Prune unneeded stack versions based on a depth criteria

src/runtime/error_costs.c

@@ -2,6 +2,8 @@
 
 static const unsigned MAX_COST_DIFFERENCE = 16 * ERROR_COST_PER_SKIPPED_TREE;
 static const unsigned MAX_PUSH_COUNT_WITH_COUNT_DIFFERENCE = 24;
+static const unsigned MAX_PUSH_COUNT_TO_ALLOW_MULTIPLE = 32;
+static const unsigned MAX_DEPTH_TO_ALLOW_MULTIPLE = 12;
 
 ErrorComparison error_status_compare(ErrorStatus a, ErrorStatus b, bool are_mergeable) {
   if (a.count < b.count) {
@@ -42,5 +44,20 @@ ErrorComparison error_status_compare(ErrorStatus a, ErrorStatus b, bool are_merg
     }
   }
 
+  if (a.count > 0) {
+    if (a.push_count > MAX_PUSH_COUNT_TO_ALLOW_MULTIPLE ||
+        b.push_count > MAX_PUSH_COUNT_TO_ALLOW_MULTIPLE ||
+        a.depth > MAX_DEPTH_TO_ALLOW_MULTIPLE ||
+        b.depth > MAX_DEPTH_TO_ALLOW_MULTIPLE) {
+      return a.depth <= b.depth ?
+        ErrorComparisonTakeLeft :
+        ErrorComparisonTakeRight;
+    } else {
+      return a.depth <= b.depth ?
+        ErrorComparisonPreferLeft :
+        ErrorComparisonPreferRight;
+    }
+  }
+
   return ErrorComparisonNone;
 }

src/runtime/error_costs.h

@@ -16,6 +16,7 @@ typedef struct {
   unsigned count;
   unsigned cost;
   unsigned push_count;
+  unsigned depth;
 } ErrorStatus;
 
 typedef enum {

src/runtime/stack.c

@@ -384,6 +384,7 @@ ErrorStatus ts_stack_error_status(const Stack *self, StackVersion version) {
     .cost = head->node->error_cost,
     .count = head->node->error_count,
     .push_count = head->push_count,
+    .depth = head->depth,
   };
 }