Respond to PR feedback

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

@@ -589,18 +589,19 @@ private TypeSymbol BindTupleType(TupleTypeSyntax syntax, DiagnosticBag diagnosti
                 throw ExceptionUtilities.UnexpectedValue(typesArray.Length);
             }
 
+            bool includeNullability = Compilation.IsFeatureEnabled(MessageID.IDS_FeatureNullableReferenceTypes);
             return TupleTypeSymbol.Create(syntax.Location,
-                                            typesArray,
-                                            locationsArray,
-                                            elementNames == null ?
-                                                default(ImmutableArray<string>) :
-                                                elementNames.ToImmutableAndFree(),
-                                            this.Compilation,
-                                            this.ShouldCheckConstraints,
-                                            includeNullability: this.ShouldCheckConstraints,
-                                            errorPositions: default(ImmutableArray<bool>),
-                                            syntax: syntax,
-                                            diagnostics: diagnostics);
+                                          typesArray,
+                                          locationsArray,
+                                          elementNames == null ?
+                                            default(ImmutableArray<string>) :
+                                            elementNames.ToImmutableAndFree(),
+                                          this.Compilation,
+                                          this.ShouldCheckConstraints,
+                                          includeNullability: this.ShouldCheckConstraints && includeNullability,
+                                          errorPositions: default(ImmutableArray<bool>),
+                                          syntax: syntax,
+                                          diagnostics: diagnostics);
         }
 
         private static void CollectTupleFieldMemberName(string name, int elementIndex, int tupleSize, ref ArrayBuilder<string> elementNames)

src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/OverloadResolution.cs

@@ -387,7 +387,7 @@ private bool FailsConstraintChecks(MethodSymbol method, out ArrayBuilder<TypePar
                 includeNullability: false,
                 this.Compilation,
                 diagnosticsBuilder,
-                nullabilityBuilderOpt: null,
+                nullabilityDiagnosticsBuilderOpt: null,
                 ref useSiteDiagnosticsBuilder);
 
             if (!constraintsSatisfied)

src/Compilers/CSharp/Portable/Symbols/ConstraintsHelper.cs

@@ -530,7 +530,6 @@ private static bool CheckConstraintsSingleType(TypeSymbol type, CheckConstraints
             Compilation currentCompilation,
             DiagnosticBag diagnosticsOpt,
             DiagnosticBag nullabilityDiagnosticsOpt)
-
         {
             NamedTypeSymbol type = tuple.TupleUnderlyingType;
             if (!RequiresChecking(type))
@@ -559,17 +558,16 @@ private static bool CheckConstraintsSingleType(TypeSymbol type, CheckConstraints
                     diagnosticsBuilder.AddRange(useSiteDiagnosticsBuilder);
                 }
 
-                populateDiagnostics(diagnosticsBuilder, diagnosticsOpt);
-                populateDiagnostics(nullabilityDiagnosticsBuilder, nullabilityDiagnosticsOpt);
+                populateDiagnosticsAndClear(diagnosticsBuilder, diagnosticsOpt);
+                populateDiagnosticsAndClear(nullabilityDiagnosticsBuilder, nullabilityDiagnosticsOpt);
 
-                diagnosticsBuilder.Clear();
-                nullabilityDiagnosticsBuilder.Clear();
                 offset += TupleTypeSymbol.RestIndex;
 
-                void populateDiagnostics(ArrayBuilder<TypeParameterDiagnosticInfo> builder, DiagnosticBag bag)
+                void populateDiagnosticsAndClear(ArrayBuilder<TypeParameterDiagnosticInfo> builder, DiagnosticBag bag)
                 {
                     if (bag is null)
                     {
+                        builder.Clear();
                         return;
                     }
 
@@ -582,6 +580,8 @@ void populateDiagnostics(ArrayBuilder<TypeParameterDiagnosticInfo> builder, Diag
                         var location = ordinal == TupleTypeSymbol.RestIndex ? typeSyntax.Location : elementLocations[ordinal + offset];
                         bag.Add(new CSDiagnostic(pair.DiagnosticInfo, location));
                     }
+
+                    builder.Clear();
                 }
 
             }
@@ -744,7 +744,7 @@ private static bool HasDuplicateInterfaces(NamedTypeSymbol type, ConsList<TypeSy
 
             var diagnosticsBuilder = ArrayBuilder<TypeParameterDiagnosticInfo>.GetInstance();
             ArrayBuilder<TypeParameterDiagnosticInfo> useSiteDiagnosticsBuilder = null;
-            var result = CheckMethodConstraints(method, conversions, includeNullability: false, currentCompilation, diagnosticsBuilder, nullabilityBuilderOpt: null, ref useSiteDiagnosticsBuilder);
+            var result = CheckMethodConstraints(method, conversions, includeNullability: false, currentCompilation, diagnosticsBuilder, nullabilityDiagnosticsBuilderOpt: null, ref useSiteDiagnosticsBuilder);
 
             if (useSiteDiagnosticsBuilder != null)
             {
@@ -775,7 +775,7 @@ private static bool HasDuplicateInterfaces(NamedTypeSymbol type, ConsList<TypeSy
 
             var diagnosticsBuilder = ArrayBuilder<TypeParameterDiagnosticInfo>.GetInstance();
             ArrayBuilder<TypeParameterDiagnosticInfo> useSiteDiagnosticsBuilder = null;
-            var result = CheckMethodConstraints(method, conversions, includeNullability: false, currentCompilation, diagnosticsBuilder, nullabilityBuilderOpt: null, ref useSiteDiagnosticsBuilder);
+            var result = CheckMethodConstraints(method, conversions, includeNullability: false, currentCompilation, diagnosticsBuilder, nullabilityDiagnosticsBuilderOpt: null, ref useSiteDiagnosticsBuilder);
 
