From eac0e2257e98129d4b1d1fdeb375d110f513a52f Mon Sep 17 00:00:00 2001
From: Siegfried Pammer <siegfriedpammer@gmail.com>
Date: Sun, 26 Jul 2020 19:22:14 +0200
Subject: [PATCH] Support MatchInstruction in DataFlowVisitor

---
 .../FlowAnalysis/DataFlowVisitor.cs           | 41 +++++++++++++++++++
 .../FlowAnalysis/DefiniteAssignmentVisitor.cs |  7 +++-
 .../ReachingDefinitionsVisitor.cs             |  7 +++-
 3 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/ICSharpCode.Decompiler/FlowAnalysis/DataFlowVisitor.cs b/ICSharpCode.Decompiler/FlowAnalysis/DataFlowVisitor.cs
index a43ac19e6..ed5d01918 100644
--- a/ICSharpCode.Decompiler/FlowAnalysis/DataFlowVisitor.cs
+++ b/ICSharpCode.Decompiler/FlowAnalysis/DataFlowVisitor.cs
@@ -646,6 +646,8 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 				} else {
 					return (state, bottomState.Clone());
 				}
+			} else if (inst is MatchInstruction match) {
+				return EvaluateMatch(match);
 			} else {
 				// other kind of condition
 				inst.AcceptVisitor(this);
@@ -653,6 +655,45 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 			}
 		}
 
+		protected internal override void VisitMatchInstruction(MatchInstruction inst)
+		{
+			var (onTrue, onFalse) = EvaluateMatch(inst);
+			state = onTrue;
+			state.JoinWith(onFalse);
+		}
+
+		/// <summary>
+		/// Evaluates a match instruction.
+		/// </summary>
+		/// <returns>
+		/// A pair of:
+		///  * The state after the pattern matches
+		///  * The state after the pattern fails to match
+		/// </returns>
+		/// <remarks>
+		/// <c>this.state</c> is invalid after this function was called, and must be overwritten
+		/// with one of the return values.
+		/// </remarks>
+		(State OnTrue, State OnFalse) EvaluateMatch(MatchInstruction inst)
+		{
+			DebugStartPoint(inst);
+			inst.TestedOperand.AcceptVisitor(this);
+			State onFalse = state.Clone();
+			if (!inst.CheckNotNull && !inst.CheckType) {
+				onFalse.ReplaceWithBottom();
+			}
+			HandleMatchStore(inst);
+			foreach (var subPattern in inst.SubPatterns) {
+				var (subTrue, subFalse) = EvaluateCondition(subPattern);
+				onFalse.JoinWith(subFalse);
+				state = subTrue;
+			}
+			DebugEndPoint(inst);
+			return (state, onFalse);
+		}
+
+		protected abstract void HandleMatchStore(MatchInstruction inst);
+
 		protected internal override void VisitNullCoalescingInstruction(NullCoalescingInstruction inst)
 		{
 			HandleBinaryWithOptionalEvaluation(inst, inst.ValueInst, inst.FallbackInst);
diff --git a/ICSharpCode.Decompiler/FlowAnalysis/DefiniteAssignmentVisitor.cs b/ICSharpCode.Decompiler/FlowAnalysis/DefiniteAssignmentVisitor.cs
index 5b465b735..726cef1f7 100644
--- a/ICSharpCode.Decompiler/FlowAnalysis/DefiniteAssignmentVisitor.cs
+++ b/ICSharpCode.Decompiler/FlowAnalysis/DefiniteAssignmentVisitor.cs
@@ -168,7 +168,12 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 			inst.Value.AcceptVisitor(this);
 			HandleStore(inst.Variable);
 		}
-		
+
+		protected override void HandleMatchStore(MatchInstruction inst)
+		{
+			HandleStore(inst.Variable);
+		}
+
 		protected override void BeginTryCatchHandler(TryCatchHandler inst)
 		{
 			HandleStore(inst.Variable);
diff --git a/ICSharpCode.Decompiler/FlowAnalysis/ReachingDefinitionsVisitor.cs b/ICSharpCode.Decompiler/FlowAnalysis/ReachingDefinitionsVisitor.cs
index 8b6d22a24..08bf2e4f2 100644
--- a/ICSharpCode.Decompiler/FlowAnalysis/ReachingDefinitionsVisitor.cs
+++ b/ICSharpCode.Decompiler/FlowAnalysis/ReachingDefinitionsVisitor.cs
@@ -380,7 +380,12 @@ namespace ICSharpCode.Decompiler.FlowAnalysis
 			inst.Value.AcceptVisitor(this);
 			HandleStore(inst, inst.Variable);
 		}
-		
+
+		protected override void HandleMatchStore(MatchInstruction inst)
+		{
+			HandleStore(inst, inst.Variable);
+		}
+
 		protected override void BeginTryCatchHandler(TryCatchHandler inst)
 		{
 			base.BeginTryCatchHandler(inst);