Add control flow analysis for the NRefactory C# AST.

NRefactory/ICSharpCode.NRefactory/CSharp/Analysis/ControlFlow.cs

@@ -0,0 +1,516 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under MIT X11 license (for details please see \doc\license.txt)
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using ICSharpCode.NRefactory.CSharp.Resolver;
+
+namespace ICSharpCode.NRefactory.CSharp.Analysis
+{
+	/// <summary>
+	/// Represents a node in the control flow graph of a C# method.
+	/// </summary>
+	public class ControlFlowNode
+	{
+		public readonly Statement PreviousStatement;
+		public readonly Statement NextStatement;
+		
+		public ControlFlowNodeType Type;
+		
+		public readonly List<ControlFlowNode> Predecessors = new List<ControlFlowNode>();
+		public readonly List<ControlFlowNode> Successors = new List<ControlFlowNode>();
+		
+		public ControlFlowNode(Statement previousStatement, Statement nextStatement)
+		{
+			if (previousStatement == null && nextStatement == null)
+				throw new ArgumentException("previousStatement and nextStatement must not be both null");
+			this.PreviousStatement = previousStatement;
+			this.NextStatement = nextStatement;
+		}
+		
+		/// <summary>
+		/// Creates a control flow edge from <c>source</c> to <c>this</c>.
+		/// </summary>
+		internal ControlFlowNode ConnectWith(ControlFlowNode source)
+		{
+			source.Successors.Add(this);
+			this.Predecessors.Add(source);
+			return this;
+		}
+	}
+	
+	public enum ControlFlowNodeType
+	{
+		/// <summary>
+		/// Unknown node type
+		/// </summary>
+		None,
+		/// <summary>
+		/// Node in front of a statement
+		/// </summary>
+		StartNode,
+		/// <summary>
+		/// Node between two statements
+		/// </summary>
+		BetweenStatements,
+		/// <summary>
+		/// Node at the end of a statement list
+		/// </summary>
+		EndNode,
+		/// <summary>
+		/// Node representing the position before evaluating the condition of a loop.
+		/// </summary>
+		LoopCondition
+	}
+	
+	public class ControlFlowGraphBuilder
+	{
+		protected virtual ControlFlowNode CreateNode(Statement previousStatement, Statement nextStatement)
+		{
+			return new ControlFlowNode(previousStatement, nextStatement);
+		}
+		
+		List<ControlFlowNode> nodes;
+		Dictionary<string, ControlFlowNode> labels;
+		List<ControlFlowNode> gotoStatements;
+		
+		public ControlFlowNode[] BuildControlFlowGraph(BlockStatement block)
+		{
+			NodeCreationVisitor nodeCreationVisitor = new NodeCreationVisitor();
+			nodeCreationVisitor.builder = this;
+			try {
+				nodes = new List<ControlFlowNode>();
+				labels = new Dictionary<string, ControlFlowNode>();
+				gotoStatements = new List<ControlFlowNode>();
+				ControlFlowNode entryPoint = CreateStartNode(block);
+				nodeCreationVisitor.VisitBlockStatement(block, entryPoint);
+				
+				// Resolve goto statements:
+				foreach (ControlFlowNode gotoStmt in gotoStatements) {
+					string label = ((GotoStatement)gotoStmt.NextStatement).Label;
+					ControlFlowNode labelNode;
+					if (labels.TryGetValue(label, out labelNode))
+						labelNode.ConnectWith(gotoStmt);
+				}
+				
+				return nodes.ToArray();
+			} finally {
+				nodes = null;
+				labels = null;
+				gotoStatements = null;
+			}
+		}
+		
+		ControlFlowNode CreateStartNode(Statement statement)
+		{
+			ControlFlowNode node = CreateNode(null, statement);
+			node.Type = ControlFlowNodeType.StartNode;
+			nodes.Add(node);
+			return node;
+		}
+		
+		ControlFlowNode CreateSpecialNode(Statement statement, ControlFlowNodeType type)
+		{
+			ControlFlowNode node = CreateNode(statement, null);
+			node.Type = type;
+			nodes.Add(node);
+			return node;
+		}
+		
+		ControlFlowNode CreateEndNode(Statement statement)
+		{
+			// Find the next statement in the same role:
+			AstNode next = statement;
+			do {
+				next = next.NextSibling;
+			} while (next != null && next.Role != statement.Role);
+			
+			Statement nextStatement = next as Statement;
+			ControlFlowNode node = CreateNode(statement, nextStatement);
+			node.Type = nextStatement != null ? ControlFlowNodeType.BetweenStatements : ControlFlowNodeType.EndNode;
+			nodes.Add(node);
+			return node;
+		}
+		
+		#region Constant evaluation
+		/// <summary>
+		/// Evaluates an expression.
