Fix #3320: detect dynamic await in pre-Roslyn state machines

The C# 5 compiler loads the awaiter into a fresh local before every
dynamic call site and before the ICriticalNotifyCompletion type test, and
the early non-aggressive inlining refuses to fold those copies. Every
await matcher identifies an await by the identity of its awaiter
variable, so each copy hid the awaiter from the matcher and the whole
await stayed undetected.

Each such copy has one store and one load, and after the dynamic call
sites are collapsed that load sits in the next instruction, which is the
case ILInlining.InlineOne already handles, including the check that the
source is not overwritten first. Folding is restricted to the IsCompleted
and GetResult call sites and the completion-interface type tests, so
dynamic calls in user code keep their locals: a blanket fold retypes
unrelated locals of the surrounding method (an enum local decompiled as
int plus a cast).

Two smaller divergences from the Roslyn shape sat behind that one: the
merge block of the AwaitOnCompleted/AwaitUnsafeOnCompleted diamond
clears doFinallyBodies before its leave, and the awaiter is restored
from its object-typed field with unbox.any rather than castclass.

The ILPretty fixture is the state machine from the issue's assembly with
its external types stubbed out, so the fix stays guarded where the legacy
compiler is unavailable. The Pretty fixture for dynamic await now runs
the pre-Roslyn configurations as well, which is the end-to-end guard on
Windows; its expected output records that the compiler copies an awaited
dynamic value into a local first and emits no debug name for it. The
dead stores an optimized build leaves before a try block containing an
await are not specific to dynamic - a plain await on a Task produces the
same three - so they sit behind an EXPECTED_OUTPUT-only block.

Checked against real legacy csc output (/o- and /o+): dynamic await in
plain code, loops, try/catch, try/finally and using.

Assisted-by: Claude:claude-opus-5[1m]:Claude Code

ICSharpCode.Decompiler.Tests/ILPrettyTestRunner.cs

@@ -51,6 +51,12 @@ namespace ICSharpCode.Decompiler.Tests
 			}
 		}
 
+		[Test]
+		public async Task Issue3320()
+		{
+			await Run();
+		}
+
 		[Test]
 		public async Task ConditionalChain()
 		{

ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs

@@ -525,7 +525,7 @@ namespace ICSharpCode.Decompiler.Tests
 		}
 
 		[Test]
-		public async Task DynamicAwait([ValueSource(nameof(roslynOnlyOptions))] CompilerOptions cscOptions)
+		public async Task DynamicAwait([ValueSource(nameof(defaultOptions))] CompilerOptions cscOptions)
 		{
 			await RunForLibrary(cscOptions: cscOptions);
 		}

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Issue3320.cs

@@ -0,0 +1,22 @@
+using System.Threading.Tasks;
+
+public interface IDapperAsyncImplementor
+{
+	Task<T> GetAsync<T>(IDbConnection connection, object id, IDbTransaction transaction, int? commandTimeout) where T : class;
+}
+public interface IDbConnection
+{
+}
+public interface IDbTransaction
+{
+}
+public static class Issue3320
+{
+	public static IDapperAsyncImplementor Instance => null;
+
+	public static async Task<T> GetAsync<T>(this IDbConnection connection, dynamic id, IDbTransaction transaction = null, int? commandTimeout = null) where T : class
+	{
+		dynamic async = Instance.GetAsync<T>(connection, id, transaction, commandTimeout);
+		return await async;
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/Issue3320.il

