Fix missing conversion on ref-reassignment.

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

@@ -26,6 +26,16 @@ internal sealed class ExtraUnsafeTests
 		return (uint*)Unsafe.AsPointer(ref managedPtr);
 	}
 
+	public static ref ulong RefAssignTypeMismatch(ref uint a, ref uint b)
+	{
+		ref ushort reference = ref Unsafe.As<uint, ushort>(ref a);
+		if (a != 0) {
+			reference = ref Unsafe.As<uint, ushort>(ref b);
+		}
+		Console.WriteLine(reference);
+		return ref Unsafe.As<ushort, ulong>(ref reference);
+	}
+
 	public unsafe static byte[] Issue1292(int val, byte[] arr)
 	{
 		//The blocks IL_0019 are reachable both inside and outside the pinned region starting at IL_0013. ILSpy has duplicated these blocks in order to place them both within and outside the `fixed` statement.

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

@@ -475,6 +475,32 @@
     ret
   }
 
+  .method public hidebysig static uint64& RefAssignTypeMismatch(uint32& a, uint32& b)
+  {
+    .maxstack 8
+    .locals (
+      [0] uint16&
+    )
+
+    ldarg.0
+    stloc.0
+    
+    ldarg.0
+    ldind.i4
+    brfalse lbl
+
+    ldarg.1
+    stloc.0
+
+lbl:
+    ldloc.0
+    ldind.i2
+    call       void [mscorlib]System.Console::WriteLine(uint16)
+
+    ldloc.0
+    ret
+  }
+
   .method public hidebysig static 
 	  uint8[] Issue1292 (
 		  int32 val,

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -640,6 +640,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			if (lhs.Expression is DirectionExpression dirExpr && lhs.ResolveResult is ByReferenceResolveResult lhsRefRR) {
 				// ref (re-)assignment, emit "ref (a = ref b)".
 				lhs = lhs.UnwrapChild(dirExpr.Expression);
+				translatedValue = translatedValue.ConvertTo(lhsRefRR.Type, this, allowImplicitConversion: true);
 				var assign = new AssignmentExpression(lhs.Expression, translatedValue.Expression)
 					.WithRR(new OperatorResolveResult(lhs.Type, ExpressionType.Assign, lhsRefRR, translatedValue.ResolveResult));
 				return new DirectionExpression(FieldDirection.Ref, assign)