[ruby/prism] Don't add an invalid identifier capture to locals

(https://github.com/ruby/prism/pull/1836)

* Don't add an invalid identifier capture to locals

Fix https://github.com/ruby/prism/pull/1815

* Delay creating a MatchWriteNode

https://github.com/ruby/prism/pull/1836#discussion_r1393716600

https://github.com/ruby/prism/commit/635f595a36

1 files changed, 39 insertions, 2 deletions

diff --git a/prism/prism.c b/prism/prism.c
index 2b027a9bde..850b35c3c7 100644
--- a/prism/prism.c
+++ b/prism/prism.c
@@ -15686,6 +15686,25 @@ parse_call_operator_write(pm_parser_t *parser, pm_call_node_t *call_node, const
     }
 }
 
+static bool
+name_is_identifier(pm_parser_t *parser, const uint8_t *source, size_t length) {
+    if (length == 0) {
+        return false;
+    }
+
+    size_t width = char_is_identifier_start(parser, source);
+    if (!width) {
+        return false;
+    }
+
+    uint8_t *cursor = ((uint8_t *)source) + width;
+    while (cursor < source + length && (width = char_is_identifier(parser, cursor))) {
+        cursor += width;
+    }
+
+    return cursor == source + length;
+}
+
 /**
  * Potentially change a =~ with a regular expression with named captures into a
  * match write node.
@@ -15696,7 +15715,9 @@ parse_regular_expression_named_captures(pm_parser_t *parser, const pm_string_t *
     pm_node_t *result;
 
     if (pm_regexp_named_capture_group_names(pm_string_source(content), pm_string_length(content), &named_captures, parser->encoding_changed, &parser->encoding) && (named_captures.length > 0)) {
-        pm_match_write_node_t *match = pm_match_write_node_create(parser, call);
+        // Since we should not create a MatchWriteNode when all capture names are invalid,
+        // creating a MatchWriteNode is delayed here.
+        pm_match_write_node_t *match = NULL;
 
         for (size_t index = 0; index < named_captures.length; index++) {
             pm_string_t *name = &named_captures.strings[index];
@@ -15704,6 +15725,10 @@ parse_regular_expression_named_captures(pm_parser_t *parser, const pm_string_t *
             const uint8_t *source = pm_string_source(name);
             size_t length = pm_string_length(name);
 
+            if (!name_is_identifier(parser, source, length)) {
+                continue;
+            }
+
             pm_constant_id_t local;
             if (content->type == PM_STRING_SHARED) {
                 // If the unescaped string is a slice of the source, then we can
@@ -15731,10 +15756,22 @@ parse_regular_expression_named_captures(pm_parser_t *parser, const pm_string_t *
                 }
             }
 
+            if (match == NULL) {
+                match = pm_match_write_node_create(parser, call);
+            }
+
+            if (pm_constant_id_list_includes(&match->locals, local)) {
+                continue;
+            }
+
             pm_constant_id_list_append(&match->locals, local);
         }
 
-        result = (pm_node_t *) match;
+        if (match != NULL) {
+            result = (pm_node_t *) match;
+        } else {
+            result = (pm_node_t *) call;
+        }
     } else {
         result = (pm_node_t *) call;
     }