Extended option 'dc4' to handle inlined class references (mainly Eclipse). See IDEA-135387 for an example.

src/org/jetbrains/java/decompiler/main/rels/MethodProcessorRunnable.java

@@ -137,6 +137,8 @@ public class MethodProcessorRunnable implements Runnable {
     ExprProcessor proc = new ExprProcessor();
     proc.processStatement(root, cl);
 
+    SequenceHelper.condenseSequences(root);
+    
     while (true) {
       StackVarsProcessor stackProc = new StackVarsProcessor();
       stackProc.simplifyStackVars(root, mt, cl);

src/org/jetbrains/java/decompiler/modules/decompiler/SimplifyExprentsHelper.java

@@ -15,24 +15,41 @@
  */
 package org.jetbrains.java.decompiler.modules.decompiler;
 
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map.Entry;
+import java.util.Set;
+
 import org.jetbrains.java.decompiler.code.CodeConstants;
 import org.jetbrains.java.decompiler.main.ClassesProcessor.ClassNode;
 import org.jetbrains.java.decompiler.main.DecompilerContext;
 import org.jetbrains.java.decompiler.main.extern.IFernflowerPreferences;
-import org.jetbrains.java.decompiler.modules.decompiler.exps.*;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.ArrayExprent;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.AssignmentExprent;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.ConstExprent;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.ExitExprent;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.Exprent;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.FunctionExprent;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.InvocationExprent;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.MonitorExprent;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.NewExprent;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.VarExprent;
 import org.jetbrains.java.decompiler.modules.decompiler.sforms.SSAConstructorSparseEx;
 import org.jetbrains.java.decompiler.modules.decompiler.stats.IfStatement;
 import org.jetbrains.java.decompiler.modules.decompiler.stats.Statement;
 import org.jetbrains.java.decompiler.modules.decompiler.vars.VarVersionPair;
 import org.jetbrains.java.decompiler.struct.StructClass;
 import org.jetbrains.java.decompiler.struct.gen.VarType;
+import org.jetbrains.java.decompiler.struct.match.MatchEngine;
 import org.jetbrains.java.decompiler.util.FastSparseSetFactory.FastSparseSet;
 
-import java.util.*;
-import java.util.Map.Entry;
-
 public class SimplifyExprentsHelper {
 
+  static MatchEngine class14Builder = new MatchEngine();
+  
   private boolean firstInvocation;
 
   public SimplifyExprentsHelper(boolean firstInvocation) {
@@ -45,6 +62,8 @@ public class SimplifyExprentsHelper {
 
     if (stat.getExprents() == null) {
 
+      boolean processClass14 = DecompilerContext.getOption(IFernflowerPreferences.DECOMPILE_CLASS_1_4);
+
       while (true) {
 
         boolean changed = false;
@@ -61,6 +80,11 @@ public class SimplifyExprentsHelper {
           if (changed = buildIff(st, ssa)) {
             break;
           }
+
+          // collapse inlined .class property in version 1.4 and before
+          if (processClass14 && (changed = collapseInlinedClass14(st))) {
+            break;
+          }
         }
 
         res |= changed;
@@ -852,4 +876,53 @@ public class SimplifyExprentsHelper {
 
     return false;
   }
+
+  static {
+    class14Builder.parse(
+          "statement type:if iftype:if exprsize:-1\n" +
+          " exprent position:head type:if\n" +
+          "  exprent type:function functype:eq\n" +
+          "   exprent type:field name:$field$\n" +
+          "   exprent type:constant consttype:null\n" +
+          " statement type:basicblock\n" +
+          "  exprent position:-1 type:assignment ret:$assignfield$\n" +
+          "   exprent type:var index:$var$\n" +
+          "   exprent type:field name:$field$\n" +
+          " statement type:sequence statsize:2\n" +
+          "  statement type:trycatch\n" +  
+          "   statement type:basicblock exprsize:1\n" +
+          "    exprent type:assignment\n" +
+          "     exprent type:var index:$var$\n" +
+          "     exprent type:invocation invclass:java/lang/Class signature:forName(Ljava/lang/String;)Ljava/lang/Class;\n" +
+          "      exprent position:0 type:constant consttype:string constvalue:$classname$\n" +
+          "   statement type:basicblock exprsize:1\n" +
+          "    exprent type:exit exittype:throw\n" + 
+          "  statement type:basicblock exprsize:1\n" + 
+          "   exprent type:assignment\n" + 
+          "    exprent type:field name:$field$\n" +
+          "    exprent type:var index:$var$"
+        );
+  }
+  
+  private static boolean collapseInlinedClass14(Statement stat) {
+
+    boolean ret = class14Builder.match(stat);
+    if(ret) {
+      
+      String class_name = (String)class14Builder.getVariableValue("$classname$");
+      AssignmentExprent assfirst = (AssignmentExprent)class14Builder.getVariableValue("$assignfield$");
+
+      assfirst.replaceExprent(assfirst.getRight(), new ConstExprent(VarType.VARTYPE_CLASS, class_name, null));
+      
+      List<Exprent> data = new ArrayList<Exprent>();
+      data.addAll(stat.getFirst().getExprents());
+
+      stat.setExprents(data);
+
+      SequenceHelper.destroyAndFlattenStatement(stat);
+    }
+    
+    return ret;
+  }
+  
 }

