[automated] Merge branch 'main' => 'main-vs-deps' (#79229)

I detected changes in the main branch which have not been merged yet to
main-vs-deps. I'm a robot and am configured to help you automatically
keep main-vs-deps up to date, so I've opened this PR.

This PR merges commits made on main by the following committers:

* AlekseyTs

## Instructions for merging from UI

This PR will not be auto-merged. When pull request checks pass, complete
this PR by creating a merge commit, *not* a squash or rebase commit.

<img alt="merge button instructions"
src="https://i.imgur.com/GepcNJV.png" width="300" />

If this repo does not allow creating merge commits from the GitHub UI,
use command line instructions.

## Instructions for merging via command line

Run these commands to merge this pull request from the command line.

``` sh
git fetch
git checkout main
git pull --ff-only
git checkout main-vs-deps
git pull --ff-only
git merge --no-ff main

# If there are merge conflicts, resolve them and then run git merge --continue to complete the merge
# Pushing the changes to the PR branch will re-trigger PR validation.
git push https://github.com/dotnet/roslyn HEAD:merge/main-to-main-vs-deps
```

<details>
<summary>or if you are using SSH</summary>

```
git push git@github.com:dotnet/roslyn HEAD:merge/main-to-main-vs-deps
```

</details>


After PR checks are complete push the branch
```
git push
```

## Instructions for resolving conflicts

:warning: If there are merge conflicts, you will need to resolve them
manually before merging. You can do this [using GitHub][resolve-github]
or using the [command line][resolve-cli].

[resolve-github]:
https://help.github.com/articles/resolving-a-merge-conflict-on-github/
[resolve-cli]:
https://help.github.com/articles/resolving-a-merge-conflict-using-the-command-line/

## Instructions for updating this pull request

Contributors to this repo have permission update this pull request by
pushing to the branch 'merge/main-to-main-vs-deps'. This can be done to
resolve conflicts or make other changes to this pull request before it
is merged.
The provided examples assume that the remote is named 'origin'. If you
have a different remote name, please replace 'origin' with the name of
your remote.

```
git fetch
git checkout -b merge/main-to-main-vs-deps origin/main-vs-deps
git pull https://github.com/dotnet/roslyn merge/main-to-main-vs-deps
(make changes)
git commit -m "Updated PR with my changes"
git push https://github.com/dotnet/roslyn HEAD:merge/main-to-main-vs-deps
```

<details>
    <summary>or if you are using SSH</summary>

```
git fetch
git checkout -b merge/main-to-main-vs-deps origin/main-vs-deps
git pull git@github.com:dotnet/roslyn merge/main-to-main-vs-deps
(make changes)
git commit -m "Updated PR with my changes"
git push git@github.com:dotnet/roslyn HEAD:merge/main-to-main-vs-deps
```

</details>

Contact .NET Core Engineering (dotnet/dnceng) if you have questions or
issues.
Also, if this PR was generated incorrectly, help us fix it. See
https://github.com/dotnet/arcade/blob/main/.github/workflows/scripts/inter-branch-merge.ps1.

Author: dotnet-policy-service[bot]

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

@@ -1092,33 +1092,49 @@ private bool BindSimpleBinaryOperatorParts(BinaryExpressionSyntax node, BindingD
             out LookupResultKind resultKind, out ImmutableArray<MethodSymbol> originalUserDefinedOperators,
             out BinaryOperatorSignature resultSignature, out BinaryOperatorAnalysisResult best)
         {
-            bool foundOperator;
-
             if (!IsTypelessExpressionAllowedInBinaryOperator(kind, left, right))
             {
                 resultKind = LookupResultKind.OverloadResolutionFailure;
                 originalUserDefinedOperators = default(ImmutableArray<MethodSymbol>);
                 best = default(BinaryOperatorAnalysisResult);
+                resultSignature = new BinaryOperatorSignature(kind, leftType: null, rightType: null, CreateErrorType());
+                return false;
             }
-            else
-            {
-                best = this.BinaryOperatorOverloadResolution(kind, isChecked: CheckOverflowAtRuntime, left, right, node, diagnostics, out resultKind, out originalUserDefinedOperators);
-            }
 
