Improved variable placement.

The variable placement step now happens much later in the decompiler pipeline, which simplifies some AST transforms.

ICSharpCode.Decompiler/Ast/AstMethodBodyBuilder.cs

@@ -22,7 +22,6 @@ namespace ICSharpCode.Decompiler.Ast
 		TypeSystem typeSystem;
 		DecompilerContext context;
 		HashSet<ILVariable> localVariablesToDefine = new HashSet<ILVariable>(); // local variables that are missing a definition
-		HashSet<ILVariable> implicitlyDefinedVariables = new HashSet<ILVariable>(); // local variables that are implicitly defined (e.g. catch handler)
 		
 		/// <summary>
 		/// Creates the body for the method definition.
@@ -89,8 +88,9 @@ namespace ICSharpCode.Decompiler.Ast
 			context.CancellationToken.ThrowIfCancellationRequested();
 			Ast.BlockStatement astBlock = TransformBlock(ilMethod);
 			CommentStatement.ReplaceAll(astBlock); // convert CommentStatements to Comments
-			foreach (ILVariable v in localVariablesToDefine.Except(implicitlyDefinedVariables)) {
-				DeclareVariableInSmallestScope.DeclareVariable(astBlock, AstBuilder.ConvertType(v.Type), v.Name);
+			foreach (ILVariable v in localVariablesToDefine) {
+				var newVarDecl = new VariableDeclarationStatement(AstBuilder.ConvertType(v.Type), v.Name);
+				astBlock.Statements.InsertAfter(null, newVarDecl);
 			}
 			
 			return astBlock;
@@ -158,8 +158,6 @@ namespace ICSharpCode.Decompiler.Ast
 				var tryCatchStmt = new Ast.TryCatchStatement();
 				tryCatchStmt.TryBlock = TransformBlock(tryCatchNode.TryBlock);
 				foreach (var catchClause in tryCatchNode.CatchBlocks) {
-					if (catchClause.ExceptionVariable != null)
-						implicitlyDefinedVariables.Add(catchClause.ExceptionVariable);
 					tryCatchStmt.CatchClauses.Add(
 						new Ast.CatchClause {
 							Type = AstBuilder.ConvertType(catchClause.ExceptionType),

ICSharpCode.Decompiler/Ast/DeclareVariableInSmallestScope.cs

@@ -1,91 +0,0 @@
-// 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.Linq;
-using ICSharpCode.NRefactory.CSharp;
-using ICSharpCode.NRefactory.CSharp.PatternMatching;
-
-namespace ICSharpCode.Decompiler.Ast
-{
-	/// <summary>
-	/// Helper class for declaring variables.
-	/// </summary>
-	public static class DeclareVariableInSmallestScope
-	{
-		static readonly ExpressionStatement assignmentPattern = new ExpressionStatement(
-			new AssignmentExpression(
-				new NamedNode("ident", new IdentifierExpression()),
-				new AnyNode("init")
-			));
-		
-		/// <summary>
-		/// Declares a variable in the smallest required scope.
-		/// </summary>
-		/// <param name="node">The root of the subtree being searched for the best insertion position</param>
-		/// <param name="type">The type of the new variable</param>
-		/// <param name="name">The name of the new variable</param>
-		/// <param name="allowPassIntoLoops">Whether the variable is allowed to be placed inside a loop</param>
-		public static VariableDeclarationStatement DeclareVariable(AstNode node, AstType type, string name, bool allowPassIntoLoops = true)
-		{
-			VariableDeclarationStatement result = null;
-			AstNode pos = FindInsertPos(node, name, allowPassIntoLoops);
-			if (pos != null) {
-				Match m = assignmentPattern.Match(pos);
-				if (m != null && m.Get<IdentifierExpression>("ident").Single().Identifier == name) {
-					result = new VariableDeclarationStatement(type, name, m.Get<Expression>("init").Single().Detach());
-					result.Variables.Single().CopyAnnotationsFrom(((ExpressionStatement)pos).Expression);
-					result.CopyAnnotationsFrom(pos);
-					pos.ReplaceWith(result);
-				} else {
-					result = new VariableDeclarationStatement(type, name);
-					pos.Parent.InsertChildBefore(pos, result, BlockStatement.StatementRole);
-				}
-			}
-			return result;
-		}
-		
-		static AstNode FindInsertPos(AstNode node, string name, bool allowPassIntoLoops)
-		{
-			AstNode pos = null;
-			AstNode withinPos = null;
-			while (node != null) {
-				IdentifierExpression ident = node as IdentifierExpression;
-				if (ident != null && ident.Identifier == name && ident.TypeArguments.Count == 0)
-					return node;
-				
-				FixedStatement fixedStatement = node as FixedStatement;
-				if (fixedStatement != null) {
-					foreach (VariableInitializer v in fixedStatement.Variables) {
-						if (v.Name == name)
-							return null; // no need to introduce the variable here
-					}
-				}
-				
-				AstNode withinCurrent = FindInsertPos(node.FirstChild, name, allowPassIntoLoops);
-				if (withinCurrent != null) {
-					if (pos == null) {
-						pos = node;
-						withinPos = withinCurrent;
-					} else {
-						return pos;
-					}
-				}
-				node = node.NextSibling;
-			}
-			if (withinPos != null && withinPos.Role == BlockStatement.StatementRole && AllowPassInto(pos, allowPassIntoLoops))
-				return withinPos;
-			else
-				return pos;
-		}
-		
-		static bool AllowPassInto(AstNode node, bool allowPassIntoLoops)
-		{
-			if (node is AnonymousMethodExpression || node is LambdaExpression)
-				return false;
-			if (node is ForStatement || node is ForeachStatement || node is DoWhileStatement || node is WhileStatement)
-				return allowPassIntoLoops;
-			return true;
-		}
-	}
-}