src/org/jetbrains/java/decompiler/modules/decompiler/exps/ConstExprent.java

@@ -23,9 +23,14 @@ import org.jetbrains.java.decompiler.main.extern.IFernflowerPreferences;
 import org.jetbrains.java.decompiler.modules.decompiler.ExprProcessor;
 import org.jetbrains.java.decompiler.struct.gen.FieldDescriptor;
 import org.jetbrains.java.decompiler.struct.gen.VarType;
+import org.jetbrains.java.decompiler.struct.match.MatchEngine;
+import org.jetbrains.java.decompiler.struct.match.MatchNode;
+import org.jetbrains.java.decompiler.struct.match.IMatchable.MatchProperties;
+import org.jetbrains.java.decompiler.struct.match.MatchNode.RuleValue;
 import org.jetbrains.java.decompiler.util.InterpreterUtil;
 
 import java.util.*;
+import java.util.Map.Entry;
 
 public class ConstExprent extends Exprent {
   private static final Map<Integer, String> ESCAPES = new HashMap<Integer, String>() {{
@@ -395,4 +400,37 @@ public class ConstExprent extends Exprent {
   public boolean isBoolPermitted() {
     return boolPermitted;
   }
+  
+  // *****************************************************************************
+  // IMatchable implementation
+  // *****************************************************************************
+  
+  public boolean match(MatchNode matchNode, MatchEngine engine) {
+
+    if(!super.match(matchNode, engine)) {
+      return false;
+    }
+    
+    for(Entry<MatchProperties, RuleValue> rule : matchNode.getRules().entrySet()) {
+      RuleValue rule_value = rule.getValue();
+      
+      switch(rule.getKey()) {
+      case EXPRENT_CONSTTYPE:
+        if(!rule_value.value.equals(this.constType)) {
+          return false;
+        }
+        break;
+      case EXPRENT_CONSTVALUE:
+        if(rule_value.isVariable()) {
+          if(!engine.checkAndSetVariableValue(rule_value.value.toString(), this.value)) {
+            return false;
+          }
+        } 
+        break;
+      }
+    }
+    
+    return true;
+  }
+  
 }

src/org/jetbrains/java/decompiler/modules/decompiler/exps/ExitExprent.java

@@ -25,11 +25,15 @@ import org.jetbrains.java.decompiler.modules.decompiler.ExprProcessor;
 import org.jetbrains.java.decompiler.modules.decompiler.vars.CheckTypesResult;
 import org.jetbrains.java.decompiler.struct.attr.StructExceptionsAttribute;
 import org.jetbrains.java.decompiler.struct.gen.VarType;
+import org.jetbrains.java.decompiler.struct.match.MatchEngine;
+import org.jetbrains.java.decompiler.struct.match.MatchNode;
+import org.jetbrains.java.decompiler.struct.match.IMatchable.MatchProperties;
 import org.jetbrains.java.decompiler.util.InterpreterUtil;
 
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
+import java.util.Map.Entry;
 
 public class ExitExprent extends Exprent {
 
@@ -151,4 +155,25 @@ public class ExitExprent extends Exprent {
   public VarType getRetType() {
     return retType;
   }
+  
+  // *****************************************************************************
+  // IMatchable implementation
+  // *****************************************************************************
+  
+  public boolean match(MatchNode matchNode, MatchEngine engine) {
+
+    if(!super.match(matchNode, engine)) {
+      return false;
+    }
+    
+    Integer type = (Integer)matchNode.getRuleValue(MatchProperties.EXPRENT_EXITTYPE);
+    if(type != null) {
+      if(this.exitType != type.intValue()) {
+        return false;
+      }
+    }
+    
+    return true;
+  }
+  
 }

src/org/jetbrains/java/decompiler/modules/decompiler/exps/Exprent.java

@@ -15,6 +15,13 @@
  */
 package org.jetbrains.java.decompiler.modules.decompiler.exps;
 
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map.Entry;
+import java.util.Set;
+
 import org.jetbrains.java.decompiler.main.DecompilerContext;
 import org.jetbrains.java.decompiler.main.TextBuffer;
 import org.jetbrains.java.decompiler.main.collectors.BytecodeMappingTracer;
@@ -22,10 +29,12 @@ import org.jetbrains.java.decompiler.main.collectors.CounterContainer;
 import org.jetbrains.java.decompiler.modules.decompiler.vars.CheckTypesResult;
 import org.jetbrains.java.decompiler.modules.decompiler.vars.VarVersionPair;
 import org.jetbrains.java.decompiler.struct.gen.VarType;
+import org.jetbrains.java.decompiler.struct.match.IMatchable;
+import org.jetbrains.java.decompiler.struct.match.MatchEngine;
+import org.jetbrains.java.decompiler.struct.match.MatchNode;
+import org.jetbrains.java.decompiler.struct.match.MatchNode.RuleValue;
 