+		/// </summary>
+		/// <returns>The constant value of the expression; or null if the expression is not a constant.</returns>
+		ConstantResolveResult EvaluateConstant(Expression expr)
+		{
+			return null; // TODO: implement this using the C# resolver
+		}
+		
+		/// <summary>
+		/// Evaluates an expression.
+		/// </summary>
+		/// <returns>The value of the constant boolean expression; or null if the value is not a constant boolean expression.</returns>
+		bool? EvaluateCondition(Expression expr)
+		{
+			ConstantResolveResult crr = EvaluateConstant(expr);
+			if (crr != null)
+				return crr.ConstantValue as bool?;
+			else
+				return null;
+		}
+		
+		bool AreEqualConstants(ConstantResolveResult c1, ConstantResolveResult c2)
+		{
+			return false; // TODO: implement this using the resolver's operator==
+		}
+		#endregion
+		
+		sealed class NodeCreationVisitor : DepthFirstAstVisitor<ControlFlowNode, ControlFlowNode>
+		{
+			// 'data' parameter: input control flow node (start of statement being visited)
+			// Return value: result control flow node (end of statement being visited)
+			
+			internal ControlFlowGraphBuilder builder;
+			Stack<ControlFlowNode> breakTargets = new Stack<ControlFlowNode>();
+			Stack<ControlFlowNode> continueTargets = new Stack<ControlFlowNode>();
+			List<ControlFlowNode> gotoCaseOrDefault = new List<ControlFlowNode>();
+			
+			protected override ControlFlowNode VisitChildren(AstNode node, ControlFlowNode data)
+			{
+				// We have overrides for all possible expressions and should visit expressions only.
+				throw new NotImplementedException();
+			}
+			
+			public override ControlFlowNode VisitBlockStatement(BlockStatement blockStatement, ControlFlowNode data)
+			{
+				// C# 4.0 spec: §8.2 Blocks
+				ControlFlowNode childNode = HandleStatementList(blockStatement.Statements, data);
+				return builder.CreateEndNode(blockStatement).ConnectWith(childNode);
+			}
+			
+			ControlFlowNode HandleStatementList(AstNodeCollection<Statement> statements, ControlFlowNode source)
+			{
+				ControlFlowNode childNode = null;
+				foreach (Statement stmt in statements) {
+					if (childNode == null) {
+						childNode = builder.CreateStartNode(stmt);
+						childNode.ConnectWith(source);
+					}
+					Debug.Assert(childNode.NextStatement == stmt);
+					childNode = stmt.AcceptVisitor(this, childNode);
+					Debug.Assert(childNode.PreviousStatement == stmt);
+				}
+				return childNode ?? source;
+			}
+			
+			public override ControlFlowNode VisitEmptyStatement(EmptyStatement emptyStatement, ControlFlowNode data)
+			{
+				return builder.CreateEndNode(emptyStatement).ConnectWith(data);
+			}
+			
+			public override ControlFlowNode VisitLabelStatement(LabelStatement labelStatement, ControlFlowNode data)
+			{
+				ControlFlowNode end = builder.CreateEndNode(labelStatement);
+				builder.labels[labelStatement.Label] = end;
+				return end.ConnectWith(data);
+			}
+			
+			public override ControlFlowNode VisitVariableDeclarationStatement(VariableDeclarationStatement variableDeclarationStatement, ControlFlowNode data)