ICSharpCode.Decompiler/Ast/Transforms/DeclareVariables.cs

@@ -0,0 +1,255 @@
+// 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 System.Linq;
+using System.Threading;
+using ICSharpCode.NRefactory.CSharp;
+using ICSharpCode.NRefactory.CSharp.Analysis;
+
+namespace ICSharpCode.Decompiler.Ast.Transforms
+{
+	/// <summary>
+	/// Moves variable declarations to improved positions.
+	/// </summary>
+	public class DeclareVariables : IAstTransform
+	{
+		sealed class DeclaredVariableAnnotation {
+			public readonly ExpressionStatement OriginalAssignmentStatement;
+			
+			public DeclaredVariableAnnotation(ExpressionStatement originalAssignmentStatement)
+			{
+				this.OriginalAssignmentStatement = originalAssignmentStatement;
+			}
+		}
+		static readonly DeclaredVariableAnnotation declaredVariableAnnotation = new DeclaredVariableAnnotation(null);
+		
+		readonly CancellationToken cancellationToken;
+		
+		public DeclareVariables(DecompilerContext context)
+		{
+			this.cancellationToken = context.CancellationToken;
+		}
+		
+		public void Run(AstNode node)
+		{
+			Run(node, null);
+		}
+		
+		void Run(AstNode node, DefiniteAssignmentAnalysis daa)
+		{
+			BlockStatement block = node as BlockStatement;
+			if (block != null) {
+				var variables = block.Statements.TakeWhile(stmt => stmt is VariableDeclarationStatement
+				                                           && stmt.Annotation<DeclaredVariableAnnotation>() == null)
+					.Cast<VariableDeclarationStatement>().ToList();
+				if (variables.Count > 0) {
+					// remove old variable declarations:
+					foreach (VariableDeclarationStatement varDecl in variables) {
+						Debug.Assert(varDecl.Variables.Single().Initializer.IsNull);
+						varDecl.Remove();
+					}
+					if (daa == null) {
+						// If possible, reuse the DefiniteAssignmentAnalysis that was created for the parent block
+						daa = new DefiniteAssignmentAnalysis(block, cancellationToken);
+					}
+					foreach (VariableDeclarationStatement varDecl in variables) {
+						string variableName = varDecl.Variables.Single().Name;
+						bool allowPassIntoLoops = varDecl.Variables.Single().Annotation<DelegateConstruction.CapturedVariableAnnotation>() == null;
+						DeclareVariableInBlock(daa, block, varDecl.Type, variableName, allowPassIntoLoops);
+					}
+				}
+			}
+			for (AstNode child = node.FirstChild; child != null; child = child.NextSibling) {
+				Run(child, daa);
+			}
+		}
+		
+		void DeclareVariableInBlock(DefiniteAssignmentAnalysis daa, BlockStatement block, AstType type, string variableName, bool allowPassIntoLoops)
+		{
+			// declarationPoint: The point where the variable would be declared, if we decide to declare it in this block
+			Statement declarationPoint = null;
+			// Check whether we can move down the variable into the sub-blocks
+			bool ok = true;
+			foreach (Statement stmt in block.Statements) {
+				if (UsesVariable(stmt, variableName)) {
+					if (declarationPoint == null)
+						declarationPoint = stmt;
+					if (!CanMoveVariableUseIntoSubBlock(stmt, variableName, allowPassIntoLoops)) {
+						// If it's not possible to move the variable use into a nested block,
+						// we need to declare the variable in this block
+						ok = false;
+						break;
+					}
+					// If we can move the variable into the sub-block, we need to ensure that the remaining code
+					// does not use the value that was assigend by the first sub-block
+					Statement nextStatement = stmt.NextStatement;
+					// The next statement might be a variable declaration that we inserted, and thus does not exist
+					// in the definite assignment graph. Thus we need to look up the corresponding instruction
+					// prior to the introduction of the VariableDeclarationStatement.
+					while (nextStatement is VariableDeclarationStatement) {
+						DeclaredVariableAnnotation annotation = nextStatement.Annotation<DeclaredVariableAnnotation>();
+						if (annotation == null)
+							break;
+						if (annotation.OriginalAssignmentStatement != null) {
+							nextStatement = annotation.OriginalAssignmentStatement;
+							break;
+						}
+						nextStatement = nextStatement.NextStatement;
+					}
+					if (nextStatement != null) {
+						// Analyze the range from the next statement to the end of the block
+						daa.SetAnalyzedRange(nextStatement, block);
+						daa.Analyze(variableName);
+						if (daa.UnassignedVariableUses.Count > 0) {
+							ok = false;
+							break;
+						}
+					}
+				}
+			}
+			if (declarationPoint == null) {
+				// The variable isn't used at all
+				return;
+			}
+			if (ok) {
+				// Declare the variable within the sub-blocks
+				foreach (Statement stmt in block.Statements) {
+					foreach (BlockStatement subBlock in stmt.Children.OfType<BlockStatement>()) {
+						DeclareVariableInBlock(daa, subBlock, type, variableName, allowPassIntoLoops);
+					}
+				}
+			} else {
