Fix #1309: Decompilation of dynamic casts.

ICSharpCode.Decompiler.Tests/TestCases/Pretty/DynamicTests.cs

@@ -435,5 +435,15 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			Console.WriteLine(GetBool(1) || GetDynamic(2));
 			Console.WriteLine(i == 1 || d == null);
 		}
+
+		private static int ImplicitCast(object o)
+		{
+			return (dynamic)o;
+		}
+
+		private static int ExplicitCast(object o)
+		{
+			return (int)(dynamic)o;
+		}
 	}
 }

ICSharpCode.Decompiler.Tests/TestCases/Pretty/DynamicTests.il

@@ -20,10 +20,10 @@
 }
 .assembly DynamicTests
 {
-  .custom instance void [mscorlib]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = ( 01 00 00 00 ) 
   .custom instance void [mscorlib]System.Runtime.CompilerServices.RuntimeCompatibilityAttribute::.ctor() = ( 01 00 01 00 54 02 16 57 72 61 70 4E 6F 6E 45 78   // ....T..WrapNonEx
                                                                                                              63 65 70 74 69 6F 6E 54 68 72 6F 77 73 01 )       // ceptionThrows.
   .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilationRelaxationsAttribute::.ctor(int32) = ( 01 00 08 00 00 00 00 00 ) 
+  .custom instance void [mscorlib]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = ( 01 00 00 00 ) 
   .permissionset reqmin
              = {[mscorlib]System.Security.Permissions.SecurityPermissionAttribute = {property bool 'SkipVerification' = bool(true)}}
   .hash algorithm 0x00008004
@@ -112,8 +112,8 @@
     .field public object Field
     .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
     .field private object '<Property>k__BackingField'
-    .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
     .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+    .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
     .method public hidebysig specialname 
             instance object  get_GetOnlyProperty() cil managed
     {
@@ -802,12 +802,26 @@
     .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`4<class [System.Core]System.Runtime.CompilerServices.CallSite,object,object,object>> '<>p__Site17b'
   } // end of class '<LogicOrExtended>o__SiteContainer170'
 
+  .class abstract auto ansi sealed nested private beforefieldinit '<ImplicitCast>o__SiteContainer17c'
+         extends [mscorlib]System.Object
+  {
+    .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+    .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> '<>p__Site17d'
+  } // end of class '<ImplicitCast>o__SiteContainer17c'
+
+  .class abstract auto ansi sealed nested private beforefieldinit '<ExplicitCast>o__SiteContainer17e'
+         extends [mscorlib]System.Object
+  {
+    .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+    .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> '<>p__Site17f'
+  } // end of class '<ExplicitCast>o__SiteContainer17e'
+
   .field private static object 'field'
   .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
   .field private static object objectField
   .field private object '<Property>k__BackingField'
-  .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
   .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+  .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
   .method public hidebysig specialname instance object 
           get_Property() cil managed
   {
@@ -15600,6 +15614,76 @@
     IL_043f:  ret
   } // end of method DynamicTests::LogicOrExtended
 
