Initial check in
Bug: 137197907
diff --git a/src/libsyntax_ext/concat_idents.rs b/src/libsyntax_ext/concat_idents.rs
new file mode 100644
index 0000000..8c9eb4b
--- /dev/null
+++ b/src/libsyntax_ext/concat_idents.rs
@@ -0,0 +1,75 @@
+use rustc_data_structures::thin_vec::ThinVec;
+
+use syntax::ast;
+use syntax::ext::base::{self, *};
+use syntax::feature_gate;
+use syntax::parse::token;
+use syntax::ptr::P;
+use syntax_pos::Span;
+use syntax_pos::symbol::Symbol;
+use syntax::tokenstream::TokenTree;
+
+pub fn expand_syntax_ext<'cx>(cx: &'cx mut ExtCtxt<'_>,
+ sp: Span,
+ tts: &[TokenTree])
+ -> Box<dyn base::MacResult + 'cx> {
+ if !cx.ecfg.enable_concat_idents() {
+ feature_gate::emit_feature_err(&cx.parse_sess,
+ "concat_idents",
+ sp,
+ feature_gate::GateIssue::Language,
+ feature_gate::EXPLAIN_CONCAT_IDENTS);
+ }
+
+ if tts.is_empty() {
+ cx.span_err(sp, "concat_idents! takes 1 or more arguments.");
+ return DummyResult::any(sp);
+ }
+
+ let mut res_str = String::new();
+ for (i, e) in tts.iter().enumerate() {
+ if i & 1 == 1 {
+ match *e {
+ TokenTree::Token(_, token::Comma) => {}
+ _ => {
+ cx.span_err(sp, "concat_idents! expecting comma.");
+ return DummyResult::any(sp);
+ }
+ }
+ } else {
+ match *e {
+ TokenTree::Token(_, token::Ident(ident, _)) =>
+ res_str.push_str(&ident.as_str()),
+ _ => {
+ cx.span_err(sp, "concat_idents! requires ident args.");
+ return DummyResult::any(sp);
+ }
+ }
+ }
+ }
+
+ let ident = ast::Ident::new(Symbol::intern(&res_str), sp.apply_mark(cx.current_expansion.mark));
+
+ struct ConcatIdentsResult { ident: ast::Ident }
+
+ impl base::MacResult for ConcatIdentsResult {
+ fn make_expr(self: Box<Self>) -> Option<P<ast::Expr>> {
+ Some(P(ast::Expr {
+ id: ast::DUMMY_NODE_ID,
+ node: ast::ExprKind::Path(None, ast::Path::from_ident(self.ident)),
+ span: self.ident.span,
+ attrs: ThinVec::new(),
+ }))
+ }
+
+ fn make_ty(self: Box<Self>) -> Option<P<ast::Ty>> {
+ Some(P(ast::Ty {
+ id: ast::DUMMY_NODE_ID,
+ node: ast::TyKind::Path(None, ast::Path::from_ident(self.ident)),
+ span: self.ident.span,
+ }))
+ }
+ }
+
+ Box::new(ConcatIdentsResult { ident })
+}
