From 4c08359a6a3ff0fbbd046c6b23ca9d2ac47841d8 Mon Sep 17 00:00:00 2001
From: Jan Jones <janjones@microsoft.com>
Date: Sun, 27 Jul 2025 16:23:02 +0200
Subject: [PATCH] Support `byreflike` constraint

---
 .../DisassemblerPrettyTestRunner.cs           |  6 +++
 .../ICSharpCode.Decompiler.Tests.csproj       |  1 +
 .../Disassembler/Pretty/GenericConstraints.il | 45 +++++++++++++++++++
 .../Disassembler/ReflectionDisassembler.cs    |  5 +++
 4 files changed, 57 insertions(+)
 create mode 100644 ICSharpCode.Decompiler.Tests/TestCases/Disassembler/Pretty/GenericConstraints.il

diff --git a/ICSharpCode.Decompiler.Tests/DisassemblerPrettyTestRunner.cs b/ICSharpCode.Decompiler.Tests/DisassemblerPrettyTestRunner.cs
index 9fa9e7e85..c4a6a0492 100644
--- a/ICSharpCode.Decompiler.Tests/DisassemblerPrettyTestRunner.cs
+++ b/ICSharpCode.Decompiler.Tests/DisassemblerPrettyTestRunner.cs
@@ -52,6 +52,12 @@ namespace ICSharpCode.Decompiler.Tests
 			}
 		}
 
+		[Test]
+		public async Task GenericConstraints()
+		{
+			await Run();
+		}
+
 		[Test]
 		public async Task SecurityDeclarations()
 		{
diff --git a/ICSharpCode.Decompiler.Tests/ICSharpCode.Decompiler.Tests.csproj b/ICSharpCode.Decompiler.Tests/ICSharpCode.Decompiler.Tests.csproj
index 2c3e9f93f..6f1bbc9dc 100644
--- a/ICSharpCode.Decompiler.Tests/ICSharpCode.Decompiler.Tests.csproj
+++ b/ICSharpCode.Decompiler.Tests/ICSharpCode.Decompiler.Tests.csproj
@@ -91,6 +91,7 @@
     <None Include="TestCases\Correctness\StackTests.il" />
     <None Include="TestCases\Correctness\StackTypes.il" />
     <None Include="TestCases\Correctness\Uninit.vb" />
+    <None Include="TestCases\Disassembler\Pretty\GenericConstraints.il" />
     <None Include="TestCases\Disassembler\Pretty\InterfaceImplAttributes.il" />
     <None Include="TestCases\Disassembler\Pretty\SortMembers.expected.il" />
     <None Include="TestCases\Disassembler\Pretty\SortMembers.il" />
diff --git a/ICSharpCode.Decompiler.Tests/TestCases/Disassembler/Pretty/GenericConstraints.il b/ICSharpCode.Decompiler.Tests/TestCases/Disassembler/Pretty/GenericConstraints.il
new file mode 100644
index 000000000..e6283ef08
--- /dev/null
+++ b/ICSharpCode.Decompiler.Tests/TestCases/Disassembler/Pretty/GenericConstraints.il
@@ -0,0 +1,45 @@
+.assembly extern mscorlib
+{
+	.publickeytoken = (
+		b7 7a 5c 56 19 34 e0 89
+	)
+	.ver 4:0:0:0
+}
+.assembly GenericConstraints
+{
+	.custom instance void [mscorlib]System.Reflection.AssemblyFileVersionAttribute::.ctor(string) = (
+		01 00 07 31 2e 30 2e 30 2e 30 00 00
+	)
+	.hash algorithm 0x00008004 // SHA1
+	.ver 1:0:0:0
+}
+
+.module GenericConstraints.dll
+.imagebase 0x10000000
+.file alignment 0x00000200
+.stackreserve 0x00100000
+.subsystem 0x0003 // WindowsCui
+.corflags 0x00000001 // ILOnly
+
+.class private auto ansi '<Module>'
+{
+} // end of class <Module>
+
+.class public auto ansi beforefieldinit TestType`1<byreflike T>
+	extends [mscorlib]System.Object
+{
+	// Methods
+	.method public hidebysig specialname rtspecialname
+		instance void .ctor () cil managed
+	{
+		// Method begins at RVA 0x2050
+		// Header size: 1
+		// Code size: 7 (0x7)
+		.maxstack 8
+
+		IL_0000: ldarg.0
+		IL_0001: call instance void [mscorlib]System.Object::.ctor()
+		IL_0006: ret
+	} // end of method TestType::.ctor
+
+} // end of class TestType
diff --git a/ICSharpCode.Decompiler/Disassembler/ReflectionDisassembler.cs b/ICSharpCode.Decompiler/Disassembler/ReflectionDisassembler.cs
index 4836276e2..76affb1ca 100644
--- a/ICSharpCode.Decompiler/Disassembler/ReflectionDisassembler.cs
+++ b/ICSharpCode.Decompiler/Disassembler/ReflectionDisassembler.cs
@@ -1733,6 +1733,11 @@ namespace ICSharpCode.Decompiler.Disassembler
 					{
 						output.Write("valuetype ");
 					}
+					const GenericParameterAttributes allowByRefLike = (GenericParameterAttributes)0x0020;
+					if ((gp.Attributes & allowByRefLike) == allowByRefLike)
+					{
+						output.Write("byreflike ");
+					}
 					if ((gp.Attributes & GenericParameterAttributes.DefaultConstructorConstraint) == GenericParameterAttributes.DefaultConstructorConstraint)
 					{
 						output.Write(".ctor ");