Expand description
§syn-locator
syn-locator helps you to find source code locations of syn nodes.
§When to use
If you read a rust file then parse the read string through the syn::parse_str,
you will lose span information. This crate finds source code locations of syntax
tree nodes by simple string comparison.
§Example
use syn_locator::*;
// Assumes that we read this code from a file.
let file_path = "/path/to/file.rs";
let code = r"
struct Foo {
a: i32,
}
";
let syn = syn::parse_str::<syn::File>(code).unwrap();
// Finds location of the syntax tree.
let syn = std::pin::Pin::new(&syn);
syn.locate_as_entry(file_path, code.to_owned());
// Picks a syntax tree node.
let item_struct = match &syn.items[0] {
syn::Item::Struct(item_struct) => item_struct,
_ => unreachable!()
};
let field_ty = &item_struct.fields.iter().next().unwrap().ty;
// Then, we can get some info from the syntax tree node.
assert_eq!(field_ty.location(), Location {
file_path,
start: 37, // Byte offset
end: 40 // Byte offset
});
assert_eq!(field_ty.location_message(), "/path/to/file.rs:3: i32");