-            // However, as an implementation detail, we never "fail to find an applicable
-            // operator" during overload resolution if we have x == null, x == default, etc. We always
-            // find at least the reference conversion object == object; the overload resolution
-            // code does not reject that.  Therefore what we should do is only bind
-            // "x == null" as a nullable-to-null comparison if overload resolution chooses
-            // the reference conversion.
+            bool isChecked = CheckOverflowAtRuntime;
+            OverloadResolution.GetStaticUserDefinedBinaryOperatorMethodNames(kind, isChecked, out string name1, out string name2Opt);
+            best = this.BinaryOperatorOverloadResolution(kind, isChecked, name1, name2Opt, left, right, node, diagnostics, out resultKind, out originalUserDefinedOperators);
+
+            return bindSimpleBinaryOperatorPartsContinue(node, diagnostics, left, right, kind, ref resultKind, ref originalUserDefinedOperators, out resultSignature, ref best, isChecked, name1, name2Opt);
 
-            if (!best.HasValue)
-            {
-                resultSignature = new BinaryOperatorSignature(kind, leftType: null, rightType: null, CreateErrorType());
-                foundOperator = false;
-            }
-            else
+            bool bindSimpleBinaryOperatorPartsContinue(
+                BinaryExpressionSyntax node,
+                BindingDiagnosticBag diagnostics,
+                BoundExpression left,
+                BoundExpression right,
+                BinaryOperatorKind kind,
+                ref LookupResultKind resultKind,
+                ref ImmutableArray<MethodSymbol> originalUserDefinedOperators,
+                out BinaryOperatorSignature resultSignature,
+                ref BinaryOperatorAnalysisResult best,
+                bool isChecked,
+                string name1,
+                string name2Opt)
             {
+                // However, as an implementation detail, we never "fail to find an applicable
+                // operator" during overload resolution if we have x == null, x == default, etc. We always
+                // find at least the reference conversion object == object; the overload resolution
+                // code does not reject that.  Therefore what we should do is only bind
+                // "x == null" as a nullable-to-null comparison if overload resolution chooses
+                // the reference conversion.
+
+                if (!best.HasValue)
+                {
+                    resultSignature = new BinaryOperatorSignature(kind, leftType: null, rightType: null, CreateErrorType());
+                    return false;
+                }
+
+                bool foundOperator;
                 var signature = best.Signature;
 
                 if (signature.Method is { } bestMethod)
@@ -1155,9 +1171,27 @@ private bool BindSimpleBinaryOperatorParts(BinaryExpressionSyntax node, BindingD
                     bool rightDefault = right.IsLiteralDefault();
                     foundOperator = !isObjectEquality || BuiltInOperators.IsValidObjectEquality(Conversions, leftType, leftNull, leftDefault, rightType, rightNull, rightDefault, ref useSiteInfo);
                     diagnostics.Add(node, useSiteInfo);
+
+                    if (!foundOperator)
+                    {
+                        Debug.Assert(isObjectEquality);
+
+                        // Try extension operators since predefined object equality was not applicable
+                        LookupResultKind extensionResultKind;
+                        ImmutableArray<MethodSymbol> extensionOriginalUserDefinedOperators;
+                        BinaryOperatorAnalysisResult? extensionBest = BinaryOperatorExtensionOverloadResolution(kind, isChecked, name1, name2Opt, left, right, node, diagnostics, out extensionResultKind, out extensionOriginalUserDefinedOperators);
+
+                        if (extensionBest.HasValue)
+                        {
+                            best = extensionBest.GetValueOrDefault();
+                            resultKind = extensionResultKind;
+                            originalUserDefinedOperators = extensionOriginalUserDefinedOperators;
+                            foundOperator = bindSimpleBinaryOperatorPartsContinue(node, diagnostics, left, right, kind, ref resultKind, ref originalUserDefinedOperators, out resultSignature, ref best, isChecked, name1, name2Opt);
+                        }
+                    }
                 }
+                return foundOperator;
             }
-            return foundOperator;
         }
 
 #nullable enable
@@ -1914,13 +1948,28 @@ private BinaryOperatorAnalysisResult BinaryOperatorOverloadResolution(
         {
             OverloadResolution.GetStaticUserDefinedBinaryOperatorMethodNames(kind, isChecked, out string name1, out string name2Opt);
 