+				// Try converting an assignment expression into a VariableDeclarationStatement
+				ExpressionStatement es = declarationPoint as ExpressionStatement;
+				if (es != null) {
+					AssignmentExpression ae = es.Expression as AssignmentExpression;
+					if (ae != null && ae.Operator == AssignmentOperatorType.Assign) {
+						IdentifierExpression ident = ae.Left as IdentifierExpression;
+						if (ident != null && ident.Identifier == variableName) {
+							// convert the declarationPoint into a VariableDeclarationStatement
+							declarationPoint.ReplaceWith(
+								new VariableDeclarationStatement {
+									Type = (AstType)type.Clone(),
+									Variables = {
+										new VariableInitializer(variableName, ae.Right.Detach()).CopyAnnotationsFrom(ae)
+									}
+								}.CopyAnnotationsFrom(es).WithAnnotation(new DeclaredVariableAnnotation(es)));
+							return;
+						}
+					}
+				}
+				// Declare the variable in front of declarationPoint
+				block.Statements.InsertBefore(
+					declarationPoint,
+					new VariableDeclarationStatement((AstType)type.Clone(), variableName)
+					.WithAnnotation(declaredVariableAnnotation));
+			}
+		}
+		
+		bool CanMoveVariableUseIntoSubBlock(Statement stmt, string variableName, bool allowPassIntoLoops)
+		{
+			if (!allowPassIntoLoops && (stmt is ForStatement || stmt is ForeachStatement || stmt is DoWhileStatement || stmt is WhileStatement))
+				return false;
+			ForStatement forStatement = stmt as ForStatement;
+			if (forStatement != null && forStatement.Initializers.Count == 1) {
+				// for-statement is special case: we can move variable declarations into the initializer
+				ExpressionStatement es = forStatement.Initializers.Single() as ExpressionStatement;
+				if (es != null) {
+					AssignmentExpression ae = es.Expression as AssignmentExpression;
+					if (ae != null && ae.Operator == AssignmentOperatorType.Assign) {
+						IdentifierExpression ident = ae.Left as IdentifierExpression;
+						if (ident != null && ident.Identifier == variableName) {
+							return !UsesVariable(ae.Right, variableName);
+						}
+					}
+				}
+			}
+			// We can move the variable into a sub-block only if the variable is used in only that sub-block
+			for (AstNode child = stmt.FirstChild; child != null; child = child.NextSibling) {
+				if (!(child is BlockStatement) && UsesVariable(child, variableName))
+					return false;
+			}
+			return true;
+		}
+		
+		bool UsesVariable(AstNode node, string variableName)
+		{
+			IdentifierExpression ie = node as IdentifierExpression;
+			if (ie != null && ie.Identifier == variableName)
+				return true;
+			
+			FixedStatement fixedStatement = node as FixedStatement;
+			if (fixedStatement != null) {
+				foreach (VariableInitializer v in fixedStatement.Variables) {
+					if (v.Name == variableName)
+						return false; // no need to introduce the variable here
+				}
+			}
+			
+			ForeachStatement foreachStatement = node as ForeachStatement;
+			if (foreachStatement != null) {
+				if (foreachStatement.VariableName == variableName)
+					return false; // no need to introduce the variable here
+			}
+			
+			for (AstNode child = node.FirstChild; child != null; child = child.NextSibling) {
+				if (UsesVariable(child, variableName))
+					return true;
+			}
+			return false;
+		}
+		
+		#region FindInsertPos
+		static AstNode FindInsertPos(AstNode node, string name, bool allowPassIntoLoops)
+		{
+			AstNode pos = null;
+			AstNode withinPos = null;
+			while (node != null) {
+				IdentifierExpression ident = node as IdentifierExpression;
+				if (ident != null && ident.Identifier == name && ident.TypeArguments.Count == 0)
+					return node;
+				
+				FixedStatement fixedStatement = node as FixedStatement;
+				if (fixedStatement != null) {
+					foreach (VariableInitializer v in fixedStatement.Variables) {
+						if (v.Name == name)
+							return null; // no need to introduce the variable here
+					}
+				}
+				ForeachStatement foreachStatement = node as ForeachStatement;
+				if (foreachStatement != null) {
+					if (foreachStatement.VariableName == name)
+						return null; // no need to introduce the variable here
+				}
+				
+				AstNode withinCurrent = FindInsertPos(node.FirstChild, name, allowPassIntoLoops);
+				if (withinCurrent != null) {
+					if (pos == null) {
+						pos = node;
+						withinPos = withinCurrent;
+					} else {
+						return pos;
+					}
+				}
+				node = node.NextSibling;
+			}
+			if (withinPos != null && withinPos.Role == BlockStatement.StatementRole && AllowPassInto(pos, allowPassIntoLoops))
+				return withinPos;
+			else
+				return pos;
+		}
+		
+		static bool AllowPassInto(AstNode node, bool allowPassIntoLoops)
+		{
+			if (node is AnonymousMethodExpression || node is LambdaExpression)
+				return false;
+			
+			return allowPassIntoLoops;
+			return true;
+		}
+		#endregion
+	}
+}

