2 files changed, 38 insertions, 0 deletions
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index 45c017df918..43101bbb9d3 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -44,6 +44,15 @@ pub trait IntoDiagnosticArg {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static>;
 }
 
+impl<'source> IntoDiagnosticArg for DiagnosticArgValue<'source> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        match self {
+            DiagnosticArgValue::Str(s) => DiagnosticArgValue::Str(Cow::Owned(s.into_owned())),
+            DiagnosticArgValue::Number(n) => DiagnosticArgValue::Number(n),
+        }
+    }
+}
+
 impl<'source> Into<FluentValue<'source>> for DiagnosticArgValue<'source> {
     fn into(self) -> FluentValue<'source> {
         match self {
@@ -205,6 +214,22 @@ impl Diagnostic {
     }
 
     #[track_caller]
+    pub fn new_with_messages(level: Level, messages: Vec<(DiagnosticMessage, Style)>) -> Self {
+        Diagnostic {
+            level,
+            message: messages,
+            code: None,
+            span: MultiSpan::new(),
+            children: vec![],
+            suggestions: Ok(vec![]),
+            args: Default::default(),
+            sort_span: DUMMY_SP,
+            is_lint: false,
+            emitted_at: DiagnosticLocation::caller(),
+        }
+    }
+
+    #[track_caller]
     pub fn new_with_code<M: Into<DiagnosticMessage>>(
         level: Level,
         code: Option<DiagnosticId>,
@@ -931,6 +956,13 @@ impl Diagnostic {
         self
     }
 
+    pub fn replace_args(
+        &mut self,
+        args: FxHashMap<DiagnosticArgName<'static>, DiagnosticArgValue<'static>>,
+    ) {
+        self.args = args;
+    }
+
     pub fn styled_message(&self) -> &[(DiagnosticMessage, Style)] {
         &self.message
     }
diff --git a/compiler/rustc_errors/src/diagnostic_impls.rs b/compiler/rustc_errors/src/diagnostic_impls.rs
index 22f6fc700fa..c6035705e39 100644
--- a/compiler/rustc_errors/src/diagnostic_impls.rs
+++ b/compiler/rustc_errors/src/diagnostic_impls.rs
@@ -107,6 +107,12 @@ impl IntoDiagnosticArg for String {
     }
 }
 
+impl<'a> IntoDiagnosticArg for Cow<'a, str> {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(Cow::Owned(self.into_owned()))
+    }
+}
+
 impl<'a> IntoDiagnosticArg for &'a Path {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
         DiagnosticArgValue::Str(Cow::Owned(self.display().to_string()))