simplified attribute parsing. Added error handling

Author: nebulark

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -472,45 +472,51 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     let mut prefix = None;
                     let mut entry = None;
                     for item in l {
-                        let Some(metaitem) = item.meta_item() else {
+                        let Some(meta_item) = item.meta_item() else {
+                            tcx.dcx().span_err(item.span(), "Expected name value pair.");
                             continue;
                         };
 
-                        let [single_segment] = &metaitem.path.segments[..] else {
+                        let Some(name_value_lit) = meta_item.name_value_literal() else {
+                            tcx.dcx().span_err(item.span(), "Expected name value pair.");
                             continue;
                         };
 
-                        let attrib_to_write = match single_segment.ident.name {
+                        let attrib_to_write = match meta_item.name_or_empty() {
                             sym::prefix_nops => &mut prefix,
-                                sym::entry_nops => &mut entry,
-                                _ => {
-                                    tcx.dcx().span_err(metaitem.span, "Unexpected parameter.");
-                                    continue;
-                                }
-                        };
-
-                        if let Some(metaitem) =
-                            item.meta_item().map(|e| e.name_value_literal()).flatten()
-                        {
-                            let rustc_ast::LitKind::Int(val, _) = metaitem.kind else {
+                            sym::entry_nops => &mut entry,
+                            _ => {
                                 tcx.dcx().span_err(
-                                    metaitem.span,
-                                    "Expected integer value between 0 and 255",
+                                    item.span(),
+                                    format!(
+                                        "Unexpected name. Allowed names: {}, {}",
+                                        sym::prefix_nops,
+                                        sym::entry_nops
+                                    ),
                                 );
                                 continue;
-                            };
+                            }
+                        };
 
-                            let Ok(val) = val.get().try_into() else {
-                                tcx.dcx().span_err(
-                                    metaitem.span,
-                                    "Integer value outside range between 0 and 255.",
-                                );
-                                continue;
-                            };
+                        let rustc_ast::LitKind::Int(val, _) = name_value_lit.kind else {
+                            tcx.dcx().span_err(
+                                name_value_lit.span,
+                                "Expected integer value between 0 and 255.",
+                            );
+                            continue;
+                        };
 
-                            *attrib_to_write = Some(val);
-                        }
+                        let Ok(val) = val.get().try_into() else {
+                            tcx.dcx().span_err(
+                                name_value_lit.span,
+                                "Integer value outside range between 0 and 255.",
+                            );
+                            continue;
+                        };
+
+                        *attrib_to_write = Some(val);
                     }
+
                     if let (None, None) = (prefix, entry) {
                         tcx.dcx().span_err(attr.span, "Must specify at least one parameter.");
                     }