[mcs] Codegen update for specialized struct initialization with awaited element initializer. Fixes #39459mono-4.4.0.40

3 files changed, 81 insertions, 2 deletions

diff --git a/mcs/mcs/expression.cs b/mcs/mcs/expression.cs
index c5139d57f67..bfba44fbb8c 100644
--- a/mcs/mcs/expression.cs
+++ b/mcs/mcs/expression.cs
@@ -6465,7 +6465,7 @@ namespace Mono.CSharp
 			}
 
 			New n_source = source as New;
-			if (n_source != null) {
+			if (n_source != null && n_source.CanEmitOptimizedLocalTarget (ec)) {
 				if (!n_source.Emit (ec, this)) {
 					if (leave_copy) {
 						EmitLoad (ec);
@@ -7605,6 +7605,11 @@ namespace Mono.CSharp
 				ec.Emit (OpCodes.Pop);
 		}
 
+		public virtual bool CanEmitOptimizedLocalTarget (EmitContext ec)
+		{
+			return true;
+		}
+
 		public override void FlowAnalysis (FlowAnalysisContext fc)
 		{
 			if (arguments != null)
@@ -12137,7 +12142,7 @@ namespace Mono.CSharp
 
 		public override void Emit (EmitContext ec)
 		{
-			if (method == null && TypeSpec.IsValueType (type) && initializers.Initializers.Count > 1 && ec.HasSet (BuilderContext.Options.AsyncBody) && initializers.ContainsEmitWithAwait ()) {
+			if (!CanEmitOptimizedLocalTarget (ec)) {
 				var fe = ec.GetTemporaryField (type);
 
 				if (!Emit (ec, fe))
@@ -12225,6 +12230,13 @@ namespace Mono.CSharp
 			return true;
 		}
 
+		public override bool CanEmitOptimizedLocalTarget (EmitContext ec)
+		{
+			return !(method == null && TypeSpec.IsValueType (type) &&
+					initializers.Initializers.Count > 1 && ec.HasSet (BuilderContext.Options.AsyncBody) &&
+					initializers.ContainsEmitWithAwait ());
+		}
+
 		protected override IMemoryLocation EmitAddressOf (EmitContext ec, AddressOp Mode)
 		{
 			instance = base.EmitAddressOf (ec, Mode);
diff --git a/mcs/tests/test-async-84.cs b/mcs/tests/test-async-84.cs
new file mode 100644
index 00000000000..03825613f1f
--- /dev/null
+++ b/mcs/tests/test-async-84.cs
@@ -0,0 +1,35 @@
+using System;
+using System.Threading.Tasks;
+
+struct S
+{
+	public int value;
+	public string str;
+}
+
+public class Program
+{
+	async Task<S> Foo ()
+	{
+		return new S {
+			value = 1,
+			str = await DoAsync ()
+		};
+
+	}
+
+	static async Task<string> DoAsync ()
+	{
+		await Task.Yield ();
+		return "asdafs";
+	}
+
+	static int Main ()
+	{
+		var res = new Program ().Foo ().Result;
+		if (res.value != 1)
+			return 1;
+
+		return 0;
+	}
+}
\ No newline at end of file
diff --git a/mcs/tests/ver-il-net_4_x.xml b/mcs/tests/ver-il-net_4_x.xml
index eca75aea8eb..55a55a8ce00 100644
--- a/mcs/tests/ver-il-net_4_x.xml
+++ b/mcs/tests/ver-il-net_4_x.xml
@@ -65617,6 +65617,38 @@
       </method>
     </type>
   </test>
+  <test name="test-async-84.cs">
+    <type name="Program">
+      <method name="System.Threading.Tasks.Task`1[S] Foo()" attrs="129">
+        <size>33</size>
+      </method>
+      <method name="System.Threading.Tasks.Task`1[System.String] DoAsync()" attrs="145">
+        <size>33</size>
+      </method>
+      <method name="Int32 Main()" attrs="145">
+        <size>46</size>
+      </method>
+      <method name="Void .ctor()" attrs="6278">
+        <size>7</size>
+      </method>
+    </type>
+    <type name="Program+&lt;Foo&gt;c__async0">
+      <method name="Void MoveNext()" attrs="486">
+        <size>204</size>
+      </method>
+      <method name="Void SetStateMachine(System.Runtime.CompilerServices.IAsyncStateMachine)" attrs="486">
+        <size>13</size>
+      </method>
+    </type>
+    <type name="Program+&lt;DoAsync&gt;c__async1">
+      <method name="Void MoveNext()" attrs="486">
+        <size>171</size>
+      </method>
+      <method name="Void SetStateMachine(System.Runtime.CompilerServices.IAsyncStateMachine)" attrs="486">
+        <size>13</size>
+      </method>
+    </type>
+  </test>
   <test name="test-cls-00.cs">
     <type name="CLSCLass_6">
       <method name="Void add_Disposed(Delegate)" attrs="2182">