From 9959fe35b0b746687fb46c7d32c063b9729d146e Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Tue, 13 Oct 2015 11:23:02 -0700
Subject: [PATCH] Allow associativity to be specified in rules w/o precedence

---
 include/tree_sitter/compiler.h                | 11 ++++-----
 .../prepare_grammar/flatten_grammar_spec.cc   | 10 ++++----
 spec/fixtures/grammars/c.cc                   |  4 ++--
 spec/fixtures/grammars/helpers.cc             |  2 +-
 spec/fixtures/grammars/javascript.cc          | 24 +++++++++----------
 src/compiler/associativity.h                  |  0
 .../build_tables/build_parse_table.cc         |  4 ++--
 .../build_tables/get_completion_status.cc     |  8 +++----
 .../build_tables/get_completion_status.h      |  3 ++-
 .../build_tables/parse_conflict_manager.cc    |  4 ++--
 src/compiler/parse_table.cc                   |  9 +++----
 src/compiler/parse_table.h                    |  6 ++---
 .../prepare_grammar/flatten_grammar.cc        |  8 ++++---
 src/compiler/rules/metadata.h                 |  6 +++++
 src/compiler/rules/rules.cc                   | 19 ++++++++++++---
 src/compiler/syntax_grammar.cc                |  9 +++----
 src/compiler/syntax_grammar.h                 |  7 +++---
 17 files changed, 78 insertions(+), 56 deletions(-)
 create mode 100644 src/compiler/associativity.h

diff --git a/include/tree_sitter/compiler.h b/include/tree_sitter/compiler.h
index dbbd3298..333b3249 100644
--- a/include/tree_sitter/compiler.h
+++ b/include/tree_sitter/compiler.h
@@ -11,12 +11,6 @@ namespace tree_sitter {
 class Rule;
 typedef std::shared_ptr<Rule> rule_ptr;
 
-enum Associativity {
-  AssociativityNone,
-  AssociativityLeft,
-  AssociativityRight,
-};
-
 rule_ptr blank();
 rule_ptr choice(const std::vector<rule_ptr> &);
 rule_ptr repeat(const rule_ptr &);
@@ -27,7 +21,10 @@ rule_ptr pattern(const std::string &);
 rule_ptr str(const std::string &);
 rule_ptr err(const rule_ptr &);
 rule_ptr prec(int precedence, const rule_ptr &);
-rule_ptr prec(int precedence, const rule_ptr &, Associativity);
+rule_ptr prec_left(const rule_ptr &);
+rule_ptr prec_left(int precedence, const rule_ptr &);
+rule_ptr prec_right(const rule_ptr &);
+rule_ptr prec_right(int precedence, const rule_ptr &);
 rule_ptr token(const rule_ptr &rule);
 
 class Grammar {
diff --git a/spec/compiler/prepare_grammar/flatten_grammar_spec.cc b/spec/compiler/prepare_grammar/flatten_grammar_spec.cc
index 44f37b3a..780d16f2 100644
--- a/spec/compiler/prepare_grammar/flatten_grammar_spec.cc
+++ b/spec/compiler/prepare_grammar/flatten_grammar_spec.cc
@@ -32,13 +32,13 @@ describe("flatten_grammar", []() {
     // When multiple precedence values are nested, the inner precedence wins.
     Variable("variable1", VariableTypeNamed, seq({
       i_sym(1),
-      prec(101, seq({
+      prec_left(101, seq({
         i_sym(2),
         choice({
-          prec(102, seq({
+          prec_right(102, seq({
             i_sym(3),
             i_sym(4)
-          }), AssociativityRight),
+          })),
           i_sym(5),
         }),
         i_sym(6),
@@ -49,11 +49,11 @@ describe("flatten_grammar", []() {
     // When a precedence is applied to the end of a rule, its value is assigned
     // to the last step of the corresponding production.
     Variable("variable2", VariableTypeHidden, seq({
-      prec(102, seq({
+      prec_left(102, seq({
         i_sym(1),
         i_sym(2),
       })),
-      prec(103, seq({
+      prec_left(103, seq({
         i_sym(3),
         i_sym(4),
       })),
diff --git a/spec/fixtures/grammars/c.cc b/spec/fixtures/grammars/c.cc
index 36b3e3d5..c75ade67 100644
--- a/spec/fixtures/grammars/c.cc
+++ b/spec/fixtures/grammars/c.cc
@@ -137,8 +137,8 @@ extern const Grammar c = Grammar({
     sym("number") }) },
 