ICSharpCode.Decompiler/Ast/Transforms/DelegateConstruction.cs

@@ -179,23 +179,33 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 			return true;
 		}
 		
+		static readonly ExpressionStatement displayClassAssignmentPattern =
+			new ExpressionStatement(new AssignmentExpression(
+				new NamedNode("variable", new IdentifierExpression()),
+				new ObjectCreateExpression { Type = new AnyNode("type") }
+			));
+		
 		public override object VisitBlockStatement(BlockStatement blockStatement, object data)
 		{
 			base.VisitBlockStatement(blockStatement, data);
-			foreach (VariableDeclarationStatement stmt in blockStatement.Statements.OfType<VariableDeclarationStatement>().ToArray()) {
-				if (stmt.Variables.Count() != 1)
+			foreach (ExpressionStatement stmt in blockStatement.Statements.OfType<ExpressionStatement>().ToArray()) {
+				Match displayClassAssignmentMatch = displayClassAssignmentPattern.Match(stmt);
+				if (displayClassAssignmentMatch == null)
+					continue;
+				
+				ILVariable variable = displayClassAssignmentMatch.Get("variable").Single().Annotation<ILVariable>();
+				if (variable == null)
 					continue;
-				var variable = stmt.Variables.Single();
-				TypeDefinition type = stmt.Type.Annotation<TypeReference>().ResolveWithinSameModule();
+				TypeDefinition type = variable.Type.ResolveWithinSameModule();
 				if (!IsPotentialClosure(context, type))
 					continue;
-				ObjectCreateExpression oce = variable.Initializer as ObjectCreateExpression;
-				if (oce == null || oce.Type.Annotation<TypeReference>().ResolveWithinSameModule() != type || oce.Arguments.Any() || !oce.Initializer.IsNull)
+				if (displayClassAssignmentMatch.Get("type").Single().Annotation<TypeReference>().ResolveWithinSameModule() != type)
 					continue;
+				
 				// Looks like we found a display class creation. Now let's verify that the variable is used only for field accesses:
 				bool ok = true;
 				foreach (var identExpr in blockStatement.Descendants.OfType<IdentifierExpression>()) {
-					if (identExpr.Identifier == variable.Name) {
+					if (identExpr.Identifier == variable.Name && identExpr != displayClassAssignmentMatch.Get("variable").Single()) {
 						if (!(identExpr.Parent is MemberReferenceExpression && identExpr.Parent.Annotation<FieldReference>() != null))
 							ok = false;
 					}
@@ -267,9 +277,10 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 				}
 				// Now insert the variable declarations (we can do this after the replacements only so that the scope detection works):
 				foreach (var tuple in variablesToDeclare) {
-					var newVarDecl = DeclareVariableInSmallestScope.DeclareVariable(blockStatement, tuple.Item1, tuple.Item2, allowPassIntoLoops: false);
+					var newVarDecl = new VariableDeclarationStatement(tuple.Item1, tuple.Item2);
 					if (newVarDecl != null)
 						newVarDecl.Variables.Single().AddAnnotation(new CapturedVariableAnnotation());
