src/test/ui-fulldeps/proc-macro/auxiliary/three-equals.rs

   1 // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // no-prefer-dynamic
  12
  13 #![crate_type = "proc-macro"]
  14 #![feature(proc_macro_diagnostic, proc_macro_span)]
  15
  16 extern crate proc_macro;
  17
  18 use proc_macro::{TokenStream, TokenTree, Span, Diagnostic};
  19
  20 fn parse(input: TokenStream) -> Result<(), Diagnostic> {
  21     let mut count = 0;
  22     let mut last_span = Span::def_site();
  23     for tree in input {
  24         let span = tree.span();
  25         if count >= 3 {
  26             return Err(span.error(format!("expected EOF, found `{}`.", tree))
  27                            .span_note(last_span, "last good input was here")
  28                            .help("input must be: `===`"))
  29         }
  30
  31         if let TokenTree::Punct(ref tt) = tree {
  32             if tt.as_char() == '=' {
  33                 count += 1;
  34                 last_span = span;
  35                 continue
  36             }
  37         }
  38         return Err(span.error(format!("expected `=`, found `{}`.", tree)));
  39     }
  40
  41     if count < 3 {
  42         return Err(Span::def_site()
  43                        .error(format!("found {} equal signs, need exactly 3", count))
  44                        .help("input must be: `===`"))
  45     }
  46
  47     Ok(())
  48 }
  49
  50 #[proc_macro]
  51 pub fn three_equals(input: TokenStream) -> TokenStream {
  52     if let Err(diag) = parse(input) {
  53         diag.emit();
  54         return TokenStream::new();
  55     }
  56
  57     "3".parse().unwrap()
  58 }