Disable ref inline assignments.

This increases the chances that we'll avoid CS8174: A declaration of a by-reference variable must have an initializer.

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

@@ -4553,6 +4553,8 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 #if !LEGACY_CSC
 		// Legacy csc generates a slightly different pattern for string compound assignment
 		// as for all other compound assignments. We'll ignore that edge case.
+		// Note: it's possible that the pre-CopyPropagation run of TransformAssignments is causing trouble there,
+		// and that the compound assignment transform would be fine if it didn't get disrupted.
 
 		private static void Issue1082(string[] strings, List<char> chars, bool flag, int i)
 		{

ICSharpCode.Decompiler/IL/Transforms/TransformAssignment.cs

@@ -350,6 +350,14 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				// 'stloc l' is implicitly truncating the stack value
 				return false;
 			}
+			if (nextInst.Variable.StackType == StackType.Ref) {
+				// ref locals need to be initialized when they are declared, so
+				// we can only use inline assignments when we know that the
+				// ref local is definitely assigned.
+				// We don't have an easy way to check for that in this transform,
+				// so avoid inline assignments to ref locals for now.
+				return false;
+			}
 			context.Step("Inline assignment to local variable", inst);
 			var value = inst.Value;
 			var var = nextInst.Variable;