@@ -0,0 +1,508 @@
+.assembly extern mscorlib
+{
+  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 )
+  .ver 4:0:0:0
+}
+.assembly extern System.Core
+{
+  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 )
+  .ver 4:0:0:0
+}
+.assembly extern Microsoft.CSharp
+{
+  .publickeytoken = (B0 3F 5F 7F 11 D5 0A 3A )
+  .ver 4:0:0:0
+}
+.assembly Issue3320
+{
+  .hash algorithm 0x00008004
+  .ver 1:0:0:0
+}
+.module Issue3320.dll
+.imagebase 0x00400000
+.file alignment 0x00000200
+.stackreserve 0x00100000
+.subsystem 0x0003       // WINDOWS_CUI
+.corflags 0x00000001    //  ILONLY
+
+.class interface public abstract auto ansi IDbConnection
+{
+}
+
+.class interface public abstract auto ansi IDbTransaction
+{
+}
+
+.class interface public abstract auto ansi IDapperAsyncImplementor
+{
+	.method public hidebysig newslot abstract virtual
+		instance class [mscorlib]System.Threading.Tasks.Task`1<!!T> GetAsync<class T> (
+			class IDbConnection connection,
+			object id,
+			class IDbTransaction transaction,
+			valuetype [mscorlib]System.Nullable`1<int32> commandTimeout
+		) cil managed
+	{
+	}
+}
+
+.class public abstract auto ansi sealed beforefieldinit Issue3320
+	extends [mscorlib]System.Object
+{
+	.method public hidebysig specialname static
+		class IDapperAsyncImplementor get_Instance () cil managed
+	{
+		.maxstack 8
+
+		IL_0000: ldnull
+		IL_0001: ret
+	}
+
+	.property class IDapperAsyncImplementor Instance()
+	{
+		.get class IDapperAsyncImplementor Issue3320::get_Instance()
+	}
+
+	.class nested private auto ansi abstract sealed beforefieldinit '<GetAsync>o__SiteContainer6`1'<T>
+		extends [mscorlib]System.Object
+	{
+		.custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = (
+			01 00 00 00
+		)
+		// Fields
+		.field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>> '<>p__Site7'
+		.field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`7<class [System.Core]System.Runtime.CompilerServices.CallSite, class IDapperAsyncImplementor, class IDbConnection, object, class IDbTransaction, valuetype [mscorlib]System.Nullable`1<int32>, object>> '<>p__Site8'
+		.field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> '<>p__Site9'
+		.field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, bool>> '<>p__Sitea'
+		.field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> '<>p__Siteb'
+		.field public static class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> '<>p__Sitec'
+
+	} // end of class <GetAsync>o__SiteContainer6`1
+
+	.class nested private auto ansi sealed beforefieldinit '<GetAsync>d__d`1'<class T>
+		extends [mscorlib]System.ValueType
+		implements [mscorlib]System.Runtime.CompilerServices.IAsyncStateMachine
+	{
+		.custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = (
+			01 00 00 00
+		)
+		// Fields
+		.field public int32 '<>1__state'
+		.field public valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!T> '<>t__builder'
+		.field public class IDbConnection connection
+		.field public object id
+		.field public class IDbTransaction transaction
+		.field public valuetype [mscorlib]System.Nullable`1<int32> commandTimeout
+		.field private object '<>u__$awaitere'
+		.field private object '<>t__stack'
+
+		// Methods
+		.method private final hidebysig newslot virtual 
+			instance void MoveNext () cil managed 
+		{
+			.override method instance void [mscorlib]System.Runtime.CompilerServices.IAsyncStateMachine::MoveNext()
+			// Method begins at RVA 0x7188
+			// Header size: 12
+			// Code size: 788 (0x314)
+			.maxstack 11
+			.locals init (
+				[0] bool,
+				[1] !T,
+				[2] class [mscorlib]System.Exception,
+				[3] int32,
+				[4] class [mscorlib]System.Type[],
+				[5] class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo[],
+				[6] object,
+				[7] class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo[],
+				[8] object,
+				[9] object,
+				[10] class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo[],
+				[11] class [mscorlib]System.Tuple`2<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>, class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>>>,
+				[12] object,
+				[13] class [mscorlib]System.Runtime.CompilerServices.ICriticalNotifyCompletion,
+				[14] object,
+				[15] class [mscorlib]System.Runtime.CompilerServices.INotifyCompletion,
+				[16] class [mscorlib]System.Tuple`2<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>, class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>>>,
+				[17] object,
+				[18] class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo[]
+			)
+
+			.try
+			{
+				IL_0000: ldc.i4.1
+				IL_0001: stloc.0
+				IL_0002: ldarg.0
+				IL_0003: ldfld int32 valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>1__state'
+				IL_0008: stloc.3
+				IL_0009: ldloc.3
+				IL_000a: ldc.i4.0
+				IL_000b: beq IL_024a
+
+				IL_0010: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !0>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site7'
+				IL_0015: brtrue.s IL_003b
+
+				IL_0017: ldc.i4.0
+				IL_0018: ldtoken !T
+				IL_001d: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+				IL_0022: ldtoken Issue3320