-import java.util.*;
-
-public class Exprent {
+public class Exprent implements IMatchable {
 
   public static final int MULTIPLE_USES = 1;
   public static final int SIDE_EFFECTS_FREE = 2;
@@ -131,4 +140,58 @@ public class Exprent {
       }
     }
   }
+  
+  // *****************************************************************************
+  // IMatchable implementation
+  // *****************************************************************************
+  
+  public IMatchable findObject(MatchNode matchNode, int index) {
+    
+    if(matchNode.getType() != MatchNode.MATCHNODE_EXPRENT) {
+      return null;
+    }
+
+    List<Exprent> lstAllExprents = getAllExprents();
+    
+    if(lstAllExprents == null || lstAllExprents.isEmpty()) {
+      return null;
+    }
+    
+    String position = (String)matchNode.getRuleValue(MatchProperties.EXPRENT_POSITION);
+    if(position != null) {
+      if(position.matches("-?\\d+")) {
+        return lstAllExprents.get((lstAllExprents.size() + Integer.parseInt(position)) % lstAllExprents.size()); // care for negative positions
+      }
+    } else if(index < lstAllExprents.size()) { // use 'index' parameter
+      return lstAllExprents.get(index);
+    }
+
+    return null;
+  }
+
+  public boolean match(MatchNode matchNode, MatchEngine engine) {
+    
+    if(matchNode.getType() != MatchNode.MATCHNODE_EXPRENT) {
+      return false;
+    }
+    
+    for(Entry<MatchProperties, RuleValue> rule : matchNode.getRules().entrySet()) {
+      switch(rule.getKey()) {
+      case EXPRENT_TYPE:
+        if(this.type != ((Integer)rule.getValue().value).intValue()) {
+          return false;
+        }
+        break;
+      case EXPRENT_RET:
+        if(!engine.checkAndSetVariableValue((String)rule.getValue().value, this)) {
+          return false;
+        }
+        break;
+      }
+      
+    }
+    
+    return true;
+  }
+  
 }

src/org/jetbrains/java/decompiler/modules/decompiler/exps/FieldExprent.java

@@ -26,6 +26,10 @@ import org.jetbrains.java.decompiler.modules.decompiler.vars.VarVersionPair;
 import org.jetbrains.java.decompiler.struct.consts.LinkConstant;
 import org.jetbrains.java.decompiler.struct.gen.FieldDescriptor;
 import org.jetbrains.java.decompiler.struct.gen.VarType;
+import org.jetbrains.java.decompiler.struct.match.MatchEngine;
+import org.jetbrains.java.decompiler.struct.match.MatchNode;
+import org.jetbrains.java.decompiler.struct.match.IMatchable.MatchProperties;
+import org.jetbrains.java.decompiler.struct.match.MatchNode.RuleValue;
 import org.jetbrains.java.decompiler.util.InterpreterUtil;
 import org.jetbrains.java.decompiler.util.TextUtil;
 
@@ -181,4 +185,31 @@ public class FieldExprent extends Exprent {
   public String getName() {
     return name;
   }
+  
+  // *****************************************************************************
+  // IMatchable implementation
+  // *****************************************************************************
+  
+  public boolean match(MatchNode matchNode, MatchEngine engine) {
+
+    if(!super.match(matchNode, engine)) {
+      return false;
+    }
+    
+    RuleValue rule = matchNode.getRules().get(MatchProperties.EXPRENT_FIELD_NAME);
+    if(rule != null) {
+      if(rule.isVariable()) {
+        if(!engine.checkAndSetVariableValue((String)rule.value, this.name)) {
+          return false;
+        }
+      } else { 
+        if(!rule.value.equals(this.name)) {
+          return false;
+        }
+      }
+    }
+    
+    return true;
+  }
+  
 }

src/org/jetbrains/java/decompiler/modules/decompiler/exps/FunctionExprent.java

@@ -21,10 +21,15 @@ import org.jetbrains.java.decompiler.main.collectors.BytecodeMappingTracer;
 import org.jetbrains.java.decompiler.modules.decompiler.ExprProcessor;
 import org.jetbrains.java.decompiler.modules.decompiler.vars.CheckTypesResult;
 import org.jetbrains.java.decompiler.struct.gen.VarType;
+import org.jetbrains.java.decompiler.struct.match.IMatchable;
+import org.jetbrains.java.decompiler.struct.match.MatchEngine;
+import org.jetbrains.java.decompiler.struct.match.MatchNode;
+import org.jetbrains.java.decompiler.struct.match.IMatchable.MatchProperties;
 import org.jetbrains.java.decompiler.util.InterpreterUtil;
 import org.jetbrains.java.decompiler.util.ListStack;
 
 import java.util.*;
+import java.util.Map.Entry;
 
