src/test/run-make/coverage/generator.rs

   1 #![feature(generators, generator_trait)]
   2
   3 use std::ops::{Generator, GeneratorState};
   4 use std::pin::Pin;
   5
   6 // The following implementation of a function called from a `yield` statement
   7 // (apparently requiring the Result and the `String` type or constructor)
   8 // creates conditions where the `generator::StateTransform` MIR transform will
   9 // drop all `Counter` `Coverage` statements from a MIR. `simplify.rs` has logic
  10 // to handle this condition, and still report dead block coverage.
  11 fn get_u32(val: bool) -> Result<u32, String> {
  12     if val { Ok(1) } else { Err(String::from("some error")) }
  13 }
  14
  15 fn main() {
  16     let is_true = std::env::args().len() == 1;
  17     let mut generator = || {
  18         yield get_u32(is_true);
  19         return "foo";
  20     };
  21
  22     match Pin::new(&mut generator).resume(()) {
  23         GeneratorState::Yielded(Ok(1)) => {}
  24         _ => panic!("unexpected return from resume"),
  25     }
  26     match Pin::new(&mut generator).resume(()) {
  27         GeneratorState::Complete("foo") => {}
  28         _ => panic!("unexpected return from resume"),
  29     }
  30 }