   { "math_expression", choice({
-    prec(1, seq({ sym("expression"), str("+"), sym("expression") })),
-    prec(2, seq({ sym("expression"), str("*"), sym("expression") })) }) },
+    prec_left(1, seq({ sym("expression"), str("+"), sym("expression") })),
+    prec_left(2, seq({ sym("expression"), str("*"), sym("expression") })) }) },
 
   { "call_expression", prec(3, seq({
     sym("expression"),
diff --git a/spec/fixtures/grammars/helpers.cc b/spec/fixtures/grammars/helpers.cc
index 4dcf061e..5d827a0b 100644
--- a/spec/fixtures/grammars/helpers.cc
+++ b/spec/fixtures/grammars/helpers.cc
@@ -29,7 +29,7 @@ rule_ptr in_brackets(rule_ptr rule) {
 }
 
 rule_ptr infix_op(std::string op, std::string rule_name, int precedence) {
-  return prec(precedence, seq({
+  return prec_left(precedence, seq({
     sym(rule_name),
     str(op),
     sym(rule_name) }));
diff --git a/spec/fixtures/grammars/javascript.cc b/spec/fixtures/grammars/javascript.cc
index e4f9eeeb..5bff9169 100644
--- a/spec/fixtures/grammars/javascript.cc
+++ b/spec/fixtures/grammars/javascript.cc
@@ -68,13 +68,13 @@ extern const Grammar javascript = Grammar({
   { "statement_block", prec(PREC_BLOCK,
     in_braces(err(repeat(sym("_statement"))))) },
 
-  { "if_statement", prec(0, seq({
+  { "if_statement", prec_right(0, seq({
     str("if"),
     sym("_paren_expression"),
     sym("_statement"),
     optional(seq({
       str("else"),
-      sym("_statement") })) }), AssociativityRight) },
+      sym("_statement") })) })) },
 
   { "switch_statement", seq({
     str("switch"),
@@ -219,13 +219,13 @@ extern const Grammar javascript = Grammar({
     sym("arguments") })) },
 
   { "constructor_call", choice({
-    prec(PREC_SHORT_NEW, seq({
+    prec_right(PREC_SHORT_NEW, seq({
       str("new"),
-      sym("_expression") }), AssociativityRight),
-    prec(PREC_MEMBER, seq({
+      sym("_expression") })),
+    prec_right(PREC_MEMBER, seq({
       str("new"),
       sym("_expression"),
-      sym("arguments") }), AssociativityRight) }) },
+      sym("arguments") })) }) },
 
   { "member_access", prec(PREC_MEMBER, seq({
     sym("_expression"),
@@ -238,28 +238,28 @@ extern const Grammar javascript = Grammar({
     err(sym("_expression")),
     str("]") })) },
 
-  { "assignment", prec(PREC_ASSIGN, seq({
+  { "assignment", prec_right(PREC_ASSIGN, seq({
     choice({
       sym("identifier"),
       sym("member_access"),
       sym("subscript_access") }),
     str("="),
-    sym("_expression") }), AssociativityRight) },
+    sym("_expression") })) },
 
-  { "math_assignment", prec(PREC_ASSIGN, seq({
+  { "math_assignment", prec_right(PREC_ASSIGN, seq({
     choice({
       sym("identifier"),
       sym("member_access"),
       sym("subscript_access") }),
     choice({ str("+="), str("-="), str("*="), str("/=") }),
-    sym("_expression") }), AssociativityRight) },
+    sym("_expression") })) },
 
-  { "ternary", prec(PREC_TERNARY, seq({
+  { "ternary", prec_right(PREC_TERNARY, seq({
     sym("_expression"),
     str("?"),
     sym("_expression"),
     str(":"),
-    sym("_expression") }), AssociativityRight) },
+    sym("_expression") })) },
 
   { "bool_op", choice({
     infix_op("||", "_expression", PREC_OR),
diff --git a/src/compiler/associativity.h b/src/compiler/associativity.h
new file mode 100644
index 00000000..e69de29b
diff --git a/src/compiler/build_tables/build_parse_table.cc b/src/compiler/build_tables/build_parse_table.cc
index 266a9e5e..ddaadaf7 100644
--- a/src/compiler/build_tables/build_parse_table.cc
+++ b/src/compiler/build_tables/build_parse_table.cc
@@ -108,7 +108,7 @@ class ParseTableBuilder {
   struct CompletionStatus {
     bool is_done;
     int precedence;
-    Associativity associativity;
+    rules::Associativity associativity;
   };
 
