[ruby/prism] Fix hash pattern rest

https://github.com/ruby/prism/commit/43c4232cfc

3 files changed, 17 insertions, 6 deletions

diff --git a/prism/diagnostic.c b/prism/diagnostic.c
index eaf6112d18..1fc8c50cb5 100644
--- a/prism/diagnostic.c
+++ b/prism/diagnostic.c
@@ -219,6 +219,7 @@ static const char* const diagnostic_messages[PM_DIAGNOSTIC_ID_LEN] = {
     [PM_ERR_PATTERN_EXPRESSION_AFTER_PIN]       = "expected a pattern expression after the `^` pin operator",
     [PM_ERR_PATTERN_EXPRESSION_AFTER_PIPE]      = "expected a pattern expression after the `|` operator",
     [PM_ERR_PATTERN_EXPRESSION_AFTER_RANGE]     = "expected a pattern expression after the range operator",
+    [PM_ERR_PATTERN_EXPRESSION_AFTER_REST]      = "unexpected pattern expression after the `**` expression",
     [PM_ERR_PATTERN_HASH_KEY]                   = "expected a key in the hash pattern",
     [PM_ERR_PATTERN_HASH_KEY_LABEL]             = "expected a label as the key in the hash pattern", // TODO // THIS // AND // ABOVE // IS WEIRD
     [PM_ERR_PATTERN_IDENT_AFTER_HROCKET]        = "expected an identifier after the `=>` operator",
diff --git a/prism/diagnostic.h b/prism/diagnostic.h
index a1e0b6d0d8..fc1f0c2b4b 100644
--- a/prism/diagnostic.h
+++ b/prism/diagnostic.h
@@ -211,6 +211,7 @@ typedef enum {
     PM_ERR_PATTERN_EXPRESSION_AFTER_PIN,
     PM_ERR_PATTERN_EXPRESSION_AFTER_PIPE,
     PM_ERR_PATTERN_EXPRESSION_AFTER_RANGE,
+    PM_ERR_PATTERN_EXPRESSION_AFTER_REST,
     PM_ERR_PATTERN_HASH_KEY,
     PM_ERR_PATTERN_HASH_KEY_LABEL,
     PM_ERR_PATTERN_IDENT_AFTER_HROCKET,
diff --git a/prism/prism.c b/prism/prism.c
index 4b15f65859..dfb1affa88 100644
--- a/prism/prism.c
+++ b/prism/prism.c
@@ -13121,10 +13121,15 @@ parse_pattern_hash(pm_parser_t *parser, pm_node_t *first_assoc) {
             break;
         }
 
-        pm_node_t *assoc;
-
         if (match1(parser, PM_TOKEN_USTAR_STAR)) {
-            assoc = parse_pattern_keyword_rest(parser);
+            pm_node_t *assoc = parse_pattern_keyword_rest(parser);
+
+            if (rest == NULL) {
+                rest = assoc;
+            } else {
+                pm_parser_err_node(parser, assoc, PM_ERR_PATTERN_EXPRESSION_AFTER_REST);
+                pm_node_list_append(&assocs, assoc);
+            }
         } else {
             expect1(parser, PM_TOKEN_LABEL, PM_ERR_PATTERN_LABEL_AFTER_COMMA);
             pm_node_t *key = (pm_node_t *) pm_symbol_node_label_create(parser, &parser->previous);
@@ -13138,10 +13143,14 @@ parse_pattern_hash(pm_parser_t *parser, pm_node_t *first_assoc) {
             }
 
             pm_token_t operator = not_provided(parser);
-            assoc = (pm_node_t *) pm_assoc_node_create(parser, key, &operator, value);
-        }
+            pm_node_t *assoc = (pm_node_t *) pm_assoc_node_create(parser, key, &operator, value);
+
+            if (rest != NULL) {
+                pm_parser_err_node(parser, assoc, PM_ERR_PATTERN_EXPRESSION_AFTER_REST);
+            }
 
-        pm_node_list_append(&assocs, assoc);
+            pm_node_list_append(&assocs, assoc);
+        }
     }
 
     pm_hash_pattern_node_t *node = pm_hash_pattern_node_node_list_create(parser, &assocs, rest);