Add ScopeRegion::ScopeType and DominatorTree extension class

src/Core/Echo.ControlFlow/Analysis/Domination/DominatorTree.cs

@@ -7,6 +7,23 @@
 
 namespace Echo.ControlFlow.Analysis.Domination
 {
+    /// <summary>
+    /// Provides extension methods for constructing dominator trees.
+    /// </summary>
+    public static class DominatorTree
+    {
+        /// <summary>
+        /// Constructs a dominator tree from a control flow graph.
+        /// </summary>
+        /// <param name="graph">The control flow graph to turn into a dominator tree.</param>
+        /// <returns>The constructed dominator tree.</returns>
+        public static DominatorTree<TInstruction> FromGraph<TInstruction>(ControlFlowGraph<TInstruction> graph)
+            where TInstruction : notnull
+        {
+            return DominatorTree<TInstruction>.FromGraph(graph);
+        }
+    }
+
     /// <summary>
     /// Represents a dominator tree, where each tree node corresponds to one node in a graph, and each
     /// is immediately dominated by its parent.

src/Core/Echo.ControlFlow/Collections/RegionCollection.cs

@@ -28,7 +28,7 @@ public RegionCollection(IControlFlowRegion<TInstruction> owner)
 
         private void AssertRegionValidity(TRegion item)
         {
-            if (item.ParentRegion is {})
+            if (item.ParentRegion is not null)
                 throw new ArgumentException("Region is already part of another graph.");
         }
 

src/Core/Echo.ControlFlow/ControlFlowGraph.cs

@@ -65,6 +65,8 @@ public NodeCollection<TInstruction> Nodes
             get;
         }
 
+        ICollection<ControlFlowNode<TInstruction>> IScopeControlFlowRegion<TInstruction>.Nodes => Nodes;
+
         /// <summary>
         /// Gets a collection of top-level regions that this control flow graph defines. 
         /// </summary>

src/Core/Echo.ControlFlow/Regions/IControlFlowRegion.cs

@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using Echo.ControlFlow.Collections;
 using Echo.Graphing;
 
 namespace Echo.ControlFlow.Regions
@@ -39,7 +38,7 @@ public interface IControlFlowRegion<TInstruction> : ISubGraph
         /// <summary>
         /// Gets a collection of all nested regions defined in this region.
         /// </summary>
-        /// <returns>The sub regions.</returns>
+        /// <returns>The subregions.</returns>
         IEnumerable<ControlFlowRegion<TInstruction>> GetSubRegions();
 
         /// <summary>
@@ -70,22 +69,6 @@ public interface IControlFlowRegion<TInstruction> : ISubGraph
         IEnumerable<ControlFlowNode<TInstruction>> GetSuccessors();
     }
 
-    /// <summary>
-    /// Represents a scope of regions. 
-    /// </summary>
-    /// <typeparam name="TInstruction">The type of data that each node in the graph stores.</typeparam>
-    public interface IScopeControlFlowRegion<TInstruction> : IControlFlowRegion<TInstruction>
-        where TInstruction : notnull
-    {
-        /// <summary>
-        /// Gets a collection of nested sub regions that this region defines.
-        /// </summary>
-        public RegionCollection<TInstruction, ControlFlowRegion<TInstruction>> Regions
-        {
-            get;
-        }
-    }
-
     /// <summary>
     /// Provides extensions to the <see cref="IControlFlowRegion{TInstruction}"/> interface.
     /// </summary>

src/Core/Echo.ControlFlow/Regions/IScopeControlFlowRegion.cs

@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+using Echo.ControlFlow.Collections;
+
+namespace Echo.ControlFlow.Regions;
+
+/// <summary>
+/// Represents a scope of nodes and regions.
+/// </summary>
+/// <typeparam name="TInstruction">The type of data that each node in the graph stores.</typeparam>
+public interface IScopeControlFlowRegion<TInstruction> : IControlFlowRegion<TInstruction>
+    where TInstruction : notnull
+{
+    /// <summary>
+    /// Gets a collection of top-level nodes stored in this region.
+    /// </summary>
+    public ICollection<ControlFlowNode<TInstruction>> Nodes { get; }
+
+    /// <summary>
+    /// Gets a collection of nested subregions that this region defines.
+    /// </summary>
+    public RegionCollection<TInstruction, ControlFlowRegion<TInstruction>> Regions { get; }
+}

