From be9e79db1bcd1412861e62a82755109dfb649c42 Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Thu, 1 Dec 2016 10:24:06 -0800
Subject: [PATCH] Avoid incorrect application of precedence

---
 spec/integration/compile_grammar_spec.cc      | 154 ++++++++++++++++++
 .../build_tables/build_parse_table.cc         |   2 +-
 2 files changed, 155 insertions(+), 1 deletion(-)

diff --git a/spec/integration/compile_grammar_spec.cc b/spec/integration/compile_grammar_spec.cc
index 36f5647e..d41d76e4 100644
--- a/spec/integration/compile_grammar_spec.cc
+++ b/spec/integration/compile_grammar_spec.cc
@@ -243,6 +243,160 @@ describe("compile_grammar", []() {
           "(block (expression (identifier)))))))");
     });
 
+    it("handles precedence applied to specific rule subsequences (regression)", [&]() {
+      TSCompileResult result = ts_compile_grammar(R"JSON({
+        "name": "precedence_on_subsequence",
+
+        "extras": [
+          {"type": "STRING", "value": " "}
+        ],
+
+        "rules": {
+          "expression": {
+            "type": "PREC_LEFT",
+            "value": 0,
+            "content": {
+              "type": "CHOICE",
+              "members": [
+                {"type": "SYMBOL", "name": "function_call"},
+                {"type": "SYMBOL", "name": "identifier"},
+                {"type": "SYMBOL", "name": "scope_resolution"}
+              ]
+            }
+          },
+
+          "function_call": {
+            "type": "CHOICE",
+            "members": [
+              {
+                "type": "SEQ",
+                "members": [
+                  {"type": "SYMBOL", "name": "identifier"},
+                  {"type": "SYMBOL", "name": "expression"}
+                ]
+              },
+
+              {
+                "type": "PREC",
+                "value": 1,
+                "content": {
+                  "type": "SEQ",
+                  "members": [
+                    {"type": "SYMBOL", "name": "identifier"},
+                    {"type": "SYMBOL", "name": "block"}
+                  ]
+                }
+              },
+
+              {
+                "type": "PREC",
+                "value": -1,
+                "content": {
+                  "type": "SEQ",
+                  "members": [
+                    {"type": "SYMBOL", "name": "identifier"},
+                    {"type": "SYMBOL", "name": "do_block"}
+                  ]
+                }
+              },
+
+              {
+                "type": "SEQ",
+                "members": [
+                  {"type": "SYMBOL", "name": "identifier"},
+                  {
+                    "type": "PREC",
+                    "value": 1,
+                    "content": {
+                      "type": "SEQ",
+                      "members": [
+                        {"type": "SYMBOL", "name": "expression"},
+                        {"type": "SYMBOL", "name": "block"}
+                      ]
+                    }
+                  }
+                ]
+              },
+
+              {
+                "type": "SEQ",
+                "members": [
+                  {"type": "SYMBOL", "name": "identifier"},
+                  {
+                    "type": "PREC",
+                    "value": -1,
+                    "content": {
+                      "type": "SEQ",
+                      "members": [
+                        {"type": "SYMBOL", "name": "expression"},
+                        {"type": "SYMBOL", "name": "do_block"}
+                      ]
+                    }
+                  }
+                ]
+              }
+            ]
+          },
+
+          "scope_resolution": {
+            "type": "PREC_LEFT",
+            "value": 1,
+            "content": {
+              "type": "CHOICE",
+              "members": [
+                {
+                  "type": "SEQ",
+                  "members": [
+                    {"type": "SYMBOL", "name": "expression"},
+                    {"type": "STRING", "value": "::"},
+                    {"type": "SYMBOL", "name": "expression"}
+                  ]
+                },
+                {
+                  "type": "SEQ",
+                  "members": [
+                    {"type": "STRING", "value": "::"},
+                    {"type": "SYMBOL", "name": "expression"},
+                  ]
+                }
+              ]
+            }
+          },
+
+          "block": {
+            "type": "STRING",
+            "value": "{}"
+          },
+
+          "do_block": {
+            "type": "STRING",
+            "value": "do end"
+          },
+
+          "identifier": {
+            "type": "PATTERN",
+            "value": "[a-zA-Z]+"
+          }
+        }
+      })JSON");
+
+      auto language = load_compile_result("precedence_on_subsequence", result);
+      ts_document_set_language(document, language);
+
+      ts_document_set_input_string(document, "a b {}");
+      ts_document_parse(document);
+      assert_root_node("(expression (function_call "
+        "(identifier) "
+        "(expression (function_call (identifier) (block)))))");
+
+      ts_document_set_input_string(document, "a b do end");
+      ts_document_parse(document);
+      assert_root_node("(expression (function_call "
+        "(identifier) "
+        "(expression (identifier)) "
+        "(do_block)))");
+    });
+
     it("does not allow conflicting precedences", [&]() {
       string grammar_template = R"JSON({
         "name": "conflicting_precedence_example",
diff --git a/src/compiler/build_tables/build_parse_table.cc b/src/compiler/build_tables/build_parse_table.cc
index 2047b4ba..91444310 100644
--- a/src/compiler/build_tables/build_parse_table.cc
+++ b/src/compiler/build_tables/build_parse_table.cc
@@ -377,7 +377,7 @@ class ParseTableBuilder {
           LookaheadSet first_set = item_set_builder.get_first_set(item.next_symbol());
           if (first_set.contains(lookahead)) {
             shift_items.insert(item);
-            shift_precedence.add(item.precedence());
+            shift_precedence.add(item.production->at(item.step_index - 1).precedence);
           }
         }
       }