Update to nightly-2025-11-02

A bunch of error messages changed.

This also brings in thread IDs in panic messages, which we need to normalize
away. I first tried implementing this normalization without regex, but
it didn't work first try, so I chose regex, which is simpler.

Also updated the builder to edition 2024 (since my initial
implementation required let chains) which requires using unsafe for
`remove_var`, but that's trivial unsafe that's fine.

I also added a note about the current version to the index.

Author: Noratrieb

builder/Cargo.lock

@@ -1,7 +1,8 @@
 [package]
 name = "builder"
 version = "0.1.0"
-edition = "2021"
+edition = "2024"
 
 [dependencies]
 eyre = "0.6.12"
+regex = "1.12.2"

builder/Cargo.toml

@@ -1,11 +1,15 @@
 use std::{path::Path, thread};
 
-use eyre::{ensure, Context, OptionExt};
+use eyre::{Context, OptionExt, ensure};
+use regex::Regex;
 
 fn main() -> eyre::Result<()> {
     // Ensure rustup picks up the rust-toolchain.toml file properly and doesn't get confused by this cargo run.
-    std::env::remove_var("CARGO");
-    std::env::remove_var("RUSTUP_TOOLCHAIN");
+    // SAFETY: This is at the start of main, no other threads are running.
+    unsafe {
+        std::env::remove_var("CARGO");
+        std::env::remove_var("RUSTUP_TOOLCHAIN");
+    }
 
     let root_dir = Path::new("..")
         .canonicalize()
@@ -87,7 +91,8 @@ fn run_example(examples_dir: &Path, filename: &str) -> eyre::Result<()> {
     cmd.arg(example_name);
 
     let out = cmd.output().wrap_err("spawning cargo")?;
-    let stderr = String::from_utf8(out.stderr).wrap_err("stderr was invalid UTF-8")?;
+    let stderr =
+        normalize_stderr(String::from_utf8(out.stderr).wrap_err("stderr was invalid UTF-8")?);
 
     let stderr_dir = examples_dir.join("stderr");
     let path = stderr_dir.join(format!("{example_name}.stderr"));
@@ -97,6 +102,15 @@ fn run_example(examples_dir: &Path, filename: &str) -> eyre::Result<()> {
     Ok(())
 }
 
+fn normalize_stderr(stderr: String) -> String {
+    // thread 'main' (16399) panicked -> thread 'main' (???) panicked
+
+    Regex::new(r"thread 'main' \(\d+\) panicked")
+        .unwrap()
+        .replace(&stderr, "thread 'main' (???) panicked")
+        .into()
+}
+
 /// Ensures there is output for the toolchain and that the installation doesn't pollute stderr.
 fn install_toolchain() -> eyre::Result<()> {
     let mut toolchain_install = std::process::Command::new("rustc");

builder/src/main.rs

@@ -11,7 +11,7 @@ error[E0308]: mismatched types
 note: function defined here
   --> examples/borrowck_1.rs:5:4
    |
-5  | fn accepts_func(f: fn(&u32), data: &u32) {
+ 5 | fn accepts_func(f: fn(&u32), data: &u32) {
    |    ^^^^^^^^^^^^ -----------
 
 For more information about this error, try `rustc --explain E0308`.

code/examples/stderr/borrowck_1.stderr

@@ -11,6 +11,14 @@ error[E0505]: cannot move out of `foo` because it is borrowed
   |     move out of `foo` occurs here
   |     borrow later used here
   |
+note: if `Foo<'_>` implemented `Clone`, you could clone the value
+ --> examples/borrowck_4.rs:2:1
+  |
+2 | struct Foo<'a>(&'a mut u32);
+  | ^^^^^^^^^^^^^^ consider implementing `Clone` for this type
+...
+7 |     mutate(&mut foo);
+  |                 --- you could clone this value
   = note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 For more information about this error, try `rustc --explain E0505`.