   CompletionStatus get_completion_status(const ParseItem &item) {
@@ -118,7 +118,7 @@ class ParseTableBuilder {
       const ProductionStep &last_step = production[item.step_index - 1];
       return { true, last_step.precedence, last_step.associativity };
     }
-    return { false, 0, AssociativityNone };
+    return { false, 0, rules::AssociativityNone };
   }
 
   void add_reduce_actions(const ParseItemSet &item_set, ParseStateId state_id) {
diff --git a/src/compiler/build_tables/get_completion_status.cc b/src/compiler/build_tables/get_completion_status.cc
index 0920b943..4cc70c60 100644
--- a/src/compiler/build_tables/get_completion_status.cc
+++ b/src/compiler/build_tables/get_completion_status.cc
@@ -16,7 +16,7 @@ class GetCompletionStatus : public rules::RuleFn<CompletionStatus> {
       if (status.is_done)
         return status;
     }
-    return { false, 0, AssociativityNone };
+    return { false, 0, rules::AssociativityNone };
   }
 
   CompletionStatus apply_to(const rules::Metadata *rule) {
@@ -24,7 +24,7 @@ class GetCompletionStatus : public rules::RuleFn<CompletionStatus> {
     if (result.is_done && !result.associativity) {
       result.precedence = rule->value_for(rules::PRECEDENCE);
       result.associativity =
-        (Associativity)(rule->value_for(rules::ASSOCIATIVITY));
+        (rules::Associativity)(rule->value_for(rules::ASSOCIATIVITY));
     }
     return result;
   }
@@ -34,7 +34,7 @@ class GetCompletionStatus : public rules::RuleFn<CompletionStatus> {
   }
 
   CompletionStatus apply_to(const rules::Blank *rule) {
-    return { true, 0, AssociativityNone };
+    return { true, 0, rules::AssociativityNone };
   }
 
   CompletionStatus apply_to(const rules::Seq *rule) {
@@ -42,7 +42,7 @@ class GetCompletionStatus : public rules::RuleFn<CompletionStatus> {
     if (left_status.is_done)
       return apply(rule->right);
     else
-      return { false, 0, AssociativityNone };
+      return { false, 0, rules::AssociativityNone };
   }
 };
 
diff --git a/src/compiler/build_tables/get_completion_status.h b/src/compiler/build_tables/get_completion_status.h
index fb341484..237f3eb2 100644
--- a/src/compiler/build_tables/get_completion_status.h
+++ b/src/compiler/build_tables/get_completion_status.h
@@ -2,6 +2,7 @@
 #define COMPILER_BUILD_TABLES_GET_COMPLETION_STATUS_H_
 
 #include "tree_sitter/compiler.h"
+#include "compiler/rules/metadata.h"
 
 namespace tree_sitter {
 namespace build_tables {
@@ -9,7 +10,7 @@ namespace build_tables {
 struct CompletionStatus {
   bool is_done;
   int precedence;
-  Associativity associativity;
+  rules::Associativity associativity;
 };
 
 CompletionStatus get_completion_status(const rule_ptr &);
diff --git a/src/compiler/build_tables/parse_conflict_manager.cc b/src/compiler/build_tables/parse_conflict_manager.cc
index 1ee3323c..967f508e 100644
--- a/src/compiler/build_tables/parse_conflict_manager.cc
+++ b/src/compiler/build_tables/parse_conflict_manager.cc
@@ -41,9 +41,9 @@ pair<bool, ConflictType> ParseConflictManager::resolve(
           return { true, ConflictTypeResolved };
         } else if (min_precedence == max_precedence) {
           switch (new_action.associativity) {
-            case AssociativityLeft:
+            case rules::AssociativityLeft:
               return { true, ConflictTypeResolved };
-            case AssociativityRight:
+            case rules::AssociativityRight:
               return { false, ConflictTypeResolved };
             default:
               return { false, ConflictTypeUnresolved };
diff --git a/src/compiler/parse_table.cc b/src/compiler/parse_table.cc
index 50788d8e..79e53a3f 100644
--- a/src/compiler/parse_table.cc
+++ b/src/compiler/parse_table.cc
@@ -14,7 +14,7 @@ using rules::Symbol;
 ParseAction::ParseAction(ParseActionType type, ParseStateId state_index,
                          Symbol symbol, size_t consumed_symbol_count,
                          PrecedenceRange precedence_range,
-                         Associativity associativity, int production_id)
+                         rules::Associativity associativity, int production_id)
     : type(type),
       symbol(symbol),
       state_index(state_index),
@@ -28,7 +28,7 @@ ParseAction::ParseAction()
       symbol(Symbol(-1)),
       state_index(-1),
       consumed_symbol_count(0),
-      associativity(AssociativityNone) {}
+      associativity(rules::AssociativityNone) {}
 
