Support parsing of checked user-defined operator declarations (#59504)

https://github.com/dotnet/csharplang/blob/main/proposals/checked-user-defined-operators.md

docs/features/CheckedUserDefinedOperators.md

@@ -0,0 +1,16 @@
+Checked user-defined operators
+=====================================
+
+C# should support defining `checked` variants of the following user-defined operators so that users can opt into or out of overflow behavior as appropriate:
+*  The `++` and `--` unary operators (https://github.com/dotnet/csharplang/blob/main/spec/expressions.md#postfix-increment-and-decrement-operators and https://github.com/dotnet/csharplang/blob/main/spec/expressions.md#prefix-increment-and-decrement-operators).
+*  The `-` unary operator (https://github.com/dotnet/csharplang/blob/main/spec/expressions.md#unary-minus-operator).
+*  The `+`, `-`, `*`, and `/` binary operators (https://github.com/dotnet/csharplang/blob/main/spec/expressions.md#arithmetic-operators).
+*  Explicit conversion operators.
+
+Proposal: 
+- https://github.com/dotnet/csharplang/issues/4665
+- https://github.com/dotnet/csharplang/blob/main/proposals/checked-user-defined-operators.md
+
+Feature branch: https://github.com/dotnet/roslyn/tree/features/CheckedUserDefinedOperators
+
+Test plan: https://github.com/dotnet/roslyn/issues/59458

src/Compilers/CSharp/Portable/Parser/DocumentationCommentParser.cs

@@ -988,6 +988,7 @@ private OperatorMemberCrefSyntax ParseOperatorMemberCref()
         {
             Debug.Assert(CurrentToken.Kind == SyntaxKind.OperatorKeyword);
             SyntaxToken operatorKeyword = EatToken();
+            SyntaxToken checkedKeyword = TryEatToken(SyntaxKind.CheckedKeyword); // PROTOTYPE(CheckedUserDefinedOperators) : consider gracefully recovering from erroneous use of 'unchecked' at this location 
 
             SyntaxToken operatorToken;
 
@@ -1067,7 +1068,7 @@ private OperatorMemberCrefSyntax ParseOperatorMemberCref()
 
             CrefParameterListSyntax parameters = ParseCrefParameterList();
 
-            return SyntaxFactory.OperatorMemberCref(operatorKeyword, operatorToken, parameters);
+            return SyntaxFactory.OperatorMemberCref(operatorKeyword, checkedKeyword, operatorToken, parameters);
         }
 
         /// <summary>
@@ -1080,12 +1081,13 @@ private ConversionOperatorMemberCrefSyntax ParseConversionOperatorMemberCref()
             SyntaxToken implicitOrExplicit = EatToken();
 
             SyntaxToken operatorKeyword = EatToken(SyntaxKind.OperatorKeyword);
+            SyntaxToken checkedKeyword = TryEatToken(SyntaxKind.CheckedKeyword); // PROTOTYPE(CheckedUserDefinedOperators) : consider gracefully recovering from erroneous use of 'unchecked' at this location 
 
             TypeSyntax type = ParseCrefType(typeArgumentsMustBeIdentifiers: false);
 
             CrefParameterListSyntax parameters = ParseCrefParameterList();
 
-            return SyntaxFactory.ConversionOperatorMemberCref(implicitOrExplicit, operatorKeyword, type, parameters);
+            return SyntaxFactory.ConversionOperatorMemberCref(implicitOrExplicit, operatorKeyword, checkedKeyword, type, parameters);
         }
 
         /// <summary>

src/Compilers/CSharp/Portable/Parser/LanguageParser.cs

@@ -3305,8 +3305,23 @@ private ConversionOperatorDeclarationSyntax TryParseConversionOperatorDeclaratio
 