+					blockStatement.Statements.InsertAfter(null, newVarDecl);
 				}
 			}
 			return null;

ICSharpCode.Decompiler/Ast/Transforms/IntroduceUsingDeclarations.cs

@@ -25,7 +25,7 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 		public void Run(AstNode compilationUnit)
 		{
 			// Don't show using when decompiling a single method or nested types:
-			if (context.CurrentMethod != null || (context.CurrentType != null && context.CurrentType.IsNested))
+			if (context.CurrentType != null)
 				return;
 			
 			// First determine all the namespaces that need to be imported:

ICSharpCode.Decompiler/Ast/Transforms/PatternStatementTransform.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using ICSharpCode.Decompiler.ILAst;
 using ICSharpCode.NRefactory.CSharp;
 using ICSharpCode.NRefactory.CSharp.PatternMatching;
 using Mono.Cecil;
@@ -37,23 +38,23 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 			return node;
 		}
 		
-		public override AstNode VisitVariableDeclarationStatement(VariableDeclarationStatement variableDeclarationStatement, object data)
+		public override AstNode VisitExpressionStatement(ExpressionStatement expressionStatement, object data)
 		{
 			AstNode result;
 			if (context.Settings.UsingStatement) {
-				result = TransformUsings(variableDeclarationStatement);
+				result = TransformUsings(expressionStatement);
 				if (result != null)
 					return result;
 			}
-			result = TransformFor(variableDeclarationStatement);
+			result = TransformFor(expressionStatement);
 			if (result != null)
 				return result;
 			if (context.Settings.LockStatement) {
-				result = TransformLock(variableDeclarationStatement);
+				result = TransformLock(expressionStatement);
 				if (result != null)
 					return result;
 			}
-			return base.VisitVariableDeclarationStatement(variableDeclarationStatement, data);
+			return base.VisitExpressionStatement(expressionStatement, data);
 		}
 		
 		public override AstNode VisitUsingStatement(UsingStatement usingStatement, object data)
@@ -117,27 +118,11 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 		/// <summary>
 		/// $type $variable = $initializer;
 		/// </summary>
-		static readonly AstNode variableDeclPattern = new VariableDeclarationStatement {
-			Type = new AnyNode("type"),
-			Variables = {
-				new NamedNode(
-					"variable",
-					new VariableInitializer {
-						Initializer = new AnyNode("initializer")
-					}
-				)
-			}
-		};
-		
-		/// <summary>
-		/// Variable declaration without initializer.
-		/// </summary>
-		static readonly AstNode simpleVariableDefinition = new VariableDeclarationStatement {
-			Type = new AnyNode(),
-			Variables = {
-				new VariableInitializer() // any name but no initializer
-			}
-		};
+		static readonly AstNode variableAssignPattern = new ExpressionStatement(
+			new AssignmentExpression(
+				new NamedNode("variable", new IdentifierExpression()),
+				new AnyNode("initializer")
+			));
 		
