compile_codegen: add compile_codegen feature

Author: Firestar99

crates/spirv-builder/Cargo.toml

@@ -18,10 +18,13 @@ no-default-features = true
 # that optional dependency, from being automatically created by Cargo, see:
 # https://doc.rust-lang.org/cargo/reference/features.html#optional-dependencies
 [features]
-# See `rustc_codegen_spirv/Cargo.toml` for details on these features.
 default = ["use-compiled-tools"]
-use-installed-tools = ["dep:rustc_codegen_spirv", "rustc_codegen_spirv?/use-installed-tools"]
-use-compiled-tools = ["dep:rustc_codegen_spirv", "rustc_codegen_spirv?/use-compiled-tools"]
+# Compile `rustc_codegen_spirv`, allows constructing SpirvBuilder without
+# explicitly passing in a path to a compiled `rustc_codegen_spirv.so` (or dll)
+compile_codegen = ["dep:rustc_codegen_spirv"]
+# See `rustc_codegen_spirv/Cargo.toml` for details on these features.
+use-installed-tools = ["compile_codegen", "rustc_codegen_spirv?/use-installed-tools"]
+use-compiled-tools = ["compile_codegen", "rustc_codegen_spirv?/use-compiled-tools"]
 skip-toolchain-check = ["rustc_codegen_spirv?/skip-toolchain-check"]
 
 watch = ["dep:notify"]

crates/spirv-builder/src/lib.rs

@@ -72,31 +72,6 @@
 // #![allow()]
 #![doc = include_str!("../README.md")]
 
-// HACK(eddyb) try to catch misuse of Cargo package features very early on
-// (see `spirv-builder/Cargo.toml` for why we go through all of this).
-#[cfg(all(
-    not(any(feature = "use-compiled-tools", feature = "use-installed-tools")),
-    not(doc)
-))]
-compile_error!(
-    "at least one of `use-compiled-tools` or `use-installed-tools` features must be enabled
-(outside of documentation builds, which require disabling both to build on stable)"
-);
-
-#[cfg(doc)]
-fn _ensure_cfg_doc_means_rustdoc() {
-    // HACK(eddyb) this relies on specific `rustdoc` behavior (i.e. it skips
-    // type-checking function bodies, so we trigger a compile-time `panic! from
-    // a type) to check that we're in fact under `rustdoc`, not just `--cfg doc`.
-    #[rustfmt::skip]
-    let _: [(); panic!("
-
-            `--cfg doc` was set outside of `rustdoc`
-            (if you are running `rustdoc` or `cargo doc`, please file an issue)
-
-")];
-}
-
 mod depfile;
 #[cfg(feature = "watch")]
 mod watch;