1 use std::env;
2 use std::fs;
3 use std::path::Path;
4 use std::process::{Command, ExitStatus, Stdio};
5 use std::str;
6
7 // This code exercises the surface area that we expect of the Error generic
8 // member access API. If the current toolchain is able to compile it, then
9 // thiserror is able to provide backtrace support.
10 const PROBE: &str = r#"
11 #![feature(error_generic_member_access)]
12
13 use std::error::{Error, Request};
14 use std::fmt::{self, Debug, Display};
15
16 struct MyError(Thing);
17 struct Thing;
18
19 impl Debug for MyError {
20 fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
21 unimplemented!()
22 }
23 }
24
25 impl Display for MyError {
26 fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
27 unimplemented!()
28 }
29 }
30
31 impl Error for MyError {
32 fn provide<'a>(&'a self, request: &mut Request<'a>) {
33 request.provide_ref(&self.0);
34 }
35 }
36 "#;
37
main()38 fn main() {
39 match compile_probe() {
40 Some(status) if status.success() => println!("cargo:rustc-cfg=error_generic_member_access"),
41 _ => {}
42 }
43 }
44
compile_probe() -> Option<ExitStatus>45 fn compile_probe() -> Option<ExitStatus> {
46 if env::var_os("RUSTC_STAGE").is_some() {
47 // We are running inside rustc bootstrap. This is a highly non-standard
48 // environment with issues such as:
49 //
50 // https://github.com/rust-lang/cargo/issues/11138
51 // https://github.com/rust-lang/rust/issues/114839
52 //
53 // Let's just not use nightly features here.
54 return None;
55 }
56
57 let rustc = env::var_os("RUSTC")?;
58 let out_dir = env::var_os("OUT_DIR")?;
59 let probefile = Path::new(&out_dir).join("probe.rs");
60 fs::write(&probefile, PROBE).ok()?;
61
62 // Make sure to pick up Cargo rustc configuration.
63 let mut cmd = if let Some(wrapper) = env::var_os("RUSTC_WRAPPER") {
64 let mut cmd = Command::new(wrapper);
65 // The wrapper's first argument is supposed to be the path to rustc.
66 cmd.arg(rustc);
67 cmd
68 } else {
69 Command::new(rustc)
70 };
71
72 cmd.stderr(Stdio::null())
73 .arg("--edition=2018")
74 .arg("--crate-name=thiserror_build")
75 .arg("--crate-type=lib")
76 .arg("--emit=metadata")
77 .arg("--out-dir")
78 .arg(out_dir)
79 .arg(probefile);
80
81 if let Some(target) = env::var_os("TARGET") {
82 cmd.arg("--target").arg(target);
83 }
84
85 // If Cargo wants to set RUSTFLAGS, use that.
86 if let Ok(rustflags) = env::var("CARGO_ENCODED_RUSTFLAGS") {
87 if !rustflags.is_empty() {
88 for arg in rustflags.split('\x1f') {
89 cmd.arg(arg);
90 }
91 }
92 }
93
94 cmd.status().ok()
95 }
96