                 if (style.IsMissing)
                 {
-                    if (this.CurrentToken.Kind != SyntaxKind.OperatorKeyword || SyntaxFacts.IsAnyOverloadableOperator(this.PeekToken(1).Kind) ||
+                    bool possibleConversion;
+
+                    if (this.CurrentToken.Kind != SyntaxKind.OperatorKeyword ||
                         explicitInterfaceOpt?.DotToken.IsMissing == true)
+                    {
+                        possibleConversion = false;
+                    }
+                    else if (this.PeekToken(1).Kind == SyntaxKind.CheckedKeyword) // PROTOTYPE(CheckedUserDefinedOperators) : consider gracefully recovering from erroneous use of 'unchecked' at this location 
+                    {
+                        possibleConversion = !SyntaxFacts.IsAnyOverloadableOperator(this.PeekToken(2).Kind);
+                    }
+                    else
+                    {
+                        possibleConversion = !SyntaxFacts.IsAnyOverloadableOperator(this.PeekToken(1).Kind);
+                    }
+
+                    if (!possibleConversion)
                     {
                         this.Reset(ref point);
                         return null;
@@ -3332,6 +3347,7 @@ private ConversionOperatorDeclarationSyntax TryParseConversionOperatorDeclaratio
                         style,
                         explicitInterfaceOpt,
                         opKeyword,
+                        checkedKeyword: null,
                         type,
                         paramList,
                         body: null,
@@ -3340,6 +3356,7 @@ private ConversionOperatorDeclarationSyntax TryParseConversionOperatorDeclaratio
                 }
 
                 opKeyword = this.EatToken(SyntaxKind.OperatorKeyword);
+                var checkedKeyword = this.TryEatToken(SyntaxKind.CheckedKeyword); // PROTOTYPE(CheckedUserDefinedOperators) : consider gracefully recovering from erroneous use of 'unchecked' at this location 
 
                 this.Release(ref point);
                 point = GetResetPoint();
@@ -3369,6 +3386,7 @@ private ConversionOperatorDeclarationSyntax TryParseConversionOperatorDeclaratio
                     style,
                     explicitInterfaceOpt,
                     opKeyword,
+                    checkedKeyword,
                     type,
                     paramList,
                     blockBody,
@@ -3463,6 +3481,7 @@ private OperatorDeclarationSyntax ParseOperatorDeclaration(
             ExplicitInterfaceSpecifierSyntax explicitInterfaceOpt)
         {
             var opKeyword = this.EatToken(SyntaxKind.OperatorKeyword);
+            var checkedKeyword = this.TryEatToken(SyntaxKind.CheckedKeyword); // PROTOTYPE(CheckedUserDefinedOperators) : consider gracefully recovering from erroneous use of 'unchecked' at this location 
             SyntaxToken opToken;
             int opTokenErrorOffset;
             int opTokenErrorWidth;
@@ -3582,6 +3601,7 @@ private OperatorDeclarationSyntax ParseOperatorDeclaration(
                 type,
                 explicitInterfaceOpt,
                 opKeyword,
+                checkedKeyword,
                 opToken,
                 paramList,
                 blockBody,