+			{
+				return builder.CreateEndNode(variableDeclarationStatement).ConnectWith(data);
+			}
+			
+			public override ControlFlowNode VisitExpressionStatement(ExpressionStatement expressionStatement, ControlFlowNode data)
+			{
+				return builder.CreateEndNode(expressionStatement).ConnectWith(data);
+			}
+			
+			public override ControlFlowNode VisitIfElseStatement(IfElseStatement ifElseStatement, ControlFlowNode data)
+			{
+				bool? cond = builder.EvaluateCondition(ifElseStatement.Condition);
+				ControlFlowNode trueBegin = builder.CreateStartNode(ifElseStatement.TrueStatement);
+				if (cond != false)
+					trueBegin.ConnectWith(data);
+				ControlFlowNode trueEnd = ifElseStatement.TrueStatement.AcceptVisitor(this, trueBegin);
+				ControlFlowNode falseEnd;
+				if (ifElseStatement.FalseStatement.IsNull) {
+					falseEnd = null;
+				} else {
+					ControlFlowNode falseBegin = builder.CreateStartNode(ifElseStatement.FalseStatement);
+					if (cond != true)
+						falseBegin.ConnectWith(data);
+					falseEnd = ifElseStatement.FalseStatement.AcceptVisitor(this, falseBegin);
+				}
+				ControlFlowNode end = builder.CreateEndNode(ifElseStatement);
+				end.ConnectWith(trueEnd);
+				if (falseEnd != null) {
+					end.ConnectWith(falseEnd);
+				} else if (cond != true) {
+					end.ConnectWith(data);
+				}
+				return end;
+			}
+			
+			public override ControlFlowNode VisitSwitchStatement(SwitchStatement switchStatement, ControlFlowNode data)
+			{
+				// First, figure out which switch section will get called (if the expression is constant):
+				ConstantResolveResult constant = builder.EvaluateConstant(switchStatement.Expression);
+				SwitchSection defaultSection = null;
+				SwitchSection sectionMatchedByConstant = null;
+				foreach (SwitchSection section in switchStatement.SwitchSections) {
+					foreach (CaseLabel label in section.CaseLabels) {
+						if (label.Expression.IsNull) {
+							defaultSection = section;
+						} else if (constant != null) {
+							ConstantResolveResult labelConstant = builder.EvaluateConstant(label.Expression);
+							if (builder.AreEqualConstants(constant, labelConstant))
+								sectionMatchedByConstant = section;
+						}
+					}
+				}
+				if (constant != null && sectionMatchedByConstant == null)
+					sectionMatchedByConstant = defaultSection;
+				
+				int gotoCaseOrDefaultInOuterScope = gotoCaseOrDefault.Count;
+				
+				ControlFlowNode end = builder.CreateEndNode(switchStatement);
+				breakTargets.Push(end);
+				foreach (SwitchSection section in switchStatement.SwitchSections) {
+					if (constant == null || section == sectionMatchedByConstant) {
+						HandleStatementList(section.Statements, data);
+					} else {
+						// This section is unreachable: pass null to HandleStatementList.
+						HandleStatementList(section.Statements, null);
+					}
+					// Don't bother connecting the ends of the sections: the 'break' statement takes care of that.
