compile_codegen: forward missing codegen backend error

Author: Firestar99

crates/spirv-builder/src/lib.rs

@@ -103,6 +103,10 @@ pub enum SpirvBuilderError {
  MissingCratePath,
  #[error("crate path {0} does not exist")]
  CratePathDoesntExist(PathBuf),
+ #[error(
+ "Without feature `compile_codegen`, you need to set the path of the codegen dylib using `rustc_codegen_spirv_location(...)`"
+ )]
+ MissingCodegenBackendDylib,
  #[error("build failed")]
  BuildFailed,
  #[error("multi-module build cannot be used with print_metadata = MetadataPrintout::Full")]
@@ -643,27 +647,23 @@ fn dylib_path() -> Vec<PathBuf> {
  }
 }
 
-#[cfg(feature = "compile_codegen")]
-fn find_rustc_codegen_spirv() -> PathBuf {
- let filename = format!(
- "{}rustc_codegen_spirv{}",
- env::consts::DLL_PREFIX,
- env::consts::DLL_SUFFIX
- );
- for mut path in dylib_path() {
- path.push(&filename);
- if path.is_file() {
- return path;
+fn find_rustc_codegen_spirv() -> Result<PathBuf, SpirvBuilderError> {
+ if cfg!(feature = "compile_codegen") {
+ let filename = format!(
+ "{}rustc_codegen_spirv{}",
+ env::consts::DLL_PREFIX,
+ env::consts::DLL_SUFFIX
+ );
+ for mut path in dylib_path() {
+ path.push(&filename);
+ if path.is_file() {
+ return Ok(path);
+ }
  }
+ panic!("Could not find {filename} in library path");
+ } else {
+ Err(SpirvBuilderError::MissingCodegenBackendDylib)
  }
- panic!("Could not find {filename} in library path");
-}
-
-#[cfg(not(feature = "compile_codegen"))]
-fn find_rustc_codegen_spirv() -> PathBuf {
- panic!(
- "Without feature `compile_codegen`, you need to set the path of the codegen dylib using `rustc_codegen_spirv_location(...)`"
- );
 }
 
 /// Joins strings together while ensuring none of the strings contain the separator.
@@ -729,10 +729,9 @@ fn invoke_rustc(builder: &SpirvBuilder) -> Result<PathBuf, SpirvBuilderError> {
  // alongside build.rs, and cargo will helpfully add it to LD_LIBRARY_PATH for us! However,
  // rustc expects a full path, instead of a filename looked up via LD_LIBRARY_PATH, so we need
  // to copy cargo's understanding of library lookup and find the library and its full path.
- let rustc_codegen_spirv = builder
- .rustc_codegen_spirv_location
- .clone()
- .unwrap_or_else(find_rustc_codegen_spirv);
+ let rustc_codegen_spirv = Ok(builder.rustc_codegen_spirv_location.clone())
+ .transpose()
+ .unwrap_or_else(find_rustc_codegen_spirv)?;
 
  let mut rustflags = vec![
  format!("-Zcodegen-backend={}", rustc_codegen_spirv.display()),