+				IL_0027: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+				IL_002c: 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_0031: 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, !T>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+				IL_0036: stsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !0>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site7'
+
+				IL_003b: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !0>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site7'
+				IL_0040: ldfld !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>>::Target
+				IL_0045: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !0>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site7'
+				IL_004a: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`7<class [System.Core]System.Runtime.CompilerServices.CallSite, class IDapperAsyncImplementor, class IDbConnection, object, class IDbTransaction, valuetype [mscorlib]System.Nullable`1<int32>, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site8'
+				IL_004f: brtrue.s IL_00c9
+
+				IL_0051: ldc.i4.0
+				IL_0052: ldstr "GetAsync"
+				IL_0057: ldc.i4.1
+				IL_0058: newarr [mscorlib]System.Type
+				IL_005d: stloc.s 4
+				IL_005f: ldloc.s 4
+				IL_0061: ldc.i4.0
+				IL_0062: ldtoken !T
+				IL_0067: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+				IL_006c: stelem.ref
+				IL_006d: ldloc.s 4
+				IL_006f: ldtoken Issue3320
+				IL_0074: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+				IL_0079: ldc.i4.5
+				IL_007a: newarr [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo
+				IL_007f: stloc.s 5
+				IL_0081: ldloc.s 5
+				IL_0083: ldc.i4.0
+				IL_0084: ldc.i4.1
+				IL_0085: ldnull
+				IL_0086: call class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo::Create(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)
+				IL_008b: stelem.ref
+				IL_008c: ldloc.s 5
+				IL_008e: ldc.i4.1
+				IL_008f: ldc.i4.1
+				IL_0090: ldnull
+				IL_0091: call class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo::Create(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)
+				IL_0096: stelem.ref
+				IL_0097: ldloc.s 5
+				IL_0099: ldc.i4.2
+				IL_009a: ldc.i4.0
+				IL_009b: ldnull
+				IL_009c: call class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo::Create(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)
+				IL_00a1: stelem.ref
+				IL_00a2: ldloc.s 5
+				IL_00a4: ldc.i4.3
+				IL_00a5: ldc.i4.1
+				IL_00a6: ldnull
+				IL_00a7: call class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo::Create(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)
+				IL_00ac: stelem.ref
+				IL_00ad: ldloc.s 5
+				IL_00af: ldc.i4.4
+				IL_00b0: ldc.i4.1
+				IL_00b1: ldnull
+				IL_00b2: call class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo::Create(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)
+				IL_00b7: stelem.ref
+				IL_00b8: ldloc.s 5
+				IL_00ba: call class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::InvokeMember(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags, string, class [mscorlib]System.Collections.Generic.IEnumerable`1<class [mscorlib]System.Type>, class [mscorlib]System.Type, class [mscorlib]System.Collections.Generic.IEnumerable`1<class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo>)
+				IL_00bf: call class [System.Core]System.Runtime.CompilerServices.CallSite`1<!0> class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`7<class [System.Core]System.Runtime.CompilerServices.CallSite, class IDapperAsyncImplementor, class IDbConnection, object, class IDbTransaction, valuetype [mscorlib]System.Nullable`1<int32>, object>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+				IL_00c4: stsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`7<class [System.Core]System.Runtime.CompilerServices.CallSite, class IDapperAsyncImplementor, class IDbConnection, object, class IDbTransaction, valuetype [mscorlib]System.Nullable`1<int32>, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site8'
+
+				IL_00c9: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`7<class [System.Core]System.Runtime.CompilerServices.CallSite, class IDapperAsyncImplementor, class IDbConnection, object, class IDbTransaction, valuetype [mscorlib]System.Nullable`1<int32>, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site8'
+				IL_00ce: ldfld !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`7<class [System.Core]System.Runtime.CompilerServices.CallSite, class IDapperAsyncImplementor, class IDbConnection, object, class IDbTransaction, valuetype [mscorlib]System.Nullable`1<int32>, object>>::Target
+				IL_00d3: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`7<class [System.Core]System.Runtime.CompilerServices.CallSite, class IDapperAsyncImplementor, class IDbConnection, object, class IDbTransaction, valuetype [mscorlib]System.Nullable`1<int32>, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site8'
+				IL_00d8: call class IDapperAsyncImplementor Issue3320::get_Instance()
+				IL_00dd: ldarg.0
+				IL_00de: ldfld class IDbConnection valuetype Issue3320/'<GetAsync>d__d`1'<!T>::connection
+				IL_00e3: ldarg.0
+				IL_00e4: ldfld object valuetype Issue3320/'<GetAsync>d__d`1'<!T>::id
+				IL_00e9: ldarg.0
+				IL_00ea: ldfld class IDbTransaction valuetype Issue3320/'<GetAsync>d__d`1'<!T>::transaction
+				IL_00ef: ldarg.0
