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C# 14: Support for user-defined increment and decrement operators. #21791

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C# 14: Support for user-defined increment and decrement operators. #21791

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ed5722f
C#: Add Increment/Decrement instance operator test example and update…
michaelnebel May 4, 2026
06e61e6
C#: Adjust the extractor to correctly handle names for user defined i…
michaelnebel May 5, 2026
78fd09b
C#: Update condition for UnaryOperators to also handle user-defined i…
michaelnebel May 5, 2026
95882e0
C#: Update PrintAst expected output.
michaelnebel May 5, 2026
5458b8a
C#: Add an increment/decrement operator test case.
michaelnebel May 5, 2026
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9 changes: 8 additions & 1 deletion csharp/extractor/Semmle.Extraction.CSharp.Util/SymbolExtensions.cs
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Expand Up @@ -52,6 +52,13 @@ public static string GetName(this ISymbol symbol, bool useMetadataName = false)
{ "op_False", "false" }
});

/// <summary>
/// The operatorname for user-defined increment and decrement operators are "op_IncrementAssignment" and
/// "op_DecrementAssignment" respectively.
/// Thus we need to handle this explicitly to avoid postfixing them with an "=".
/// </summary>
private static bool isIncrementOrDecrement(string operatorName) => operatorName == "++" || operatorName == "--";

/// <summary>
/// Convert an operator method name in to a symbolic name.
/// A return value indicates whether the conversion succeeded.
Expand All @@ -72,7 +79,7 @@ public static bool TryGetOperatorSymbol(this ISymbol symbol, out string operator
if (match.Success && methodToOperator.TryGetValue($"op_{match.Groups[2]}", out var rawOperatorName))
{
var prefix = match.Groups[1].Success ? "checked " : "";
var postfix = match.Groups[3].Success ? "=" : "";
var postfix = match.Groups[3].Success && !isIncrementOrDecrement(rawOperatorName) ? "=" : "";
operatorName = $"{prefix}{rawOperatorName}{postfix}";
return true;
}
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3 changes: 3 additions & 0 deletions csharp/ql/lib/semmle/code/csharp/Callable.qll
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Expand Up @@ -613,6 +613,9 @@ class UnaryOperator extends Operator {
this.getNumberOfParameters() = 1 and
not this instanceof ConversionOperator and
not this instanceof CompoundAssignmentOperator
or
// Instance increment and decrement operators don't have a parameter (only a qualifier).
this.getNumberOfParameters() = 0 and not this.isStatic()
}
}

