Merge pull request #36425 from dotnet/merges/master-to-features/param-nullchecking

Merge master to features/param-nullchecking

Author: dotnet-automerge-bot

docs/features/nullable-reference-types.md

@@ -289,7 +289,9 @@ A `class?` constraint is allowed, which, like class, requires the type argument
 [Nullable strawman](https://github.com/dotnet/csharplang/issues/790)
 [4/25/18](https://github.com/dotnet/csharplang/blob/master/meetings/2018/LDM-2018-04-25.md)
 
-An explicit `object` (or `System.Object`) constraint is allowed, which requires the type to be non-nullable (value or reference type).
+Explicit `object` (or `System.Object`) constraints of any nullability are disallowed. However, type substitution can lead to
+`object!` or `object~` constraints to appear among the constraint types, when their nullability is significant by comparison to
+other constraints. An `object!` constraint requires the type to be non-nullable (value or reference type).
 However, an explicit `object?` constraint is not allowed.
 An unconstrained (here it means - no type constraints, and no `class`, `struct`, or `unmanaged` constraints) type parameter is essentially
 equivalent to one constrained by `object?` when it is declared in a context where nullable annotations are enabled. If annotations are disabled,

eng/config/PublishData.json

@@ -24,16 +24,7 @@
       "nuget": [ "https://dotnet.myget.org/F/roslyn/api/v2/package" ],
       "vsix": [ "https://dotnet.myget.org/F/roslyn/vsix/upload" ],
       "channels": [ "dev16.1" ],
-      "vsBranch": "lab/d16.1stg",
-      "vsMajorVersion": 16
-    },
-    "release/dev16.2-preview2-vs-deps": {
-      "nugetKind": ["Shipping", "NonShipping"],
-      "version": "3.2.*",
-      "nuget": [ "https://dotnet.myget.org/F/roslyn/api/v2/package" ],
-      "vsix": [ "https://dotnet.myget.org/F/roslyn/vsix/upload" ],
-      "channels": [ "dev16.2p2" ],
-      "vsBranch": "rel/d16.2",
+      "vsBranch": "rel/d16.1",
       "vsMajorVersion": 16
     },
     "release/dev16.2-preview3-vs-deps": {
@@ -42,7 +33,7 @@
       "nuget": [ "https://dotnet.myget.org/F/roslyn/api/v2/package" ],
       "vsix": [ "https://dotnet.myget.org/F/roslyn/vsix/upload" ],
       "channels": [ "dev16.2p3" ],
-      "vsBranch": "lab/d16.2stg",
+      "vsBranch": "rel/d16.2",
       "vsMajorVersion": 16
     },
     "master-vs-deps": {

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

@@ -483,18 +483,6 @@ private static bool IsValidConstraintType(TypeConstraintSyntax syntax, TypeWithA
                     break;
 
                 case SpecialType.System_Object:
-                    if (typeWithAnnotations.NullableAnnotation.IsAnnotated())
-                    {
-                        // "Constraint cannot be special class '{0}'"
-                        Error(diagnostics, ErrorCode.ERR_SpecialTypeAsBound, syntax, typeWithAnnotations);
-                        return false;
-                    }
-
-                    // "Constraint cannot be special class '{0}'"
-                    Error(diagnostics, ErrorCode.WRN_SpecialTypeAsBound, syntax, typeWithAnnotations);
-                    CheckFeatureAvailability(syntax, MessageID.IDS_FeatureObjectGenericTypeConstraint, diagnostics);
-                    break;
-
                 case SpecialType.System_ValueType:
                 case SpecialType.System_Array:
                     // "Constraint cannot be special class '{0}'"

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

@@ -154,7 +154,7 @@ private NamespaceOrTypeOrAliasSymbolWithAnnotations BindTypeOrAliasOrConstraintK
                             CheckFeatureAvailability(syntax, MessageID.IDS_FeatureUnmanagedGenericTypeConstraint, diagnostics);
                             break;
                         case ConstraintContextualKeyword.NotNull:
-                            CheckFeatureAvailability(identifierSyntax, MessageID.IDS_NotNullGenericTypeConstraint, diagnostics);
+                            CheckFeatureAvailability(identifierSyntax, MessageID.IDS_FeatureNotNullGenericTypeConstraint, diagnostics);
                             break;
                         default:
                             throw ExceptionUtilities.UnexpectedValue(keyword);

