compiler/rustc_builtin_macros/src/concat_idents.rs

   1 use rustc_ast as ast;
   2 use rustc_ast::ptr::P;
   3 use rustc_ast::token::{self, Token};
   4 use rustc_ast::tokenstream::{TokenStream, TokenTree};
   5 use rustc_expand::base::{self, *};
   6 use rustc_span::symbol::{Ident, Symbol};
   7 use rustc_span::Span;
   8
   9 pub fn expand_concat_idents<'cx>(
  10     cx: &'cx mut ExtCtxt<'_>,
  11     sp: Span,
  12     tts: TokenStream,
  13 ) -> Box<dyn base::MacResult + 'cx> {
  14     if tts.is_empty() {
  15         cx.span_err(sp, "concat_idents! takes 1 or more arguments.");
  16         return DummyResult::any(sp);
  17     }
  18
  19     let mut res_str = String::new();
  20     for (i, e) in tts.into_trees().enumerate() {
  21         if i & 1 == 1 {
  22             match e {
  23                 TokenTree::Token(Token { kind: token::Comma, .. }) => {}
  24                 _ => {
  25                     cx.span_err(sp, "concat_idents! expecting comma.");
  26                     return DummyResult::any(sp);
  27                 }
  28             }
  29         } else {
  30             if let TokenTree::Token(token) = e {
  31                 if let Some((ident, _)) = token.ident() {
  32                     res_str.push_str(&ident.name.as_str());
  33                     continue;
  34                 }
  35             }
  36
  37             cx.span_err(sp, "concat_idents! requires ident args.");
  38             return DummyResult::any(sp);
  39         }
  40     }
  41
  42     let ident = Ident::new(Symbol::intern(&res_str), cx.with_call_site_ctxt(sp));
  43
  44     struct ConcatIdentsResult {
  45         ident: Ident,
  46     }
  47
  48     impl base::MacResult for ConcatIdentsResult {
  49         fn make_expr(self: Box<Self>) -> Option<P<ast::Expr>> {
  50             Some(P(ast::Expr {
  51                 id: ast::DUMMY_NODE_ID,
  52                 kind: ast::ExprKind::Path(None, ast::Path::from_ident(self.ident)),
  53                 span: self.ident.span,
  54                 attrs: ast::AttrVec::new(),
  55                 tokens: None,
  56             }))
  57         }
  58
  59         fn make_ty(self: Box<Self>) -> Option<P<ast::Ty>> {
  60             Some(P(ast::Ty {
  61                 id: ast::DUMMY_NODE_ID,
  62                 kind: ast::TyKind::Path(None, ast::Path::from_ident(self.ident)),
  63                 span: self.ident.span,
  64                 tokens: None,
  65             }))
  66         }
  67     }
  68
  69     Box::new(ConcatIdentsResult { ident })
  70 }