refactor lexer to use idiomatic borrowing

[matklad]

No description provided.

[matklad]

r? @petrochenkov

[rust-highfive]

r? @pnkfelix

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[matklad]

One thing I find confusing is

    fn name_from(&self, start: BytePos) -> ast::Name {
        debug!("taking an ident from {:?} to {:?}", start, self.pos);
        Symbol::intern(self.str_from(start))
    }

It's not obvious that ast::Name and SYmbol are aliases. Perhaps something like

    fn intern_from(&self, start: BytePos) -> Symbol {
        debug!("taking an ident from {:?} to {:?}", start, self.pos);
        Symbol::intern(self.str_from(start))
    }

would be better? If so, it makes sense to do this in this PR as well

[petrochenkov]

@matklad
ast::Name is conventionally used for identifier symbols from ast::Ident (although people just use Symbol randomly now).

In this case the symbols are not necessarily identifiers, so they shouldn't use Name/name.
(I'd rather use symbol_from than intern_from).

[matklad]

Makes sense, added the second commit with rename

[matklad]

... and replaced the few remaning usages of ast::Name in the lexer: it's hard to maintain convention unless it is of the form "always do X" :)

[petrochenkov]

@bors r+

[bors]

📌 Commit 57db25e has been approved by petrochenkov