Rollup merge of #120865 - saethlin:missing-o-files, r=nnethercote

Turn the "no saved object file in work product" ICE into a translatable fatal error

I don't know if it's fair to say this fixes https://github.com/rust-lang/rust/issues/120854 but it surely makes the error reporting better and should encourage people with good instincts like ```@CinchBlue.```

2 files changed, 9 insertions, 1 deletions

diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index 9b24339d255..a63642d76b9 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -913,7 +913,9 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
 
     let object = load_from_incr_comp_dir(
         cgcx.output_filenames.temp_path(OutputType::Object, Some(&module.name)),
-        module.source.saved_files.get("o").expect("no saved object file in work product"),
+        module.source.saved_files.get("o").unwrap_or_else(|| {
+            cgcx.create_dcx().emit_fatal(errors::NoSavedObjectFile { cgu_name: &module.name })
+        }),
     );
     let dwarf_object =
         module.source.saved_files.get("dwo").as_ref().and_then(|saved_dwarf_object_file| {
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index 06ea5b9e8f4..3d7903b5efb 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -122,6 +122,12 @@ pub struct NoNatvisDirectory {
 }
 
 #[derive(Diagnostic)]
+#[diag(codegen_ssa_no_saved_object_file)]
+pub struct NoSavedObjectFile<'a> {
+    pub cgu_name: &'a str,
+}
+
+#[derive(Diagnostic)]
 #[diag(codegen_ssa_copy_path_buf)]
 pub struct CopyPathBuf {
     pub source_file: PathBuf,