Ensure ranges are non-associative

Author: kddnewton

config.yml

@@ -267,6 +267,7 @@ errors:
   - UNEXPECTED_INDEX_BLOCK
   - UNEXPECTED_INDEX_KEYWORDS
   - UNEXPECTED_MULTI_WRITE
+  - UNEXPECTED_RANGE_OPERATOR
   - UNEXPECTED_SAFE_NAVIGATION
   - UNEXPECTED_TOKEN_CLOSE_CONTEXT
   - UNEXPECTED_TOKEN_IGNORE

src/prism.c

@@ -17737,6 +17737,15 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, b
             parser_lex(parser);
 
             pm_node_t *right = parse_expression(parser, pm_binding_powers[operator.type].left, false, PM_ERR_EXPECT_EXPRESSION_AFTER_OPERATOR);
+
+            // Unary .. and ... are special because these are non-associative
+            // operators that can also be unary operators. In this case we need
+            // to explicitly reject code that has a .. or ... that follows this
+            // expression.
+            if (match2(parser, PM_TOKEN_DOT_DOT, PM_TOKEN_DOT_DOT_DOT)) {
+                pm_parser_err_current(parser, PM_ERR_UNEXPECTED_RANGE_OPERATOR);
+            }
+
             return (pm_node_t *) pm_range_node_create(parser, NULL, &operator, right);
         }
         case PM_TOKEN_FLOAT:
@@ -20987,15 +20996,6 @@ parse_expression(pm_parser_t *parser, pm_binding_power_t binding_power, bool acc
                 return node;
             }
             break;
-        case PM_RANGE_NODE:
-            // Range operators are non-associative, so that it does not
-            // associate with other range operators (i.e. `..1..` should be
-            // rejected). For this reason, we check such a case for unary ranges
-            // here, and if so, it returns the node immediately.
-            if ((((pm_range_node_t *) node)->left == NULL) && pm_binding_powers[parser->current.type].left >= PM_BINDING_POWER_RANGE) {
-                return node;
-            }
-            break;
         default:
             break;
     }

templates/src/diagnostic.c.erb

@@ -348,6 +348,7 @@ static const pm_diagnostic_data_t diagnostic_messages[PM_DIAGNOSTIC_ID_MAX] = {
     [PM_ERR_UNEXPECTED_INDEX_BLOCK]             = { "unexpected block arg given in index assignment; blocks are not allowed in index assignment expressions", PM_ERROR_LEVEL_SYNTAX },
     [PM_ERR_UNEXPECTED_INDEX_KEYWORDS]          = { "unexpected keyword arg given in index assignment; keywords are not allowed in index assignment expressions", PM_ERROR_LEVEL_SYNTAX },
     [PM_ERR_UNEXPECTED_MULTI_WRITE]             = { "unexpected multiple assignment; multiple assignment is not allowed in this context", PM_ERROR_LEVEL_SYNTAX },
+    [PM_ERR_UNEXPECTED_RANGE_OPERATOR]          = { "unexpected range operator; .. and ... are non-associative and cannot be chained", PM_ERROR_LEVEL_SYNTAX },
     [PM_ERR_UNEXPECTED_SAFE_NAVIGATION]         = { "&. inside multiple assignment destination", PM_ERROR_LEVEL_SYNTAX },
     [PM_ERR_UNEXPECTED_TOKEN_CLOSE_CONTEXT]     = { "unexpected %s, assuming it is closing the parent %s", PM_ERROR_LEVEL_SYNTAX },
     [PM_ERR_UNEXPECTED_TOKEN_IGNORE]            = { "unexpected %s, ignoring it", PM_ERROR_LEVEL_SYNTAX },

test/prism/errors_test.rb

@@ -1975,8 +1975,8 @@ def test_binary_range_with_left_unary_range
       RUBY
 
       assert_errors expression(source), source, [
-        ["unexpected .., expecting end-of-input", 3..5],
-        ["unexpected .., ignoring it", 3..5],
+        ["unexpected range operator; .. and ... are non-associative and cannot be chained", 3..5],
+        ["unexpected range operator; .. and ... are non-associative and cannot be chained", 10..12],
         ["unexpected .., expecting end-of-input", 10..12],
         ["unexpected .., ignoring it", 10..12]
       ]