remove references to crate2nix other than a link to its docs

doc/languages-frameworks/rust.section.md

@@ -648,99 +648,13 @@ buildPythonPackage rec {
 
 When run, `cargo build` produces a file called `Cargo.lock`,
 containing pinned versions of all dependencies. Nixpkgs contains a
-tool called `crate2Nix` (`nix-shell -p crate2nix`), which can be used
-to turn a `Cargo.lock` into a Nix expression.
+tool called `crate2Nix` (`nix-shell -p crate2nix`), which can be
+used to turn a `Cargo.lock` into a Nix expression. That Nix
+expression calls `rustc` directly (hence bypassing Cargo), and can
+be used to compile a crate and all its dependencies.
 
-That Nix expression calls `rustc` directly (hence bypassing Cargo),
-and can be used to compile a crate and all its dependencies. Here is
-an example for a minimal `hello` crate:
-
-```ShellSession
-$ cargo new hello
-$ cd hello
-$ cargo build
- Compiling hello v0.1.0 (file:https:///tmp/hello)
- Finished dev [unoptimized + debuginfo] target(s) in 0.20 secs
-$ carnix -o hello.nix --src ./. Cargo.lock --standalone
-$ nix-build hello.nix -A hello_0_1_0
-```
-
-Now, the file produced by the call to `carnix`, called `hello.nix`, looks like:
-
-```nix
-# Generated by carnix 0.6.5: carnix -o hello.nix --src ./. Cargo.lock --standalone
-{ stdenv, buildRustCrate, fetchgit }:
-let kernel = stdenv.buildPlatform.parsed.kernel.name;
- # ... (content skipped)
-in
-rec {
- hello = f: hello_0_1_0 { features = hello_0_1_0_features { hello_0_1_0 = f; }; };
- hello_0_1_0_ = { dependencies?[], buildDependencies?[], features?[] }: buildRustCrate {
- crateName = "hello";
- version = "0.1.0";
- authors = [ "[email protected] <[email protected]>" ];
- src = ./.;
- inherit dependencies buildDependencies features;
- };
- hello_0_1_0 = { features?(hello_0_1_0_features {}) }: hello_0_1_0_ {};
- hello_0_1_0_features = f: updateFeatures f (rec {
- hello_0_1_0.default = (f.hello_0_1_0.default or true);
- }) [ ];
-}
-```
-
-In particular, note that the argument given as `--src` is copied
-verbatim to the source. If we look at a more complicated
-dependencies, for instance by adding a single line `libc="*"` to our
-`Cargo.toml`, we first need to run `cargo build` to update the
-`Cargo.lock`. Then, `crate2nix` needs to be run again, and produces the
-following nix file:
-
-```nix
-# Generated by carnix 0.6.5: carnix -o hello.nix --src ./. Cargo.lock --standalone
-{ stdenv, buildRustCrate, fetchgit }:
-let kernel = stdenv.buildPlatform.parsed.kernel.name;
- # ... (content skipped)
-in
-rec {
- hello = f: hello_0_1_0 { features = hello_0_1_0_features { hello_0_1_0 = f; }; };
- hello_0_1_0_ = { dependencies?[], buildDependencies?[], features?[] }: buildRustCrate {
- crateName = "hello";
- version = "0.1.0";
- authors = [ "[email protected] <[email protected]>" ];
- src = ./.;
- inherit dependencies buildDependencies features;
- };
- libc_0_2_36_ = { dependencies?[], buildDependencies?[], features?[] }: buildRustCrate {
- crateName = "libc";
- version = "0.2.36";
- authors = [ "The Rust Project Developers" ];
- sha256 = "01633h4yfqm0s302fm0dlba469bx8y6cs4nqc8bqrmjqxfxn515l";
- inherit dependencies buildDependencies features;
- };
- hello_0_1_0 = { features?(hello_0_1_0_features {}) }: hello_0_1_0_ {
- dependencies = mapFeatures features ([ libc_0_2_36 ]);
- };
- hello_0_1_0_features = f: updateFeatures f (rec {
- hello_0_1_0.default = (f.hello_0_1_0.default or true);
- libc_0_2_36.default = true;
- }) [ libc_0_2_36_features ];
- libc_0_2_36 = { features?(libc_0_2_36_features {}) }: libc_0_2_36_ {
- features = mkFeatures (features.libc_0_2_36 or {});
- };
- libc_0_2_36_features = f: updateFeatures f (rec {
- libc_0_2_36.default = (f.libc_0_2_36.default or true);
- libc_0_2_36.use_std =
- (f.libc_0_2_36.use_std or false) ||
- (f.libc_0_2_36.default or false) ||
- (libc_0_2_36.default or false);
- }) [];
-}
-```
-
-Here, the `libc` crate has no `src` attribute, so `buildRustCrate`
-will fetch it from [crates.io](https://crates.io). A `sha256`
-attribute is still needed for Nix purity.
+See [`crate2nix`'s documentation](https://github.com/kolloch/crate2nix#known-restrictions)
+for instructions on how to use it.
 
 ### Handling external dependencies {#handling-external-dependencies}
 
@@ -848,21 +762,6 @@ general. A number of other parameters can be overridden:
  };
  ```
 
-### Features {#features}
-
-One can also supply features switches. For example, if we want to
-compile `diesel_cli` only with the `postgres` feature, and no default
-features, we would write:
-
-```nix
-(callPackage ./diesel.nix {}).diesel {
- default = false;
- postgres = true;
-}
-```
-
-Where `diesel.nix` is the file generated by Carnix, as explained above.
-
 ### Setting Up `nix-shell` {#setting-up-nix-shell}
 
 Oftentimes you want to develop code from within `nix-shell`. Unfortunately