 ParseAction ParseAction::Error() {
   return ParseAction();
@@ -43,7 +43,7 @@ ParseAction ParseAction::Accept() {
 ParseAction ParseAction::Shift(ParseStateId state_index,
                                PrecedenceRange precedence_range) {
   return ParseAction(ParseActionTypeShift, state_index, Symbol(-1), 0,
-                     precedence_range, AssociativityNone, -1);
+                     precedence_range, rules::AssociativityNone, -1);
 }
 
 ParseAction ParseAction::ShiftExtra() {
@@ -60,7 +60,8 @@ ParseAction ParseAction::ReduceExtra(Symbol symbol) {
 }
 
 ParseAction ParseAction::Reduce(Symbol symbol, size_t consumed_symbol_count,
-                                int precedence, Associativity associativity,
+                                int precedence,
+                                rules::Associativity associativity,
                                 unsigned int production_id) {
   return ParseAction(ParseActionTypeReduce, 0, symbol, consumed_symbol_count,
                      { precedence, precedence }, associativity, production_id);
diff --git a/src/compiler/parse_table.h b/src/compiler/parse_table.h
index e546c929..36f11187 100644
--- a/src/compiler/parse_table.h
+++ b/src/compiler/parse_table.h
@@ -27,7 +27,7 @@ typedef enum {
 class ParseAction {
   ParseAction(ParseActionType type, ParseStateId state_index,
               rules::Symbol symbol, size_t consumed_symbol_count,
-              PrecedenceRange range, Associativity, int production_id);
+              PrecedenceRange range, rules::Associativity, int production_id);
 
  public:
   ParseAction();
@@ -35,7 +35,7 @@ class ParseAction {
   static ParseAction Error();
   static ParseAction Shift(ParseStateId state_index, PrecedenceRange precedence);
   static ParseAction Reduce(rules::Symbol symbol, size_t consumed_symbol_count,
-                            int precedence, Associativity,
+                            int precedence, rules::Associativity,
                             unsigned int production_id);
   static ParseAction ShiftExtra();
   static ParseAction ReduceExtra(rules::Symbol symbol);
@@ -47,7 +47,7 @@ class ParseAction {
   ParseStateId state_index;
   size_t consumed_symbol_count;
   PrecedenceRange precedence_range;
-  Associativity associativity;
+  rules::Associativity associativity;
   int production_id;
 };
 
diff --git a/src/compiler/prepare_grammar/flatten_grammar.cc b/src/compiler/prepare_grammar/flatten_grammar.cc
index 4b6a7f50..d787e31f 100644
--- a/src/compiler/prepare_grammar/flatten_grammar.cc
+++ b/src/compiler/prepare_grammar/flatten_grammar.cc
@@ -20,7 +20,7 @@ using std::vector;
 class FlattenRule : public rules::RuleFn<void> {
  private:
   vector<int> precedence_stack;
-  vector<Associativity> associativity_stack;
+  vector<rules::Associativity> associativity_stack;
   Production production;
 
   void apply_to(const rules::Symbol *sym) {
@@ -35,7 +35,8 @@ class FlattenRule : public rules::RuleFn<void> {
     if (precedence != 0)
       precedence_stack.push_back(precedence);
     if (associativity != 0)
-      associativity_stack.push_back(static_cast<Associativity>(associativity));
+      associativity_stack.push_back(
+        static_cast<rules::Associativity>(associativity));
 
     apply(metadata->rule);
 
@@ -57,7 +58,8 @@ class FlattenRule : public rules::RuleFn<void> {
 
  public:
   FlattenRule()
-      : precedence_stack({ 0 }), associativity_stack({ AssociativityNone }) {}
+      : precedence_stack({ 0 }),
+        associativity_stack({ rules::AssociativityNone }) {}
 
   Production flatten(const rule_ptr &rule) {
     apply(rule);
diff --git a/src/compiler/rules/metadata.h b/src/compiler/rules/metadata.h
index d93bbc9f..ea4f9ba5 100644
--- a/src/compiler/rules/metadata.h
+++ b/src/compiler/rules/metadata.h
@@ -9,6 +9,12 @@
 namespace tree_sitter {
 namespace rules {
 