+  .method private hidebysig static int32 
+          ImplicitCast(object o) cil managed
+  {
+    // Code size       72 (0x48)
+    .maxstack  3
+    .locals init (int32 V_0)
+    IL_0000:  nop
+    IL_0001:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ImplicitCast>o__SiteContainer17c'::'<>p__Site17d'
+    IL_0006:  brtrue.s   IL_002e
+
+    IL_0008:  ldc.i4.0
+    IL_0009:  ldtoken    [mscorlib]System.Int32
+    IL_000e:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_0013:  ldtoken    ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests
+    IL_0018:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_001d:  call       class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::Convert(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags,
+                                                                                                                                                            class [mscorlib]System.Type,
+                                                                                                                                                            class [mscorlib]System.Type)
+    IL_0022:  call       class [System.Core]System.Runtime.CompilerServices.CallSite`1<!0> class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+    IL_0027:  stsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ImplicitCast>o__SiteContainer17c'::'<>p__Site17d'
+    IL_002c:  br.s       IL_002e
+
+    IL_002e:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ImplicitCast>o__SiteContainer17c'::'<>p__Site17d'
+    IL_0033:  ldfld      !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Target
+    IL_0038:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ImplicitCast>o__SiteContainer17c'::'<>p__Site17d'
+    IL_003d:  ldarg.0
+    IL_003e:  callvirt   instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>::Invoke(!0,
+                                                                                                                                                     !1)
+    IL_0043:  stloc.0
+    IL_0044:  br.s       IL_0046
+
+    IL_0046:  ldloc.0
+    IL_0047:  ret
+  } // end of method DynamicTests::ImplicitCast
+
+  .method private hidebysig static int32 
+          ExplicitCast(object o) cil managed
+  {
+    // Code size       73 (0x49)
+    .maxstack  3
+    .locals init (int32 V_0)
+    IL_0000:  nop
+    IL_0001:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ExplicitCast>o__SiteContainer17e'::'<>p__Site17f'
+    IL_0006:  brtrue.s   IL_002f
+
+    IL_0008:  ldc.i4.s   16
+    IL_000a:  ldtoken    [mscorlib]System.Int32
+    IL_000f:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_0014:  ldtoken    ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests
+    IL_0019:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_001e:  call       class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::Convert(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags,
+                                                                                                                                                            class [mscorlib]System.Type,
+                                                                                                                                                            class [mscorlib]System.Type)
+    IL_0023:  call       class [System.Core]System.Runtime.CompilerServices.CallSite`1<!0> class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+    IL_0028:  stsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ExplicitCast>o__SiteContainer17e'::'<>p__Site17f'
+    IL_002d:  br.s       IL_002f
+
+    IL_002f:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ExplicitCast>o__SiteContainer17e'::'<>p__Site17f'
+    IL_0034:  ldfld      !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Target
+    IL_0039:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ExplicitCast>o__SiteContainer17e'::'<>p__Site17f'
+    IL_003e:  ldarg.0
+    IL_003f:  callvirt   instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>::Invoke(!0,
+                                                                                                                                                     !1)
+    IL_0044:  stloc.0
+    IL_0045:  br.s       IL_0047
+
+    IL_0047:  ldloc.0
+    IL_0048:  ret
+  } // end of method DynamicTests::ExplicitCast
+
   .property instance object Property()
   {
     .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 

ICSharpCode.Decompiler.Tests/TestCases/Pretty/DynamicTests.opt.il

@@ -20,10 +20,10 @@
 }
 .assembly DynamicTests.opt
 {
-  .custom instance void [mscorlib]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = ( 01 00 00 00 ) 
   .custom instance void [mscorlib]System.Runtime.CompilerServices.RuntimeCompatibilityAttribute::.ctor() = ( 01 00 01 00 54 02 16 57 72 61 70 4E 6F 6E 45 78   // ....T..WrapNonEx
                                                                                                              63 65 70 74 69 6F 6E 54 68 72 6F 77 73 01 )       // ceptionThrows.
   .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilationRelaxationsAttribute::.ctor(int32) = ( 01 00 08 00 00 00 00 00 ) 
+  .custom instance void [mscorlib]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = ( 01 00 00 00 ) 
   .permissionset reqmin
              = {[mscorlib]System.Security.Permissions.SecurityPermissionAttribute = {property bool 'SkipVerification' = bool(true)}}
   .hash algorithm 0x00008004
@@ -105,8 +105,8 @@
     .field public object Field
     .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
     .field private object '<Property>k__BackingField'
-    .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
     .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+    .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
     .method public hidebysig specialname 
             instance object  get_GetOnlyProperty() cil managed
     {
@@ -783,12 +783,26 @@
     .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`4<class [System.Core]System.Runtime.CompilerServices.CallSite,object,object,object>> '<>p__Site17b'
   } // end of class '<LogicOrExtended>o__SiteContainer170'
 
+  .class abstract auto ansi sealed nested private beforefieldinit '<ImplicitCast>o__SiteContainer17c'
+         extends [mscorlib]System.Object
+  {
+    .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+    .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> '<>p__Site17d'
+  } // end of class '<ImplicitCast>o__SiteContainer17c'
+
+  .class abstract auto ansi sealed nested private beforefieldinit '<ExplicitCast>o__SiteContainer17e'
+         extends [mscorlib]System.Object
+  {
+    .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+    .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> '<>p__Site17f'
+  } // end of class '<ExplicitCast>o__SiteContainer17e'
+
   .field private static object 'field'
   .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
   .field private static object objectField
   .field private object '<Property>k__BackingField'
-  .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
   .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+  .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
   .method public hidebysig specialname instance object 
           get_Property() cil managed
   {
@@ -14889,6 +14903,60 @@
     IL_044b:  ret
   } // end of method DynamicTests::LogicOrExtended
 
