Add pm_unexpected_node_create function

Author: thomasmarshall

config.yml

@@ -3687,8 +3687,12 @@ nodes:
           /(?<foo>bar)/ =~ baz
           ^^^^^^^^^^^^^^^^^^^^
   - name: ErrorRecoveryNode
+    fields:
+      - name: child
+        type: node?
+        kind: Node
     comment: |
-      Represents a node that is missing from the source and results in a syntax error.
+      Represents a node that is either missing or unexpected and results in a syntax error.
   - name: ModuleNode
     fields:
       - name: locals

lib/prism/node_ext.rb

@@ -208,7 +208,7 @@ def child
       if name
         ConstantReadNode.new(source, -1, name_loc, 0, name)
       else
-        ErrorRecoveryNode.new(source, -1, location, 0)
+        ErrorRecoveryNode.new(source, -1, location, 0, nil)
       end
     end
   end
@@ -249,7 +249,7 @@ def child
       if name
         ConstantReadNode.new(source, -1, name_loc, 0, name)
       else
-        ErrorRecoveryNode.new(source, -1, location, 0)
+        ErrorRecoveryNode.new(source, -1, location, 0, nil)
       end
     end
   end

src/prism.c

@@ -1965,7 +1965,23 @@ pm_missing_node_create(pm_parser_t *parser, const uint8_t *start, const uint8_t
     pm_error_recovery_node_t *node = PM_NODE_ALLOC(parser, pm_error_recovery_node_t);
 
     *node = (pm_error_recovery_node_t) {
-        .base = PM_NODE_INIT(parser, PM_ERROR_RECOVERY_NODE, 0, start, end)
+        .base = PM_NODE_INIT(parser, PM_ERROR_RECOVERY_NODE, 0, start, end),
+        .child = NULL
+    };
+
+    return node;
+}
+
+/**
+ * Allocate a new ErrorRecoveryNode node that wraps an unexpected child node.
+ */
+PRISM_ATTRIBUTE_UNUSED static pm_error_recovery_node_t *
+pm_unexpected_node_create(pm_parser_t *parser, pm_node_t *child) {
+    pm_error_recovery_node_t *node = PM_NODE_ALLOC(parser, pm_error_recovery_node_t);
+
+    *node = (pm_error_recovery_node_t) {
+        .base = PM_NODE_INIT(parser, PM_ERROR_RECOVERY_NODE, 0, child->location.start, child->location.end),
+        .child = child
     };
 
     return node;