 public class FunctionExprent extends Exprent {
 
@@ -604,4 +609,25 @@ public class FunctionExprent extends Exprent {
   public void setImplicitType(VarType implicitType) {
     this.implicitType = implicitType;
   }
+  
+  // *****************************************************************************
+  // IMatchable implementation
+  // *****************************************************************************
+  
+  public boolean match(MatchNode matchNode, MatchEngine engine) {
+
+    if(!super.match(matchNode, engine)) {
+      return false;
+    }
+    
+    Integer type = (Integer)matchNode.getRuleValue(MatchProperties.EXPRENT_FUNCTYPE);
+    if(type != null) {
+      if(this.funcType != type.intValue()) {
+        return false;
+      }
+    }
+    
+    return true;
+  }
+  
 }

src/org/jetbrains/java/decompiler/modules/decompiler/exps/InvocationExprent.java

@@ -15,6 +15,13 @@
  */
 package org.jetbrains.java.decompiler.modules.decompiler.exps;
 
+import java.util.ArrayList;
+import java.util.BitSet;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map.Entry;
+import java.util.Set;
+
 import org.jetbrains.java.decompiler.code.CodeConstants;
 import org.jetbrains.java.decompiler.main.ClassesProcessor.ClassNode;
 import org.jetbrains.java.decompiler.main.DecompilerContext;
@@ -31,12 +38,13 @@ import org.jetbrains.java.decompiler.struct.StructMethod;
 import org.jetbrains.java.decompiler.struct.consts.LinkConstant;
 import org.jetbrains.java.decompiler.struct.gen.MethodDescriptor;
 import org.jetbrains.java.decompiler.struct.gen.VarType;
+import org.jetbrains.java.decompiler.struct.match.MatchEngine;
+import org.jetbrains.java.decompiler.struct.match.MatchNode;
+import org.jetbrains.java.decompiler.struct.match.MatchNode.RuleValue;
 import org.jetbrains.java.decompiler.util.InterpreterUtil;
 import org.jetbrains.java.decompiler.util.ListStack;
 import org.jetbrains.java.decompiler.util.TextUtil;
 
-import java.util.*;
-
 public class InvocationExprent extends Exprent {
 
   public static final int INVOKE_SPECIAL = 1;
@@ -87,6 +95,7 @@ public class InvocationExprent extends Exprent {
         break;
       case CodeConstants.opc_invokedynamic:
         invocationTyp = INVOKE_DYNAMIC;
+
         classname = "java/lang/Class"; // dummy class name
         invokeDynamicClassSuffix = "##Lambda_" + cn.index1 + "_" + cn.index2;
     }
@@ -482,4 +491,47 @@ public class InvocationExprent extends Exprent {
   public String getInvokeDynamicClassSuffix() {
     return invokeDynamicClassSuffix;
   }
+
+  // *****************************************************************************
+  // IMatchable implementation
+  // *****************************************************************************
+  
+  public boolean match(MatchNode matchNode, MatchEngine engine) {
+
+    if(!super.match(matchNode, engine)) {
+      return false;
+    }
+    
+    for(Entry<MatchProperties, RuleValue> rule : matchNode.getRules().entrySet()) {
+      RuleValue value = rule.getValue();
+      
+      switch(rule.getKey()) {
+      case EXPRENT_INVOCATION_PARAMETER:
+        if(value.isVariable()) {
+          if(value.parameter < lstParameters.size()) {
+            if(!engine.checkAndSetVariableValue(value.value.toString(), lstParameters.get(value.parameter))) {
+              return false;
+            }
+          } else {
+            return false;
+          }
+        }
+        break;
+      case EXPRENT_INVOCATION_CLASS:
+        if(!value.value.equals(this.classname)) {
+          return false;
+        }
+        break;
+      case EXPRENT_INVOCATION_SIGNATURE:
+        if(!value.value.equals(this.name + this.stringDescriptor)) {
+          return false;
+        }
+        break;
+      }
+      
+    }
+    
+    return true;
+  }
+
 }

src/org/jetbrains/java/decompiler/modules/decompiler/exps/VarExprent.java

@@ -26,6 +26,10 @@ import org.jetbrains.java.decompiler.modules.decompiler.vars.VarProcessor;
 import org.jetbrains.java.decompiler.modules.decompiler.vars.VarTypeProcessor;
 import org.jetbrains.java.decompiler.modules.decompiler.vars.VarVersionPair;
 import org.jetbrains.java.decompiler.struct.gen.VarType;
+import org.jetbrains.java.decompiler.struct.match.MatchEngine;
+import org.jetbrains.java.decompiler.struct.match.MatchNode;
+import org.jetbrains.java.decompiler.struct.match.IMatchable.MatchProperties;
+import org.jetbrains.java.decompiler.struct.match.MatchNode.RuleValue;
 import org.jetbrains.java.decompiler.util.InterpreterUtil;
 