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2 changes: 1 addition & 1 deletion csharp/ql/test/library-tests/operators/Operators3.expected
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@@ -1 +1 @@
| operators.cs:96:32:96:39 | implicit conversion |
| operators.cs:118:36:118:43 | implicit conversion |
2 changes: 1 addition & 1 deletion csharp/ql/test/library-tests/operators/Operators4.expected
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@@ -1 +1 @@
| operators.cs:101:32:101:39 | explicit conversion |
| operators.cs:123:36:123:43 | explicit conversion |
30 changes: 15 additions & 15 deletions csharp/ql/test/library-tests/operators/Operators5.expected
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@@ -1,15 +1,15 @@
| operators.cs:23:30:23:31 | += | operators.cs:61:13:61:22 | ... += ... |
| operators.cs:31:38:31:39 | checked += | operators.cs:77:17:77:26 | ... += ... |
| operators.cs:33:38:33:39 | checked -= | operators.cs:78:17:78:26 | ... -= ... |
| operators.cs:34:30:34:31 | -= | operators.cs:64:13:64:22 | ... -= ... |
| operators.cs:36:38:36:39 | checked *= | operators.cs:79:17:79:26 | ... *= ... |
| operators.cs:37:30:37:31 | *= | operators.cs:65:13:65:22 | ... *= ... |
| operators.cs:39:38:39:39 | checked /= | operators.cs:80:17:80:26 | ... /= ... |
| operators.cs:40:30:40:31 | /= | operators.cs:66:13:66:22 | ... /= ... |
| operators.cs:42:30:42:31 | %= | operators.cs:67:13:67:22 | ... %= ... |
| operators.cs:43:30:43:31 | &= | operators.cs:68:13:68:22 | ... &= ... |
| operators.cs:44:30:44:31 | \|= | operators.cs:69:13:69:22 | ... \|= ... |
| operators.cs:45:30:45:31 | ^= | operators.cs:70:13:70:22 | ... ^= ... |
| operators.cs:46:30:46:32 | <<= | operators.cs:71:13:71:23 | ... <<= ... |
| operators.cs:47:30:47:32 | >>= | operators.cs:72:13:72:23 | ... >>= ... |
| operators.cs:48:30:48:33 | >>>= | operators.cs:73:13:73:24 | ... >>>= ... |
| operators.cs:23:30:23:31 | += | operators.cs:70:13:70:22 | ... += ... |
| operators.cs:31:38:31:39 | checked += | operators.cs:86:17:86:26 | ... += ... |
| operators.cs:33:38:33:39 | checked -= | operators.cs:87:17:87:26 | ... -= ... |
| operators.cs:34:30:34:31 | -= | operators.cs:73:13:73:22 | ... -= ... |
| operators.cs:36:38:36:39 | checked *= | operators.cs:88:17:88:26 | ... *= ... |
| operators.cs:37:30:37:31 | *= | operators.cs:74:13:74:22 | ... *= ... |
| operators.cs:39:38:39:39 | checked /= | operators.cs:89:17:89:26 | ... /= ... |
| operators.cs:40:30:40:31 | /= | operators.cs:75:13:75:22 | ... /= ... |
| operators.cs:42:30:42:31 | %= | operators.cs:76:13:76:22 | ... %= ... |
| operators.cs:43:30:43:31 | &= | operators.cs:77:13:77:22 | ... &= ... |
| operators.cs:44:30:44:31 | \|= | operators.cs:78:13:78:22 | ... \|= ... |
| operators.cs:45:30:45:31 | ^= | operators.cs:79:13:79:22 | ... ^= ... |
| operators.cs:46:30:46:32 | <<= | operators.cs:80:13:80:23 | ... <<= ... |
| operators.cs:47:30:47:32 | >>= | operators.cs:81:13:81:23 | ... >>= ... |
| operators.cs:48:30:48:33 | >>>= | operators.cs:82:13:82:24 | ... >>>= ... |
10 changes: 10 additions & 0 deletions csharp/ql/test/library-tests/operators/Operators6.expected
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@@ -0,0 +1,10 @@
| operators.cs:15:42:15:43 | ++ | operators.cs:66:19:66:23 | call to operator ++ |
| operators.cs:15:42:15:43 | ++ | operators.cs:67:19:67:23 | call to operator ++ |
| operators.cs:54:38:54:39 | checked ++ | operators.cs:100:17:100:19 | call to operator checked ++ |
| operators.cs:54:38:54:39 | checked ++ | operators.cs:101:17:101:19 | call to operator checked ++ |
| operators.cs:55:30:55:31 | ++ | operators.cs:93:13:93:15 | call to operator ++ |
| operators.cs:55:30:55:31 | ++ | operators.cs:94:13:94:15 | call to operator ++ |
| operators.cs:56:38:56:39 | checked -- | operators.cs:102:17:102:19 | call to operator checked -- |
| operators.cs:56:38:56:39 | checked -- | operators.cs:103:17:103:19 | call to operator checked -- |
| operators.cs:57:30:57:31 | -- | operators.cs:95:13:95:15 | call to operator -- |
| operators.cs:57:30:57:31 | -- | operators.cs:96:13:96:15 | call to operator -- |
17 changes: 17 additions & 0 deletions csharp/ql/test/library-tests/operators/Operators6.ql
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@@ -0,0 +1,17 @@
/**
* @name Test for operators
*/

import csharp

from Operator op, OperatorCall call
where
op.fromSource() and
(
op instanceof IncrementOperator or
op instanceof CheckedIncrementOperator or
op instanceof DecrementOperator or
op instanceof CheckedDecrementOperator
) and
call.getTarget() = op
select op, call
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