From c1b6d9f5be4dda2d3306692a2670ca64b4d7d71a Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Thu, 1 Sep 2016 11:39:23 -0700
Subject: [PATCH] Improve error comparison criteria

Signed-off-by: Nathan Sobo <nathan@github.com>
---
 spec/fixtures/error_corpus/c_errors.txt       |  5 ++-
 .../error_corpus/javascript_errors.txt        | 14 +++----
 src/runtime/error_costs.h                     | 38 ++++++++-----------
 3 files changed, 24 insertions(+), 33 deletions(-)

diff --git a/spec/fixtures/error_corpus/c_errors.txt b/spec/fixtures/error_corpus/c_errors.txt
index a8a56037..4dfb0894 100644
--- a/spec/fixtures/error_corpus/c_errors.txt
+++ b/spec/fixtures/error_corpus/c_errors.txt
@@ -122,9 +122,10 @@ int b() {
     (identifier) (function_declarator (identifier))
     (compound_statement
       (declaration
-        (ERROR (identifier) (identifier))
         (identifier)
-        (init_declarator (identifier) (number_literal)))
+        (init_declarator
+          (ERROR (identifier) (identifier))
+          (identifier) (number_literal)))
       (declaration
         (ERROR (identifier) (identifier))
         (identifier)
diff --git a/spec/fixtures/error_corpus/javascript_errors.txt b/spec/fixtures/error_corpus/javascript_errors.txt
index d9e88a3e..b8ddc33a 100644
--- a/spec/fixtures/error_corpus/javascript_errors.txt
+++ b/spec/fixtures/error_corpus/javascript_errors.txt
@@ -14,12 +14,9 @@ e f;
     (ERROR (identifier))
     (identifier)
     (statement_block
-      (expression_statement
-        (ERROR (identifier))
-        (identifier))))
-  (expression_statement
-    (ERROR (identifier))
-    (identifier)))
+      (ERROR (identifier))
+      (expression_statement (identifier))))
+  (expression_statement (ERROR (identifier)) (identifier)))
 
 =======================================================
 multiple invalid tokens right after the viable prefix
@@ -37,9 +34,8 @@ h i j k;
     (ERROR (identifier) (identifier))
     (identifier)
     (statement_block
-      (expression_statement
-        (ERROR (identifier) (identifier) (identifier))
-        (identifier))))
+      (ERROR (identifier) (identifier) (identifier))
+      (expression_statement (identifier))))
   (expression_statement
     (ERROR (identifier) (identifier) (identifier))
     (identifier)))
diff --git a/src/runtime/error_costs.h b/src/runtime/error_costs.h
index c628672e..e7c8ed71 100644
--- a/src/runtime/error_costs.h
+++ b/src/runtime/error_costs.h
@@ -11,34 +11,28 @@ typedef struct {
   unsigned push_count;
 } ErrorStatus;
 
-static double error_threshold(unsigned push_count) {
-  return 6 * ERROR_COST_PER_SKIPPED_TREE / (1 + push_count / 2);
+static inline unsigned error_status_min_cost(ErrorStatus status) {
+  return status.cost +
+    ERROR_COST_PER_SKIPPED_TREE * status.count * status.count;
+}
+
+static inline unsigned error_status_max_cost(ErrorStatus status) {
+  return status.cost +
+    ERROR_COST_PER_SKIPPED_TREE * status.count * status.count +
+    (6 * ERROR_COST_PER_SKIPPED_TREE * status.count + 12 * ERROR_COST_PER_SKIPPED_TREE) /
+    (1 + status.push_count / 2);
 }
 
 static inline int error_status_compare(ErrorStatus a, ErrorStatus b) {
-  // TODO remove
-  a.cost += ERROR_COST_PER_SKIPPED_TREE * a.count;
-  b.cost += ERROR_COST_PER_SKIPPED_TREE * b.count;
-
-  if ((a.count + 1 < b.count) ||
-      (a.count < b.count && a.cost <= b.cost)) {
+  if ((a.count + 1 < b.count) || (a.count < b.count && a.cost <= b.cost))
     return -1;
-  }
-
-  if ((b.count + 1 < a.count) ||
-      (b.count < a.count && b.cost <= a.cost)) {
+  if ((a.count > b.count + 1) || (b.count < a.count && b.cost <= a.cost))
     return 1;
-  }
 
-  if (a.cost == b.cost) {
-    if (a.cost + error_threshold(a.push_count) < b.cost) {
-      return -1;
-    }
-
-    if (b.cost + error_threshold(b.push_count) < a.cost) {
-      return 1;
-    }
-  }
+  if (error_status_max_cost(a) < error_status_min_cost(b))
+    return -1;
+  if (error_status_min_cost(a) > error_status_max_cost(b))
+    return 1;
 
   return 0;
 }