+  .method private hidebysig static int32 
+          ImplicitCast(object o) cil managed
+  {
+    // Code size       65 (0x41)
+    .maxstack  3
+    IL_0000:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ImplicitCast>o__SiteContainer17c'::'<>p__Site17d'
+    IL_0005:  brtrue.s   IL_002b
+
+    IL_0007:  ldc.i4.0
+    IL_0008:  ldtoken    [mscorlib]System.Int32
+    IL_000d:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_0012:  ldtoken    ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests
+    IL_0017:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_001c:  call       class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::Convert(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags,
+                                                                                                                                                            class [mscorlib]System.Type,
+                                                                                                                                                            class [mscorlib]System.Type)
+    IL_0021:  call       class [System.Core]System.Runtime.CompilerServices.CallSite`1<!0> class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+    IL_0026:  stsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ImplicitCast>o__SiteContainer17c'::'<>p__Site17d'
+    IL_002b:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ImplicitCast>o__SiteContainer17c'::'<>p__Site17d'
+    IL_0030:  ldfld      !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Target
+    IL_0035:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ImplicitCast>o__SiteContainer17c'::'<>p__Site17d'
+    IL_003a:  ldarg.0
+    IL_003b:  callvirt   instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>::Invoke(!0,
+                                                                                                                                                     !1)
+    IL_0040:  ret
+  } // end of method DynamicTests::ImplicitCast
+
+  .method private hidebysig static int32 
+          ExplicitCast(object o) cil managed
+  {
+    // Code size       66 (0x42)
+    .maxstack  3
+    IL_0000:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ExplicitCast>o__SiteContainer17e'::'<>p__Site17f'
+    IL_0005:  brtrue.s   IL_002c
+
+    IL_0007:  ldc.i4.s   16
+    IL_0009:  ldtoken    [mscorlib]System.Int32
+    IL_000e:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_0013:  ldtoken    ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests
+    IL_0018:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_001d:  call       class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::Convert(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags,
+                                                                                                                                                            class [mscorlib]System.Type,
+                                                                                                                                                            class [mscorlib]System.Type)
+    IL_0022:  call       class [System.Core]System.Runtime.CompilerServices.CallSite`1<!0> class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+    IL_0027:  stsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ExplicitCast>o__SiteContainer17e'::'<>p__Site17f'
+    IL_002c:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ExplicitCast>o__SiteContainer17e'::'<>p__Site17f'
+    IL_0031:  ldfld      !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Target
+    IL_0036:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<ExplicitCast>o__SiteContainer17e'::'<>p__Site17f'
+    IL_003b:  ldarg.0
+    IL_003c:  callvirt   instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>::Invoke(!0,
+                                                                                                                                                     !1)
+    IL_0041:  ret
+  } // end of method DynamicTests::ExplicitCast
+
   .property instance object Property()
   {
     .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 

ICSharpCode.Decompiler.Tests/TestCases/Pretty/DynamicTests.opt.roslyn.il

@@ -785,6 +785,20 @@
     .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Action`3<class [System.Core]System.Runtime.CompilerServices.CallSite,class [mscorlib]System.Type,object>> '<>p__10'
   } // end of class '<>o__55'
 
+  .class abstract auto ansi sealed nested private beforefieldinit '<>o__56'
+         extends [mscorlib]System.Object
+  {
+    .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+    .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> '<>p__0'
+  } // end of class '<>o__56'
+
+  .class abstract auto ansi sealed nested private beforefieldinit '<>o__57'
+         extends [mscorlib]System.Object
+  {
+    .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+    .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> '<>p__0'
+  } // end of class '<>o__57'
+
   .field private static object 'field'
   .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
   .field private static object objectField
@@ -13951,6 +13965,60 @@
     IL_040a:  ret
   } // end of method DynamicTests::LogicOrExtended
 