+            return BinaryOperatorOverloadResolution(kind, isChecked, name1, name2Opt, left, right, node, diagnostics, out resultKind, out originalUserDefinedOperators);
+        }
+
+        private BinaryOperatorAnalysisResult BinaryOperatorOverloadResolution(
+            BinaryOperatorKind kind,
+            bool isChecked,
+            string name1,
+            string name2Opt,
+            BoundExpression left,
+            BoundExpression right,
+            CSharpSyntaxNode node,
+            BindingDiagnosticBag diagnostics,
+            out LookupResultKind resultKind,
+            out ImmutableArray<MethodSymbol> originalUserDefinedOperators)
+        {
             BinaryOperatorAnalysisResult possiblyBest = BinaryOperatorNonExtensionOverloadResolution(kind, isChecked, name1, name2Opt, left, right, node, diagnostics, out resultKind, out originalUserDefinedOperators);
 
             if (!possiblyBest.HasValue && resultKind != LookupResultKind.Ambiguous)
             {
                 LookupResultKind extensionResultKind;
                 ImmutableArray<MethodSymbol> extensionOriginalUserDefinedOperators;
-                BinaryOperatorAnalysisResult? extensionBest = extensionOverloadResolution(kind, isChecked, name1, name2Opt, left, right, node, diagnostics, out extensionResultKind, out extensionOriginalUserDefinedOperators);
+                BinaryOperatorAnalysisResult? extensionBest = BinaryOperatorExtensionOverloadResolution(kind, isChecked, name1, name2Opt, left, right, node, diagnostics, out extensionResultKind, out extensionOriginalUserDefinedOperators);
 
                 if (extensionBest.HasValue && (extensionBest.GetValueOrDefault().HasValue || (originalUserDefinedOperators.IsEmpty && !extensionOriginalUserDefinedOperators.IsEmpty)))
                 {
@@ -1931,55 +1980,55 @@ private BinaryOperatorAnalysisResult BinaryOperatorOverloadResolution(
             }
 
             return possiblyBest;
+        }
 
-#nullable enable 
+#nullable enable
 
-            BinaryOperatorAnalysisResult? extensionOverloadResolution(
-                BinaryOperatorKind kind,
-                bool isChecked,
-                string name1,
-                string name2Opt,
-                BoundExpression left,
-                BoundExpression right,
-                CSharpSyntaxNode node,
-                BindingDiagnosticBag diagnostics,
-                out LookupResultKind resultKind,
-                out ImmutableArray<MethodSymbol> originalUserDefinedOperators)
+        private BinaryOperatorAnalysisResult? BinaryOperatorExtensionOverloadResolution(
+            BinaryOperatorKind kind,
+            bool isChecked,
+            string name1,
+            string name2Opt,
+            BoundExpression left,
+            BoundExpression right,
+            CSharpSyntaxNode node,
+            BindingDiagnosticBag diagnostics,
+            out LookupResultKind resultKind,
+            out ImmutableArray<MethodSymbol> originalUserDefinedOperators)
+        {
+            resultKind = LookupResultKind.Empty;
+            originalUserDefinedOperators = [];
+
+            if (left.Type is null && right.Type is null)
             {
-                resultKind = LookupResultKind.Empty;
-                originalUserDefinedOperators = [];
+                return null;
+            }
 
-                if (left.Type is null && right.Type is null)
-                {
-                    return null;
-                }
+            var result = BinaryOperatorOverloadResolutionResult.GetInstance();
+            CompoundUseSiteInfo<AssemblySymbol> useSiteInfo = GetNewCompoundUseSiteInfo(diagnostics);
+            var extensionDeclarationsInSingleScope = ArrayBuilder<NamedTypeSymbol>.GetInstance();
+            BinaryOperatorAnalysisResult? possiblyBest = null;
 
-                var result = BinaryOperatorOverloadResolutionResult.GetInstance();
-                CompoundUseSiteInfo<AssemblySymbol> useSiteInfo = GetNewCompoundUseSiteInfo(diagnostics);
-                var extensionDeclarationsInSingleScope = ArrayBuilder<NamedTypeSymbol>.GetInstance();
-                BinaryOperatorAnalysisResult? possiblyBest = null;
+            foreach (var scope in new ExtensionScopes(this))
+            {
+                extensionDeclarationsInSingleScope.Clear();
+                scope.Binder.GetExtensionDeclarations(extensionDeclarationsInSingleScope, this);
 