+				}
+				breakTargets.Pop();
+				if (defaultSection == null && sectionMatchedByConstant == null) {
+					end.ConnectWith(data);
+				}
+				
+				if (gotoCaseOrDefault.Count > gotoCaseOrDefaultInOuterScope) {
+					// Resolve 'goto case' statements:
+					throw new NotImplementedException();
+				}
+				
+				return end;
+			}
+			
+			public override ControlFlowNode VisitGotoCaseStatement(GotoCaseStatement gotoCaseStatement, ControlFlowNode data)
+			{
+				gotoCaseOrDefault.Add(data);
+				return builder.CreateEndNode(gotoCaseStatement);
+			}
+			
+			public override ControlFlowNode VisitGotoDefaultStatement(GotoDefaultStatement gotoDefaultStatement, ControlFlowNode data)
+			{
+				gotoCaseOrDefault.Add(data);
+				return builder.CreateEndNode(gotoDefaultStatement);
+			}
+			
+			public override ControlFlowNode VisitWhileStatement(WhileStatement whileStatement, ControlFlowNode data)
+			{
+				// <data> <condition> while (cond) { <bodyStart> embeddedStmt; <bodyEnd> } <end>
+				ControlFlowNode end = builder.CreateEndNode(whileStatement);
+				ControlFlowNode conditionNode = builder.CreateSpecialNode(whileStatement, ControlFlowNodeType.LoopCondition);
+				breakTargets.Push(end);
+				continueTargets.Push(conditionNode);
+				
+				conditionNode.ConnectWith(data);
+				
+				bool? cond = builder.EvaluateCondition(whileStatement.Condition);
+				ControlFlowNode bodyStart = builder.CreateStartNode(whileStatement.EmbeddedStatement);
+				if (cond != false)
+					bodyStart.ConnectWith(conditionNode);
+				ControlFlowNode bodyEnd = whileStatement.EmbeddedStatement.AcceptVisitor(this, bodyStart);
+				conditionNode.ConnectWith(bodyEnd);
+				if (cond != true)
+					end.ConnectWith(conditionNode);
+				
+				breakTargets.Pop();
+				continueTargets.Pop();
+				return end;
+			}
+			
+			public override ControlFlowNode VisitDoWhileStatement(DoWhileStatement doWhileStatement, ControlFlowNode data)
+			{
+				// <data> do { <bodyStart> embeddedStmt; <bodyEnd>} <condition> while(cond); <end>
+				ControlFlowNode end = builder.CreateEndNode(doWhileStatement);
+				ControlFlowNode conditionNode = builder.CreateSpecialNode(doWhileStatement, ControlFlowNodeType.LoopCondition);
+				breakTargets.Push(end);
+				continueTargets.Push(conditionNode);
+				
+				ControlFlowNode bodyStart = builder.CreateStartNode(doWhileStatement.EmbeddedStatement);
+				bodyStart.ConnectWith(data);
+				ControlFlowNode bodyEnd = doWhileStatement.EmbeddedStatement.AcceptVisitor(this, bodyStart);
+				conditionNode.ConnectWith(bodyEnd);
+				
+				bool? cond = builder.EvaluateCondition(doWhileStatement.Condition);
+				if (cond != false)
+					bodyStart.ConnectWith(conditionNode);
+				if (cond != true)
+					end.ConnectWith(conditionNode);
+				
+				breakTargets.Pop();
+				continueTargets.Pop();
+				return end;
+			}
+			
+			public override ControlFlowNode VisitForStatement(ForStatement forStatement, ControlFlowNode data)
+			{
+				data = HandleStatementList(forStatement.Initializers, data);
+				// for (initializers <data>; <condition>cond; <iteratorStart>iterators<iteratorEnd>) { <bodyStart> embeddedStmt; <bodyEnd> } <end>
+				ControlFlowNode end = builder.CreateEndNode(forStatement);
+				ControlFlowNode conditionNode = builder.CreateSpecialNode(forStatement, ControlFlowNodeType.LoopCondition);
+				conditionNode.ConnectWith(data);
+				
+				int iteratorStartNodeID = builder.nodes.Count;
+				ControlFlowNode iteratorEnd = HandleStatementList(forStatement.Iterators, null);
+				ControlFlowNode iteratorStart;
+				if (iteratorEnd != null) {
+					iteratorStart = builder.nodes[iteratorStartNodeID];