             if (useSiteDiagnosticsBuilder != null)
             {
@@ -819,7 +819,7 @@ private static bool HasDuplicateInterfaces(NamedTypeSymbol type, ConsList<TypeSy
             bool includeNullability,
             Compilation currentCompilation,
             ArrayBuilder<TypeParameterDiagnosticInfo> diagnosticsBuilder,
-            ArrayBuilder<TypeParameterDiagnosticInfo> nullabilityBuilderOpt,
+            ArrayBuilder<TypeParameterDiagnosticInfo> nullabilityDiagnosticsBuilderOpt,
             ref ArrayBuilder<TypeParameterDiagnosticInfo> useSiteDiagnosticsBuilder,
             BitVector skipParameters = default(BitVector))
         {
@@ -832,7 +832,7 @@ private static bool HasDuplicateInterfaces(NamedTypeSymbol type, ConsList<TypeSy
                 method.TypeArguments,
                 currentCompilation,
                 diagnosticsBuilder,
-                nullabilityBuilderOpt,
+                nullabilityDiagnosticsBuilderOpt,
                 ref useSiteDiagnosticsBuilder,
                 skipParameters);
         }

src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs

@@ -53357,10 +53357,10 @@ class C {
         string s1;
         string? s2;
         C c = new C();
-        (s1, s1) = (string.Empty, string.Empty);
-        (s2, s1) = ((string)null, string.Empty);
-        var v1 = (s2, s1) = ((string)null, string.Empty); // 1
-        var v2 = (s1, s1) = ((string)null, string.Empty); // 2
+        (s1, s1) = ("""", """");
+        (s2, s1) = ((string)null, """");
+        var v1 = (s2, s1) = ((string)null, """"); // 1
+        var v2 = (s1, s1) = ((string)null, """"); // 2
         (s2, s1) = c;
         (string? s3, string s4) = c;
         var v2 = (s2, s1) = c; // 3
@@ -53377,6 +53377,67 @@ class C {
                 );
         }
 
+        [Fact]
+        [WorkItem(33303, "https://github.com/dotnet/roslyn/issues/33303")]
+        public void Constraints_79()
+        {
+            var source = @"
+using System;
+#nullable enable
+#pragma warning disable 168
+class C {
+    void TupleTypes() {
+        (string?, string) t1;
+        Type t2 = typeof((string?, string));
+    }
+}
+";
+            var compilation = CreateCompilation(new[] { Tuple2NonNullable, TupleRestNonNullable, source }, targetFramework: TargetFramework.Mscorlib46, parseOptions: TestOptions.Regular7_3, skipUsesIsNullable: true);
+            compilation.VerifyDiagnostics(
+                // (3,2): error CS8652: The feature 'nullable reference types' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                // #nullable enable
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "nullable").WithArguments("nullable reference types").WithLocation(3, 2),
+                // (4,2): error CS8652: The feature 'nullable reference types' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                // #nullable enable
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "nullable").WithArguments("nullable reference types").WithLocation(4, 2),
+                // (5,2): error CS8652: The feature 'nullable reference types' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                // #nullable enable
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "nullable").WithArguments("nullable reference types").WithLocation(5, 2),
+                // (6,20): error CS8652: The feature 'object generic type constraint' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         where T1 : object
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "object").WithArguments("object generic type constraint").WithLocation(6, 20),
+                // (7,16): error CS8652: The feature 'nullable reference types' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         (string?, string) t1;
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "?").WithArguments("nullable reference types").WithLocation(7, 16),
+                // (7,20): error CS8652: The feature 'object generic type constraint' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         where T2 : object
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "object").WithArguments("object generic type constraint").WithLocation(7, 20),
+                // (8,20): error CS8652: The feature 'object generic type constraint' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         where T3 : object
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "object").WithArguments("object generic type constraint").WithLocation(8, 20),
+                // (8,20): error CS8652: The feature 'object generic type constraint' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         where T1 : object
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "object").WithArguments("object generic type constraint").WithLocation(8, 20),
+                // (8,33): error CS8652: The feature 'nullable reference types' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         Type t2 = typeof((string?, string));
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "?").WithArguments("nullable reference types").WithLocation(8, 33),
+                // (9,20): error CS8652: The feature 'object generic type constraint' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         where T4 : object
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "object").WithArguments("object generic type constraint").WithLocation(9, 20),
+                // (9,20): error CS8652: The feature 'object generic type constraint' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         where T2 : object
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "object").WithArguments("object generic type constraint").WithLocation(9, 20),
+                // (10,20): error CS8652: The feature 'object generic type constraint' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         where T5 : object
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "object").WithArguments("object generic type constraint").WithLocation(10, 20),
+                // (11,20): error CS8652: The feature 'object generic type constraint' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         where T6 : object
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "object").WithArguments("object generic type constraint").WithLocation(11, 20),
+                // (12,20): error CS8652: The feature 'object generic type constraint' is currently in Preview and *unsupported*. To use Preview features, use the 'preview' language version.
+                //         where T7 : object
+                Diagnostic(ErrorCode.ERR_FeatureInPreview, "object").WithArguments("object generic type constraint").WithLocation(12, 20));
+        }
+
         [Fact]
         public void UnconstrainedTypeParameter_Local()
         {