 		#region using
 		static readonly AstNode usingTryCatchPattern = new TryCatchStatement {
@@ -163,20 +148,18 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 			}
 		};
 		
-		public UsingStatement TransformUsings(VariableDeclarationStatement node)
+		public UsingStatement TransformUsings(ExpressionStatement node)
 		{
-			Match m1 = variableDeclPattern.Match(node);
+			Match m1 = variableAssignPattern.Match(node);
 			if (m1 == null) return null;
 			AstNode tryCatch = node.NextSibling;
-			while (simpleVariableDefinition.Match(tryCatch) != null)
-				tryCatch = tryCatch.NextSibling;
 			Match m2 = usingTryCatchPattern.Match(tryCatch);
 			if (m2 == null) return null;
-			if (m1.Get<VariableInitializer>("variable").Single().Name == m2.Get<IdentifierExpression>("ident").Single().Identifier) {
+			if (m1.Get<IdentifierExpression>("variable").Single().Identifier == m2.Get<IdentifierExpression>("ident").Single().Identifier) {
 				if (m2.Has("valueType")) {
 					// if there's no if(x!=null), then it must be a value type
-					TypeReference tr = m1.Get<AstType>("type").Single().Annotation<TypeReference>();
-					if (tr == null || !tr.IsValueType)
+					ILVariable v = m1.Get("variable").Single().Annotation<ILVariable>();
+					if (v == null || v.Type == null || !v.Type.IsValueType)
 						return null;
 				}
 				BlockStatement body = m2.Get<BlockStatement>("body").Single();
@@ -184,6 +167,8 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 				usingStatement.ResourceAcquisition = node.Detach();
 				usingStatement.EmbeddedStatement = body.Detach();
 				tryCatch.ReplaceWith(usingStatement);
+				// TODO: Move the variable declaration into the resource acquisition, if possible
+				// This is necessary for the foreach-pattern to work on the result of the using-pattern
 				return usingStatement;
 			}
 			return null;
@@ -203,55 +188,22 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 					)
 				}
 			},
-			EmbeddedStatement = new Choice {
-				// There are two forms of the foreach statement:
-				// one where the item variable is declared inside the loop,
-				// and one where it is declared outside of the loop.
-				// In the former case, we can apply the foreach pattern only if the variable wasn't captured.
-				{ "itemVariableInsideLoop",
-					new BlockStatement {
-						new WhileStatement {
-							Condition = new IdentifierExpressionBackreference("enumeratorVariable").ToExpression().Invoke("MoveNext"),
-							EmbeddedStatement = new BlockStatement {
-								new VariableDeclarationStatement {
-									Type = new AnyNode("itemType"),
-									Variables = {
-										new NamedNode(
-											"itemVariable",
-											new VariableInitializer {
-												Initializer = new IdentifierExpressionBackreference("enumeratorVariable").ToExpression().Member("Current")
-											}
-										)
-									}
-								},
-								new Repeat(new AnyNode("statement")).ToStatement()
-							}
-						}
-					}
-				},
-				{ "itemVariableOutsideLoop",
-					new BlockStatement {
-						new VariableDeclarationStatement {
-							Type = new AnyNode("itemType"),
-							Variables = {
-								new NamedNode("itemVariable", new VariableInitializer())
-							}
+			EmbeddedStatement = new BlockStatement {
+				new Repeat(
+					new NamedNode("variableDeclaration", new VariableDeclarationStatement { Type = new AnyNode(), Variables = { new AnyNode() } })
+				).ToStatement(),
+				new WhileStatement {
+					Condition = new IdentifierExpressionBackreference("enumeratorVariable").ToExpression().Invoke("MoveNext"),
+					EmbeddedStatement = new BlockStatement {
+						new AssignmentExpression {
+							Left = new NamedNode("itemVariable", new IdentifierExpression()),
+							Operator = AssignmentOperatorType.Assign,
+							Right = new IdentifierExpressionBackreference("enumeratorVariable").ToExpression().Member("Current")
 						},
-						new WhileStatement {
-							Condition = new IdentifierExpressionBackreference("enumeratorVariable").ToExpression().Invoke("MoveNext"),
-							EmbeddedStatement = new BlockStatement {
-								new AssignmentExpression {
-									Left = new IdentifierExpressionBackreference("itemVariable"),
-									Operator = AssignmentOperatorType.Assign,
-									Right = new IdentifierExpressionBackreference("enumeratorVariable").ToExpression().Member("Current")
-								},
-								new Repeat(new AnyNode("statement")).ToStatement()
-							}
-						}
+						new Repeat(new AnyNode("statement")).ToStatement()
 					}
 				}
-			}.ToStatement()
-		};
+			}};
 		