+				IL_00f0: ldfld valuetype [mscorlib]System.Nullable`1<int32> valuetype Issue3320/'<GetAsync>d__d`1'<!T>::commandTimeout
+				IL_00f5: callvirt instance !6 class [mscorlib]System.Func`7<class [System.Core]System.Runtime.CompilerServices.CallSite, class IDapperAsyncImplementor, class IDbConnection, object, class IDbTransaction, valuetype [mscorlib]System.Nullable`1<int32>, object>::Invoke(!0, !1, !2, !3, !4, !5)
+				IL_00fa: stloc.s 6
+				IL_00fc: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site9'
+				IL_0101: brtrue.s IL_0138
+
+				IL_0103: ldc.i4.0
+				IL_0104: ldstr "GetAwaiter"
+				IL_0109: ldnull
+				IL_010a: ldtoken Issue3320
+				IL_010f: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+				IL_0114: ldc.i4.1
+				IL_0115: newarr [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo
+				IL_011a: stloc.s 7
+				IL_011c: ldloc.s 7
+				IL_011e: ldc.i4.0
+				IL_011f: ldc.i4.0
+				IL_0120: ldnull
+				IL_0121: call class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo::Create(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)
+				IL_0126: stelem.ref
+				IL_0127: ldloc.s 7
+				IL_0129: call class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::InvokeMember(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags, string, class [mscorlib]System.Collections.Generic.IEnumerable`1<class [mscorlib]System.Type>, class [mscorlib]System.Type, class [mscorlib]System.Collections.Generic.IEnumerable`1<class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo>)
+				IL_012e: 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, object>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+				IL_0133: stsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site9'
+
+				IL_0138: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site9'
+				IL_013d: ldfld !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>>::Target
+				IL_0142: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Site9'
+				IL_0147: ldloc.s 6
+				IL_0149: callvirt instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>::Invoke(!0, !1)
+				IL_014e: stloc.s 8
+				IL_0150: ldloc.s 8
+				IL_0152: stloc.s 9
+				IL_0154: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, bool>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Sitea'
+				IL_0159: brtrue.s IL_017f
+
+				IL_015b: ldc.i4.0
+				IL_015c: ldtoken [mscorlib]System.Boolean
+				IL_0161: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+				IL_0166: ldtoken Issue3320
+				IL_016b: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+				IL_0170: 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_0175: 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, bool>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+				IL_017a: stsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, bool>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Sitea'
+
+				IL_017f: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, bool>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Sitea'
+				IL_0184: ldfld !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, bool>>::Target
+				IL_0189: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, bool>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Sitea'
+				IL_018e: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Siteb'
+				IL_0193: brtrue.s IL_01c9
+
+				IL_0195: ldc.i4.0
+				IL_0196: ldstr "IsCompleted"
+				IL_019b: ldtoken Issue3320
+				IL_01a0: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+				IL_01a5: ldc.i4.1
+				IL_01a6: newarr [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo
+				IL_01ab: stloc.s 10
+				IL_01ad: ldloc.s 10
+				IL_01af: ldc.i4.0
+				IL_01b0: ldc.i4.0
+				IL_01b1: ldnull
+				IL_01b2: call class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo::Create(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)
+				IL_01b7: stelem.ref
+				IL_01b8: ldloc.s 10
+				IL_01ba: call class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::GetMember(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags, string, class [mscorlib]System.Type, class [mscorlib]System.Collections.Generic.IEnumerable`1<class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo>)
+				IL_01bf: 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, object>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+				IL_01c4: stsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Siteb'
+
+				IL_01c9: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Siteb'
+				IL_01ce: ldfld !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>>::Target
+				IL_01d3: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Siteb'
+				IL_01d8: ldloc.s 9
+				IL_01da: callvirt instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>::Invoke(!0, !1)
+				IL_01df: callvirt instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, bool>::Invoke(!0, !1)
+				IL_01e4: brtrue IL_0287
+
+				IL_01e9: newobj instance void class [mscorlib]System.Tuple`2<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>, class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>>>::.ctor(!0, !1)
+				IL_01ee: stloc.s 11
+				IL_01f0: ldarg.0
+				IL_01f1: ldloc.s 11
+				IL_01f3: stfld object valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>t__stack'
+				IL_01f8: ldarg.0
+				IL_01f9: ldc.i4.0
