Replace custom errors with native panic codes in DoubleEndedQueue (#4872)

Co-authored-by: ernestognw <ernestognw@gmail.com>

docs/templates/contract.hbs

@@ -74,6 +74,23 @@ import "@openzeppelin/{{__item_context.file.absolutePath}}";
 --
 {{/if}}
 
+{{#if has-internal-variables}}
+[.contract-index]
+.Internal Variables
+--
+{{#each inheritance}}
+{{#unless @first}}
+[.contract-subindex-inherited]
+.{{name}}
+{{/unless}}
+{{#each internal-variables}}
+* {xref-{{anchor~}} }[`++{{typeDescriptions.typeString}} {{#if constant}}constant{{/if}} {{name}}++`]
+{{/each}}
+
+{{/each}}
+--
+{{/if}}
+
 {{#each modifiers}}
 [.contract-item]
 [[{{anchor}}]]
@@ -109,3 +126,12 @@ import "@openzeppelin/{{__item_context.file.absolutePath}}";
 {{{natspec.dev}}}
 
 {{/each}}
+
+{{#each internal-variables}}
+[.contract-item]
+[[{{anchor}}]]
+==== `{{typeDescriptions.typeString}} [.contract-item-name]#++{{name}}++#` [.item-kind]#internal{{#if constant}} constant{{/if}}#
+
+{{{natspec.dev}}}
+
+{{/each}}

docs/templates/properties.js

@@ -39,6 +39,14 @@ module.exports['has-errors'] = function ({ item }) {
   return item.inheritance.some(c => c.errors.length > 0);
 };
 
+module.exports['internal-variables'] = function ({ item }) {
+  return item.variables.filter(({ visibility }) => visibility === 'internal');
+};
+
+module.exports['has-internal-variables'] = function ({ item }) {
+  return module.exports['internal-variables']({ item }).length > 0;
+};
+
 module.exports.functions = function ({ item }) {
   return [
     ...[...findAll('FunctionDefinition', item)].filter(f => f.visibility !== 'private'),