+  .method private hidebysig static int32 
+          ImplicitCast(object o) cil managed
+  {
+    // Code size       65 (0x41)
+    .maxstack  3
+    IL_0000:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__56'::'<>p__0'
+    IL_0005:  brtrue.s   IL_002b
+
+    IL_0007:  ldc.i4.0
+    IL_0008:  ldtoken    [mscorlib]System.Int32
+    IL_000d:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_0012:  ldtoken    ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests
+    IL_0017:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_001c:  call       class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::Convert(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags,
+                                                                                                                                                            class [mscorlib]System.Type,
+                                                                                                                                                            class [mscorlib]System.Type)
+    IL_0021:  call       class [System.Core]System.Runtime.CompilerServices.CallSite`1<!0> class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+    IL_0026:  stsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__56'::'<>p__0'
+    IL_002b:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__56'::'<>p__0'
+    IL_0030:  ldfld      !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Target
+    IL_0035:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__56'::'<>p__0'
+    IL_003a:  ldarg.0
+    IL_003b:  callvirt   instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>::Invoke(!0,
+                                                                                                                                                     !1)
+    IL_0040:  ret
+  } // end of method DynamicTests::ImplicitCast
+
+  .method private hidebysig static int32 
+          ExplicitCast(object o) cil managed
+  {
+    // Code size       66 (0x42)
+    .maxstack  3
+    IL_0000:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__57'::'<>p__0'
+    IL_0005:  brtrue.s   IL_002c
+
+    IL_0007:  ldc.i4.s   16
+    IL_0009:  ldtoken    [mscorlib]System.Int32
+    IL_000e:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_0013:  ldtoken    ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests
+    IL_0018:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_001d:  call       class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::Convert(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags,
+                                                                                                                                                            class [mscorlib]System.Type,
+                                                                                                                                                            class [mscorlib]System.Type)
+    IL_0022:  call       class [System.Core]System.Runtime.CompilerServices.CallSite`1<!0> class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+    IL_0027:  stsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__57'::'<>p__0'
+    IL_002c:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__57'::'<>p__0'
+    IL_0031:  ldfld      !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Target
+    IL_0036:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__57'::'<>p__0'
+    IL_003b:  ldarg.0
+    IL_003c:  callvirt   instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>::Invoke(!0,
+                                                                                                                                                     !1)
+    IL_0041:  ret
+  } // end of method DynamicTests::ExplicitCast
+
   .property instance object Property()
   {
     .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 

ICSharpCode.Decompiler.Tests/TestCases/Pretty/DynamicTests.roslyn.il

@@ -792,6 +792,20 @@
     .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Action`3<class [System.Core]System.Runtime.CompilerServices.CallSite,class [mscorlib]System.Type,object>> '<>p__10'
   } // end of class '<>o__55'
 
+  .class abstract auto ansi sealed nested private beforefieldinit '<>o__56'
+         extends [mscorlib]System.Object
+  {
+    .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+    .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> '<>p__0'
+  } // end of class '<>o__56'
+
+  .class abstract auto ansi sealed nested private beforefieldinit '<>o__57'
+         extends [mscorlib]System.Object
+  {
+    .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
+    .field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> '<>p__0'
+  } // end of class '<>o__57'
+
   .field private static object 'field'
   .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 
   .field private static object objectField
@@ -14904,6 +14918,76 @@
     IL_0425:  ret
   } // end of method DynamicTests::LogicOrExtended
 