+				IL_01fa: stfld int32 valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>1__state'
+				IL_01ff: ldarg.0
+				IL_0200: ldloc.s 8
+				IL_0202: stfld object valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>u__$awaitere'
+				IL_0207: ldloc.s 8
+				IL_0209: stloc.s 12
+				IL_020b: ldloc.s 12
+				IL_020d: isinst [mscorlib]System.Runtime.CompilerServices.ICriticalNotifyCompletion
+				IL_0212: stloc.s 13
+				IL_0214: ldloc.s 13
+				IL_0216: brtrue.s IL_0235
+
+				IL_0218: ldloc.s 8
+				IL_021a: stloc.s 14
+				IL_021c: ldloc.s 14
+				IL_021e: castclass [mscorlib]System.Runtime.CompilerServices.INotifyCompletion
+				IL_0223: stloc.s 15
+				IL_0225: ldarg.0
+				IL_0226: ldflda valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!0> valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>t__builder'
+				IL_022b: ldloca.s 15
+				IL_022d: ldarg.0
+				IL_022e: call instance void valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!T>::AwaitOnCompleted<class [mscorlib]System.Runtime.CompilerServices.INotifyCompletion, valuetype Issue3320/'<GetAsync>d__d`1'<!T>>(!!0&, !!1&)
+				IL_0233: br.s IL_0243
+
+				IL_0235: ldarg.0
+				IL_0236: ldflda valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!0> valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>t__builder'
+				IL_023b: ldloca.s 13
+				IL_023d: ldarg.0
+				IL_023e: call instance void valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!T>::AwaitUnsafeOnCompleted<class [mscorlib]System.Runtime.CompilerServices.ICriticalNotifyCompletion, valuetype Issue3320/'<GetAsync>d__d`1'<!T>>(!!0&, !!1&)
+
+				IL_0243: ldc.i4.0
+				IL_0244: stloc.0
+				IL_0245: leave IL_0313
+
+				IL_024a: ldarg.0
+				IL_024b: ldfld object valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>t__stack'
+				IL_0250: unbox.any class [mscorlib]System.Tuple`2<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>, class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>>>
+				IL_0255: stloc.s 16
+				IL_0257: ldloc.s 16
+				IL_0259: callvirt instance !0 class [mscorlib]System.Tuple`2<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>, class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>>>::get_Item1()
+				IL_025e: ldloc.s 16
+				IL_0260: callvirt instance !1 class [mscorlib]System.Tuple`2<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>, class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>>>::get_Item2()
+				IL_0265: ldarg.0
+				IL_0266: ldnull
+				IL_0267: stfld object valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>t__stack'
+				IL_026c: ldarg.0
+				IL_026d: ldfld object valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>u__$awaitere'
+				IL_0272: unbox.any [mscorlib]System.Object
+				IL_0277: stloc.s 8
+				IL_0279: ldarg.0
+				IL_027a: ldnull
+				IL_027b: stfld object valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>u__$awaitere'
+				IL_0280: ldarg.0
+				IL_0281: ldc.i4.m1
+				IL_0282: stfld int32 valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>1__state'
+
+				IL_0287: ldloc.s 8
+				IL_0289: stloc.s 17
+				IL_028b: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Sitec'
+				IL_0290: brtrue.s IL_02c7
+
+				IL_0292: ldc.i4.0
+				IL_0293: ldstr "GetResult"
+				IL_0298: ldnull
+				IL_0299: ldtoken Issue3320
+				IL_029e: call class [mscorlib]System.Type [mscorlib]System.Type::GetTypeFromHandle(valuetype [mscorlib]System.RuntimeTypeHandle)
+				IL_02a3: ldc.i4.1
+				IL_02a4: newarr [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo
+				IL_02a9: stloc.s 18
+				IL_02ab: ldloc.s 18
+				IL_02ad: ldc.i4.0
+				IL_02ae: ldc.i4.0
+				IL_02af: ldnull
+				IL_02b0: call class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo::Create(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfoFlags, string)
+				IL_02b5: stelem.ref
+				IL_02b6: ldloc.s 18
+				IL_02b8: call class [System.Core]System.Runtime.CompilerServices.CallSiteBinder [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.Binder::InvokeMember(valuetype [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpBinderFlags, string, class [mscorlib]System.Collections.Generic.IEnumerable`1<class [mscorlib]System.Type>, class [mscorlib]System.Type, class [mscorlib]System.Collections.Generic.IEnumerable`1<class [Microsoft.CSharp]Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo>)
+				IL_02bd: 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, object>>::Create(class [System.Core]System.Runtime.CompilerServices.CallSiteBinder)
+				IL_02c2: stsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Sitec'
+
+				IL_02c7: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Sitec'
+				IL_02cc: ldfld !0 class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>>::Target
+				IL_02d1: ldsfld class [System.Core]System.Runtime.CompilerServices.CallSite`1<class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>> class Issue3320/'<GetAsync>o__SiteContainer6`1'<!T>::'<>p__Sitec'
+				IL_02d6: ldloc.s 17
+				IL_02d8: callvirt instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, object>::Invoke(!0, !1)
+				IL_02dd: ldnull
+				IL_02de: stloc.s 8
+				IL_02e0: callvirt instance !2 class [mscorlib]System.Func`3<class [System.Core]System.Runtime.CompilerServices.CallSite, object, !T>::Invoke(!0, !1)
