如何匹配关键字与pest？

Question

我正在尝试解析如下所示的行

MyTupleComponent str, str

使用语法

cname = _{ (ASCII_ALPHANUMERIC | "_")+ }

ints = { "i8" | "i16" | "i32" | "i64" | "i128" | "isize" }
uints = { "u8" | "u16" | "u32" | "u64" | "u128" | "usize" }
strings = { "str" | "String" }
types = { strings | ints | uints }

tuple_component = { cname ~ (types ~ ("," ~ types)?)+ }

但最终结果是

Err(Error { variant: ParsingError { positives: [types], negatives: [] }, location: Pos(20), line_col: Pos((1, 21)), path: None, line: "MyTupleComponent str, str", continued_line: None })

有人知道为什么规则不能正确匹配吗？

Answer 1

你可以走两条路：

正如@ZachThompson指出的，定义WHITESPACE。如果这样做，请将cname设置为原子的，以防止它捕获字母数字和空格。

下面的测试语法看起来不错：

WHITESPACE = _{ " " }
cname = @{ (ASCII_ALPHANUMERIC | "_")+ }

ints = { "i8" | "i16" | "i32" | "i64" | "i128" | "isize" }
uints = { "u8" | "u16" | "u32" | "u64" | "u128" | "usize" }
strings = { "str" | "String" }
types = { strings | ints | uints }

tuple_component = { cname ~ (types ~ ("," ~ types)?)+ }

file = { tuple_component ~ EOI }

否则，您可以手动考虑空间。这种方法也可以，但它不能随着语法的增长而扩展。

附注:您是否打算解析像MyTupleComponent str, str str, str这样的表达式，而不使用逗号将第二个元组与第一个元组分开？它目前可以很好地解析。您可能希望将该规则简化为

tuple_component = { cname ~ types ~ ("," ~ types)* }