 import java.util.ArrayList;
@@ -180,4 +184,31 @@ public class VarExprent extends Exprent {
   public void setStack(boolean stack) {
     this.stack = stack;
   }
+  
+  // *****************************************************************************
+  // IMatchable implementation
+  // *****************************************************************************
+  
+  public boolean match(MatchNode matchNode, MatchEngine engine) {
+
+    if(!super.match(matchNode, engine)) {
+      return false;
+    }
+    
+    RuleValue rule = matchNode.getRules().get(MatchProperties.EXPRENT_VAR_INDEX);
+    if(rule != null) {
+      if(rule.isVariable()) {
+        if(!engine.checkAndSetVariableValue((String)rule.value, this.index)) {
+          return false;
+        }
+      } else { 
+        if(this.index != Integer.valueOf((String)rule.value).intValue()) {
+          return false;
+        }
+      }
+    }
+    
+    return true;
+  }
+  
 }

src/org/jetbrains/java/decompiler/modules/decompiler/stats/IfStatement.java

@@ -22,10 +22,15 @@ import org.jetbrains.java.decompiler.modules.decompiler.ExprProcessor;
 import org.jetbrains.java.decompiler.modules.decompiler.StatEdge;
 import org.jetbrains.java.decompiler.modules.decompiler.exps.Exprent;
 import org.jetbrains.java.decompiler.modules.decompiler.exps.IfExprent;
+import org.jetbrains.java.decompiler.struct.match.IMatchable;
+import org.jetbrains.java.decompiler.struct.match.MatchEngine;
+import org.jetbrains.java.decompiler.struct.match.MatchNode;
+import org.jetbrains.java.decompiler.struct.match.IMatchable.MatchProperties;
 import org.jetbrains.java.decompiler.util.InterpreterUtil;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map.Entry;
 
 
 public class IfStatement extends Statement {
@@ -421,4 +426,42 @@ public class IfStatement extends Statement {
   public StatEdge getElseEdge() {
     return elseedge;
   }
+  
+  // *****************************************************************************
+  // IMatchable implementation
+  // *****************************************************************************
+  
+  public IMatchable findObject(MatchNode matchNode, int index) {
+
+    IMatchable object = super.findObject(matchNode, index);
+    if(object != null) {
+      return object;
+    }
+    
+    if(matchNode.getType() == MatchNode.MATCHNODE_EXPRENT) {
+      String position = (String)matchNode.getRuleValue(MatchProperties.EXPRENT_POSITION);
+      if("head".equals(position)) {
+        return getHeadexprent();
+      }
+    }
+
+    return null;
+  }
+
+  public boolean match(MatchNode matchNode, MatchEngine engine) {
+
+    if(!super.match(matchNode, engine)) {
+      return false;
+    }
+
+    Integer type = (Integer)matchNode.getRuleValue(MatchProperties.STATEMENT_IFTYPE);
+    if(type != null) {
+      if(this.iftype != type.intValue()) {
+        return false;
+      }
+    }
+        
+    return true;
+  }
+  
 }

src/org/jetbrains/java/decompiler/modules/decompiler/stats/Statement.java

@@ -15,6 +15,15 @@
  */
 package org.jetbrains.java.decompiler.modules.decompiler.stats;
 
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+
 import org.jetbrains.java.decompiler.code.CodeConstants;
 import org.jetbrains.java.decompiler.code.InstructionSequence;
 import org.jetbrains.java.decompiler.main.DecompilerContext;
@@ -24,11 +33,13 @@ import org.jetbrains.java.decompiler.main.collectors.CounterContainer;
 import org.jetbrains.java.decompiler.modules.decompiler.StatEdge;
 import org.jetbrains.java.decompiler.modules.decompiler.StrongConnectivityHelper;
 import org.jetbrains.java.decompiler.modules.decompiler.exps.Exprent;
+import org.jetbrains.java.decompiler.struct.match.IMatchable;
+import org.jetbrains.java.decompiler.struct.match.MatchEngine;
+import org.jetbrains.java.decompiler.struct.match.MatchNode;
+import org.jetbrains.java.decompiler.struct.match.MatchNode.RuleValue;
 import org.jetbrains.java.decompiler.util.VBStyleCollection;
 
-import java.util.*;
-
-public class Statement {
+public class Statement implements IMatchable {
 
