From ede99234c48c120b909990ee2ee51dd87cfed6f5 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Sat, 17 Feb 2024 10:51:35 +1100
Subject: [PATCH] Make `CodegenBackend::join_codegen` infallible.

Because they all are, in practice.
---
 compiler/rustc_codegen_cranelift/src/lib.rs               | 6 +++---
 compiler/rustc_codegen_gcc/src/lib.rs                     | 8 +++-----
 compiler/rustc_codegen_llvm/src/lib.rs                    | 4 ++--
 compiler/rustc_codegen_ssa/src/traits/backend.rs          | 2 +-
 compiler/rustc_interface/src/queries.rs                   | 2 +-
 .../hotplug_codegen_backend/the_backend.rs                | 4 ++--
 6 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/compiler/rustc_codegen_cranelift/src/lib.rs b/compiler/rustc_codegen_cranelift/src/lib.rs
index 7c432e9c590..7e2e1f7c6ac 100644
--- a/compiler/rustc_codegen_cranelift/src/lib.rs
+++ b/compiler/rustc_codegen_cranelift/src/lib.rs
@@ -233,11 +233,11 @@ fn join_codegen(
         ongoing_codegen: Box<dyn Any>,
         sess: &Session,
         _outputs: &OutputFilenames,
-    ) -> Result<(CodegenResults, FxIndexMap<WorkProductId, WorkProduct>), ErrorGuaranteed> {
-        Ok(ongoing_codegen
+    ) -> (CodegenResults, FxIndexMap<WorkProductId, WorkProduct>) {
+        ongoing_codegen
             .downcast::<driver::aot::OngoingCodegen>()
             .unwrap()
-            .join(sess, self.config.borrow().as_ref().unwrap()))
+            .join(sess, self.config.borrow().as_ref().unwrap())
     }
 
     fn link(
diff --git a/compiler/rustc_codegen_gcc/src/lib.rs b/compiler/rustc_codegen_gcc/src/lib.rs
index 863b6333bcc..09ce059476e 100644
--- a/compiler/rustc_codegen_gcc/src/lib.rs
+++ b/compiler/rustc_codegen_gcc/src/lib.rs
@@ -217,13 +217,11 @@ fn codegen_crate<'tcx>(&self, tcx: TyCtxt<'tcx>, metadata: EncodedMetadata, need
         Box::new(res)
     }
 
-    fn join_codegen(&self, ongoing_codegen: Box<dyn Any>, sess: &Session, _outputs: &OutputFilenames) -> Result<(CodegenResults, FxIndexMap<WorkProductId, WorkProduct>), ErrorGuaranteed> {
-        let (codegen_results, work_products) = ongoing_codegen
+    fn join_codegen(&self, ongoing_codegen: Box<dyn Any>, sess: &Session, _outputs: &OutputFilenames) -> (CodegenResults, FxIndexMap<WorkProductId, WorkProduct>) {
+        ongoing_codegen
             .downcast::<rustc_codegen_ssa::back::write::OngoingCodegen<GccCodegenBackend>>()
             .expect("Expected GccCodegenBackend's OngoingCodegen, found Box<Any>")
-            .join(sess);
-
-        Ok((codegen_results, work_products))
+            .join(sess)
     }
 
     fn link(&self, sess: &Session, codegen_results: CodegenResults, outputs: &OutputFilenames) -> Result<(), ErrorGuaranteed> {
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index e688e84db61..35210b0b2e8 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -369,7 +369,7 @@ fn join_codegen(
         ongoing_codegen: Box<dyn Any>,
         sess: &Session,
         outputs: &OutputFilenames,
-    ) -> Result<(CodegenResults, FxIndexMap<WorkProductId, WorkProduct>), ErrorGuaranteed> {
+    ) -> (CodegenResults, FxIndexMap<WorkProductId, WorkProduct>) {
         let (codegen_results, work_products) = ongoing_codegen
             .downcast::<rustc_codegen_ssa::back::write::OngoingCodegen<LlvmCodegenBackend>>()
             .expect("Expected LlvmCodegenBackend's OngoingCodegen, found Box<Any>")
@@ -382,7 +382,7 @@ fn join_codegen(
             });
         }
 
-        Ok((codegen_results, work_products))
+        (codegen_results, work_products)
     }
 
     fn link(
diff --git a/compiler/rustc_codegen_ssa/src/traits/backend.rs b/compiler/rustc_codegen_ssa/src/traits/backend.rs
index 8e9907ed8bb..cb1feff1336 100644
--- a/compiler/rustc_codegen_ssa/src/traits/backend.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/backend.rs
@@ -102,7 +102,7 @@ fn join_codegen(
         ongoing_codegen: Box<dyn Any>,
         sess: &Session,
         outputs: &OutputFilenames,
-    ) -> Result<(CodegenResults, FxIndexMap<WorkProductId, WorkProduct>), ErrorGuaranteed>;
+    ) -> (CodegenResults, FxIndexMap<WorkProductId, WorkProduct>);
 
     /// This is called on the returned `CodegenResults` from `join_codegen`
     fn link(
diff --git a/compiler/rustc_interface/src/queries.rs b/compiler/rustc_interface/src/queries.rs
index 2a4eefb7f77..211bcb9da94 100644
--- a/compiler/rustc_interface/src/queries.rs
+++ b/compiler/rustc_interface/src/queries.rs
@@ -259,7 +259,7 @@ pub struct Linker {
 impl Linker {
     pub fn link(self, sess: &Session, codegen_backend: &dyn CodegenBackend) -> Result<()> {
         let (codegen_results, work_products) =
-            codegen_backend.join_codegen(self.ongoing_codegen, sess, &self.output_filenames)?;
+            codegen_backend.join_codegen(self.ongoing_codegen, sess, &self.output_filenames);
 
         sess.compile_status()?;
 
diff --git a/tests/run-make-fulldeps/hotplug_codegen_backend/the_backend.rs b/tests/run-make-fulldeps/hotplug_codegen_backend/the_backend.rs
index 9e0a7ba63d0..28a1e27cccc 100644
--- a/tests/run-make-fulldeps/hotplug_codegen_backend/the_backend.rs
+++ b/tests/run-make-fulldeps/hotplug_codegen_backend/the_backend.rs
@@ -49,11 +49,11 @@ fn join_codegen(
         ongoing_codegen: Box<dyn Any>,
         _sess: &Session,
         _outputs: &OutputFilenames,
-    ) -> Result<(CodegenResults, FxIndexMap<WorkProductId, WorkProduct>), ErrorGuaranteed> {
+    ) -> (CodegenResults, FxIndexMap<WorkProductId, WorkProduct>) {
         let codegen_results = ongoing_codegen
             .downcast::<CodegenResults>()
             .expect("in join_codegen: ongoing_codegen is not a CodegenResults");
-        Ok((*codegen_results, FxIndexMap::default()))
+        (*codegen_results, FxIndexMap::default())
     }
 
     fn link(