code/examples/stderr/borrowck_4.stderr

@@ -11,10 +11,18 @@ error[E0382]: use of moved value: `x`
 note: consider changing this parameter type in function `r2_once` to borrow instead if owning the value isn't necessary
   --> examples/borrowck_6.rs:5:15
    |
-5  | fn r2_once(_: R2){}
+ 5 | fn r2_once(_: R2){}
    |    -------    ^^ this parameter takes ownership of the value
    |    |
    |    in this function
+note: if `R2<'_>` implemented `Clone`, you could clone the value
+  --> examples/borrowck_6.rs:2:1
+   |
+ 2 | struct R2<'a>(&'a mut i32);
+   | ^^^^^^^^^^^^^ consider implementing `Clone` for this type
+...
+13 |     r2_once(x);
+   |             - you could clone this value
 
 For more information about this error, try `rustc --explain E0382`.
 error: could not compile `code` (example "borrowck_6") due to 1 previous error

code/examples/stderr/borrowck_6.stderr

@@ -1,15 +1,13 @@
 error[E0277]: `*const i32` cannot be sent between threads safely
-  --> examples/misc_10.rs:12:19
+  --> examples/misc_10.rs:12:5
    |
 12 |       requires_send(async move {
-   |       ------------- ^---------
-   |       |             |
-   |  _____|_____________within this `{async block@examples/misc_10.rs:12:19: 12:29}`
-   | |     |
-   | |     required by a bound introduced by this call
+   |       ^             ---------- within this `{async block@examples/misc_10.rs:12:19: 12:29}`
+   |  _____|
+   | |
 13 | |         println!("{}", unsafe{*y.0})
 14 | |     })
-   | |_____^ `*const i32` cannot be sent between threads safely
+   | |______^ `*const i32` cannot be sent between threads safely
    |
    = help: within `{async block@examples/misc_10.rs:12:19: 12:29}`, the trait `Send` is not implemented for `*const i32`
 note: required because it's used within this `async` block
@@ -20,7 +18,7 @@ note: required because it's used within this `async` block
 note: required by a bound in `requires_send`
   --> examples/misc_10.rs:6:36
    |
-6  | fn requires_send(_f: impl Future + Send) {}
+ 6 | fn requires_send(_f: impl Future + Send) {}
    |                                    ^^^^ required by this bound in `requires_send`
 
 For more information about this error, try `rustc --explain E0277`.

code/examples/stderr/misc_10.stderr

@@ -1,7 +1,7 @@
 error[E0599]: no method named `func` found for struct `Foo` in the current scope
   --> examples/misc_3.rs:10:9
    |
-1  | struct Foo {
+ 1 | struct Foo {
    | ---------- method `func` not found for this struct
 ...
 10 |     foo.func();

code/examples/stderr/misc_3.stderr

@@ -10,7 +10,7 @@ error[E0423]: expected value, found struct `Struct`
 error[E0423]: expected value, found struct `Struct`
   --> examples/misc_9.rs:20:5
    |
-3  | struct Struct {}
+ 3 | struct Struct {}
    | ---------------- `Struct` defined here
 ...
 20 |     Struct = Struct {};
@@ -19,7 +19,7 @@ error[E0423]: expected value, found struct `Struct`
 error[E0618]: expected function, found struct `Unit`
   --> examples/misc_9.rs:10:5
    |
-1  | struct Unit;
+ 1 | struct Unit;
    | ----------- struct `Unit` defined here
 ...
 10 |     Unit();
@@ -36,7 +36,7 @@ help: `Unit` is a unit struct, and does not take parentheses to be constructed
 error[E0423]: expected function, tuple struct or tuple variant, found struct `Struct`
   --> examples/misc_9.rs:12:5
    |
-3  | struct Struct {}
+ 3 | struct Struct {}
    | ---------------- `Struct` defined here
 ...
 12 |     Struct();