src/Core/Echo.ControlFlow/Regions/ScopeRegion.cs

@@ -7,45 +7,52 @@ namespace Echo.ControlFlow.Regions
     /// Represents a simple unordered region defining an inner scope in the control flow graph.
     /// </summary>
     /// <typeparam name="TInstruction">The type of data that each node in the graph stores.</typeparam>
-    public class ScopeRegion<TInstruction> : ControlFlowRegion<TInstruction>
+    public class ScopeRegion<TInstruction> : ControlFlowRegion<TInstruction>, IScopeControlFlowRegion<TInstruction>
         where TInstruction : notnull
     {
         /// <summary>
-        /// Creates a new instance of the <see cref="ScopeRegion{TInstruction}"/> class.
+        /// Creates a new empty scope region with no extra semantics attached.
         /// </summary>
         public ScopeRegion()
+            : this(ScopeRegionType.None)
+        {
+        }
+
+        /// <summary>
+        /// Creates a new empty scope region of the provided scope type.
+        /// </summary>
+        /// <param name="type">The type.</param>
+        public ScopeRegion(ScopeRegionType type)
         {
             Regions = new RegionCollection<TInstruction, ControlFlowRegion<TInstruction>>(this);
             Nodes = new RegionNodeCollection<TInstruction>(this);
+            ScopeType = type;
         }
 
         /// <summary>
         /// Gets or sets the first node that is executed in the region.
         /// </summary>
-        public ControlFlowNode<TInstruction>? EntryPoint
-        {
-            get;
-            set;
-        }
+        public ControlFlowNode<TInstruction>? EntryPoint { get; set; }
 
         /// <summary>
         /// Gets a collection of top-level nodes that this region consists of.
         /// </summary>
         /// <remarks>
         /// This collection does not include any nodes in the nested sub regions.
         /// </remarks>
-        public RegionNodeCollection<TInstruction> Nodes
-        {
-            get;
-        }
+        public RegionNodeCollection<TInstruction> Nodes { get; }
+
+        ICollection<ControlFlowNode<TInstruction>> IScopeControlFlowRegion<TInstruction>.Nodes => Nodes;
 
         /// <summary>
-        /// Gets a collection of nested sub regions that this region defines.
+        /// Gets a collection of nested subregions that this region defines.
         /// </summary>
-        public RegionCollection<TInstruction, ControlFlowRegion<TInstruction>> Regions
-        {
-            get;
-        }
+        public RegionCollection<TInstruction, ControlFlowRegion<TInstruction>> Regions { get; }
+
+        /// <summary>
+        /// Gets or sets the type of scope.
+        /// </summary>
+        public ScopeRegionType ScopeType { get; set; }
 
         /// <inheritdoc />
         public override IEnumerable<ControlFlowNode<TInstruction>> GetNodes()

src/Core/Echo.ControlFlow/Regions/ScopeRegionType.cs

@@ -0,0 +1,25 @@
+namespace Echo.ControlFlow.Regions;
+
+/// <summary>
+/// Provides members describing all possible types a scope region can be.
+/// </summary>
+public enum ScopeRegionType
+{
+    /// <summary>
+    /// Indicates no special semantics.
+    /// </summary>
+    None,
+
+    /// <summary>
+    /// Indicates the scope was introduced as a result of a conditional branch (e.g., if-else or switch).
+    /// The entry point node of the scope implements the condition and the true/false branches.
+    /// </summary>
+    Conditional,
+
+    /// <summary>
+    /// Indicates the scope was introduced as a result of one or more back-edges and forms a loop.
+    /// The entry point node of the scope is the loop header, and all incoming edges originating from within the scope
+    /// define all back-edges.
+    /// </summary>
+    Loop,
+}

src/Core/Echo.ControlFlow/Serialization/Dot/ExceptionHandlerAdorner.cs

@@ -213,19 +213,13 @@ private static string GetScopeRegionPrefix(ScopeRegion<TInstruction> basicRegion
 
         private (DotEntityStyle Style, string Label) GetSubGraphStyle(IControlFlowRegion<TInstruction> region)
         {
-            switch (region)
+            return region switch
             {
-                case ScopeRegion<TInstruction> basicRegion:
-                    return GetScopeStyle(basicRegion);
-
-                case ExceptionHandlerRegion<TInstruction> _:
-                    return (ExceptionHandlerStyle, ExceptionHandlerLabel);
-
-                case HandlerRegion<TInstruction> _:
-                    return (HandlerStyle, HandlerLabel);
-            }
-
-            return (DefaultStyle, string.Empty);
+                ScopeRegion<TInstruction> basicRegion => GetScopeStyle(basicRegion),
+                ExceptionHandlerRegion<TInstruction> _ => (ExceptionHandlerStyle, ExceptionHandlerLabel),
+                HandlerRegion<TInstruction> _ => (HandlerStyle, HandlerLabel),
+                _ => (DefaultStyle, string.Empty)
+            };
         }
 
         private (DotEntityStyle Style, string Label) GetScopeStyle(ScopeRegion<TInstruction> basicRegion)
@@ -251,7 +245,11 @@ private static string GetScopeRegionPrefix(ScopeRegion<TInstruction> basicRegion
                 }
             }
 
-            return (DefaultStyle, "Scope");
+            string label = basicRegion.ScopeType != ScopeRegionType.None
+                ? basicRegion.ScopeType.ToString()
+                : "Scope";
+
+            return (DefaultStyle, label);
         }
 
     }