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C# 14: User defined compound assignment operators. #21372

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C# 14: User defined compound assignment operators. #21372

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2383a5a
C#: Use a dictionary for translating operator methods to operator sym…
michaelnebel Feb 25, 2026
9f67a33
C#: Support user defined compound assignment operators.
michaelnebel Feb 25, 2026
5fdd980
C#: Add new name for multiplication used in conjunction with compound…
michaelnebel Mar 6, 2026
0ab7e31
C#: Re-factor TargetSymbol into an extension method.
michaelnebel Feb 26, 2026
a55841e
C#: Extract calls to user defined compound assignments as operator ca…
michaelnebel Feb 26, 2026
770bfce
C#: Add QL implementation for the new operators.
michaelnebel Mar 5, 2026
2c6064f
C#: Add compound assignment operator call class.
michaelnebel Mar 5, 2026
7651aa7
C#: Add QL compound assignment operator tests and updated expected te…
michaelnebel Mar 6, 2026
f08c98a
C#: Add compound assignment operator data flow example.
michaelnebel Mar 6, 2026
ea04efc
C#: Add dispatch logic for compound assignment operator calls.
michaelnebel Mar 6, 2026
c739bb6
C#: Update test expected file for data flow.
michaelnebel Mar 6, 2026
e237344
C#: Take compound assignment operator argument shift into account for…
michaelnebel Mar 9, 2026
fabb502
C#: Add extension data flow example for user defined compound assignm…
michaelnebel Mar 9, 2026
fafe360
C#: Add change note.
michaelnebel Mar 6, 2026
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143 changes: 47 additions & 96 deletions csharp/extractor/Semmle.Extraction.CSharp.Util/SymbolExtensions.cs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
using System.Collections.Generic;
using System.Text.RegularExpressions;
using Microsoft.CodeAnalysis;

Expand All @@ -18,111 +19,61 @@ public static string GetName(this ISymbol symbol, bool useMetadataName = false)
return symbol.CanBeReferencedByName ? name : name.Substring(symbol.Name.LastIndexOf('.') + 1);
}

private static readonly Dictionary<string, string> methodToOperator = new Dictionary<string, string>
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@hvitved hvitved Mar 17, 2026

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Nit: Can be a ReadOnlyDictionary.

{
{ "op_LogicalNot", "!" },
{ "op_BitwiseAnd", "&" },
{ "op_Equality", "==" },
{ "op_Inequality", "!=" },
{ "op_UnaryPlus", "+" },
{ "op_Addition", "+" },
{ "op_UnaryNegation", "-" },
{ "op_Subtraction", "-" },
{ "op_Multiply", "*" },
{ "op_Division", "/" },
{ "op_Modulus", "%" },
{ "op_GreaterThan", ">" },
{ "op_GreaterThanOrEqual", ">=" },
{ "op_LessThan", "<" },
{ "op_LessThanOrEqual", "<=" },
{ "op_Decrement", "--" },
{ "op_Increment", "++" },
{ "op_Implicit", "implicit conversion" },
{ "op_Explicit", "explicit conversion" },
{ "op_OnesComplement", "~" },
{ "op_RightShift", ">>" },
{ "op_UnsignedRightShift", ">>>" },
{ "op_LeftShift", "<<" },
{ "op_BitwiseOr", "|" },
{ "op_ExclusiveOr", "^" },
{ "op_True", "true" },
{ "op_False", "false" }
};

/// <summary>
/// Convert an operator method name in to a symbolic name.
/// A return value indicates whether the conversion succeeded.
/// </summary>
public static bool TryGetOperatorSymbol(this ISymbol symbol, out string operatorName)
{
static bool TryGetOperatorSymbolFromName(string methodName, out string operatorName)
var methodName = symbol.GetName(useMetadataName: false);

// Most common use-case.
if (methodToOperator.TryGetValue(methodName, out var opName))
{
var success = true;
switch (methodName)
{
case "op_LogicalNot":
operatorName = "!";
break;
case "op_BitwiseAnd":
operatorName = "&";
break;
case "op_Equality":
operatorName = "==";
break;
case "op_Inequality":
operatorName = "!=";
break;
case "op_UnaryPlus":
case "op_Addition":
operatorName = "+";
break;
case "op_UnaryNegation":
case "op_Subtraction":
operatorName = "-";
break;
case "op_Multiply":
operatorName = "*";
break;
case "op_Division":
operatorName = "/";
break;
case "op_Modulus":
operatorName = "%";
break;
case "op_GreaterThan":
operatorName = ">";
break;
case "op_GreaterThanOrEqual":
operatorName = ">=";
break;
case "op_LessThan":
operatorName = "<";
break;
case "op_LessThanOrEqual":
operatorName = "<=";
break;
case "op_Decrement":
operatorName = "--";
break;
case "op_Increment":
operatorName = "++";
break;
case "op_Implicit":
operatorName = "implicit conversion";
break;
case "op_Explicit":
operatorName = "explicit conversion";
break;
case "op_OnesComplement":
operatorName = "~";
break;
case "op_RightShift":
operatorName = ">>";
break;
case "op_UnsignedRightShift":
operatorName = ">>>";
break;
case "op_LeftShift":
operatorName = "<<";
break;
case "op_BitwiseOr":
operatorName = "|";
break;
case "op_ExclusiveOr":
operatorName = "^";
break;
case "op_True":
operatorName = "true";
break;
case "op_False":
operatorName = "false";
break;
default:
var match = CheckedRegex().Match(methodName);
if (match.Success)
{
TryGetOperatorSymbolFromName($"op_{match.Groups[1]}", out var uncheckedName);
operatorName = $"checked {uncheckedName}";
break;
}
operatorName = methodName;
success = false;
break;
}
return success;
operatorName = opName;
return true;
}

var methodName = symbol.GetName(useMetadataName: false);
return TryGetOperatorSymbolFromName(methodName, out operatorName);
var match = CheckedRegex().Match(methodName);
if (match.Success && methodToOperator.TryGetValue($"op_{match.Groups[1]}", out var uncheckedName))
{
operatorName = $"checked {uncheckedName}";
return true;
}

operatorName = methodName;
return false;
}

[GeneratedRegex("^op_Checked(.*)$")]
Expand Down