[java-decompiler] Patch 0048 from ForgeFlower.Improve output of loops inside trycatch

GitOrigin-RevId: 44c74aef2d7f6da9c2f7da6f7a53abbc463111cc

plugins/java-decompiler/engine/src/org/jetbrains/java/decompiler/modules/decompiler/DecHelper.java

@@ -192,6 +192,26 @@ public final class DecHelper {
     return setHandlers;
   }
 
+  public static boolean invalidHeadMerge(Statement head) {
+    // 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.
+    Statement ifhead = findIfHead(head);
+
+    return ifhead != null && head.getContinueSet().contains(ifhead.getFirst());
+  }
+
+  private static Statement findIfHead(Statement head) {
+    while (head != null && head.type != Statement.StatementType.IF) {
+      if (head.type != Statement.StatementType.SEQUENCE) {
+        return null;
+      }
+
+      head = head.getFirst();
+    }
+
+    return head;
+  }
+
   public static List<Exprent> copyExprentList(List<? extends Exprent> lst) {
     List<Exprent> ret = new ArrayList<>();
     for (Exprent expr : lst) {
@@ -199,4 +219,4 @@ public final class DecHelper {
     }
     return ret;
   }
-}
+}

plugins/java-decompiler/engine/src/org/jetbrains/java/decompiler/modules/decompiler/stats/CatchAllStatement.java

@@ -85,6 +85,10 @@ public final class CatchAllStatement extends Statement {
             return null;
           }
 
+          if (DecHelper.invalidHeadMerge(head)) {
+            return null;
+          }
+
           if (DecHelper.checkStatementExceptions(Arrays.asList(head, exc))) {
             return new CatchAllStatement(head, exc);
           }

plugins/java-decompiler/engine/src/org/jetbrains/java/decompiler/modules/decompiler/stats/CatchStatement.java

@@ -129,6 +129,10 @@ public final class CatchStatement extends Statement {
           }
         }
 
+        if (DecHelper.invalidHeadMerge(head)) {
+          return null;
+        }
+
         if (DecHelper.checkStatementExceptions(lst)) {
           return new CatchStatement(head, next, setHandlers);
         }