+  .method private hidebysig static int32 
+          ImplicitCast(object o) cil managed
+  {
+    // Code size       72 (0x48)
+    .maxstack  3
+    .locals init (int32 V_0)
+    IL_0000:  nop
+    IL_0001:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__56'::'<>p__0'
+    IL_0006:  brfalse.s  IL_000a
+
+    IL_0008:  br.s       IL_002e
+
+    IL_000a:  ldc.i4.0
+    IL_000b:  ldtoken    [mscorlib]System.Int32
+    IL_0010:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_0015:  ldtoken    ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests
+    IL_001a:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_001f:  call       class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::Convert(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags,
+                                                                                                                                                            class [mscorlib]System.Type,
+                                                                                                                                                            class [mscorlib]System.Type)
+    IL_0024:  call       class [System.Core]System.Runtime.CompilerServices.CallSite`1<!0> class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+    IL_0029:  stsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__56'::'<>p__0'
+    IL_002e:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__56'::'<>p__0'
+    IL_0033:  ldfld      !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Target
+    IL_0038:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__56'::'<>p__0'
+    IL_003d:  ldarg.0
+    IL_003e:  callvirt   instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>::Invoke(!0,
+                                                                                                                                                     !1)
+    IL_0043:  stloc.0
+    IL_0044:  br.s       IL_0046
+
+    IL_0046:  ldloc.0
+    IL_0047:  ret
+  } // end of method DynamicTests::ImplicitCast
+
+  .method private hidebysig static int32 
+          ExplicitCast(object o) cil managed
+  {
+    // Code size       73 (0x49)
+    .maxstack  3
+    .locals init (int32 V_0)
+    IL_0000:  nop
+    IL_0001:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__57'::'<>p__0'
+    IL_0006:  brfalse.s  IL_000a
+
+    IL_0008:  br.s       IL_002f
+
+    IL_000a:  ldc.i4.s   16
+    IL_000c:  ldtoken    [mscorlib]System.Int32
+    IL_0011:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_0016:  ldtoken    ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests
+    IL_001b:  call       class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+    IL_0020:  call       class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::Convert(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags,
+                                                                                                                                                            class [mscorlib]System.Type,
+                                                                                                                                                            class [mscorlib]System.Type)
+    IL_0025:  call       class [System.Core]System.Runtime.CompilerServices.CallSite`1<!0> class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+    IL_002a:  stsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__57'::'<>p__0'
+    IL_002f:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__57'::'<>p__0'
+    IL_0034:  ldfld      !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>>::Target
+    IL_0039:  ldsfld     class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>> ICSharpCode.Decompiler.Tests.TestCases.Pretty.DynamicTests/'<>o__57'::'<>p__0'
+    IL_003e:  ldarg.0
+    IL_003f:  callvirt   instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite,object,int32>::Invoke(!0,
+                                                                                                                                                     !1)
+    IL_0044:  stloc.0
+    IL_0045:  br.s       IL_0047
+
+    IL_0047:  ldloc.0
+    IL_0048:  ret
+  } // end of method DynamicTests::ExplicitCast
+
   .property instance object Property()
   {
     .custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = ( 01 00 00 00 ) 

ICSharpCode.Decompiler.Tests/TestCases/Pretty/ExpressionTrees.cs

@@ -533,7 +533,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		public void MembersBuiltin()
 		{
 			ToCode(X(), () => 1.23m.ToString());
-			ToCode(X(), () => AttributeTargets.All.HasFlag((Enum)AttributeTargets.Assembly));
+			ToCode(X(), () => AttributeTargets.All.HasFlag(AttributeTargets.Assembly));
 			ToCode(X(), () => "abc".Length == 3);
 			ToCode(X(), () => 'a'.CompareTo('b') < 0);
 		}

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -2425,9 +2425,15 @@ namespace ICSharpCode.Decompiler.CSharp
 
 		protected internal override TranslatedExpression VisitDynamicConvertInstruction(DynamicConvertInstruction inst, TranslationContext context)
 		{
-			// TODO : make conversions implicit, if !inst.IsExplicit
-			// currently this leads to stack type mismatch assertions, if the expected type is not O
-			return Translate(inst.Argument).ConvertTo(inst.Type, this, inst.IsChecked, allowImplicitConversion: false);
+			var operand = Translate(inst.Argument).ConvertTo(SpecialType.Dynamic, this);
+			var result = new CastExpression(ConvertType(inst.Type), operand)
+				.WithILInstruction(inst)
+				.WithRR(new ConversionResolveResult(
+					inst.Type, operand.ResolveResult,
+					inst.IsExplicit ? Conversion.ExplicitDynamicConversion : Conversion.ImplicitDynamicConversion
+				));
+			result.Expression.AddAnnotation(inst.IsChecked ? AddCheckedBlocks.CheckedAnnotation : AddCheckedBlocks.UncheckedAnnotation);
+			return result;
 		}
 
 		protected internal override TranslatedExpression VisitDynamicGetIndexInstruction(DynamicGetIndexInstruction inst, TranslationContext context)

ICSharpCode.Decompiler/CSharp/Resolver/CSharpConversions.cs

@@ -650,9 +650,9 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 				|| kind == TypeKind.Delegate || kind == TypeKind.Anonymous;
 		}
 		#endregion
-		
+
 		#region Boxing Conversions
-		public bool IsBoxingConversion(IType fromType, IType toType)
+		bool IsBoxingConversion(IType fromType, IType toType)
 		{
 			// C# 4.0 spec: §6.1.7
 			fromType = NullableType.GetUnderlyingType(fromType);
@@ -661,7 +661,18 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 			else
 				return false;
 		}
-		
+
+		/// <summary>
+		/// Gets whether the conversion from fromType to toType is a boxing conversion,
+		/// or an implicit conversion involving a type parameter that might be
+		/// a boxing conversion when instantiated with a value type.
+		/// </summary>
+		public bool IsBoxingConversionOrInvolvingTypeParameter(IType fromType, IType toType)
+		{
+			return IsBoxingConversion(fromType, toType)
+				|| ImplicitTypeParameterConversion(fromType, toType);
+		}
+
 		bool UnboxingConversion(IType fromType, IType toType)
 		{
 			// C# 4.0 spec: §6.2.5

