Fix #2378: DeconstructionTransform produced invalid ILAst with some optimized deconstruction patterns.

Author: siegfriedpammer

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

@@ -219,6 +219,22 @@ public void LocalVariable_NoConversion_Tuple_ReferenceTypes()
 			Console.WriteLine(value2);
 		}
 
+		public void Issue2378(Tuple<object, object> tuple)
+		{
+			var (value, value2) = tuple;
+			Console.WriteLine(value2);
+			Console.WriteLine(value);
+		}
+
+		public void Issue2378_IntToLongConversion(Tuple<int, int> tuple)
+		{
+			int value;
+			long value2;
+			(value, value2) = tuple;
+			Console.WriteLine(value2);
+			Console.WriteLine(value);
+		}
+
 		public void LocalVariable_IntToLongConversion_Custom()
 		{
 			int value;

ICSharpCode.Decompiler/IL/Transforms/DeconstructionTransform.cs

@@ -378,6 +378,28 @@ bool MatchAssignments(Block block, ref int pos,
 				previousIndex = index;
 			}
 			AddMissingAssignmentsForConversions(int.MaxValue, ref delayedActions);
+
+			if (deconstructionResults != null)
+			{
+				int i = previousIndex + 1;
+				while (i < deconstructionResults.Length)
+				{
+					var v = deconstructionResults[i];
+					// this should only happen in release mode, where usually the last deconstruction element
+					// is not stored to a temporary, if it is used directly (and only once!)
+					// after the deconstruction.
+					if (v?.LoadCount == 1)
+					{
+						delayedActions += (DeconstructInstruction deconstructInst) => {
+							var freshVar = context.Function.RegisterVariable(VariableKind.StackSlot, v.Type);
+							deconstructInst.Assignments.Instructions.Add(new StLoc(freshVar, new LdLoc(v)));
+							v.LoadInstructions[0].Variable = freshVar;
+						};
+					}
+					i++;
+				}
+			}
+
 			return startPos != pos;
 
 			void AddMissingAssignmentsForConversions(int index, ref Action<DeconstructInstruction> delayedActions)
@@ -397,6 +419,7 @@ void AddMissingAssignmentsForConversions(int index, ref Action<DeconstructInstru
 							stLoc.Variable = freshVar;
 						};
 					}
+					previousIndex = conversionResultIndex;
 					conversionStLocIndex++;
 				}
 			}