update error not to leak implementation details

Author: alexandruradovici

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -626,35 +626,31 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL)
         && codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NO_MANGLE)
     {
-        let (span, lang_item) = lang_items::extract(attrs)
-            .map_or((None, None), |(name, span)| (Some(span), LangItem::from_name(name)));
+        let lang_item =
+            lang_items::extract(attrs).map_or(None, |(name, _span)| LangItem::from_name(name));
         // This should never use the default as `no_mangle` is present in the attributes list
         let no_mangle_span = no_mangle_span.unwrap_or_default();
-        let label = if let Some(lang_item) = lang_item {
-            format!("should be the {} item", lang_item.name())
-        } else {
-            format!("should be the internal language item")
-        };
         let mut err = tcx
             .dcx()
             .struct_span_err(
                 no_mangle_span,
                 "`#[no_mangle]` cannot be used on internal language items",
             )
             .with_note("Rustc requires this item to have a specific mangled name.")
-            .with_note("If you are trying to prevent mangling to ease debugging, many")
-            .with_note("debuggers support a command such as `rbreak {sym}` to")
-            .with_note("match `.*{sym}.*` instead of `break {sym}` on a specific name")
-            .with_span_label(tcx.def_span(did), label);
+            .with_span_label(tcx.def_span(did), "should be the internal language item");
         if let Some(lang_item) = lang_item {
-            if let Some(span) = span {
-                let label_attr = format!("this defines it as the `{}` item", lang_item.name());
-                err = err.with_span_label(span, label_attr);
-            }
             if let Some(link_name) = lang_item.link_name() {
-                let renamed =
-                    format!("In this case it is automatically renamed to `{}`", link_name);
-                err = err.with_note(renamed);
+                // let renamed =
+                //     format!("In this case it is automatically renamed to `{}`", link_name);
+                // err = err.with_note(renamed);
+                err = err
+                    .with_note("If you are trying to prevent mangling to ease debugging, many")
+                    .with_note(format!(
+                        "debuggers support a command such as `rbreak {link_name}` to"
+                    ))
+                    .with_note(format!(
+                        "match `.*{link_name}.*` instead of `break {link_name}` on a specific name"
+                    ))
             }
         }
 

tests/ui/codegen/no-mangle-on-internal-lang-items.stderr

@@ -6,10 +6,7 @@ LL | #[unsafe(no_mangle)]
 LL | fn internal_lang_function () {
    | ---------------------------- should be the internal language item
    |
-   = note: The linker requires specific names for internal language items.
-   = note: If you are trying to prevent mangling to ease debugging, many
-   = note: debuggers support a command such as `rbreak {sym}` to
-   = note: match `.*{sym}.*` instead of `break {sym}` on a specific name
+   = note: Rustc requires this item to have a specific mangled name.
 
 error: aborting due to 1 previous error
 

tests/ui/codegen/no-mangle-on-panic-handler.stderr

@@ -4,15 +4,13 @@ error: `#[no_mangle]` cannot be used on internal language items
 LL | #[unsafe(no_mangle)]
    | ^^^^^^^^^^^^^^^^^^^^
 LL | #[panic_handler]
-   | ---------------- this defines it as the `panic_impl` item
 LL | pub unsafe fn panic_fmt(pi: &PanicInfo) -> ! {
-   | -------------------------------------------- should be the panic_impl item
+   | -------------------------------------------- should be the internal language item
    |
-   = note: The linker requires specific names for internal language items.
+   = note: Rustc requires this item to have a specific mangled name.
    = note: If you are trying to prevent mangling to ease debugging, many
-   = note: debuggers support a command such as `rbreak {sym}` to
-   = note: match `.*{sym}.*` instead of `break {sym}` on a specific name
-   = note: In this case it is automatically renamed to `rust_begin_unwind`
+   = note: debuggers support a command such as `rbreak rust_begin_unwind` to
+   = note: match `.*rust_begin_unwind.*` instead of `break rust_begin_unwind` on a specific name
 
 error: aborting due to 1 previous error