Improve the experimental try-loop fix

- It now properly decompiles more things, and doesn't cause extra problems and decompilation failures as a side effect. It specifically targets when if statements are built and triggers a full postdominator set calculation and general statement finding, which properly decomposes the graph.

Author: jaskarth

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

@@ -27,7 +27,7 @@
 public class ClassWrapper {
   // Sometimes when debugging you want to be able to only analyze a specific method.
   // When not null, this skips processing of every method except the one with the name specified.
-  private static final String DEBUG_METHOD_FILTER = null;
+  private static final String DEBUG_METHOD_FILTER = "test";
   private final StructClass classStruct;
   private final Set<String> hiddenMembers = new HashSet<>();
   private final VBStyleCollection<Exprent, String> staticFieldInitializers = new VBStyleCollection<>();

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

@@ -46,28 +46,14 @@ private static RootStatement graphToStatement(ControlFlowGraph graph, StructMeth
       return root;
     }
 
-    boolean firstIsException = false;
-
-    if (DecompilerContext.getOption(IFernflowerPreferences.EXPERIMENTAL_TRY_LOOP_FIX)) {
-      // Check if the first block in the graph is covered by an exception range.
-      // If it is, we need to avoid setting the edge type to continue, as that causes problems later down the line.
-
-      for (ExceptionRangeCFG exception : graph.getExceptions()) {
-        if (exception.getProtectedRange().contains(firstblock)) {
-          firstIsException = true;
-          break;
-        }
-      }
-    }
-
     for (BasicBlock block : blocks) {
       Statement stat = stats.getWithKey(block.id);
 
       for (BasicBlock succ : block.getSuccs()) {
         Statement stsucc = stats.getWithKey(succ.id);
 
         int type;
-        if (stsucc == firstst && !firstIsException) {
+        if (stsucc == firstst) {
           type = StatEdge.TYPE_CONTINUE;
           stsucc = general;
         }

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

@@ -4,6 +4,7 @@
 import org.jetbrains.java.decompiler.code.CodeConstants;
 import org.jetbrains.java.decompiler.code.cfg.BasicBlock;
 import org.jetbrains.java.decompiler.main.DecompilerContext;
+import org.jetbrains.java.decompiler.main.extern.IFernflowerPreferences;
 import org.jetbrains.java.decompiler.modules.decompiler.exps.AssignmentExprent;
 import org.jetbrains.java.decompiler.modules.decompiler.exps.Exprent;
 import org.jetbrains.java.decompiler.util.TextBuffer;
@@ -131,6 +132,14 @@ else if (next != statn) {
           }
         }
 
+        // Don't build a trycatch around a loop-head if statement, as we know that DoStatement should be built first.
+        // Since CatchStatement's isHead is run after DoStatement's, we can assume that a loop was not able to be built.
+        if (DecompilerContext.getOption(IFernflowerPreferences.EXPERIMENTAL_TRY_LOOP_FIX)) {
+          if (head.type == Statement.TYPE_IF && head.getContinueSet().contains(head.first)) {
+            return null;
+          }
+        }
+
         if (DecHelper.checkStatementExceptions(lst)) {
           return new CatchStatement(head, next, setHandlers);
         }

test/org/jetbrains/java/decompiler/SingleClassesTest.java

@@ -590,6 +590,7 @@ private void registerLVT() {
 
   private void registerTryLoop() {
     register(JAVA_8, "TestTryLoop");
+    register(JAVA_8, "TestTryLoop2");
     register(JAVA_8, "TestTryLoopRecompile");
     register(JAVA_8, "TestTryLoopSimpleFinally");
     // TODO: Still doesn't properly decompile, loop needs to be in the try block

testData/results/pkg/TestTryLoop.dec

@@ -2,9 +2,12 @@ package pkg;
 
 import java.io.File;
 import java.io.FileNotFoundException;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
 import java.nio.file.Path;
 import java.util.Iterator;
 import java.util.Scanner;
+import java.util.ServiceConfigurationError;
 
 public class TestTryLoop {
    private boolean field;
@@ -20,54 +23,91 @@ public class TestTryLoop {
 
    }// 22
 
-   public boolean hasNext(Path param1, Iterator<File> param2) {
-      // $FF: Couldn't be decompiled
-      // Bytecode:
-      // 00: aload 1
-      // 01: bipush 0
-      // 02: anewarray 7
-      // 05: invokestatic java/nio/file/Files.exists (Ljava/nio/file/Path;[Ljava/nio/file/LinkOption;)Z
-      // 08: ifeq 17
-      // 0b: aload 2
-      // 0c: invokeinterface java/util/Iterator.next ()Ljava/lang/Object; 1
-      // 11: checkcast java/io/File
-      // 14: astore 3
-      // 15: bipush 1
-      // 16: ireturn
-      // 17: bipush 0
-      // 18: ireturn
-      // 19: astore 4
-      // 1b: getstatic java/lang/System.out Ljava/io/PrintStream;
-      // 1e: bipush 1
-      // 1f: invokevirtual java/io/PrintStream.println (I)V
-      // 22: goto 00
-      // 25: astore 4
-      // 27: getstatic java/lang/System.out Ljava/io/PrintStream;
-      // 2a: bipush 2
-      // 2b: invokevirtual java/io/PrintStream.println (I)V
-      // 2e: goto 00
+   public boolean hasNext(Path p, Iterator<File> f) {
+      while(true) {
+         try {
+            if (Files.exists(p, new LinkOption[0])) {// 28
+               File a = (File)f.next();// 29
+               return true;// 30
+            }
+
+            return false;// 32
+         } catch (ServiceConfigurationError var5) {// 33
+            System.out.println(1);// 34
+         } catch (NoClassDefFoundError var6) {// 35
+            System.out.println(2);// 36
+         }
+      }
    }
 }
 