+				IL_02e5: stloc.1
+				IL_02e6: leave.s IL_02ff
+			} // end .try
+			catch [mscorlib]System.Exception
+			{
+				IL_02e8: stloc.2
+				IL_02e9: ldarg.0
+				IL_02ea: ldc.i4.s -2
+				IL_02ec: stfld int32 valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>1__state'
+				IL_02f1: ldarg.0
+				IL_02f2: ldflda valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!0> valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>t__builder'
+				IL_02f7: ldloc.2
+				IL_02f8: call instance void valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!T>::SetException(class [mscorlib]System.Exception)
+				IL_02fd: leave.s IL_0313
+			} // end handler
+
+			IL_02ff: ldarg.0
+			IL_0300: ldc.i4.s -2
+			IL_0302: stfld int32 valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>1__state'
+			IL_0307: ldarg.0
+			IL_0308: ldflda valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!0> valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>t__builder'
+			IL_030d: ldloc.1
+			IL_030e: call instance void valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!T>::SetResult(!0)
+
+			IL_0313: ret
+		} // end of method '<GetAsync>d__d`1'::MoveNext
+
+		.method private final hidebysig newslot virtual 
+			instance void SetStateMachine (
+				class [mscorlib]System.Runtime.CompilerServices.IAsyncStateMachine param0
+			) cil managed 
+		{
+			.custom instance void [mscorlib]System.Diagnostics.DebuggerHiddenAttribute::.ctor() = (
+				01 00 00 00
+			)
+			.override method instance void [mscorlib]System.Runtime.CompilerServices.IAsyncStateMachine::SetStateMachine(class [mscorlib]System.Runtime.CompilerServices.IAsyncStateMachine)
+			// Method begins at RVA 0x74c4
+			// Header size: 1
+			// Code size: 13 (0xd)
+			.maxstack 8
+
+			IL_0000: ldarg.0
+			IL_0001: ldflda valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!0> valuetype Issue3320/'<GetAsync>d__d`1'<!T>::'<>t__builder'
+			IL_0006: ldarg.1
+			IL_0007: call instance void valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!T>::SetStateMachine(class [mscorlib]System.Runtime.CompilerServices.IAsyncStateMachine)
+			IL_000c: ret
+		} // end of method '<GetAsync>d__d`1'::SetStateMachine
+
+	} // end of class <GetAsync>d__d`1
+
+
+	.method public hidebysig static 
+		class [mscorlib]System.Threading.Tasks.Task`1<!!T> GetAsync<class T> (
+			class IDbConnection connection,
+			object id,
+			[opt] class IDbTransaction transaction,
+			[opt] valuetype [mscorlib]System.Nullable`1<int32> commandTimeout
+		) cil managed 
+	{
+		.custom instance void [mscorlib]System.Diagnostics.DebuggerStepThroughAttribute::.ctor() = (
+			01 00 00 00
+		)
+		.custom instance void [mscorlib]System.Runtime.CompilerServices.AsyncStateMachineAttribute::.ctor(class [mscorlib]System.Type) = (
+			01 00 37 44 61 70 70 65 72 45 78 74 65 6e 73 69
+			6f 6e 73 2e 44 61 70 70 65 72 41 73 79 6e 63 45
+			78 74 65 6e 73 69 6f 6e 73 2b 3c 47 65 74 41 73
+			79 6e 63 3e 64 5f 5f 64 60 31 00 00
+		)
+		.custom instance void [mscorlib]System.Runtime.CompilerServices.ExtensionAttribute::.ctor() = (
+			01 00 00 00
+		)
+		.param [2]
+			.custom instance void [System.Core]System.Runtime.CompilerServices.DynamicAttribute::.ctor() = (
+				01 00 00 00
+			)
+		.param [3] = nullref
+		.param [4] = nullref
+		// Method begins at RVA 0x74d4
+		// Header size: 12
+		// Code size: 82 (0x52)
+		.maxstack 2
+		.locals init (
+			[0] valuetype Issue3320/'<GetAsync>d__d`1'<!!T>,
+			[1] valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!!T>
+		)
+
+		IL_0000: ldloca.s 0
+		IL_0002: ldarg.0
+		IL_0003: stfld class IDbConnection valuetype Issue3320/'<GetAsync>d__d`1'<!!T>::connection
+		IL_0008: ldloca.s 0
+		IL_000a: ldarg.1
+		IL_000b: stfld object valuetype Issue3320/'<GetAsync>d__d`1'<!!T>::id
+		IL_0010: ldloca.s 0
+		IL_0012: ldarg.2
+		IL_0013: stfld class IDbTransaction valuetype Issue3320/'<GetAsync>d__d`1'<!!T>::transaction
+		IL_0018: ldloca.s 0
+		IL_001a: ldarg.3
+		IL_001b: stfld valuetype [mscorlib]System.Nullable`1<int32> valuetype Issue3320/'<GetAsync>d__d`1'<!!T>::commandTimeout
+		IL_0020: ldloca.s 0
+		IL_0022: call valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!0> valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!!T>::Create()
+		IL_0027: stfld valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!0> valuetype Issue3320/'<GetAsync>d__d`1'<!!T>::'<>t__builder'
+		IL_002c: ldloca.s 0
+		IL_002e: ldc.i4.m1
+		IL_002f: stfld int32 valuetype Issue3320/'<GetAsync>d__d`1'<!!T>::'<>1__state'
+		IL_0034: ldloca.s 0
+		IL_0036: ldfld valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!0> valuetype Issue3320/'<GetAsync>d__d`1'<!!T>::'<>t__builder'
+		IL_003b: stloc.1
+		IL_003c: ldloca.s 1
+		IL_003e: ldloca.s 0
+		IL_0040: call instance void valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!!T>::Start<valuetype Issue3320/'<GetAsync>d__d`1'<!!T>>(!!0&)
+		IL_0045: ldloca.s 0
+		IL_0047: ldflda valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!0> valuetype Issue3320/'<GetAsync>d__d`1'<!!T>::'<>t__builder'
+		IL_004c: call instance class [mscorlib]System.Threading.Tasks.Task`1<!0> valuetype [mscorlib]System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1<!!T>::get_Task()
+		IL_0051: ret
+	} // end of method Issue3320::GetAsync
+}