 		public ForeachStatement TransformForeach(UsingStatement node)
 		{
@@ -259,14 +211,18 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 			if (m == null)
 				return null;
 			VariableInitializer enumeratorVar = m.Get<VariableInitializer>("enumeratorVariable").Single();
-			VariableInitializer itemVar = m.Get<VariableInitializer>("itemVariable").Single();
-			if (m.Has("itemVariableInsideLoop") && itemVar.Annotation<DelegateConstruction.CapturedVariableAnnotation>() != null) {
-				// cannot move captured variables out of loops
+			ILVariable itemVar = m.Get("itemVariable").Single().Annotation<ILVariable>();
+			if (itemVar == null)
 				return null;
-			}
+			return null; // TODO
+//			if (m.Has("itemVariableInsideLoop") && itemVar.Annotation<DelegateConstruction.CapturedVariableAnnotation>() != null) {
+//				// cannot move captured variables out of loops
+//				return null;
+//			}
 			BlockStatement newBody = new BlockStatement();
 			foreach (Statement stmt in m.Get<Statement>("statement"))
 				newBody.Add(stmt.Detach());
+			
 			ForeachStatement foreachStatement = new ForeachStatement {
 				VariableType = m.Get<AstType>("itemType").Single().Detach(),
 				VariableName = itemVar.Name,
@@ -299,17 +255,15 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 				}
 			}};
 		
-		public ForStatement TransformFor(VariableDeclarationStatement node)
+		public ForStatement TransformFor(ExpressionStatement node)
 		{
-			Match m1 = variableDeclPattern.Match(node);
+			Match m1 = variableAssignPattern.Match(node);
 			if (m1 == null) return null;
 			AstNode next = node.NextSibling;
-			while (simpleVariableDefinition.Match(next) != null)
-				next = next.NextSibling;
 			Match m2 = forPattern.Match(next);
 			if (m2 == null) return null;
 			// ensure the variable in the for pattern is the same as in the declaration
-			if (m1.Get<VariableInitializer>("variable").Single().Name != m2.Get<IdentifierExpression>("ident").Single().Identifier)
+			if (m1.Get<IdentifierExpression>("variable").Single().Identifier != m2.Get<IdentifierExpression>("ident").Single().Identifier)
 				return null;
 			WhileStatement loop = (WhileStatement)next;
 			node.Remove();
@@ -374,16 +328,11 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 		#endregion
 		
 		#region lock
-		static readonly AstNode lockFlagInitPattern = new VariableDeclarationStatement {
-			Type = new PrimitiveType("bool"),
-			Variables = {
-				new NamedNode(
-					"variable",
-					new VariableInitializer {
-						Initializer = new PrimitiveExpression(false)
-					}
-				)
-			}};
+		static readonly AstNode lockFlagInitPattern = new ExpressionStatement(
+			new AssignmentExpression(
+				new NamedNode("variable", new IdentifierExpression()),
+				new PrimitiveExpression(false)
+			));
 		
 		static readonly AstNode lockTryCatchPattern = new TryCatchStatement {
 			TryBlock = new BlockStatement {
@@ -404,16 +353,14 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 				}
 			}};
 		
