fix various linker warnings

compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs

@@ -253,7 +253,10 @@ impl DiagnosticDeriveVariantBuilder {
         let mut field_binding = binding_info.binding.clone();
         field_binding.set_span(field.ty.span());
 
-        let ident = field.ident.as_ref().unwrap();
+        let Some(ident) = field.ident.as_ref() else {
+            span_err(field.span().unwrap(), "tuple structs are not supported").emit();
+            return TokenStream::new();
+        };
         let ident = format_ident!("{}", ident); // strip `r#` prefix, if present
 
         quote! {

compiler/rustc_macros/src/diagnostics/error.rs

@@ -56,7 +56,7 @@ fn path_to_string(path: &syn::Path) -> String {
 /// Returns an error diagnostic on span `span` with msg `msg`.
 #[must_use]
 pub(crate) fn span_err<T: Into<String>>(span: impl MultiSpan, msg: T) -> Diagnostic {
-    Diagnostic::spanned(span, Level::Error, msg)
+    Diagnostic::spanned(span, Level::Error, format!("derive(Diagnostic): {}", msg.into()))
 }
 
 /// Emit a diagnostic on span `$span` with msg `$msg` (optionally performing additional decoration

compiler/rustc_macros/src/diagnostics/utils.rs

@@ -243,7 +243,7 @@ impl<T> SetOnce<T> for SpannedOption<T> {
                 *self = Some((value, span));
             }
             Some((_, prev_span)) => {
-                span_err(span, "specified multiple times")
+                span_err(span, "attribute specified multiple times")
                     .span_note(*prev_span, "previously specified here")
                     .emit();
             }

src/etc/cat-and-grep.sh

@@ -33,7 +33,6 @@ while getopts ':vieh' OPTION; do
     case "$OPTION" in
         v)
             INVERT=1
-            ERROR_MSG='should not be found'
             ;;
         i)
             GREPFLAGS="i$GREPFLAGS"

src/tools/compiletest/src/runtest.rs

@@ -1096,6 +1096,10 @@ impl<'test> TestCx<'test> {
         self.config.target.contains("vxworks") && !self.is_vxworks_pure_static()
     }
 
+    fn has_aux_dir(&self) -> bool {
+        !self.props.aux.builds.is_empty() || !self.props.aux.crates.is_empty()
+    }
+
     fn aux_output_dir(&self) -> PathBuf {
         let aux_dir = self.aux_output_dir_name();
 
@@ -1649,7 +1653,11 @@ impl<'test> TestCx<'test> {
         }
 
         if let LinkToAux::Yes = link_to_aux {
-            rustc.arg("-L").arg(self.aux_output_dir_name());
+            // if we pass an `-L` argument to a directory that doesn't exist,
+            // macOS ld emits warnings which disrupt the .stderr files
+            if self.has_aux_dir() {
+                rustc.arg("-L").arg(self.aux_output_dir_name());
+            }
         }
 
         rustc.args(&self.props.compile_flags);

tests/run-make/linkage-attr-framework/main.rs

@@ -0,0 +1,17 @@
+#![cfg_attr(any(weak, both), feature(link_arg_attribute))]
+
+#[cfg_attr(any(link, both), link(name = "CoreFoundation", kind = "framework"))]
+#[cfg_attr(
+    any(weak, both),
+    link(name = "-weak_framework", kind = "link-arg", modifiers = "+verbatim"),
+    link(name = "CoreFoundation", kind = "link-arg", modifiers = "+verbatim")
+)]
+extern "C" {
+    fn CFRunLoopGetTypeID() -> core::ffi::c_ulong;
+}
+
+fn main() {
+    unsafe {
+        CFRunLoopGetTypeID();
+    }
+}

tests/run-make/linkage-attr-framework/rmake.rs

@@ -0,0 +1,26 @@
+//! Check that linking frameworks on Apple platforms works.
+
+//@ only-apple
+
+use run_make_support::{Rustc, run, rustc};
+
+fn compile(cfg: &str) -> Rustc {
+    let mut rustc = rustc();
+    rustc.cfg(cfg).input("main.rs");
+    rustc
+}
+
+fn main() {
+    for cfg in ["link", "weak", "both"] {
+        compile(cfg).run();
+        run("main");
+    }
+
+    let errs = compile("omit").run_fail();
+    // The linker's exact error output changes between Xcode versions, depends on
+    // linker invocation details, and the linker sometimes outputs more warnings.
+    errs.assert_stderr_contains_regex(r"error: linking with `.*` failed");
+    errs.assert_stderr_contains_regex(r"(Undefined symbols|ld: symbol[^\s]* not found)");
+    errs.assert_stderr_contains_regex(r".?_CFRunLoopGetTypeID.?, referenced from:");
+    errs.assert_stderr_contains("clang: error: linker command failed with exit code 1");
+}