Fix stats desync issue and add validation checks (#603)

Author: Kroppeb

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

@@ -38,21 +38,36 @@ public static void validateStatement(RootStatement statement) {
     while (!stack.isEmpty()) {
       Statement stat = stack.pop();
 
-      statements.putWithKey(stat, stat.id);
-
-      stack.addAll(stat.getStats());
+      if (statements.containsKey(stat.id)) {
+        if (statements.getWithKey(stat.id) != stat){
+          throw new IllegalStateException("2 stats with the same id: " + stat + " vs " + statements.getWithKey(stat.id));
+        }
+        // The else case means multiple parent. A later check will produce better error than we could do here.
+      } else {
+        statements.putWithKey(stat, stat.id);
+        stack.addAll(stat.getStats());
+      }
     }
 
     for (Statement stat : statements) {
       for (StatEdge edge : stat.getAllSuccessorEdges()) {
+        if (edge.getSource() != stat) {
+          throw new IllegalStateException("Stat " + stat + " has successor edge for which it isn't the source: " + edge);
+        }
         validateEdgeContext(statements, stat, edge);
       }
 
       for (StatEdge edge : stat.getAllPredecessorEdges()) {
+        if (edge.getDestination() != stat) {
+          throw new IllegalStateException("Stat " + stat + " has predecessor edge for which it isn't the destination: " + edge);
+        }
         validateEdgeContext(statements, stat, edge);
       }
 
       for (StatEdge edge : stat.getLabelEdges()) {
+        if (edge.closure != stat) {
+          throw new IllegalStateException("Stat " + stat + " has a labelled edge for which it isn't the closure: " + edge);
+        }
         validateEdgeContext(statements, stat, edge);
       }
 
@@ -74,6 +89,9 @@ public static void validateStatement(RootStatement statement) {
         if (statStat.getParent() != stat) {
           throw new IllegalStateException("Statement parent is not set correctly [" + statStat + "]: Expected " + stat + " but was " + statStat.getParent());
         }
+        if (!stat.getStats().containsKey(statStat.id)){
+          throw new IllegalStateException("Statement " + stat + " contains non stat without id lookup: " + statStat);
+        }
       }
 
       validateSingleStatement(stat);

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

@@ -578,7 +578,7 @@ public void addCase(int index, List<Exprent> values, Statement stat) {
 
   private void addCaseInternal(int index, List<@Nullable Exprent> values, Statement stat) {
     // Basichead is always the first stat
-    this.getStats().add(1 + index, stat);
+    this.getStats().addWithKeyAndIndex(1 + index, stat, stat.id);
     this.getCaseStatements().add(index, stat);
     this.getCaseValues().add(index, values);