Migrate weak_lang_items.rs

compiler/rustc_error_messages/locales/en-US/passes.ftl

@@ -271,3 +271,12 @@ passes_collapse_debuginfo = `collapse_debuginfo` attribute should be applied to
 
 passes_deprecated_annotation_has_no_effect = this `#[deprecated]` annotation has no effect
     .suggestion = remove the unnecessary deprecation attribute
+    
+passes_missing_panic_handler = `#[panic_handler]` function required, but not found
+
+passes_missing_alloc_error_handler = `#[alloc_error_handler]` function required, but not found
+    .note = use `#![feature(default_alloc_error_handler)]` for a default error handler
+
+passes_missing_lang_item = language item required, but not found: `{$name}`
+    .note = this can occur when a binary crate with `#![no_std]` is compiled for a target where `{$name}` is defined in the standard library
+    .help = you may be able to compile for a target that doesn't need `{$name}`, specify a target with `--target` or in `.cargo/config`

compiler/rustc_passes/src/errors.rs

@@ -665,3 +665,20 @@ pub struct DeprecatedAnnotationHasNoEffect {
     #[suggestion(applicability = "machine-applicable", code = "")]
     pub span: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag(passes::missing_panic_handler)]
+pub struct MissingPanicHandler;
+
+#[derive(Diagnostic)]
+#[diag(passes::missing_alloc_error_handler)]
+#[note]
+pub struct MissingAllocErrorHandler;
+
+#[derive(Diagnostic)]
+#[diag(passes::missing_lang_item)]
+#[note]
+#[help]
+pub struct MissingLangItem {
+    pub name: Symbol,
+}

compiler/rustc_passes/src/weak_lang_items.rs

@@ -8,6 +8,8 @@ use rustc_middle::middle::lang_items::required;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::CrateType;
 
+use crate::errors::{MissingAllocErrorHandler, MissingLangItem, MissingPanicHandler};
+
 /// Checks the crate for usage of weak lang items, returning a vector of all the
 /// language items required by this crate, but not defined yet.
 pub fn check_crate<'tcx>(tcx: TyCtxt<'tcx>, items: &mut lang_items::LanguageItems) {
@@ -71,20 +73,13 @@ fn verify<'tcx>(tcx: TyCtxt<'tcx>, items: &lang_items::LanguageItems) {
     for (name, &item) in WEAK_ITEMS_REFS.iter() {
         if missing.contains(&item) && required(tcx, item) && items.require(item).is_err() {
             if item == LangItem::PanicImpl {
-                tcx.sess.err("`#[panic_handler]` function required, but not found");
+                tcx.sess.emit_err(MissingPanicHandler);
             } else if item == LangItem::Oom {
                 if !tcx.features().default_alloc_error_handler {
-                    tcx.sess.err("`#[alloc_error_handler]` function required, but not found");
+                    tcx.sess.emit_err(MissingAllocErrorHandler);
-                    tcx.sess.note_without_error("use `#![feature(default_alloc_error_handler)]` for a default error handler");
                 }
             } else {
-                tcx
+                tcx.sess.emit_err(MissingLangItem { name: *name });
-                    .sess
-                    .diagnostic()
-                    .struct_err(&format!("language item required, but not found: `{}`", name))
-                    .note(&format!("this can occur when a binary crate with `#![no_std]` is compiled for a target where `{}` is defined in the standard library", name))
-                    .help(&format!("you may be able to compile for a target that doesn't need `{}`, specify a target with `--target` or in `.cargo/config`", name))
-                    .emit();
             }
         }
     }