ICSharpCode.Decompiler/CSharp/TranslatedExpression.cs

@@ -185,11 +185,12 @@ namespace ICSharpCode.Decompiler.CSharp
 				if (allowImplicitConversion) {
 					switch (ResolveResult) {
 						case ConversionResolveResult conversion: {
-							if (Expression is CastExpression cast
-							&& ((type.IsKnownType(KnownTypeCode.Object) && conversion.Conversion.IsBoxingConversion
-								|| conversion.Conversion.IsAnonymousFunctionConversion
-								|| (conversion.Conversion.IsImplicit && (conversion.Conversion.IsUserDefined || targetType.IsKnownType(KnownTypeCode.Decimal)))
-							) || (conversion.Conversion.IsInterpolatedStringConversion))) {
+							if (Expression is CastExpression cast && CastCanBeMadeImplicit(
+									Resolver.CSharpConversions.Get(expressionBuilder.compilation),
+									conversion.Conversion,
+									conversion.Input.Type,
+									type, targetType
+								)) {
 								return this.UnwrapChild(cast.Expression);
 							} else if (Expression is ObjectCreateExpression oce && conversion.Conversion.IsMethodGroupConversion
 									&& oce.Arguments.Count == 1 && expressionBuilder.settings.UseImplicitMethodGroupConversion) {
@@ -228,7 +229,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			var compilation = expressionBuilder.compilation;
 			var conversions = Resolver.CSharpConversions.Get(compilation);
 			if (ResolveResult is ConversionResolveResult conv && Expression is CastExpression cast2 &&
-				IsBoxingOrInterpolatedStringConversion(conversions, conv.Conversion, conv.Input.Type, targetType))
+				CastCanBeMadeImplicit(conversions, conv.Conversion, conv.Input.Type, type, targetType))
 			{
 				var unwrapped = this.UnwrapChild(cast2.Expression);
 				if (allowImplicitConversion)
@@ -393,14 +394,31 @@ namespace ICSharpCode.Decompiler.CSharp
 			}
 			return castExpr.WithoutILInstruction().WithRR(rr);
 		}
-
-		bool IsBoxingOrInterpolatedStringConversion(Resolver.CSharpConversions conversions, Conversion conversion, IType inputType, IType targetType)
+		
+		/// <summary>
+		/// Gets whether an implicit conversion from 'inputType' to 'newTargetType'
+		/// would have the same semantics as the existing cast from 'inputType' to 'oldTargetType'.
+		/// The existing cast is classified in 'conversion'.
+		/// </summary>
+		bool CastCanBeMadeImplicit(Resolver.CSharpConversions conversions, Conversion conversion, IType inputType, IType oldTargetType, IType newTargetType)
 		{
-			if (conversion.IsBoxingConversion && conversions.IsBoxingConversion(inputType, targetType))
-				return true;
-			if (conversion.IsInterpolatedStringConversion && (targetType.IsKnownType(KnownTypeCode.FormattableString)
-				|| targetType.IsKnownType(KnownTypeCode.IFormattable)))
-				return true;
+			if (!conversion.IsImplicit) {
+				// If the cast was required for the old conversion, avoid making it implicit.
+				return false;
+			}
+			if (conversion.IsBoxingConversion) {
+				return conversions.IsBoxingConversionOrInvolvingTypeParameter(inputType, newTargetType);
+			}
+			if (conversion.IsInterpolatedStringConversion) {
+				return newTargetType.IsKnownType(KnownTypeCode.FormattableString)
+					|| newTargetType.IsKnownType(KnownTypeCode.IFormattable);
+			}
+			if (conversion.IsAnonymousFunctionConversion) {
+				return oldTargetType.Equals(newTargetType);
+			}
+			if (conversion.IsUserDefined || newTargetType.IsKnownType(KnownTypeCode.Decimal) || conversion.IsDynamicConversion) {
+				return oldTargetType.Equals(newTargetType);
+			}
 			return false;
 		}