+enum Associativity {
+  AssociativityNone,
+  AssociativityLeft,
+  AssociativityRight,
+};
+
 enum MetadataKey {
   START_TOKEN,
   PRECEDENCE,
diff --git a/src/compiler/rules/rules.cc b/src/compiler/rules/rules.cc
index 93941df6..49bb7ead 100644
--- a/src/compiler/rules/rules.cc
+++ b/src/compiler/rules/rules.cc
@@ -63,13 +63,26 @@ rule_ptr err(const rule_ptr &rule) {
   return choice({ rule, rules::ERROR().copy() });
 }
 
-rule_ptr prec(int precedence, const rule_ptr &rule, Associativity associativity) {
+rule_ptr prec_left(const rule_ptr &rule) {
+  return metadata(rule, { { rules::ASSOCIATIVITY, rules::AssociativityLeft } });
+}
+
+rule_ptr prec_left(int precedence, const rule_ptr &rule) {
   return metadata(rule, { { rules::PRECEDENCE, precedence },
-                          { rules::ASSOCIATIVITY, associativity } });
+                          { rules::ASSOCIATIVITY, rules::AssociativityLeft } });
+}
+
+rule_ptr prec_right(const rule_ptr &rule) {
+  return metadata(rule, { { rules::ASSOCIATIVITY, rules::AssociativityRight } });
+}
+
+rule_ptr prec_right(int precedence, const rule_ptr &rule) {
+  return metadata(rule, { { rules::PRECEDENCE, precedence },
+                          { rules::ASSOCIATIVITY, rules::AssociativityRight } });
 }
 
 rule_ptr prec(int precedence, const rule_ptr &rule) {
-  return prec(precedence, rule, AssociativityLeft);
+  return metadata(rule, { { rules::PRECEDENCE, precedence } });
 }
 
 rule_ptr token(const rule_ptr &rule) {
diff --git a/src/compiler/syntax_grammar.cc b/src/compiler/syntax_grammar.cc
index ac313a29..11681f69 100644
--- a/src/compiler/syntax_grammar.cc
+++ b/src/compiler/syntax_grammar.cc
@@ -14,11 +14,12 @@ using std::vector;
 using std::set;
 
 static const vector<Production> START_PRODUCTIONS_TOKEN_ONLY({
-  Production({ ProductionStep(rules::Symbol(0, true), 0, AssociativityNone) }),
+  Production({ ProductionStep(rules::Symbol(0, true), 0,
+                              rules::AssociativityNone) }),
 });
 
 static const vector<Production> START_PRODUCTIONS({
-  Production({ ProductionStep(rules::Symbol(0), 0, AssociativityNone) }),
+  Production({ ProductionStep(rules::Symbol(0), 0, rules::AssociativityNone) }),
 });
 
 static const vector<Production> NO_PRODUCTIONS({});
@@ -28,14 +29,14 @@ SyntaxVariable::SyntaxVariable(const string &name, VariableType type,
     : name(name), productions(productions), type(type) {}
 
 ProductionStep::ProductionStep(const rules::Symbol &symbol, int precedence,
-                               Associativity associativity)
+                               rules::Associativity associativity)
     : symbol(symbol),
       precedence(precedence),
       associativity(associativity),
       rule_id(0) {}
 
 ProductionStep::ProductionStep(const rules::Symbol &symbol, int precedence,
-                               Associativity associativity, int rule_id)
+                               rules::Associativity associativity, int rule_id)
     : symbol(symbol),
       precedence(precedence),
       associativity(associativity),
diff --git a/src/compiler/syntax_grammar.h b/src/compiler/syntax_grammar.h
index 7b18eec9..8ec876bf 100644
--- a/src/compiler/syntax_grammar.h
+++ b/src/compiler/syntax_grammar.h
@@ -6,18 +6,19 @@
 #include <set>
 #include "tree_sitter/compiler.h"
 #include "compiler/rules/symbol.h"
+#include "compiler/rules/metadata.h"
 #include "compiler/variable.h"
 
 namespace tree_sitter {
 
 struct ProductionStep {
-  ProductionStep(const rules::Symbol &, int, Associativity);
-  ProductionStep(const rules::Symbol &, int, Associativity, int);
+  ProductionStep(const rules::Symbol &, int, rules::Associativity);
+  ProductionStep(const rules::Symbol &, int, rules::Associativity, int);
   bool operator==(const ProductionStep &) const;
 
   rules::Symbol symbol;
   int precedence;
-  Associativity associativity;
+  rules::Associativity associativity;
   int rule_id;
 };