   public static final int STATEDGE_ALL = 1 << 31;
   public static final int STATEDGE_DIRECT_ALL = 1 << 30;
@@ -859,4 +870,78 @@ public class Statement {
   public String toString() {
     return id.toString();
   }
+  
+  // *****************************************************************************
+  // IMatchable implementation
+  // *****************************************************************************
+  
+  public IMatchable findObject(MatchNode matchNode, int index) {
+    
+    int node_type = matchNode.getType();
+    
+    if(node_type == MatchNode.MATCHNODE_STATEMENT) {
+      String position = (String)matchNode.getRuleValue(MatchProperties.STATEMENT_POSITION);
+      if(position != null) {
+        if(position.matches("-?\\d+")) {
+          return this.stats.get((this.stats.size() + Integer.parseInt(position)) % this.stats.size()); // care for negative positions
+        }
+      } else if(index < this.stats.size()) { // use 'index' parameter
+        return this.stats.get(index);
+      }
+    } else if(node_type == MatchNode.MATCHNODE_EXPRENT && this.exprents != null) {
+      String position = (String)matchNode.getRuleValue(MatchProperties.EXPRENT_POSITION);
+      if(position != null) {
+        if(position.matches("-?\\d+")) {
+          return this.exprents.get((this.exprents.size() + Integer.parseInt(position)) % this.exprents.size()); // care for negative positions
+        }
+      } else if(index < this.exprents.size()) { // use 'index' parameter
+        return this.exprents.get(index);
+      }
+    }
+
+    return null;
+  }
+
+  public boolean match(MatchNode matchNode, MatchEngine engine) {
+    
+    if(matchNode.getType() != MatchNode.MATCHNODE_STATEMENT) {
+      return false;
+    }
+    
+    for(Entry<MatchProperties, RuleValue> rule : matchNode.getRules().entrySet()) {
+      switch(rule.getKey()) {
+      case STATEMENT_TYPE:
+        if(this.type != ((Integer)rule.getValue().value).intValue()) {
+          return false;
+        }
+        break;
+      case STATEMENT_STATSIZE:
+        if(this.stats.size() != ((Integer)rule.getValue().value).intValue()) {
+          return false;
+        }
+        break;
+      case STATEMENT_EXPRSIZE:
+        int exprsize = ((Integer)rule.getValue().value).intValue();
+        if(exprsize == -1) {
+          if(this.exprents != null) {
+            return false;
+          }
+        } else {
+          if(this.exprents == null || this.exprents.size() != exprsize) {
+            return false;
+          }
+        }
+        break;
+      case STATEMENT_RET:
+        if(!engine.checkAndSetVariableValue((String)rule.getValue().value, this)) {
+          return false;
+        }
+        break;
+      }
+      
+    }
+    
+    return true;
+  }
+  
 }

src/org/jetbrains/java/decompiler/struct/match/IMatchable.java

@@ -0,0 +1,32 @@
+package org.jetbrains.java.decompiler.struct.match;
+
+
+public interface IMatchable {
+
+  public enum MatchProperties {
+    STATEMENT_TYPE,
+    STATEMENT_RET,
+    STATEMENT_STATSIZE,
+    STATEMENT_EXPRSIZE,
+    STATEMENT_POSITION,
+    STATEMENT_IFTYPE,
+    
+    EXPRENT_TYPE,
+    EXPRENT_RET,
+    EXPRENT_POSITION,
+    EXPRENT_FUNCTYPE,
+    EXPRENT_EXITTYPE,
+    EXPRENT_CONSTTYPE,
+    EXPRENT_CONSTVALUE,
+    EXPRENT_INVOCATION_CLASS,
+    EXPRENT_INVOCATION_SIGNATURE,
+    EXPRENT_INVOCATION_PARAMETER,
+    EXPRENT_VAR_INDEX,
+    EXPRENT_FIELD_NAME,
+  }
+  
+  public IMatchable findObject(MatchNode matchNode, int index);
+
+  public boolean match(MatchNode matchNode, MatchEngine engine);
+  
+}

