1 files changed, 172 insertions, 0 deletions

diff --git a/crates/proc_macro_srv/src/proc_macro/diagnostic.rs b/crates/proc_macro_srv/src/proc_macro/diagnostic.rs
new file mode 100644
index 000000000..55d93917c
--- /dev/null
+++ b/crates/proc_macro_srv/src/proc_macro/diagnostic.rs
@@ -0,0 +1,172 @@
+//! lib-proc-macro diagnostic
+//!
+//! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/diagnostic.rs
+//! augmented with removing unstable features
+
+use crate::proc_macro::Span;
+
+/// An enum representing a diagnostic level.
+#[derive(Copy, Clone, Debug)]
+#[non_exhaustive]
+pub enum Level {
+    /// An error.
+    Error,
+    /// A warning.
+    Warning,
+    /// A note.
+    Note,
+    /// A help message.
+    Help,
+}
+
+/// Trait implemented by types that can be converted into a set of `Span`s.
+pub trait MultiSpan {
+    /// Converts `self` into a `Vec<Span>`.
+    fn into_spans(self) -> Vec<Span>;
+}
+
+impl MultiSpan for Span {
+    fn into_spans(self) -> Vec<Span> {
+        vec![self]
+    }
+}
+
+impl MultiSpan for Vec<Span> {
+    fn into_spans(self) -> Vec<Span> {
+        self
+    }
+}
+
+impl<'a> MultiSpan for &'a [Span] {
+    fn into_spans(self) -> Vec<Span> {
+        self.to_vec()
+    }
+}
+
+/// A structure representing a diagnostic message and associated children
+/// messages.
+#[derive(Clone, Debug)]
+pub struct Diagnostic {
+    level: Level,
+    message: String,
+    spans: Vec<Span>,
+    children: Vec<Diagnostic>,
+}
+
+macro_rules! diagnostic_child_methods {
+    ($spanned:ident, $regular:ident, $level:expr) => {
+        /// Adds a new child diagnostic message to `self` with the level
+        /// identified by this method's name with the given `spans` and
+        /// `message`.
+        pub fn $spanned<S, T>(mut self, spans: S, message: T) -> Diagnostic
+        where
+            S: MultiSpan,
+            T: Into<String>,
+        {
+            self.children.push(Diagnostic::spanned(spans, $level, message));
+            self
+        }
+
+        /// Adds a new child diagnostic message to `self` with the level
+        /// identified by this method's name with the given `message`.
+        pub fn $regular<T: Into<String>>(mut self, message: T) -> Diagnostic {
+            self.children.push(Diagnostic::new($level, message));
+            self
+        }
+    };
+}
+
+/// Iterator over the children diagnostics of a `Diagnostic`.
+#[derive(Debug, Clone)]
+pub struct Children<'a>(std::slice::Iter<'a, Diagnostic>);
+
+impl<'a> Iterator for Children<'a> {
+    type Item = &'a Diagnostic;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.0.next()
+    }
+}
+
+impl Diagnostic {
+    /// Creates a new diagnostic with the given `level` and `message`.
+    pub fn new<T: Into<String>>(level: Level, message: T) -> Diagnostic {
+        Diagnostic { level: level, message: message.into(), spans: vec![], children: vec![] }
+    }
+
+    /// Creates a new diagnostic with the given `level` and `message` pointing to
+    /// the given set of `spans`.
+    pub fn spanned<S, T>(spans: S, level: Level, message: T) -> Diagnostic
+    where
+        S: MultiSpan,
+        T: Into<String>,
+    {
+        Diagnostic {
+            level: level,
+            message: message.into(),
+            spans: spans.into_spans(),
+            children: vec![],
+        }
+    }
+
+    diagnostic_child_methods!(span_error, error, Level::Error);
+    diagnostic_child_methods!(span_warning, warning, Level::Warning);
+    diagnostic_child_methods!(span_note, note, Level::Note);
+    diagnostic_child_methods!(span_help, help, Level::Help);
+
+    /// Returns the diagnostic `level` for `self`.
+    pub fn level(&self) -> Level {
+        self.level
+    }
+
+    /// Sets the level in `self` to `level`.
+    pub fn set_level(&mut self, level: Level) {
+        self.level = level;
+    }
+
+    /// Returns the message in `self`.
+    pub fn message(&self) -> &str {
+        &self.message
+    }
+
+    /// Sets the message in `self` to `message`.
+    pub fn set_message<T: Into<String>>(&mut self, message: T) {
+        self.message = message.into();
+    }
+
+    /// Returns the `Span`s in `self`.
+    pub fn spans(&self) -> &[Span] {
+        &self.spans
+    }
+
+    /// Sets the `Span`s in `self` to `spans`.
+    pub fn set_spans<S: MultiSpan>(&mut self, spans: S) {
+        self.spans = spans.into_spans();
+    }
+
+    /// Returns an iterator over the children diagnostics of `self`.
+    pub fn children(&self) -> Children<'_> {
+        Children(self.children.iter())
+    }
+
+    /// Emit the diagnostic.
+    pub fn emit(self) {
+        fn to_internal(spans: Vec<Span>) -> crate::proc_macro::bridge::client::MultiSpan {
+            let mut multi_span = crate::proc_macro::bridge::client::MultiSpan::new();
+            for span in spans {
+                multi_span.push(span.0);
+            }
+            multi_span
+        }
+
+        let mut diag = crate::proc_macro::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();
+    }
+}