+					iteratorEnd.ConnectWith(conditionNode);
+				} else {
+					iteratorStart = conditionNode;
+				}
+				
+				breakTargets.Push(end);
+				continueTargets.Push(iteratorStart);
+				
+				ControlFlowNode bodyStart = builder.CreateStartNode(forStatement.EmbeddedStatement);
+				ControlFlowNode bodyEnd = forStatement.EmbeddedStatement.AcceptVisitor(this, bodyStart);
+				iteratorStart.ConnectWith(bodyEnd);
+				
+				breakTargets.Pop();
+				continueTargets.Pop();
+				
+				bool? cond = forStatement.Condition.IsNull ? true : builder.EvaluateCondition(forStatement.Condition);
+				if (cond != false)
+					bodyStart.ConnectWith(conditionNode);
+				if (cond != true)
+					end.ConnectWith(conditionNode);
+				
+				return end;
+			}
+			
+			ControlFlowNode HandleEmbeddedStatement(Statement embeddedStatement, ControlFlowNode source)
+			{
+				if (embeddedStatement == null || embeddedStatement.IsNull)
+					return source;
+				ControlFlowNode bodyStart = builder.CreateStartNode(embeddedStatement);
+				if (source != null)
+					bodyStart.ConnectWith(source);
+				return embeddedStatement.AcceptVisitor(this, bodyStart);
+			}
+			
+			public override ControlFlowNode VisitForeachStatement(ForeachStatement foreachStatement, ControlFlowNode data)
+			{
+				// <data> foreach (<condition>...) { <bodyStart>embeddedStmt<bodyEnd> } <end>
+				ControlFlowNode end = builder.CreateEndNode(foreachStatement);
+				ControlFlowNode conditionNode = builder.CreateSpecialNode(foreachStatement, ControlFlowNodeType.LoopCondition);
+				conditionNode.ConnectWith(data);
+				
+				breakTargets.Push(end);
+				continueTargets.Push(conditionNode);
+				
+				ControlFlowNode bodyEnd = HandleEmbeddedStatement(foreachStatement.EmbeddedStatement, conditionNode);
+				conditionNode.ConnectWith(bodyEnd);
+				
+				breakTargets.Pop();
+				continueTargets.Pop();
+				
+				return end.ConnectWith(conditionNode);
+			}
+			
+			public override ControlFlowNode VisitBreakStatement(BreakStatement breakStatement, ControlFlowNode data)
+			{
+				if (breakTargets.Count > 0)
+					breakTargets.Peek().ConnectWith(data);
+				return builder.CreateEndNode(breakStatement);
+			}
+			
+			public override ControlFlowNode VisitContinueStatement(ContinueStatement continueStatement, ControlFlowNode data)
+			{
+				if (continueTargets.Count > 0)
+					continueTargets.Peek().ConnectWith(data);
+				return builder.CreateEndNode(continueStatement);
+			}
+			
+			public override ControlFlowNode VisitGotoStatement(GotoStatement gotoStatement, ControlFlowNode data)
+			{
+				builder.gotoStatements.Add(data);
+				return builder.CreateEndNode(gotoStatement);
+			}
+			
+			public override ControlFlowNode VisitReturnStatement(ReturnStatement returnStatement, ControlFlowNode data)
+			{
+				return builder.CreateEndNode(returnStatement); // end not connected with data
+			}
+			
+			public override ControlFlowNode VisitThrowStatement(ThrowStatement throwStatement, ControlFlowNode data)
+			{
+				return builder.CreateEndNode(throwStatement); // end not connected with data
+			}
+			
+			public override ControlFlowNode VisitTryCatchStatement(TryCatchStatement tryCatchStatement, ControlFlowNode data)
+			{
+				ControlFlowNode end = builder.CreateEndNode(tryCatchStatement);
+				end.ConnectWith(HandleEmbeddedStatement(tryCatchStatement.TryBlock, data));
+				foreach (CatchClause cc in tryCatchStatement.CatchClauses) {
+					end.ConnectWith(HandleEmbeddedStatement(cc.Body, data));
+				}
+				if (!tryCatchStatement.FinallyBlock.IsNull) {
+					// Don't connect the end of the try-finally block to anything.