src/org/jetbrains/java/decompiler/struct/match/MatchEngine.java

@@ -0,0 +1,239 @@
+package org.jetbrains.java.decompiler.struct.match;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+
+import org.jetbrains.java.decompiler.modules.decompiler.exps.ExitExprent;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.Exprent;
+import org.jetbrains.java.decompiler.modules.decompiler.exps.FunctionExprent;
+import org.jetbrains.java.decompiler.modules.decompiler.stats.IfStatement;
+import org.jetbrains.java.decompiler.modules.decompiler.stats.Statement;
+import org.jetbrains.java.decompiler.struct.gen.VarType;
+import org.jetbrains.java.decompiler.struct.match.IMatchable.MatchProperties;
+import org.jetbrains.java.decompiler.struct.match.MatchNode.RuleValue;
+
+
+public class MatchEngine {
+
+  private MatchNode rootNode = null;
+  
+  private Map<String, Object> variables = new HashMap<String, Object>();
+  
+  private static Map<String, MatchProperties> stat_properties = new HashMap<String, MatchProperties>();
+  private static Map<String, MatchProperties> expr_properties = new HashMap<String, MatchProperties>();
+  private static Map<String, Integer> stat_type = new HashMap<String, Integer>();
+  private static Map<String, Integer> expr_type = new HashMap<String, Integer>();
+  private static Map<String, Integer> expr_func_type = new HashMap<String, Integer>();
+  private static Map<String, Integer> expr_exit_type = new HashMap<String, Integer>();
+  private static Map<String, Integer> stat_if_type = new HashMap<String, Integer>();
+  private static Map<String, VarType> expr_const_type = new HashMap<String, VarType>();
+  
+  static {
+    stat_properties.put("type", MatchProperties.STATEMENT_TYPE);
+    stat_properties.put("ret", MatchProperties.STATEMENT_RET);
+    stat_properties.put("position", MatchProperties.STATEMENT_POSITION);
+    stat_properties.put("statsize", MatchProperties.STATEMENT_STATSIZE);
+    stat_properties.put("exprsize", MatchProperties.STATEMENT_EXPRSIZE);
+    stat_properties.put("iftype", MatchProperties.STATEMENT_IFTYPE);
+    
+    expr_properties.put("type", MatchProperties.EXPRENT_TYPE);
+    expr_properties.put("ret", MatchProperties.EXPRENT_RET);
+    expr_properties.put("position", MatchProperties.EXPRENT_POSITION);
+    expr_properties.put("functype", MatchProperties.EXPRENT_FUNCTYPE);
+    expr_properties.put("exittype", MatchProperties.EXPRENT_EXITTYPE);
+    expr_properties.put("consttype", MatchProperties.EXPRENT_CONSTTYPE);
+    expr_properties.put("constvalue", MatchProperties.EXPRENT_CONSTVALUE);
+    expr_properties.put("invclass", MatchProperties.EXPRENT_INVOCATION_CLASS);
+    expr_properties.put("signature", MatchProperties.EXPRENT_INVOCATION_SIGNATURE);
+    expr_properties.put("parameter", MatchProperties.EXPRENT_INVOCATION_PARAMETER);
+    expr_properties.put("index", MatchProperties.EXPRENT_VAR_INDEX);
+    expr_properties.put("name", MatchProperties.EXPRENT_FIELD_NAME);
+    
+    stat_type.put("if", Statement.TYPE_IF);
+    stat_type.put("do", Statement.TYPE_DO);
+    stat_type.put("switch", Statement.TYPE_SWITCH);
+    stat_type.put("trycatch", Statement.TYPE_TRYCATCH);
+    stat_type.put("basicblock", Statement.TYPE_BASICBLOCK);
+    stat_type.put("sequence", Statement.TYPE_SEQUENCE);
+    
+    expr_type.put("array", Exprent.EXPRENT_ARRAY);
+    expr_type.put("assignment", Exprent.EXPRENT_ASSIGNMENT);
+    expr_type.put("constant", Exprent.EXPRENT_CONST);
+    expr_type.put("exit", Exprent.EXPRENT_EXIT);
+    expr_type.put("field", Exprent.EXPRENT_FIELD);
+    expr_type.put("function", Exprent.EXPRENT_FUNCTION);
+    expr_type.put("if", Exprent.EXPRENT_IF);
+    expr_type.put("invocation", Exprent.EXPRENT_INVOCATION);
+    expr_type.put("monitor", Exprent.EXPRENT_MONITOR);
+    expr_type.put("new", Exprent.EXPRENT_NEW);
+    expr_type.put("switch", Exprent.EXPRENT_SWITCH);
+    expr_type.put("var", Exprent.EXPRENT_VAR);
+    expr_type.put("annotation", Exprent.EXPRENT_ANNOTATION);
+    expr_type.put("assert", Exprent.EXPRENT_ASSERT);
+    
+    expr_func_type.put("eq", FunctionExprent.FUNCTION_EQ);
+    
+    expr_exit_type.put("return", ExitExprent.EXIT_RETURN);
+    expr_exit_type.put("throw", ExitExprent.EXIT_THROW);
+
+    stat_if_type.put("if", IfStatement.IFTYPE_IF);
+    stat_if_type.put("ifelse", IfStatement.IFTYPE_IFELSE);
+
+    expr_const_type.put("null", VarType.VARTYPE_NULL);
+    expr_const_type.put("string", VarType.VARTYPE_STRING);
+  }
+  
+
+  public void parse(String description) {
+    
+    // each line is a separate statement/exprent 
+    String[] lines = description.split("\n");
+
+    int depth = 0; 
+    LinkedList<MatchNode> stack = new LinkedList<MatchNode>(); 
+    
+    for(String line : lines) {
+      
+      List<String> properties = new ArrayList<String>(Arrays.asList(line.split("\\s+"))); // split on any number of whitespaces
+      if(properties.get(0).isEmpty()) {
+        properties.remove(0);
+      }
+      
+      int node_type = "statement".equals(properties.get(0)) ? MatchNode.MATCHNODE_STATEMENT : MatchNode.MATCHNODE_EXPRENT;
+      
+      // create new node
+      MatchNode matchNode = new MatchNode(node_type);
+      for(int i = 1; i < properties.size(); ++i) {
+        String[] values = properties.get(i).split(":");
+        
+        MatchProperties property = (node_type == MatchNode.MATCHNODE_STATEMENT ? stat_properties : expr_properties).get(values[0]);
+        if(property == null) { // unknown property defined
+          throw new RuntimeException("Unknown matching property");
+        } else {
+          
+          Object value = null;
+          int parameter = 0;
+          
+          String strValue = values[1];
+          if(values.length == 3) {
+            parameter = Integer.parseInt(values[1]);
+            strValue = values[2];
+          }
+          
+          switch(property) {
+          case STATEMENT_TYPE:
+            value = stat_type.get(strValue);
+            break;
+          case STATEMENT_STATSIZE:
+          case STATEMENT_EXPRSIZE:
+            value = Integer.valueOf(strValue);
+            break;
+          case STATEMENT_POSITION:
+          case EXPRENT_POSITION:
+          case EXPRENT_INVOCATION_CLASS:
+          case EXPRENT_INVOCATION_SIGNATURE:
+          case EXPRENT_INVOCATION_PARAMETER:
+          case EXPRENT_VAR_INDEX:
+          case EXPRENT_FIELD_NAME:
+          case EXPRENT_CONSTVALUE:
+          case STATEMENT_RET:
+          case EXPRENT_RET:
+            value = strValue;
+            break;
+          case STATEMENT_IFTYPE:
+            value = stat_if_type.get(strValue);
+            break;
+          case EXPRENT_FUNCTYPE:
+            value = expr_func_type.get(strValue);
+            break;
+          case EXPRENT_EXITTYPE:
+            value = expr_exit_type.get(strValue);
+            break;
+          case EXPRENT_CONSTTYPE:
+            value = expr_const_type.get(strValue);
+            break;
+          case EXPRENT_TYPE:
+            value = expr_type.get(strValue);
+            break;
+          default:
+            throw new RuntimeException("Unhandled matching property");
+          }
+
+          matchNode.addRule(property, new RuleValue(parameter, value));
+        }
+      }
+      
+      if(stack.isEmpty()) { // first line, root node
+        stack.push(matchNode);
+      } else {
+      
+        // return to the correct parent on the stack  
+        int new_depth = line.lastIndexOf(' ', depth) + 1;
+        for(int i = new_depth; i <= depth; ++i) {
+          stack.pop();
+        }
+  
+        // insert new node
+        stack.getFirst().addChild(matchNode);
+        stack.push(matchNode);
+        
+        depth = new_depth; 
+      }
+    }
+    
+    this.rootNode = stack.getLast();
+  }
+  
+  public boolean match(IMatchable object) {
+    variables.clear();
+    return match(this.rootNode, object);
+  }
+  
+  private boolean match(MatchNode matchNode, IMatchable object) {
+    
+    if(!object.match(matchNode, this)) { 
+      return false;
+    }
+    
+    int expr_index = 0;
+    int stat_index = 0;
+
+    for(MatchNode childNode : matchNode.getChildren()) {
+      boolean isStatement = childNode.getType() == MatchNode.MATCHNODE_STATEMENT;
+      
+      IMatchable childObject = object.findObject(childNode, isStatement ? stat_index : expr_index);
+      if(childObject == null || !match(childNode, childObject)) {
+        return false;
+      }
+      
+      if(isStatement) {
+        stat_index++;
+      } else {
+        expr_index++;
+      }
+    }
+    
+    return true;
+  }
+
+  public boolean checkAndSetVariableValue(String name, Object value) {
+    
+    Object old_value = variables.get(name);
+    if(old_value == null) {
+      variables.put(name, value);
+    } else if(!old_value.equals(value)) {
+      return false;
+    }
+    
+    return true;
+  }
+  
+  public Object getVariableValue(String name) {
+    return variables.get(name);
+  }
+  
+}

