rust: test on stable

doc/doxygen/src/using-rust.md

@@ -84,31 +84,26 @@ Toolchain {#toolchain}
 
 To install the necessary Rust components, it is easiest use [**rustup**, installed as described on its website].
 
-Using most of Rust on RIOT requires a nightly version of Rust,
-because some transpiled expressions for RIOT make use of unstable features,
-and because the RIOT wrappers use some unstable idioms.
+Using Rust on RIOT needs the latest stable or nightly version of Rust,
+depending on the precise example used.
+(Several modules, such as CoAP, SAUL or the shell, need features not yet available on stable yet;
+the minimal test is performed on stable, and examples are configured to use stable as it becomes available).
 
-@note
-Building on stable is supported for some examples and platforms starting with Rust 1.59
-(e.g., the rust-hello-world on any ARM Cortex, but not yet on native).
-Try it out by adding `CARGO_CHANNEL=stable` to the project's Makefile;
-where it doesn't work, rustc will complain that "`#![feature]` may not be used on the stable release channel".
-
-@note
-A stable version of Rust is not currently provided with the Docker images;
-consequently, builds on stable are not tested as regularly as builds on nightly.
-
-Make sure you have both the nightly **toolchain**
+Make sure you have both the nightly and stable **toolchains**
 and the core library for the CPU (**target**) of your choice available:
 
 ```
 $ rustup toolchain add nightly
+$ rustup toolchain add stable
 $ rustup target add thumbv7m-none-eabi --toolchain nightly
+$ rustup target add thumbv7m-none-eabi --toolchain stable
 ```
 
-(Substitute thumbv7m-none-eavi with the value of `RUST_TARGET`
+Substitute thumbv7m-none-eabi with the value of `RUST_TARGET`
 in the output of `make info-build` of an application that has your current board selected,
 or just add it later whenever the Rust compiler complains about not finding the core library for a given target).
+Installing only nightly will work just as well,
+but you may need to remove the `CARGO_CHANNEL = stable` lines from tests or examples.
 
 
 While Rust comes with its own [cargo] dependency tracker for any Rust code,

tests/rust_minimal/Cargo.toml

@@ -8,6 +8,12 @@ resolver = "2"
 [lib]
 crate-type = ["staticlib"]
 
+[profile.release]
+# Setting the panic mode has little effect on the built code (as Rust on RIOT
+# supports no unwinding), but setting it allows builds on native without using
+# the nightly-only lang_items feature.
+panic = "abort"
+
 [dependencies]
 # `default-features = false` can be removed with 0.8, and enables building on stable during the 0.7 series
 riot-wrappers = { version = "0.7", features = [ "set_panic_handler" ], default-features = false }

tests/rust_minimal/Makefile

@@ -5,6 +5,11 @@ BASELIBS += $(APPLICATION_RUST_MODULE).module
 
 FEATURES_REQUIRED += rust_target
 
+# This example can, on all platforms, be built with a stable version of Rust.
+# For most advanced features (eg. when using CoAP, SAUL or the shell with
+# Rust), this needs to be set to "nightly" for the time being.
+CARGO_CHANNEL = stable
+
 # Currently unknown, something related to the LED_PORT definition that doesn't
 # pass C2Rust's transpilation
 BOARD_BLACKLIST := ek-lm4f120xl