Commits on Sep 7, 2020

1. Give a better error message for cargo check on libstd itself …

   Previously, the errors looked like this:
   
   ```
   $ cargo check
       Checking std v0.0.0 (/home/joshua/rustc/library/std)
   error: duplicate lang item in crate `core`: `bool`.
     |
     = note: the lang item is first defined in crate `core` (which `std` depends on)
     = note: first definition in `core` loaded from /home/joshua/.local/lib/cargo/target/debug/deps/libcore-afaeeb022194dcf3.rmeta
     = note: second definition in `core` loaded from /home/joshua/.local/lib/rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-2675a9a46b5cec89.rlib
   
   error[E0119]: conflicting implementations of trait `ffi::c_str::CString::new::SpecIntoVec` for type `&str`:
      --> library/std/src/ffi/c_str.rs:392:9
       |
   379 |         impl<T: Into<Vec<u8>>> SpecIntoVec for T {
       |         ---------------------------------------- first implementation here
   ...
   392 |         impl SpecIntoVec for &'_ str {
       |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `&str`
       |
       = note: upstream crates may add a new impl of trait `core::convert::Into<alloc_crate::vec::Vec<u8>>` for type `&str` in future versions
   
   error: aborting due to 119 previous errors; 93 warnings emitted
   ```
   
   Now, they're much more helpful:
   
   ```
   $ cargo check
      Compiling core v0.0.0 (/home/joshua/rustc2/library/core)
   error: failed to run custom build command for `core v0.0.0 (/home/joshua/rustc2/library/core)`
   
   Caused by:
     process didn't exit successfully: `/home/joshua/.local/lib/cargo/target/debug/build/core-ea3b18d34c1ee1c8/build-script-build` (exit code: 101)
     --- stderr
     error: you are attempting to build libcore without going through bootstrap
     help: use `x.py build --stage 0 library/std`, not `cargo build`
     help: use `x.py check`, not `cargo check`
     note: if you're sure you want to do this, use `RUSTC_BOOTSTRAP=0` or some other dummy value
     thread 'main' panicked at 'explicit panic', library/core/build.rs:7:9
     note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
   ```
   
   The metric here is 'did you set RUSTC_BOOTSTRAP'; if so, it's assumed
   you know what you're doing and no error is given. It's very unlikely (or
   at least should be!) that someone will have RUSTC_BOOTSTRAP globally
   set, so I think this is a good heuristic.

   

   jyn514 committed Sep 7, 2020
   Configuration menu

   • View commit details
   • Copy full SHA for 3a3b62a
   • Browse repository at this point

   Copy the full SHA

   3a3b62a View commit details

   Browse the repository at this point in the history