bug: braced default argument (= {}) in a parameter list is an ERROR
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评估
- 难度
- 2/5
- 预计耗时
- 1-3 小时
- 新手友好度
- 84/100
- Issue 类型
- 缺陷
- 描述清晰度
- 描述清楚
- 活跃度
- 活跃
- 技术栈
- javascript
- 领域
- compilers
调研方向
Issue 指出 optional_parameter_declaration 对 default_value 只接受表达式，并以附近接受 initializer_list 的 init_declarator 为例。阅读这些语法规则，然后用 tree-sitter 解析 repro 中的三个声明，以确认当前的错误。当三个默认花括号列表都能作为 initializer_list 解析且没有错误时，任务即告完成。
由索引模型根据 Issue 内容生成。
描述
Did you check existing issues?
- I have read all the tree-sitter docs if it relates to using the parser
- I have searched the existing issues of tree-sitter-cpp
Tree-Sitter CLI Version, if relevant (output of tree-sitter --version)
No response
Describe the bug
A default argument written as a braced initializer list, valid since C++11 ([dcl.fct.default] allows an initializer-clause, which includes a braced-init-list), makes the tree contain an error. The default value is recovered as a compound_literal_expression with a MISSING type_identifier, so has_error is true for the whole file.
This is common in modern code (Options = {}, std::vector v = {1, 2}). In one C++20 project it was the most frequent cause of parse errors: 16 of 131 files failed only because of it.
optional_parameter_declaration accepts only an expression as default_value, both in v0.23.4 and on master (c009222), while init_declarator already accepts initializer_list.
Steps To Reproduce/Bad Parse Tree
Save the repro below as repro.cpp.
Run tree-sitter parse repro.cpp, or parse it with any binding.
Parse tree from tree-sitter-cpp 0.23.4 (named nodes only), first declaration:
translation_unit
declaration
type: primitive_type
declarator: function_declarator
declarator: identifier
parameters: parameter_list
optional_parameter_declaration
type: primitive_type
declarator: identifier
default_value: compound_literal_expression
type: type_identifier (MISSING)
value: initializer_list
The other two declarations give the same compound_literal_expression with a MISSING type_identifier.
Expected Behavior/Parse Tree
No error; the braced list is the default value:
optional_parameter_declaration
type: primitive_type
declarator: identifier
default_value: initializer_list
A possible fix is field('default_value', choice($.expression, $.initializer_list)) in optional_parameter_declaration, as init_declarator does for its value.
Repro
void f(int x = {});
void g(std::vector<int> v = {1, 2});
struct Options {};
void h(Options = {});
- 主要语言
- JavaScript
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- 30 天内没有已合并 PR
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