[Debugger] Fix crash when there is a generic struct with a field that is an enumerator. (#12368)

* [Debugger]  Debugger crashes when inside a class, there is an internal struct, with a field that is an enumerator.
files.myBucket.GetEnumerator().get_Current().Key
Fixes #10735

* [Debugger] Debugger crashes when there is a generic struct with a field that is an enumerator.
Example: files.get_Current().Key
A unit test that reproduces this crash was added too.
Fixes #10735

* Removing the extra space.

2 files changed, 53 insertions, 2 deletions

diff --git a/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs b/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs
index cf166e5c1da..b6ea142262a 100644
--- a/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs
+++ b/mcs/class/Mono.Debugger.Soft/Test/dtest-app.cs
@@ -14,6 +14,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Net.Sockets;
 using System.Collections.Concurrent;
+using System.Collections;
 #if !MOBILE
 using MonoTests.Helpers;
 #endif
@@ -86,6 +87,31 @@ public class Tests2 {
 	}
 }
 
+public struct TestEnumeratorInsideGenericStruct<TKey, TValue>
+{
+	private KeyValuePair<TKey, TValue> _bucket;
+	private Position _currentPosition;
+	internal TestEnumeratorInsideGenericStruct(KeyValuePair<TKey, TValue> bucket)
+	{
+		_bucket = bucket;
+		_currentPosition = Position.BeforeFirst;
+	}
+
+	public KeyValuePair<TKey, TValue> Current
+	{
+		get
+		{
+			if (_currentPosition == Position.BeforeFirst)
+				return _bucket;
+			return _bucket;
+		}
+	}
+	private enum Position
+	{
+		BeforeFirst
+	}
+}
+
 public struct AStruct : ITest2 {
 	public int i;
 	public string s;
@@ -448,6 +474,7 @@ public class Tests : TestsBase, ITest2
 		new Tests ().evaluate_method ();
 		Bug59649 ();
 		elapsed_time();
+		inspect_enumerator_in_generic_struct();
 		return 3;
 	}
 
@@ -650,9 +677,9 @@ public class Tests : TestsBase, ITest2
 	[MethodImplAttribute (MethodImplOptions.NoInlining)]
 	public static void ss_nested_twice_with_two_args_wrapper () {
 		ss_nested_with_two_args(ss_nested_arg1 (), ss_nested_with_two_args(ss_nested_arg2 (), ss_nested_arg3 ()));
-  }
+	}
   
-  [MethodImplAttribute (MethodImplOptions.NoInlining)]
+	[MethodImplAttribute (MethodImplOptions.NoInlining)]
 	public static void elapsed_time () {
 		Thread.Sleep(200);
 		Thread.Sleep(00);
@@ -661,6 +688,11 @@ public class Tests : TestsBase, ITest2
 	}
 	
 	[MethodImplAttribute (MethodImplOptions.NoInlining)]
+	public static void inspect_enumerator_in_generic_struct() {
+		TestEnumeratorInsideGenericStruct<String, String> generic_struct = new TestEnumeratorInsideGenericStruct<String, String>(new KeyValuePair<string, string>("0", "f1"));
+	}
+
+	[MethodImplAttribute (MethodImplOptions.NoInlining)]
 	public static int ss_nested_with_two_args (int a1, int a2) {
 		return a1 + a2;
 	}
diff --git a/mcs/class/Mono.Debugger.Soft/Test/dtest.cs b/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
index c0aefeab751..0ef677e0e07 100644
--- a/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
+++ b/mcs/class/Mono.Debugger.Soft/Test/dtest.cs
@@ -4603,6 +4603,25 @@ public class DebuggerTests
 	}
 
 	[Test]
+	public void InspectEnumeratorInGenericStruct() {
+		//files.myBucket.GetEnumerator().get_Current().Key watching this generates an exception in Debugger
+		Event e = run_until("inspect_enumerator_in_generic_struct");
+		var req = create_step(e);
+		req.Enable();
+		e = step_once();
+		e = step_over();
+		StackFrame frame = e.Thread.GetFrames () [0];
+		var ginst = frame.Method.GetLocal ("generic_struct");
+		Value variable = frame.GetValue (ginst);
+		StructMirror thisObj = (StructMirror)variable;
+		TypeMirror thisType = thisObj.Type;
+		variable = thisObj.InvokeMethod(e.Thread, thisType.GetMethod("get_Current"), null);
+		thisObj = (StructMirror)variable;
+		thisType = thisObj.Type;
+		AssertValue ("f1", thisObj["value"]);
+	}
+
+	[Test]
 	public void CheckElapsedTime() {
 		Event e = run_until ("elapsed_time");