src/Compilers/CSharp/Portable/PublicAPI.Unshipped.txt

@@ -28,3 +28,20 @@ static Microsoft.CodeAnalysis.CSharp.SyntaxFactory.TryStatement(Microsoft.CodeAn
 static Microsoft.CodeAnalysis.CSharp.SyntaxFactory.TryStatement(Microsoft.CodeAnalysis.SyntaxToken tryKeyword, Microsoft.CodeAnalysis.CSharp.Syntax.BlockSyntax! block, Microsoft.CodeAnalysis.SyntaxList<Microsoft.CodeAnalysis.CSharp.Syntax.CatchClauseSyntax!> catches, Microsoft.CodeAnalysis.CSharp.Syntax.FinallyClauseSyntax? finally) -> Microsoft.CodeAnalysis.CSharp.Syntax.TryStatementSyntax!
 *REMOVED*static Microsoft.CodeAnalysis.CSharp.SyntaxFactory.TryStatement(Microsoft.CodeAnalysis.SyntaxToken tryKeyword, Microsoft.CodeAnalysis.CSharp.Syntax.BlockSyntax! block, Microsoft.CodeAnalysis.SyntaxList<Microsoft.CodeAnalysis.CSharp.Syntax.CatchClauseSyntax!> catches, Microsoft.CodeAnalysis.CSharp.Syntax.FinallyClauseSyntax! finally) -> Microsoft.CodeAnalysis.CSharp.Syntax.TryStatementSyntax!
 static Microsoft.CodeAnalysis.CSharp.SyntaxFactory.InterpolatedStringExpression(Microsoft.CodeAnalysis.SyntaxToken stringStartToken, Microsoft.CodeAnalysis.SyntaxToken stringEndToken) -> Microsoft.CodeAnalysis.CSharp.Syntax.InterpolatedStringExpressionSyntax!
+
+Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorDeclarationSyntax.CheckedKeyword.get -> Microsoft.CodeAnalysis.SyntaxToken
+Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorDeclarationSyntax.Update(Microsoft.CodeAnalysis.SyntaxList<Microsoft.CodeAnalysis.CSharp.Syntax.AttributeListSyntax!> attributeLists, Microsoft.CodeAnalysis.SyntaxTokenList modifiers, Microsoft.CodeAnalysis.SyntaxToken implicitOrExplicitKeyword, Microsoft.CodeAnalysis.CSharp.Syntax.ExplicitInterfaceSpecifierSyntax? explicitInterfaceSpecifier, Microsoft.CodeAnalysis.SyntaxToken operatorKeyword, Microsoft.CodeAnalysis.SyntaxToken checkedKeyword, Microsoft.CodeAnalysis.CSharp.Syntax.TypeSyntax! type, Microsoft.CodeAnalysis.CSharp.Syntax.ParameterListSyntax! parameterList, Microsoft.CodeAnalysis.CSharp.Syntax.BlockSyntax? body, Microsoft.CodeAnalysis.CSharp.Syntax.ArrowExpressionClauseSyntax? expressionBody, Microsoft.CodeAnalysis.SyntaxToken semicolonToken) -> Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorDeclarationSyntax!
+Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorDeclarationSyntax.WithCheckedKeyword(Microsoft.CodeAnalysis.SyntaxToken checkedKeyword) -> Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorDeclarationSyntax!
+Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorMemberCrefSyntax.CheckedKeyword.get -> Microsoft.CodeAnalysis.SyntaxToken
+Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorMemberCrefSyntax.Update(Microsoft.CodeAnalysis.SyntaxToken implicitOrExplicitKeyword, Microsoft.CodeAnalysis.SyntaxToken operatorKeyword, Microsoft.CodeAnalysis.SyntaxToken checkedKeyword, Microsoft.CodeAnalysis.CSharp.Syntax.TypeSyntax! type, Microsoft.CodeAnalysis.CSharp.Syntax.CrefParameterListSyntax? parameters) -> Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorMemberCrefSyntax!
+Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorMemberCrefSyntax.WithCheckedKeyword(Microsoft.CodeAnalysis.SyntaxToken checkedKeyword) -> Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorMemberCrefSyntax!
+Microsoft.CodeAnalysis.CSharp.Syntax.OperatorDeclarationSyntax.CheckedKeyword.get -> Microsoft.CodeAnalysis.SyntaxToken
+Microsoft.CodeAnalysis.CSharp.Syntax.OperatorDeclarationSyntax.Update(Microsoft.CodeAnalysis.SyntaxList<Microsoft.CodeAnalysis.CSharp.Syntax.AttributeListSyntax!> attributeLists, Microsoft.CodeAnalysis.SyntaxTokenList modifiers, Microsoft.CodeAnalysis.CSharp.Syntax.TypeSyntax! returnType, Microsoft.CodeAnalysis.CSharp.Syntax.ExplicitInterfaceSpecifierSyntax? explicitInterfaceSpecifier, Microsoft.CodeAnalysis.SyntaxToken operatorKeyword, Microsoft.CodeAnalysis.SyntaxToken checkedKeyword, Microsoft.CodeAnalysis.SyntaxToken operatorToken, Microsoft.CodeAnalysis.CSharp.Syntax.ParameterListSyntax! parameterList, Microsoft.CodeAnalysis.CSharp.Syntax.BlockSyntax? body, Microsoft.CodeAnalysis.CSharp.Syntax.ArrowExpressionClauseSyntax? expressionBody, Microsoft.CodeAnalysis.SyntaxToken semicolonToken) -> Microsoft.CodeAnalysis.CSharp.Syntax.OperatorDeclarationSyntax!