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

@@ -92,6 +92,14 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 
 		private static async Task DynamicAwaitInTryCatch(dynamic d)
 		{
+			// Optimized pre-Roslyn state machines keep the bookkeeping of an await inside a try
+			// block in locals that survive decompilation as dead stores; a plain await on a Task
+			// produces the same three stores.
+#if EXPECTED_OUTPUT && OPT && LEGACY_CSC
+			int num = default(int);
+			int num2 = num;
+			int num3 = 0;
+#endif
 			try
 			{
 				d.Before = 1;
@@ -151,7 +159,13 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		// awaited dynamic stored in a dynamic local, then used (#1388)
 		private static async Task<dynamic> AwaitDynamicIntoUsedLocal()
 		{
+			// The pre-Roslyn compiler copies the awaited value into its own local first.
+#if LEGACY_CSC
+			dynamic dynamic = GetDynamic();
+			dynamic val = await dynamic;
+#else
 			dynamic val = await GetDynamic();
+#endif
 			val.UseMe();
 			return val;
 		}
@@ -159,7 +173,12 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 		// dynamic-dispatched awaited call with a dynamic-converted result (#1928)
 		private static async Task<string> AwaitDynamicConvertResult(dynamic d)
 		{
+#if LEGACY_CSC
+			dynamic val = d.RunAsync();
+			return (string)(await val);
+#else
 			return (string)(await d.RunAsync());
+#endif
 		}
 
 		// --- static-type call target spilled across an await ---
@@ -182,13 +201,19 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 
 		private static async Task AwaitDynamicMethodResult(dynamic d)
 		{
+#if LEGACY_CSC
+			dynamic val = d.RunAsync();
+			await val;
+#else
 			await d.RunAsync();
+#endif
 		}
 
 		private static async Task AwaitDynamicLocalWithStatementBefore()
 		{
-			// Optimized builds drop the local's debug name, so the decompiler regenerates one from the type.
-#if OPT
+			// Optimized builds drop the local's debug name, so the decompiler regenerates one from
+			// the type; the pre-Roslyn compiler never emits the name in the first place.
+#if OPT || LEGACY_CSC
 			dynamic dynamic = GetDynamic();
 			Console.WriteLine("before await");
 			await dynamic;

ICSharpCode.Decompiler/IL/ControlFlow/AsyncAwaitDecompiler.cs

@@ -1344,6 +1344,8 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			smallestAwaiterVarIndex = int.MaxValue;
 			foreach (var container in function.Descendants.OfType<BlockContainer>())
 			{
+				foreach (var block in container.Blocks)
+					InlineAwaiterCopies(block);
 				// Fold the runtime ICriticalNotifyCompletion type-check that the compiler emits when the
 				// awaiter's static type is not known to implement it (dynamic awaiters, some generic awaiters)
 				// into the canonical single-call form that AnalyzeAwaitBlock recognizes.
@@ -1629,7 +1631,10 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			if (!onCompletedBlock.Instructions[2].MatchBranch(out var mergeBlock2) || mergeBlock2 != mergeBlock)
 				return false;
 
-			if (mergeBlock.Instructions.Count != 1 || !(mergeBlock.Instructions[0] is Leave mergeLeave))
+			// The pre-Roslyn compiler clears doFinallyBodies right before leaving MoveNext;
+			// AnalyzeAwaitBlock expects that store directly in front of the leave.
+			int leavePos = MatchStoreDoFinallyBodies(mergeBlock.Instructions.FirstOrDefault()) ? 1 : 0;
+			if (mergeBlock.Instructions.Count != leavePos + 1 || !(mergeBlock.Instructions[leavePos] is Leave mergeLeave))
 				return false;
 
