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Keep 'delegate {}' when a parameter type is inaccessible
The parameter-list-less anonymous method form is compatible with any delegate signature, and C# code must rely on exactly that when a delegate's parameter types cannot be named at the use site: IL, unlike C#, permits a delegate signature to reference less accessible types. Expanding such an anonymous method into a lambda would force the unnameable type into a parameter list. Keep the delegate form, with its parameter list dropped, when the parameters are unused and one of their types is not accessible from the current context. Assisted-by: Claude:claude-fable-5:Claude Code
1 parent 5319969 commit 0116f24

5 files changed

Lines changed: 219 additions & 9 deletions

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‎ICSharpCode.Decompiler.Tests/ICSharpCode.Decompiler.Tests.csproj‎

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@@ -105,6 +105,7 @@
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<None Include="TestCases\ILPretty\ExtensionEncodingV2.il" />
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<None Include="testcases\ilpretty\ExtensionEncodingV1.il" />
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<None Include="TestCases\ILPretty\GuessAccessors.il" />
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<None Include="TestCases\ILPretty\InaccessibleParameterTypes.il" />
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<None Include="TestCases\ILPretty\Issue2260SwitchString.il" />
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<None Include="TestCases\ILPretty\Issue3442.il" />
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<None Include="TestCases\ILPretty\Issue3344CkFinite.il" />
@@ -209,6 +210,8 @@
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<None Include="TestCases\ILPretty\FSharpUsing_Release.cs" />
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<Compile Remove="TestCases\ILPretty\GuessAccessors.cs" />
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<None Include="TestCases\ILPretty\GuessAccessors.cs" />
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<Compile Remove="TestCases\ILPretty\InaccessibleParameterTypes.cs" />
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<None Include="TestCases\ILPretty\InaccessibleParameterTypes.cs" />
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<Compile Remove="TestCases\ILPretty\NoAccessorProperties.cs" />
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<None Include="TestCases\ILPretty\NoAccessorProperties.cs" />
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<Compile Remove="TestCases\ILPretty\Issue1145.cs" />

‎ICSharpCode.Decompiler.Tests/ILPrettyTestRunner.cs‎

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@@ -353,6 +353,12 @@ public async Task GuessAccessors()
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await Run();
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}
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[Test]
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public async Task InaccessibleParameterTypes()
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{
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await Run();
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}
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[Test]
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public async Task EmptyBodies()
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{

‎ICSharpCode.Decompiler.Tests/TestCases/ILPretty/InaccessibleParameterTypes.cs‎

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using System;
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namespace ICSharpCode.Decompiler.Tests.TestCases.ILPretty
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{
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public class InaccessibleParameterTypes
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{
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private class Hidden
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{
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}
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public delegate void Handler(Hidden h);
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public static void Register(Action<Hidden> callback)
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{
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}
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}
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public class InaccessibleParameterTypesConsumer
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{
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public InaccessibleParameterTypes.Handler Create()
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{
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return delegate {
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};
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}
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public void Run()
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{
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InaccessibleParameterTypes.Register(delegate {
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});
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}
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}
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}

‎ICSharpCode.Decompiler.Tests/TestCases/ILPretty/InaccessibleParameterTypes.il‎

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// Anonymous methods whose delegate signature contains a type the use site cannot name.
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// IL (unlike C#) permits a public delegate with a less-accessible parameter type, so the
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// parameter-list-less "delegate {}" form is the only C# syntax the consumer class below
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// could legally have used - the decompiler must not expand it to a lambda parameter list.
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.assembly extern mscorlib
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{
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.publickeytoken = (B7 7A 5C 56 19 34 E0 89 ) // .z\V.4..
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.ver 4:0:0:0
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}
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.assembly extern System.Core
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{
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.publickeytoken = (B7 7A 5C 56 19 34 E0 89 ) // .z\V.4..
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.ver 4:0:0:0
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}
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.assembly InaccessibleParameterTypes
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{
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.ver 1:0:0:0
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}
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.module InaccessibleParameterTypes.dll
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.imagebase 0x00400000
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.file alignment 0x00000200
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.stackreserve 0x00100000
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.subsystem 0x0003 // WINDOWS_CUI
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.corflags 0x00020003 // ILONLY 32BITPREFERRED
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.class public auto ansi beforefieldinit ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes
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extends [mscorlib]System.Object
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{
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.class nested private auto ansi beforefieldinit Hidden
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extends [mscorlib]System.Object
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{
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.method public hidebysig specialname rtspecialname instance void .ctor () cil managed
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{
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.maxstack 8
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ldarg.0
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call instance void [mscorlib]System.Object::.ctor()
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ret
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}
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}
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.class nested public auto ansi sealed Handler
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extends [mscorlib]System.MulticastDelegate
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{
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.method public hidebysig specialname rtspecialname instance void .ctor (object 'object', native int 'method') runtime managed
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{
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}
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.method public hidebysig newslot virtual instance void Invoke (class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden h) runtime managed
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{
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}
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}
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.method public hidebysig static void Register (class [System.Core]System.Action`1<class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden> callback) cil managed
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{
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.maxstack 8
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ret
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}
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.method public hidebysig specialname rtspecialname instance void .ctor () cil managed
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{
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.maxstack 8
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ldarg.0
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call instance void [mscorlib]System.Object::.ctor()
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ret
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}
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}
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.class public auto ansi beforefieldinit ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypesConsumer
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extends [mscorlib]System.Object
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{
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// Fields
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.field private static class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Handler '<>f__am$cache0'
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.custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 )
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.field private static class [System.Core]System.Action`1<class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden> '<>f__am$cache1'
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.custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 )
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// Methods
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.method public hidebysig instance class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Handler Create () cil managed
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{
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.maxstack 8
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ldsfld class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Handler ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypesConsumer::'<>f__am$cache0'
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brtrue.s IL_0016
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ldnull
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ldftn void ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypesConsumer::'<Create>m__0'(class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden)
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newobj instance void ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Handler::.ctor(object, native int)
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stsfld class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Handler ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypesConsumer::'<>f__am$cache0'
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IL_0016: ldsfld class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Handler ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypesConsumer::'<>f__am$cache0'
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ret
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}
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.method public hidebysig instance void Run () cil managed
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{
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.maxstack 8
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ldsfld class [System.Core]System.Action`1<class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden> ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypesConsumer::'<>f__am$cache1'
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brtrue.s IL_0016
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ldnull
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ldftn void ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypesConsumer::'<Run>m__1'(class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden)
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newobj instance void class [System.Core]System.Action`1<class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden>::.ctor(object, native int)
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stsfld class [System.Core]System.Action`1<class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden> ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypesConsumer::'<>f__am$cache1'
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IL_0016: ldsfld class [System.Core]System.Action`1<class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden> ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypesConsumer::'<>f__am$cache1'
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call void ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes::Register(class [System.Core]System.Action`1<class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden>)
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ret
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}
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.method private hidebysig static void '<Create>m__0' (class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden '') cil managed
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{
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.custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 )
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.maxstack 8
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ret
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}
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.method private hidebysig static void '<Run>m__1' (class ICSharpCode.Decompiler.Tests.TestCases.ILPretty.InaccessibleParameterTypes/Hidden '') cil managed
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{
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.custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 )
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.maxstack 8
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ret
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}
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.method public hidebysig specialname rtspecialname instance void .ctor () cil managed
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{
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.maxstack 8
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ldarg.0
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call instance void [mscorlib]System.Object::.ctor()
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ret
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}
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}

