4 files changed, 20 insertions, 34 deletions
diff --git a/library/proc_macro/src/bridge/client.rs b/library/proc_macro/src/bridge/client.rs
index 1516f084ab8..4461b21802a 100644
--- a/library/proc_macro/src/bridge/client.rs
+++ b/library/proc_macro/src/bridge/client.rs
@@ -176,8 +176,6 @@ define_handles! {
     FreeFunctions,
     TokenStream,
     SourceFile,
-    MultiSpan,
-    Diagnostic,
 
     'interned:
     Span,
diff --git a/library/proc_macro/src/bridge/mod.rs b/library/proc_macro/src/bridge/mod.rs
index 5cde966bf17..4c1e196b5ad 100644
--- a/library/proc_macro/src/bridge/mod.rs
+++ b/library/proc_macro/src/bridge/mod.rs
@@ -57,6 +57,7 @@ macro_rules! with_api {
                 fn track_env_var(var: &str, value: Option<&str>);
                 fn track_path(path: &str);
                 fn literal_from_str(s: &str) -> Result<Literal<$S::Span, $S::Symbol>, ()>;
+                fn emit_diagnostic(diagnostic: Diagnostic<$S::Span>);
             },
             TokenStream {
                 fn drop($self: $S::TokenStream);
@@ -87,22 +88,6 @@ macro_rules! with_api {
                 fn path($self: &$S::SourceFile) -> String;
                 fn is_real($self: &$S::SourceFile) -> bool;
             },
-            MultiSpan {
-                fn drop($self: $S::MultiSpan);
-                fn new() -> $S::MultiSpan;
-                fn push($self: &mut $S::MultiSpan, span: $S::Span);
-            },
-            Diagnostic {
-                fn drop($self: $S::Diagnostic);
-                fn new(level: Level, msg: &str, span: $S::MultiSpan) -> $S::Diagnostic;
-                fn sub(
-                    $self: &mut $S::Diagnostic,
-                    level: Level,
-                    msg: &str,
-                    span: $S::MultiSpan,
-                );
-                fn emit($self: $S::Diagnostic);
-            },
             Span {
                 fn debug($self: $S::Span) -> String;
                 fn source_file($self: $S::Span) -> $S::SourceFile;
@@ -510,6 +495,18 @@ compound_traits!(
     }
 );
 
+#[derive(Clone, Debug)]
+pub struct Diagnostic<Span> {
+    pub level: Level,
+    pub message: String,
+    pub spans: Vec<Span>,
+    pub children: Vec<Diagnostic<Span>>,
+}
+
+compound_traits!(
+    struct Diagnostic<Span> { level, message, spans, children }
+);
+
 /// Globals provided alongside the initial inputs for a macro expansion.
 /// Provides values such as spans which are used frequently to avoid RPC.
 #[derive(Clone)]
diff --git a/library/proc_macro/src/bridge/server.rs b/library/proc_macro/src/bridge/server.rs
index e068ec60b6a..e47a77f6c13 100644
--- a/library/proc_macro/src/bridge/server.rs
+++ b/library/proc_macro/src/bridge/server.rs
@@ -11,8 +11,6 @@ pub trait Types {
     type FreeFunctions: 'static;
     type TokenStream: 'static + Clone;
     type SourceFile: 'static + Clone;
-    type MultiSpan: 'static;
-    type Diagnostic: 'static;
     type Span: 'static + Copy + Eq + Hash;
     type Symbol: 'static;
 }
diff --git a/library/proc_macro/src/diagnostic.rs b/library/proc_macro/src/diagnostic.rs
index 6e46dc0367d..5a209f7c7aa 100644
--- a/library/proc_macro/src/diagnostic.rs
+++ b/library/proc_macro/src/diagnostic.rs
@@ -161,22 +161,15 @@ impl Diagnostic {
     /// Emit the diagnostic.
     #[unstable(feature = "proc_macro_diagnostic", issue = "54140")]
     pub fn emit(self) {
-        fn to_internal(spans: Vec<Span>) -> crate::bridge::client::MultiSpan {
-            let mut multi_span = crate::bridge::client::MultiSpan::new();
-            for span in spans {
-                multi_span.push(span.0);
+        fn to_internal(diag: Diagnostic) -> crate::bridge::Diagnostic<crate::bridge::client::Span> {
+            crate::bridge::Diagnostic {
+                level: diag.level,
+                message: diag.message,
+                spans: diag.spans.into_iter().map(|s| s.0).collect(),
+                children: diag.children.into_iter().map(to_internal).collect(),
             }
-            multi_span
         }
 
-        let mut diag = crate::bridge::client::Diagnostic::new(
-            self.level,
-            &self.message[..],
-            to_internal(self.spans),
-        );
-        for c in self.children {
-            diag.sub(c.level, &c.message[..], to_internal(c.spans));
-        }
-        diag.emit();
+        crate::bridge::client::FreeFunctions::emit_diagnostic(to_internal(self));
     }
 }