Call impStoreStruct in impStoreNullableFields (dotnet#105529)

src/coreclr/jit/importer.cpp

@@ -3012,6 +3012,12 @@ GenTree* Compiler::impStoreNullableFields(CORINFO_CLASS_HANDLE nullableCls, GenT
     ClassLayout* layout        = valueType == TYP_STRUCT ? typGetObjLayout(valueStructCls) : nullptr;
     GenTree*     valueStore    = gtNewStoreLclFldNode(resultTmp, valueType, layout, valueOffset, value);
 
+    // ABI handling for struct values
+    if (varTypeIsStruct(valueStore))
+    {
+        valueStore = impStoreStruct(valueStore, CHECK_SPILL_ALL);
+    }
+
     impAppendTree(hasValueStore, CHECK_SPILL_ALL, impCurStmtDI);
     impAppendTree(valueStore, CHECK_SPILL_ALL, impCurStmtDI);
     return gtNewLclvNode(resultTmp, TYP_STRUCT);

src/tests/JIT/Regression/JitBlue/Runtime_105518/Runtime_105518.cs

@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Runtime.CompilerServices;
+using Xunit;
+
+public class Runtime_105518
+{
+    [Fact]
+    public static void TestEntryPoint()
+    {
+        Problem<decimal?, decimal>();
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static T GetValue<T>() => (T)(object)100M;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static TTo Problem<TTo, TFrom>() => (TTo)(object)GetValue<TFrom>();
+}

src/tests/JIT/Regression/JitBlue/Runtime_105518/Runtime_105518.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>