-		public LockStatement TransformLock(VariableDeclarationStatement node)
+		public LockStatement TransformLock(ExpressionStatement node)
 		{
 			Match m1 = lockFlagInitPattern.Match(node);
 			if (m1 == null) return null;
 			AstNode tryCatch = node.NextSibling;
-			while (simpleVariableDefinition.Match(tryCatch) != null)
-				tryCatch = tryCatch.NextSibling;
 			Match m2 = lockTryCatchPattern.Match(tryCatch);
 			if (m2 == null) return null;
-			if (m1.Get<VariableInitializer>("variable").Single().Name == m2.Get<IdentifierExpression>("flag").Single().Identifier) {
+			if (m1.Get<IdentifierExpression>("variable").Single().Identifier == m2.Get<IdentifierExpression>("flag").Single().Identifier) {
 				Expression enter = m2.Get<Expression>("enter").Single();
 				IdentifierExpression exit = m2.Get<IdentifierExpression>("exit").Single();
 				if (exit.Match(enter) == null) {
@@ -630,32 +577,25 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 		#region Automatic Events
 		static readonly Accessor automaticEventPatternV4 = new Accessor {
 			Body = new BlockStatement {
-				new VariableDeclarationStatement {
-					Type = new AnyNode("type"),
-					Variables = {
-						new NamedNode(
-							"var1", new VariableInitializer {
-								Initializer = new NamedNode("field", new MemberReferenceExpression { Target = new ThisReferenceExpression() })
-							})}
-				},
-				new VariableDeclarationStatement {
-					Type = new Backreference("type"),
-					Variables = { new NamedNode("var2", new VariableInitializer()) }
+				new VariableDeclarationStatement { Type = new AnyNode("type"), Variables = { new AnyNode() } },
+				new VariableDeclarationStatement { Type = new Backreference("type"), Variables = { new AnyNode() } },
+				new VariableDeclarationStatement { Type = new Backreference("type"), Variables = { new AnyNode() } },
+				new AssignmentExpression {
+					Left = new NamedNode("var1", new IdentifierExpression()),
+					Operator = AssignmentOperatorType.Assign,
+					Right = new NamedNode("field", new MemberReferenceExpression { Target = new ThisReferenceExpression() })
 				},
 				new DoWhileStatement {
 					EmbeddedStatement = new BlockStatement {
-						new AssignmentExpression(new IdentifierExpressionBackreference("var2"), new IdentifierExpressionBackreference("var1")),
-						new VariableDeclarationStatement {
-							Type = new Backreference("type"),
-							Variables = {
-								new NamedNode(
-									"var3", new VariableInitializer {
-										Initializer = new AnyNode("delegateCombine").ToExpression().Invoke(
-											new IdentifierExpressionBackreference("var2"),
-											new IdentifierExpression("value")
-										).CastTo(new Backreference("type"))
-									})
-							}},
+						new AssignmentExpression(new NamedNode("var2", new IdentifierExpression()), new IdentifierExpressionBackreference("var1")),
+						new AssignmentExpression {
+							Left = new NamedNode("var3", new IdentifierExpression()),
+							Operator = AssignmentOperatorType.Assign,
+							Right = new AnyNode("delegateCombine").ToExpression().Invoke(
+								new IdentifierExpressionBackreference("var2"),
+								new IdentifierExpression("value")
+							).CastTo(new Backreference("type"))
+						},
 						new AssignmentExpression {
 							Left = new IdentifierExpressionBackreference("var1"),
 							Right = new TypePattern(typeof(System.Threading.Interlocked)).ToType().Invoke(

ICSharpCode.Decompiler/Ast/Transforms/TransformationPipeline.cs

@@ -23,6 +23,7 @@ namespace ICSharpCode.Decompiler.Ast.Transforms
 				new ConvertConstructorCallIntoInitializer(),
 				new ReplaceMethodCallsWithOperators(),
 				new IntroduceUnsafeModifier(),
+				new DeclareVariables(context),
 				new IntroduceUsingDeclarations(context)
 			};
 		}

ICSharpCode.Decompiler/ICSharpCode.Decompiler.csproj

@@ -53,13 +53,13 @@
     <Compile Include="Ast\AstMethodBodyBuilder.cs" />
     <Compile Include="Ast\CecilTypeResolveContext.cs" />
     <Compile Include="Ast\CommentStatement.cs" />
-    <Compile Include="Ast\DeclareVariableInSmallestScope.cs" />
     <Compile Include="Ast\DecompilerContext.cs" />
     <Compile Include="Ast\NameVariables.cs" />
     <Compile Include="Ast\NRefactoryExtensions.cs" />
     <Compile Include="Ast\TextOutputFormatter.cs" />
     <Compile Include="Ast\Transforms\ContextTrackingVisitor.cs" />
     <Compile Include="Ast\Transforms\ConvertConstructorCallIntoInitializer.cs" />
+    <Compile Include="Ast\Transforms\DeclareVariables.cs" />
     <Compile Include="Ast\Transforms\DelegateConstruction.cs" />
     <Compile Include="Ast\Transforms\IntroduceUnsafeModifier.cs" />
     <Compile Include="Ast\Transforms\IntroduceUsingDeclarations.cs" />