src/org/jetbrains/java/decompiler/struct/match/MatchNode.java

@@ -0,0 +1,70 @@
+package org.jetbrains.java.decompiler.struct.match;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.jetbrains.java.decompiler.struct.match.IMatchable.MatchProperties;
+
+public class MatchNode {
+
+  public static class RuleValue {
+    public int parameter;
+    public Object value;
+    
+    public RuleValue(int parameter, Object value) {
+      this.parameter = parameter;
+      this.value = value;
+    }
+    
+    public boolean isVariable() {
+      String strValue = value.toString();
+      return (strValue.charAt(0) == '$' && strValue.charAt(strValue.length() - 1) == '$');
+    }
+    
+    public String toString() {
+      return value.toString();
+    }
+  }
+  
+  public static final int MATCHNODE_STATEMENT = 0;
+  public static final int MATCHNODE_EXPRENT = 1;
+  
+  private int type;
+  
+  private Map<MatchProperties, RuleValue> rules = new HashMap<MatchProperties, RuleValue>();
+  
+  private List<MatchNode> children = new ArrayList<MatchNode>();
+  
+  
+  public MatchNode(int type) {
+    this.type = type;
+  }
+
+  public void addChild(MatchNode child) {
+    children.add(child);
+  }
+  
+  public void addRule(MatchProperties property, RuleValue value) {
+    rules.put(property, value);
+  }
+
+  public int getType() {
+    return type;
+  }
+
+  public List<MatchNode> getChildren() {
+    return children;
+  }
+
+  public Map<MatchProperties, RuleValue> getRules() {
+    return rules;
+  }
+  
+  public Object getRuleValue(MatchProperties property) {
+    RuleValue rule = rules.get(property);
+    return rule == null ? null : rule.value;
+  }
+  
+}