target state="new">struct</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_ThrowExpression">
         <source>&lt;throw expression&gt;</source>
         <target state="translated">&lt;výraz throw&gt;</target>
@@ -1389,6 +1409,11 @@
         <target state="new">top-level statements</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Unmanaged">
+        <source>unmanaged</source>
+        <target state="new">unmanaged</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_XMLIGNORED">
         <source>&lt;!-- Badly formed XML comment ignored for member "{0}" --&gt;</source>
         <target state="translated">&lt;!-- Badly formed XML comment ignored for member "{0}" --&gt;</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf
@@ -152,6 +152,11 @@
         <target state="translated">Fehler in der Befehlszeilensyntax: "{0}" ist kein gültiger Wert für die Option "{1}". Der Wert muss im Format "{2}" vorliegen.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_CannotCombineTypeConstraints">
+        <source>The '{0}' constraint cannot be combined with the '{1}' constraint</source>
+        <target state="new">The '{0}' constraint cannot be combined with the '{1}' constraint</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -1114,6 +1119,11 @@
 </target>
         <note>Visual C# Compiler Options</note>
       </trans-unit>
+      <trans-unit id="IDS_Class">
+        <source>class</source>
+        <target state="new">class</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_DefaultInterfaceImplementation">
         <source>default interface implementation</source>
         <target state="translated">Standardschnittstellenimplementierung</target>
@@ -1364,11 +1374,21 @@
         <target state="translated">&lt;NULL&gt;</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Notnull">
+        <source>notnull</source>
+        <target state="new">notnull</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_OverrideWithConstraints">
         <source>constraints for override and explicit interface implementation methods</source>
         <target state="translated">Einschränkungen für Außerkraftsetzung und explizite Schnittstellenimplementierungsmethoden</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Struct">
+        <source>struct</source>
+        <target state="new">struct</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_ThrowExpression">
         <source>&lt;throw expression&gt;</source>
         <target state="translated">throw-Ausdruck</target>
@@ -1389,6 +1409,11 @@
         <target state="new">top-level statements</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Unmanaged">
+        <source>unmanaged</source>
+        <target state="new">unmanaged</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_XMLIGNORED">
         <source>&lt;!-- Badly formed XML comment ignored for member "{0}" --&gt;</source>
         <target state="translated">&lt;!-- Badly formed XML comment ignored for member "{0}" --&gt;</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf
@@ -152,6 +152,11 @@
         <target state="translated">Error de sintaxis de la línea de comandos: "{0}" no es un valor válido para la opción "{1}". El valor debe tener el formato "{2}".</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_CannotCombineTypeConstraints">
+        <source>The '{0}' constraint cannot be combined with the '{1}' constraint</source>
+        <target state="new">The '{0}' constraint cannot be combined with the '{1}' constraint</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -1114,6 +1119,11 @@
 </target>
         <note>Visual C# Compiler Options</note>
       </trans-unit>
+      <trans-unit id="IDS_Class">
+        <source>class</source>
+        <target state="new">class</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_DefaultInterfaceImplementation">
         <source>default interface implementation</source>
         <target state="translated">implementación de interfaz predeterminada</target>
@@ -1364,11 +1374,21 @@
         <target state="translated">&lt;NULL&gt;</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Notnull">
+        <source>notnull</source>
+        <target state="new">notnull</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_OverrideWithConstraints">
         <source>constraints for override and explicit interface implementation methods</source>
         <target state="translated">restricciones para métodos de implementación de interfaz explícita e invalidación</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Struct">
+        <source>struct</source>
+        <target state="new">struct</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_ThrowExpression">
         <source>&lt;throw expression&gt;</source>
         <target state="translated">&lt;expresión throw&gt;</target>
@@ -1389,6 +1409,11 @@
         <target state="new">top-level statements</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Unmanaged">
+        <source>unmanaged</source>
+        <target state="new">unmanaged</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_XMLIGNORED">
         <source>&lt;!-- Badly formed XML comment ignored for member "{0}" --&gt;</source>
         <target state="translated">&lt;!-- Badly formed XML comment ignored for member "{0}" --&gt;</target>

diff --git a/src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf b/src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf
@@ -152,6 +152,11 @@
         <target state="translated">Erreur de syntaxe de ligne de commande : '{0}' est une valeur non valide pour l'option '{1}'. La valeur doit se présenter sous la forme '{2}'.</target>
         <note />
       </trans-unit>
+      <trans-unit id="ERR_CannotCombineTypeConstraints">
+        <source>The '{0}' constraint cannot be combined with the '{1}' constraint</source>
+        <target state="new">The '{0}' constraint cannot be combined with the '{1}' constraint</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ERR_CannotConvertAddressOfToDelegate">
         <source>Cannot convert &amp;method group '{0}' to delegate type '{0}'.</source>
         <target state="new">Cannot convert &amp;method group '{0}' to delegate type '{0}'.</target>
@@ -1114,6 +1119,11 @@
 </target>
         <note>Visual C# Compiler Options</note>
       </trans-unit>
+      <trans-unit id="IDS_Class">
+        <source>class</source>
+        <target state="new">class</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_DefaultInterfaceImplementation">
         <source>default interface implementation</source>
         <target state="translated">implémentation d'interface par défaut</target>
@@ -1364,11 +1374,21 @@
         <target state="translated">&lt;Null&gt;</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Notnull">
+        <source>notnull</source>
+        <target state="new">notnull</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_OverrideWithConstraints">
         <source>constraints for override and explicit interface implementation methods</source>
         <target state="translated">contraintes des méthodes d'implémentation d'interface par remplacement et explicites</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Struct">
+        <source>struct</source>
+        <target state="new">struct</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_ThrowExpression">
         <source>&lt;throw expression&gt;</source>
         <target state="translated">&lt;expression throw&gt;</target>
@@ -1389,6 +1409,11 @@
         <target state="new">top-level statements</target>
         <note />
       </trans-unit>
+      <trans-unit id="IDS_Unmanaged">
+        <source>unmanaged</source>
+        <target state="new">unmanaged</target>
+        <note />
+      </trans-unit>
       <trans-unit id="IDS_XMLIGNORED">
         <source>&lt;!-- Badly formed XML comment ignored for member "{0}" --&gt;</source>
         <target state="translated">&lt;!-- Badly formed XML comment ignored for member "{0}" --&gt;</target>