Support multidimensional subscripts

This change allows commas inside subscripts. ```cpp auto x = a[1, 2, 3]; ``` From C++23, array subscripts work like arguments to `operator[]` as an n-ary function. Before C++23, `operator[]` must be a unary function, but before C++20, it's possible to use the comma operator inside subscript expressions - and this is done in libraries that use expression templates to achieve multidimensional array syntax. Use of the comma operator in subscript expressions was deprecated in C++20 to make way for the C++23 change to n-ary `operator[]`.
tree-sitter · Aug 6, 2023 · 472002f · 472002f
1 parent f88bf81
commit 472002f
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Showing 5 changed files with 318,112 additions and 316,202 deletions.
diff --git a/grammar.js b/grammar.js
@@ -880,11 +880,14 @@ module.exports = grammar(C, {
 
     subscript_expression: $ => prec(PREC.SUBSCRIPT, seq(
       field('argument', $._expression),
-      '[',
-      field('index', choice($._expression, $.initializer_list)),
-      ']',
+      field('indices', $.subscript_argument_list),
     )),
 
+    subscript_argument_list: $ => seq(
+      '[',
+      commaSep(choice($._expression, $.initializer_list)),
+      ']',
+    ),
 
     call_expression: ($, original) => choice(original, seq(
       field('function', $.primitive_type),

diff --git a/src/grammar.json b/src/grammar.json
@@ -6860,30 +6860,13 @@
               "name": "_expression"
             }
           },
-          {
-            "type": "STRING",
-            "value": "["
-          },
           {
             "type": "FIELD",
-            "name": "index",
+            "name": "indices",
             "content": {
-              "type": "CHOICE",
-              "members": [
-                {
-                  "type": "SYMBOL",
-                  "name": "_expression"
-                },
-                {
-                  "type": "SYMBOL",
-                  "name": "initializer_list"
-                }
-              ]
+              "type": "SYMBOL",
+              "name": "subscript_argument_list"
             }
-          },
-          {
-            "type": "STRING",
-            "value": "]"
           }
         ]
       }
@@ -11439,6 +11422,70 @@
         }
       ]
     },
+    "subscript_argument_list": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "["
+        },
+        {
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "SEQ",
+              "members": [
+                {
+                  "type": "CHOICE",
+                  "members": [
+                    {
+                      "type": "SYMBOL",
+                      "name": "_expression"
+                    },
+                    {
+                      "type": "SYMBOL",
+                      "name": "initializer_list"
+                    }
+                  ]
+                },
+                {
+                  "type": "REPEAT",
+                  "content": {
+                    "type": "SEQ",
+                    "members": [
+                      {
+                        "type": "STRING",
+                        "value": ","
+                      },
+                      {
+                        "type": "CHOICE",
+                        "members": [
+                          {
+                            "type": "SYMBOL",
+                            "name": "_expression"
+                          },
+                          {
+                            "type": "SYMBOL",
+                            "name": "initializer_list"
+                          }
+                        ]
+                      }
+                    ]
+                  }
+                }
+              ]
+            },
+            {
+              "type": "BLANK"
+            }
+          ]
+        },
+        {
+          "type": "STRING",
+          "value": "]"
+        }
+      ]
+    },
     "co_await_expression": {
       "type": "PREC_LEFT",
       "value": 14,