+Microsoft.CodeAnalysis.CSharp.Syntax.OperatorDeclarationSyntax.WithCheckedKeyword(Microsoft.CodeAnalysis.SyntaxToken checkedKeyword) -> Microsoft.CodeAnalysis.CSharp.Syntax.OperatorDeclarationSyntax!
+Microsoft.CodeAnalysis.CSharp.Syntax.OperatorMemberCrefSyntax.CheckedKeyword.get -> Microsoft.CodeAnalysis.SyntaxToken
+Microsoft.CodeAnalysis.CSharp.Syntax.OperatorMemberCrefSyntax.Update(Microsoft.CodeAnalysis.SyntaxToken operatorKeyword, Microsoft.CodeAnalysis.SyntaxToken checkedKeyword, Microsoft.CodeAnalysis.SyntaxToken operatorToken, Microsoft.CodeAnalysis.CSharp.Syntax.CrefParameterListSyntax? parameters) -> Microsoft.CodeAnalysis.CSharp.Syntax.OperatorMemberCrefSyntax!
+Microsoft.CodeAnalysis.CSharp.Syntax.OperatorMemberCrefSyntax.WithCheckedKeyword(Microsoft.CodeAnalysis.SyntaxToken checkedKeyword) -> Microsoft.CodeAnalysis.CSharp.Syntax.OperatorMemberCrefSyntax!
+static Microsoft.CodeAnalysis.CSharp.SyntaxFactory.OperatorDeclaration(Microsoft.CodeAnalysis.SyntaxList<Microsoft.CodeAnalysis.CSharp.Syntax.AttributeListSyntax!> attributeLists, Microsoft.CodeAnalysis.SyntaxTokenList modifiers, Microsoft.CodeAnalysis.CSharp.Syntax.TypeSyntax! returnType, Microsoft.CodeAnalysis.CSharp.Syntax.ExplicitInterfaceSpecifierSyntax? explicitInterfaceSpecifier, Microsoft.CodeAnalysis.SyntaxToken operatorKeyword, Microsoft.CodeAnalysis.SyntaxToken checkedKeyword, Microsoft.CodeAnalysis.SyntaxToken operatorToken, Microsoft.CodeAnalysis.CSharp.Syntax.ParameterListSyntax! parameterList, Microsoft.CodeAnalysis.CSharp.Syntax.BlockSyntax? body, Microsoft.CodeAnalysis.CSharp.Syntax.ArrowExpressionClauseSyntax? expressionBody, Microsoft.CodeAnalysis.SyntaxToken semicolonToken) -> Microsoft.CodeAnalysis.CSharp.Syntax.OperatorDeclarationSyntax!
+static Microsoft.CodeAnalysis.CSharp.SyntaxFactory.ConversionOperatorDeclaration(Microsoft.CodeAnalysis.SyntaxList<Microsoft.CodeAnalysis.CSharp.Syntax.AttributeListSyntax!> attributeLists, Microsoft.CodeAnalysis.SyntaxTokenList modifiers, Microsoft.CodeAnalysis.SyntaxToken implicitOrExplicitKeyword, Microsoft.CodeAnalysis.CSharp.Syntax.ExplicitInterfaceSpecifierSyntax? explicitInterfaceSpecifier, Microsoft.CodeAnalysis.SyntaxToken operatorKeyword, Microsoft.CodeAnalysis.SyntaxToken checkedKeyword, Microsoft.CodeAnalysis.CSharp.Syntax.TypeSyntax! type, Microsoft.CodeAnalysis.CSharp.Syntax.ParameterListSyntax! parameterList, Microsoft.CodeAnalysis.CSharp.Syntax.BlockSyntax? body, Microsoft.CodeAnalysis.CSharp.Syntax.ArrowExpressionClauseSyntax? expressionBody, Microsoft.CodeAnalysis.SyntaxToken semicolonToken) -> Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorDeclarationSyntax!
+static Microsoft.CodeAnalysis.CSharp.SyntaxFactory.OperatorMemberCref(Microsoft.CodeAnalysis.SyntaxToken operatorKeyword, Microsoft.CodeAnalysis.SyntaxToken checkedKeyword, Microsoft.CodeAnalysis.SyntaxToken operatorToken, Microsoft.CodeAnalysis.CSharp.Syntax.CrefParameterListSyntax? parameters) -> Microsoft.CodeAnalysis.CSharp.Syntax.OperatorMemberCrefSyntax!
+static Microsoft.CodeAnalysis.CSharp.SyntaxFactory.ConversionOperatorMemberCref(Microsoft.CodeAnalysis.SyntaxToken implicitOrExplicitKeyword, Microsoft.CodeAnalysis.SyntaxToken operatorKeyword, Microsoft.CodeAnalysis.SyntaxToken checkedKeyword, Microsoft.CodeAnalysis.CSharp.Syntax.TypeSyntax! type, Microsoft.CodeAnalysis.CSharp.Syntax.CrefParameterListSyntax? parameters) -> Microsoft.CodeAnalysis.CSharp.Syntax.ConversionOperatorMemberCrefSyntax!

