remove unused return types such as empty Results or Options that would always be Some(..)

remove unused return type of dropck::check_drop_obligations()
don't wrap return type in Option in get_macro_by_def_id() since we would always return Some(..)
remove redundant return type of back::write::optimize()
don't Option-wrap return type of compute_type_parameters() since we always return Some(..)
don't return empty Result in assemble_generator_candidates()
don't return empty Result in assemble_closure_candidates()
don't return empty result in assemble_fn_pointer_candidates()
don't return empty result in assemble_candidates_from_impls()
don't return empty result in assemble_candidates_from_auto_impls()
don't return emtpy result in assemble_candidates_for_trait_alias()
don't return empty result in assemble_builtin_bound_candidates()
don't return empty results in assemble_extension_candidates_for_traits_in_scope() and assemble_extension_candidates_for_trait()
remove redundant wrapping of return type of StripItem::strip() since it always returns Some(..)
remove unused return type of assemble_extension_candidates_for_all_traits()

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -485,7 +485,7 @@ pub(crate) unsafe fn optimize(
     diag_handler: &Handler,
     module: &ModuleCodegen<ModuleLlvm>,
     config: &ModuleConfig,
-) -> Result<(), FatalError> {
+) {
     let _timer = cgcx.prof.generic_activity_with_arg("LLVM_module_optimize", &module.name[..]);
 
     let llmod = module.module_llvm.llmod();
@@ -511,7 +511,7 @@ pub(crate) unsafe fn optimize(
                 _ => llvm::OptStage::PreLinkNoLTO,
             };
             optimize_with_new_llvm_pass_manager(cgcx, module, config, opt_level, opt_stage);
-            return Ok(());
+            return;
         }
 
         if cgcx.prof.llvm_recording_enabled() {
@@ -634,7 +634,6 @@ pub(crate) unsafe fn optimize(
         llvm::LLVMDisposePassManager(fpm);
         llvm::LLVMDisposePassManager(mpm);
     }
-    Ok(())
 }
 
 unsafe fn add_sanitizer_passes(config: &ModuleConfig, passes: &mut Vec<&'static mut llvm::Pass>) {

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -2322,13 +2322,13 @@ fn set_members_of_composite_type(
             DIB(cx),
             composite_type_metadata,
             Some(type_array),
-            type_params,
+            Some(type_params),
         );
     }
 }
 
 /// Computes the type parameters for a type, if any, for the given metadata.
-fn compute_type_parameters(cx: &CodegenCx<'ll, 'tcx>, ty: Ty<'tcx>) -> Option<&'ll DIArray> {
+fn compute_type_parameters(cx: &CodegenCx<'ll, 'tcx>, ty: Ty<'tcx>) -> &'ll DIArray {
     if let ty::Adt(def, substs) = *ty.kind() {
         if substs.types().next().is_some() {
             let generics = cx.tcx.generics_of(def.did);
@@ -2358,10 +2358,10 @@ fn compute_type_parameters(cx: &CodegenCx<'ll, 'tcx>, ty: Ty<'tcx>) -> Option<&'
                 })
                 .collect();
 
-            return Some(create_DIArray(DIB(cx), &template_params[..]));
+            return create_DIArray(DIB(cx), &template_params[..]);
         }
     }
-    return Some(create_DIArray(DIB(cx), &[]));
+    return create_DIArray(DIB(cx), &[]);
 
     fn get_parameter_names(cx: &CodegenCx<'_, '_>, generics: &ty::Generics) -> Vec<Symbol> {
         let mut names = generics

compiler/rustc_codegen_llvm/src/lib.rs

@@ -160,7 +160,7 @@ impl WriteBackendMethods for LlvmCodegenBackend {
         module: &ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
     ) -> Result<(), FatalError> {
-        back::write::optimize(cgcx, diag_handler, module, config)
+        Ok(back::write::optimize(cgcx, diag_handler, module, config))
     }
     unsafe fn optimize_thin(
         cgcx: &CodegenContext<Self>,