backtrace problem on nightly

[Sven Kanoldt]

In a strange constellation I'm running into the following error:

error[E0308]: mismatched types
   --> /Users/I563162/.cargo/registry/src/github.com-1ecc6299db9ec823/http-types-2.12.0/src/error.rs:114:18
    |
114 |             Some(backtrace)
    |             ---- ^^^^^^^^^ expected `&Backtrace`, found enum `std::option::Option`
    |             |
    |             arguments to this enum variant are incorrect
    |
    = note: expected reference `&Backtrace`
                    found enum `std::option::Option<&Backtrace>`

looking at the code:

http-types/src/error.rs

Lines 111 to 118 in 6f38b3e

 pub fn backtrace(&self) -> Option<&std::backtrace::Backtrace> { 
     let backtrace = self.error.backtrace(); 
     if let std::backtrace::BacktraceStatus::Captured = backtrace.status() { 
         Some(backtrace) 
     } else { 
         None 
     } 
 } 

I see no change in over 2 years. Also on the anyhow crate (self.error is of type anyhow::Error) I cannot see any change on the backtrace() method.

However a fix like this would solve the problem:

- let backtrace = self.error.backtrace();
+ let backtrace = self.error.backtrace()?;

Things I've used:

• depdency tree to http-types:

  http-types v2.12.0
  ├── async-h1 v2.3.3
  │   └── tide v0.16.0
  

• http-types version 2.12.0
• anyhow version 1.0.65
• rust version

  cargo --version && rustc --version
  cargo 1.63.0-nightly (38472bc19 2022-05-31)
  rustc 1.63.0-nightly (5435ed691 2022-06-07)

[Sven Kanoldt]

it turns out that versions of anyhow < 1.0.39 don't have that problem, because there the return type is &Backtrace. Newer versions wrap this with Option<>.