‎ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs‎

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@@ -2537,6 +2537,12 @@ internal ExpressionWithResolveResult TranslateFunction(IType delegateType, ILFun
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attributeSections.Add(new AttributeSection(astBuilder.ConvertAttribute(attr)) { AttributeTarget = "return" });
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}
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bool parametersAreUsed = (
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from ident in body.Descendants.OfType<IdentifierExpression>()
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let v = ident.GetILVariable()
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where v != null && v.Function == function && v.Kind == VariableKind.Parameter
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select ident).Any();
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bool isLambda = false;
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if (ame.Parameters.Any(p => p.Type is null))
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{
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// C# 10 lambdas can have attributes, but anonymous methods cannot
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isLambda = true;
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}
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else if (settings.UseLambdaSyntax && ame.Parameters.All(p => p.ParameterModifier == ReferenceKind.None && !p.IsParams))
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else if (settings.UseLambdaSyntax && ame.Parameters.All(p => p.ParameterModifier == ReferenceKind.None && !p.IsParams)
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&& (parametersAreUsed || ParameterTypesAreAccessible(function)))
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{
2553-
// Lambdas cover statement bodies too; anonymous method syntax remains only for
2554-
// parameter shapes a lambda cannot express (ref/out/in and params modifiers).
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// Lambdas cover statement bodies too; anonymous method syntax remains for
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// parameter shapes a lambda cannot express (ref/out/in and params modifiers)
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// and for unused parameters whose types the current context cannot name:
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// only the parameter-list-less "delegate {}" form, which is compatible with
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// any delegate signature, can legally occur in such code.
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isLambda = true;
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}
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// Remove the parameter list from an AnonymousMethodExpression if the parameters are not used in the method body
2558-
var parameterReferencingIdentifiers =
2559-
from ident in body.Descendants.OfType<IdentifierExpression>()
2560-
let v = ident.GetILVariable()
2561-
where v != null && v.Function == function && v.Kind == VariableKind.Parameter
2562-
select ident;
2563-
if (!isLambda && !parameterReferencingIdentifiers.Any())
2568+
if (!isLambda && !parametersAreUsed)
25642569
{
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ame.Parameters.Clear();
25662571
}
@@ -2608,6 +2613,33 @@ from ident in body.Descendants.OfType<IdentifierExpression>()
26082613
.WithRR(new ConversionResolveResult(delegateType, rr, LambdaConversion.Instance));
26092614
}
26102615

2616+
bool ParameterTypesAreAccessible(ILFunction function)
2617+
{
2618+
var currentTypeDefinition = resolver.CurrentTypeDefinition;
2619+
if (currentTypeDefinition == null)
2620+
return true;
2621+
var lookup = new MemberLookup(currentTypeDefinition, currentTypeDefinition.ParentModule);
2622+
return function.Parameters.All(p => IsAccessible(p.Type));
2623+
2624+
bool IsAccessible(IType type)
2625+
{
2626+
switch (type)
2627+
{
2628+
case ParameterizedType pt:
2629+
return IsAccessible(pt.GenericType) && pt.TypeArguments.All(IsAccessible);
2630+
case TypeWithElementType t:
2631+
return IsAccessible(t.ElementType);
2632+
default:
2633+
for (var td = type.GetDefinition(); td != null; td = td.DeclaringTypeDefinition)
2634+
{
2635+
if (!lookup.IsAccessible(td, allowProtectedAccess: true))
2636+
return false;
2637+
}
2638+
return true;
2639+
}
2640+
}
2641+
}
2642+
26112643
protected internal override TranslatedExpression VisitILFunction(ILFunction function, TranslationContext context)
26122644
{
26132645
return TranslateFunction(function.DelegateType!, function)

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