Wrong definition of identifiers in Rust Reference

[matklad]

Rust reference says:

An identifier is any nonempty Unicode2 string of the following form:

• The first character has property XID_start
• The remaining characters have property XID_continue

The problem with this is that _ (LOW LINE) is not XID_start (reference: http://www.unicode.org/Public/UCD/latest/ucd/DerivedCoreProperties.txt), but _ignored is a valid Rust identifier. Rust lexer explicitly tests for the _ https://github.com/rust-lang/rust/blob/master/src/libsyntax/parse/lexer/mod.rs#L1399.

I guess the correct wording would be (keeping in mind that _ by itself is not a valid identifier):

EIther
   * The first character has property XID_start
   * The remaining characters have property XID_continue
Or
   * The first character is _
   * The second character has property XID_continue
   * The remaining characters have property XID_continue