 class 'pkg/TestTryLoop' {
    method 'test (Ljava/io/File;)V' {
-      0      13
-      1      13
-      2      13
-      3      13
-      b      14
-      16      16
-      18      17
-      1b      20
+      0      16
+      1      16
+      2      16
+      3      16
+      b      17
+      16      19
+      18      20
+      1b      23
+   }
+
+   method 'hasNext (Ljava/nio/file/Path;Ljava/util/Iterator;)Z' {
+      0      28
+      1      28
+      5      28
+      6      28
+      7      28
+      8      28
+      b      29
+      c      29
+      d      29
+      e      29
+      f      29
+      10      29
+      11      29
+      12      29
+      13      29
+      14      29
+      15      30
+      16      30
+      17      33
+      18      33
+      19      34
+      1b      35
+      1c      35
+      1d      35
+      1e      35
+      1f      35
+      20      35
+      21      35
+      25      36
+      27      37
+      28      37
+      29      37
+      2a      37
+      2b      37
+      2c      37
+      2d      37
    }
 }
 
 Lines mapping:
-16 <-> 14
-17 <-> 15
-19 <-> 17
-20 <-> 18
-22 <-> 21
+16 <-> 17
+17 <-> 18
+19 <-> 20
+20 <-> 21
+22 <-> 24
+28 <-> 29
+29 <-> 30
+30 <-> 31
+32 <-> 34
+33 <-> 35
+34 <-> 36
+35 <-> 37
+36 <-> 38
 Not mapped:
 18
 21
+37

testData/results/pkg/TestTryLoop2.dec

@@ -0,0 +1,50 @@
+package pkg;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.util.Scanner;
+
+public class TestTryLoop2 {
+   private boolean field;
+
+   public void test(File file) {
+      while(true) {
+         try {
+            if (!this.field) {// 13
+               return;// 24
+            }
+
+            new Scanner(file);// 14
+         } catch (FileNotFoundException var3) {// 20
+            var3.printStackTrace();// 21
+         }
+      }
+   }
+}
+
+class 'pkg/TestTryLoop2' {
+   method 'test (Ljava/io/File;)V' {
+      0      12
+      1      12
+      2      12
+      3      12
+      4      12
+      b      16
+      16      17
+      18      18
+      19      18
+      1a      18
+      1e      13
+   }
+}
+
+Lines mapping:
+13 <-> 13
+14 <-> 17
+20 <-> 18
+21 <-> 19
+24 <-> 14
+Not mapped:
+16
+19
+22

testData/results/pkg/TestTryLoopRecompile.dec

@@ -10,18 +10,17 @@ public class TestTryLoopRecompile {
    public void test(File file) {
       while(true) {
          try {
-            if (!this.field) {// 13
-               break;
+            if (this.field) {// 13
+               new Scanner(file);// 14
+               continue;
             }
-
-            new Scanner(file);// 14
          } catch (FileNotFoundException var3) {// 17
             var3.printStackTrace();// 18
-            break;
          }
-      }
 
-   }// 21
+         return;// 21
+      }
+   }
 }
 
 class 'pkg/TestTryLoopRecompile' {
@@ -31,19 +30,19 @@ class 'pkg/TestTryLoopRecompile' {
       2      12
       3      12
       4      12
-      b      16
-      16      17
-      18      18
-      1b      23
+      b      13
+      16      16
+      18      17
+      1b      20
    }
 }
 
 Lines mapping:
 13 <-> 13
-14 <-> 17
-17 <-> 18
-18 <-> 19
-21 <-> 24
+14 <-> 14
+17 <-> 17
+18 <-> 18
+21 <-> 21
 Not mapped:
 15
 19

testData/src/java8/pkg/TestTryLoop2.java

@@ -0,0 +1,25 @@
+package pkg;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.util.Scanner;
+
+public class TestTryLoop2 {
+  private boolean field;
+
+  public void test(File file) {
+    while (true) {
+      try {
+        if (this.field) {
+          Scanner scanner = new Scanner(file);
+
+          continue;
+        }
+
+        break;
+      } catch (FileNotFoundException e) {
+        e.printStackTrace();
+      }
+    }
+  }
+}