-                foreach (var scope in new ExtensionScopes(this))
+                if (this.OverloadResolution.BinaryOperatorExtensionOverloadResolutionInSingleScope(extensionDeclarationsInSingleScope, kind, isChecked, name1, name2Opt, left, right, result, ref useSiteInfo))
                 {
-                    extensionDeclarationsInSingleScope.Clear();
-                    scope.Binder.GetExtensionDeclarations(extensionDeclarationsInSingleScope, this);
-
-                    if (this.OverloadResolution.BinaryOperatorExtensionOverloadResolutionInSingleScope(extensionDeclarationsInSingleScope, kind, isChecked, name1, name2Opt, left, right, result, ref useSiteInfo))
-                    {
-                        possiblyBest = BinaryOperatorAnalyzeOverloadResolutionResult(result, out resultKind, out originalUserDefinedOperators);
-                        break;
-                    }
+                    possiblyBest = BinaryOperatorAnalyzeOverloadResolutionResult(result, out resultKind, out originalUserDefinedOperators);
+                    break;
                 }
+            }
 
-                diagnostics.Add(node, useSiteInfo);
+            diagnostics.Add(node, useSiteInfo);
 
-                extensionDeclarationsInSingleScope.Free();
-                result.Free();
-                return possiblyBest;
-            }
+            extensionDeclarationsInSingleScope.Free();
+            result.Free();
+            return possiblyBest;
+        }
 
 #nullable disable
-        }
 
         private BinaryOperatorAnalysisResult BinaryOperatorNonExtensionOverloadResolution(
             BinaryOperatorKind kind,
@@ -3758,18 +3807,18 @@ private bool CheckConstraintLanguageVersionAndRuntimeSupportForOperator(SyntaxNo
 
                 if (Compilation.SourceModule != methodOpt.ContainingModule)
                 {
-                    if (SyntaxFacts.IsCheckedOperator(methodOpt.Name))
+                    if (methodOpt.GetIsNewExtensionMember())
+                    {
+                        result &= CheckFeatureAvailability(node, MessageID.IDS_FeatureExtensions, diagnostics);
+                    }
+                    else if (SyntaxFacts.IsCheckedOperator(methodOpt.Name))
                     {
                         result &= CheckFeatureAvailability(node, MessageID.IDS_FeatureCheckedUserDefinedOperators, diagnostics);
                     }
                     else if (isUnsignedRightShift)
                     {
                         result &= CheckFeatureAvailability(node, MessageID.IDS_FeatureUnsignedRightShift, diagnostics);
                     }
-                    else if (methodOpt.GetIsNewExtensionMember())
-                    {
-                        result &= CheckFeatureAvailability(node, MessageID.IDS_FeatureExtensions, diagnostics);
-                    }
                 }
             }
 

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

@@ -95,8 +95,6 @@ private TupleBinaryOperatorInfo BindTupleBinaryOperatorInfo(BinaryExpressionSynt
                 return BindTupleBinaryOperatorNestedInfo(node, kind, left, right, diagnostics);
             }
 
-            // https://github.com/dotnet/roslyn/issues/76130: Add test coverage for this code path
-
             BoundExpression comparison = BindSimpleBinaryOperator(node, diagnostics, left, right, leaveUnconvertedIfInterpolatedString: false);
             switch (comparison)
             {

src/Compilers/CSharp/Portable/Symbols/Source/SourceUserDefinedOperatorSymbolBase.cs

@@ -179,18 +179,13 @@ protected static DeclarationModifiers MakeDeclarationModifiers(bool isCompoundAs
             bool isExplicitInterfaceImplementation = methodKind == MethodKind.ExplicitInterfaceImplementation;
             var defaultAccess = inInterface && !isExplicitInterfaceImplementation ? DeclarationModifiers.Public : DeclarationModifiers.Private;
             var allowedModifiers =
-                DeclarationModifiers.Unsafe;
+                DeclarationModifiers.Unsafe | DeclarationModifiers.Extern;
 
             if (!isCompoundAssignmentOrIncrementAssignment)
             {
                 allowedModifiers |= DeclarationModifiers.Static;
             }
 
-            if (!inExtension)
-            {
-                allowedModifiers |= DeclarationModifiers.Extern;
-            }
-
             if (!isExplicitInterfaceImplementation)
             {
                 allowedModifiers |= DeclarationModifiers.AccessibilityMask;