+					// Consumers of the CFG will have to special-case try-finally.
+					HandleEmbeddedStatement(tryCatchStatement.FinallyBlock, data);
+				}
+				return end;
+			}
+			
+			public override ControlFlowNode VisitCheckedStatement(CheckedStatement checkedStatement, ControlFlowNode data)
+			{
+				ControlFlowNode bodyEnd = HandleEmbeddedStatement(checkedStatement.Body, data);
+				return builder.CreateEndNode(checkedStatement).ConnectWith(bodyEnd);
+			}
+			
+			public override ControlFlowNode VisitUncheckedStatement(UncheckedStatement uncheckedStatement, ControlFlowNode data)
+			{
+				ControlFlowNode bodyEnd = HandleEmbeddedStatement(uncheckedStatement.Body, data);
+				return builder.CreateEndNode(uncheckedStatement).ConnectWith(bodyEnd);
+			}
+			
+			public override ControlFlowNode VisitLockStatement(LockStatement lockStatement, ControlFlowNode data)
+			{
+				ControlFlowNode bodyEnd = HandleEmbeddedStatement(lockStatement.EmbeddedStatement, data);
+				return builder.CreateEndNode(lockStatement).ConnectWith(bodyEnd);
+			}
+			
+			public override ControlFlowNode VisitUsingStatement(UsingStatement usingStatement, ControlFlowNode data)
+			{
+				data = HandleEmbeddedStatement(usingStatement.ResourceAcquisition as Statement, data);
+				ControlFlowNode bodyEnd = HandleEmbeddedStatement(usingStatement.EmbeddedStatement, data);
+				return builder.CreateEndNode(usingStatement).ConnectWith(bodyEnd);
+			}
+			
+			public override ControlFlowNode VisitYieldStatement(YieldStatement yieldStatement, ControlFlowNode data)
+			{
+				return builder.CreateEndNode(yieldStatement).ConnectWith(data);
+			}
+			
+			public override ControlFlowNode VisitYieldBreakStatement(YieldBreakStatement yieldBreakStatement, ControlFlowNode data)
+			{
+				return builder.CreateEndNode(yieldBreakStatement); // end not connected with data
+			}
+			
+			public override ControlFlowNode VisitUnsafeStatement(UnsafeStatement unsafeStatement, ControlFlowNode data)
+			{
+				ControlFlowNode bodyEnd = HandleEmbeddedStatement(unsafeStatement.Body, data);
+				return builder.CreateEndNode(unsafeStatement).ConnectWith(bodyEnd);
+			}
+			
+			public override ControlFlowNode VisitFixedStatement(FixedStatement fixedStatement, ControlFlowNode data)
+			{
+				ControlFlowNode bodyEnd = HandleEmbeddedStatement(fixedStatement.EmbeddedStatement, data);
+				return builder.CreateEndNode(fixedStatement).ConnectWith(bodyEnd);
+			}
+		}
+	}
+}

NRefactory/ICSharpCode.NRefactory/ICSharpCode.NRefactory.csproj

@@ -61,6 +61,7 @@
     </Reference>
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="CSharp\Analysis\ControlFlow.cs" />
     <Compile Include="CSharp\Ast\AstNodeCollection.cs" />
     <Compile Include="CSharp\Ast\Expressions\TypeReferenceExpression.cs" />
     <Compile Include="CSharp\Ast\IAstVisitor.cs" />
@@ -354,5 +355,8 @@
       <Name>Mono.Cecil</Name>
     </ProjectReference>
   </ItemGroup>
+  <ItemGroup>
+    <Folder Include="CSharp\Analysis" />
+  </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
 </Project>