src/Compilers/CSharp/Portable/Syntax/ConversionOperatorDeclarationSyntax.cs

@@ -29,5 +29,31 @@ public ConversionOperatorDeclarationSyntax Update(
                 expressionBody: expressionBody,
                 semicolonToken: semicolonToken);
         }
+
+        public ConversionOperatorDeclarationSyntax Update(
+            SyntaxList<AttributeListSyntax> attributeLists,
+            SyntaxTokenList modifiers,
+            SyntaxToken implicitOrExplicitKeyword,
+            ExplicitInterfaceSpecifierSyntax? explicitInterfaceSpecifier,
+            SyntaxToken operatorKeyword,
+            TypeSyntax type,
+            ParameterListSyntax parameterList,
+            BlockSyntax? body,
+            ArrowExpressionClauseSyntax? expressionBody,
+            SyntaxToken semicolonToken)
+        {
+            return Update(
+                attributeLists: attributeLists,
+                modifiers: modifiers,
+                implicitOrExplicitKeyword: implicitOrExplicitKeyword,
+                explicitInterfaceSpecifier: explicitInterfaceSpecifier,
+                operatorKeyword: operatorKeyword,
+                checkedKeyword: this.CheckedKeyword,
+                type: type,
+                parameterList: parameterList,
+                body: body,
+                expressionBody: expressionBody,
+                semicolonToken: semicolonToken);
+        }
     }
 }

src/Compilers/CSharp/Portable/Syntax/ConversionOperatorMemberCrefSyntax.cs

@@ -0,0 +1,19 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.CodeAnalysis.CSharp.Syntax
+{
+    public partial class ConversionOperatorMemberCrefSyntax
+    {
+        public ConversionOperatorMemberCrefSyntax Update(SyntaxToken implicitOrExplicitKeyword, SyntaxToken operatorKeyword, TypeSyntax type, CrefParameterListSyntax? parameters)
+        {
+            return Update(
+                implicitOrExplicitKeyword: implicitOrExplicitKeyword,
+                operatorKeyword: operatorKeyword,
+                checkedKeyword: this.CheckedKeyword,
+                type: type,
+                parameters: parameters);
+        }
+    }
+}

src/Compilers/CSharp/Portable/Syntax/OperatorDeclarationSyntax.cs

@@ -29,5 +29,31 @@ public OperatorDeclarationSyntax Update(
                 expressionBody: expressionBody,
                 semicolonToken: semicolonToken);
         }
+
+        public OperatorDeclarationSyntax Update(
+            SyntaxList<AttributeListSyntax> attributeLists,
+            SyntaxTokenList modifiers,
+            TypeSyntax returnType,
+            ExplicitInterfaceSpecifierSyntax? explicitInterfaceSpecifier,
+            SyntaxToken operatorKeyword,
+            SyntaxToken operatorToken,
+            ParameterListSyntax parameterList,
+            BlockSyntax? body,
+            ArrowExpressionClauseSyntax? expressionBody,
+            SyntaxToken semicolonToken)
+        {
+            return Update(
+                attributeLists: attributeLists,
+                modifiers: modifiers,
+                returnType: returnType,
+                explicitInterfaceSpecifier: explicitInterfaceSpecifier,
+                operatorKeyword: operatorKeyword,
+                checkedKeyword: this.CheckedKeyword,
+                operatorToken: operatorToken,
+                parameterList: parameterList,
+                body: body,
+                expressionBody: expressionBody,
+                semicolonToken: semicolonToken);
+        }
     }
 }

src/Compilers/CSharp/Portable/Syntax/OperatorMemberCrefSyntax.cs

@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Microsoft.CodeAnalysis.CSharp.Syntax
+{
+    public partial class OperatorMemberCrefSyntax
+    {
+        public OperatorMemberCrefSyntax Update(SyntaxToken operatorKeyword, SyntaxToken operatorToken, CrefParameterListSyntax? parameters)
+        {
+            return Update(
+                operatorKeyword: operatorKeyword,
+                checkedKeyword: this.CheckedKeyword,
+                operatorToken: operatorToken,
+                parameters: parameters);
+        }
+    }
+}