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

@@ -5718,9 +5718,6 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="WRN_NullabilityMismatchInTypeParameterReferenceTypeConstraint_Title" xml:space="preserve">
     <value>The type cannot be used as type parameter in the generic type or method. Nullability of type argument doesn't match 'class' constraint.</value>
   </data>
-  <data name="IDS_FeatureObjectGenericTypeConstraint" xml:space="preserve">
-    <value>object generic type constraint</value>
-  </data>
   <data name="ERR_TripleDotNotAllowed" xml:space="preserve">
     <value>Unexpected character sequence '...'</value>
   </data>
@@ -5913,13 +5910,7 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="WRN_NullabilityMismatchInTypeParameterNotNullConstraint_Title" xml:space="preserve">
     <value>The type cannot be used as type parameter in the generic type or method. Nullability of type argument doesn't match 'notnull' constraint.</value>
   </data>
-  <data name="WRN_SpecialTypeAsBound" xml:space="preserve">
-    <value>Constraint cannot be special class '{0}'</value>
-  </data>
-  <data name="WRN_SpecialTypeAsBound_Title" xml:space="preserve">
-    <value>Constraint cannot be special class</value>
-  </data>
-  <data name="IDS_NotNullGenericTypeConstraint" xml:space="preserve">
+  <data name="IDS_FeatureNotNullGenericTypeConstraint" xml:space="preserve">
     <value>notnull generic type constraint</value>
   </data>
   <data name="ERR_NeedSpaceBetweenExclamationAndEquals" xml:space="preserve">

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -1722,7 +1722,6 @@ internal enum ErrorCode
         ERR_AbstractEventHasAccessors = 8712,
         ERR_NotNullConstraintMustBeFirst = 8713,
         WRN_NullabilityMismatchInTypeParameterNotNullConstraint = 8714,
-        WRN_SpecialTypeAsBound = 8715,
 
         ERR_NeedSpaceBetweenExclamationAndEquals = 8716,
         ERR_MustNullCheckInImplementation = 8717,

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

@@ -411,7 +411,6 @@ internal static int GetWarningLevel(ErrorCode code)
                 case ErrorCode.WRN_UnconsumedEnumeratorCancellationAttributeUsage:
                 case ErrorCode.WRN_UndecoratedCancellationTokenParameter:
                 case ErrorCode.WRN_NullabilityMismatchInTypeParameterNotNullConstraint:
-                case ErrorCode.WRN_SpecialTypeAsBound:
                 case ErrorCode.WRN_DisallowNullAttributeForbidsMaybeNullAssignment:
                     return 1;
                 default:

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

@@ -165,7 +165,7 @@ internal enum MessageID
         IDS_FeatureAltInterpolatedVerbatimStrings = MessageBase + 12745,
         IDS_FeatureCoalesceAssignmentExpression = MessageBase + 12746,
         IDS_FeatureUnconstrainedTypeParameterInNullCoalescingOperator = MessageBase + 12747,
-        IDS_FeatureObjectGenericTypeConstraint = MessageBase + 12748,
+        IDS_FeatureNotNullGenericTypeConstraint = MessageBase + 12748,
         IDS_FeatureIndexOperator = MessageBase + 12749,
         IDS_FeatureRangeOperator = MessageBase + 12750,
         IDS_FeatureAsyncStreams = MessageBase + 12751,
@@ -180,7 +180,6 @@ internal enum MessageID
         IDS_DefaultInterfaceImplementation = MessageBase + 12760,
         IDS_OverrideWithConstraints = MessageBase + 12761,
         IDS_FeatureNestedStackalloc = MessageBase + 12762,
-        IDS_NotNullGenericTypeConstraint = MessageBase + 12763,
     }
 
     // Message IDs may refer to strings that need to be localized.
@@ -276,7 +275,6 @@ internal static LanguageVersion RequiredVersion(this MessageID feature)
                 case MessageID.IDS_FeatureUnconstrainedTypeParameterInNullCoalescingOperator:
                 case MessageID.IDS_FeatureNullableReferenceTypes: // syntax and semantic check
                 case MessageID.IDS_FeaturePragmaWarningEnable:
-                case MessageID.IDS_FeatureObjectGenericTypeConstraint:   // semantic check
                 case MessageID.IDS_FeatureIndexOperator: // semantic check
                 case MessageID.IDS_FeatureRangeOperator: // semantic check
                 case MessageID.IDS_FeatureAsyncStreams:
@@ -290,7 +288,7 @@ internal static LanguageVersion RequiredVersion(this MessageID feature)
                 case MessageID.IDS_DefaultInterfaceImplementation: // semantic check
                 case MessageID.IDS_OverrideWithConstraints: // semantic check
                 case MessageID.IDS_FeatureNestedStackalloc: // semantic check
-                case MessageID.IDS_NotNullGenericTypeConstraint:// semantic check
+                case MessageID.IDS_FeatureNotNullGenericTypeConstraint:// semantic check
                     return LanguageVersion.CSharp8;
 
                 // C# 7.3 features.