 			// Rewrite `block` into the canonical single-call form.
@@ -1641,12 +1646,57 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			block.Instructions.RemoveRange(count - 2, 2); // if + br
 			block.Instructions.RemoveAt(isInstPos); // isinst store
 			block.Instructions.Add(awaitCall);
+			if (leavePos > 0)
+			{
+				block.Instructions.Add(mergeBlock.Instructions[0].Clone());
+			}
 			var newLeave = (Leave)mergeLeave.Clone();
 			moveNextLeaves.Add(newLeave);
 			block.Instructions.Add(newLeave);
 			return true;
 		}
 
+		/// <summary>
+		/// Matches the 'stloc doFinallyBodies(ldc.i4 0)' the pre-Roslyn compiler emits before leaving MoveNext.
+		/// </summary>
+		bool MatchStoreDoFinallyBodies(ILInstruction inst)
+		{
+			if (doFinallyBodies == null || inst == null)
+				return false;
+			return inst.MatchStLoc(out var v, out var value)
+				&& v.Kind == VariableKind.Local
+				&& v.Type.IsKnownType(KnownTypeCode.Boolean)
+				&& v.Index == doFinallyBodies.Index
+				&& value.MatchLdcI4(0);
+		}
+
+		/// <summary>
+		/// The pre-Roslyn compiler copies the awaiter into a fresh local right before each dynamic call site
+		/// and each completion-interface type test on it. The await matchers identify an await by its awaiter
+		/// variable, so inline those copies.
+		/// </summary>
+		void InlineAwaiterCopies(Block block)
+		{
+			for (int i = block.Instructions.Count - 1; i >= 0; i--)
+			{
+				if (block.Instructions[i] is StLoc { Variable: { Kind: VariableKind.Local, IsSingleDefinition: true, LoadCount: 1 } copy, Value: LdLoc } store
+					&& IsAwaiterAccess(copy.LoadInstructions[0].Parent))
+				{
+					ILInlining.InlineOne(store, InliningOptions.Aggressive, context);
+				}
+			}
+
+			static bool IsAwaiterAccess(ILInstruction inst)
+			{
+				if (inst is DynamicGetMemberInstruction { Name: "IsCompleted" } or DynamicInvokeMemberInstruction { Name: "GetResult" })
+					return true;
+				if (!inst.MatchIsInst(out _, out var type) && !inst.MatchCastClass(out _, out type))
+					return false;
+				return type.FullName is "System.Runtime.CompilerServices.ICriticalNotifyCompletion"
+					or "System.Runtime.CompilerServices.INotifyCompletion";
+			}
+		}
+
 		bool AnalyzeAwaitBlock(Block block, out ILVariable awaiter, out IField awaiterField, out int state, out int yieldOffset)
 		{
 			awaiter = null;
@@ -1654,15 +1704,9 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			state = 0;
 			yieldOffset = -1;
 			int pos = block.Instructions.Count - 2;
-			if (pos >= 0 && doFinallyBodies != null && block.Instructions[pos] is StLoc storeDoFinallyBodies)
+			if (pos >= 0 && doFinallyBodies != null && block.Instructions[pos] is StLoc)
 			{
-				if (!(storeDoFinallyBodies.Variable.Kind == VariableKind.Local
-					  && storeDoFinallyBodies.Variable.Type.IsKnownType(KnownTypeCode.Boolean)
-					  && storeDoFinallyBodies.Variable.Index == doFinallyBodies.Index))
-				{
-					return false;
-				}
-				if (!storeDoFinallyBodies.Value.MatchLdcI4(0))
+				if (!MatchStoreDoFinallyBodies(block.Instructions[pos]))
 					return false;
 				pos--;
 			}
@@ -2008,6 +2052,8 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				{
 					// keep pulling in trivial branch targets until this block can grow no further
 				}
+				// Only now is each awaiter copy in the same block as the call site that uses it.
+				InlineAwaiterCopies(block);
 			}
 		}
 
@@ -2085,11 +2131,12 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				// stloc awaiterVar(ldfld awaiterField(ldloc this))
 				if (!instr.MatchStLoc(awaiterVar, out var value))
 					return false;
-				if (value is CastClass cast && cast.Type.Equals(awaiterVar.Type))
+				// If the awaiter is a reference type, it might get stored in a field of type `object`
+				// and cast back to the awaiter type in the resume block (pre-Roslyn: with unbox.any)
+				if ((value.MatchCastClass(out var castArg, out var castType) || value.MatchUnboxAny(out castArg, out castType))
+					&& castType.Equals(awaiterVar.Type))
 				{
-					// If the awaiter is a reference type, it might get stored in a field of type `object`
-					// and cast back to the awaiter type in the resume block
-					value = cast.Argument;
+					value = castArg;
 				}
 				if (!value.MatchLdFld(out var target, out var field))
 					return false;