parse nullary range operator (#25)

Co-authored-by: Jonatan Kłosko <jonatanklosko@gmail.com>

grammar.js

@@ -16,6 +16,7 @@ const PREC = {
   XOR_OP: 140,
   TERNARY_OP: 150,
   CONCAT_OPS: 160,
+  RANGE_OP: 160,
   ADD_OPS: 170,
   MULT_OPS: 180,
   POWER_OP: 190,
@@ -33,13 +34,13 @@ const COMP_OPS = ["==", "!=", "=~", "===", "!=="];
 const REL_OPS = ["<", ">", "<=", ">="];
 const ARROW_OPS = ["|>", "<<<", ">>>", "<<~", "~>>", "<~", "~>", "<~>", "<|>"];
 const IN_OPS = ["in", "not in"];
-const CONCAT_OPS = ["++", "--", "+++", "---", "..", "<>"];
+const CONCAT_OPS = ["++", "--", "+++", "---", "<>"];
 const ADD_OPS = ["+", "-"];
 const MULT_OPS = ["*", "/"];
 const UNARY_OPS = ["+", "-", "!", "^", "~~~", "not"];
 
 const ALL_OPS = [
-  ["->", "when", "::", "|", "=>", "&", "=", "^^^", "//", "**", ".", "@"],
+  ["->", "when", "::", "|", "=>", "&", "=", "^^^", "//", "..", "**", ".", "@"],
   IN_MATCH_OPS,
   OR_OPS,
   AND_OPS,
@@ -213,6 +214,7 @@ module.exports = grammar({
         $.tuple,
         $.bitstring,
         $.map,
+        $._nullary_operator,
         $.unary_operator,
         $.binary_operator,
         $.dot,
@@ -426,6 +428,11 @@ module.exports = grammar({
         )
       ),
 
+    _nullary_operator: ($) =>
+      // Nullary operators don't have any child nodes, so we reuse the
+      // operator_identifier node
+      alias(prec(PREC.RANGE_OP, ".."), $.operator_identifier),
+
     unary_operator: ($) =>
       choice(
         unaryOp($, prec, PREC.CAPTURE_OP, "&", $._capture_expression),
@@ -480,6 +487,7 @@ module.exports = grammar({
         binaryOp($, prec.left, PREC.XOR_OP, "^^^"),
         binaryOp($, prec.right, PREC.TERNARY_OP, "//"),
         binaryOp($, prec.right, PREC.CONCAT_OPS, choice(...CONCAT_OPS)),
+        binaryOp($, prec.right, PREC.RANGE_OP, ".."),
         binaryOp($, prec.left, PREC.ADD_OPS, choice(...ADD_OPS)),
         binaryOp($, prec.left, PREC.MULT_OPS, choice(...MULT_OPS)),
         binaryOp($, prec.left, PREC.POWER_OP, "**"),
@@ -524,6 +532,10 @@ module.exports = grammar({
         alias($._not_in, "not in"),
         "^^",
         ...CONCAT_OPS,
+        // The range operator has both a binary and a nullary version.
+        // The nullary version is already parsed as operator_identifier,
+        // so it covers this case
+        // ".."
         ...MULT_OPS,
         "**",
         "->",

test/corpus/expression/operator.txt

@@ -656,6 +656,31 @@ x +y +z
             (unary_operator
               (identifier))))))))
 
+=====================================
+nullary range
+=====================================
+
+..
+Enum.to_list(..)
+not ..
+range = ..
+
+---
+
+(source
+  (operator_identifier)
+  (call
+    (dot
+      (alias)
+      (identifier))
+    (arguments
+      (operator_identifier)))
+  (unary_operator
+    (operator_identifier))
+  (binary_operator
+    (identifier)
+    (operator_identifier)))
+
 =====================================
 stepped range
 =====================================

test/highlight/operators.ex

@@ -82,3 +82,8 @@ y = true and false
 #                           ^ module
 #                                 ^ operator
 #                                  ^ function
+
+range = ..
+# <- variable
+#     ^ operator
+#        ^ operator