Fix #88256, remove duplicated diagnostic

compiler/rustc_errors/src/diagnostic.rs

@@ -9,9 +9,10 @@ use rustc_lint_defs::Applicability;
 use rustc_serialize::json::Json;
 use rustc_span::{MultiSpan, Span, DUMMY_SP};
 use std::fmt;
+use std::hash::{Hash, Hasher};
 
 #[must_use]
-#[derive(Clone, Debug, PartialEq, Hash, Encodable, Decodable)]
+#[derive(Clone, Debug, Encodable, Decodable)]
 pub struct Diagnostic {
     pub level: Level,
     pub message: Vec<(String, Style)>,
@@ -24,6 +25,10 @@ pub struct Diagnostic {
     /// as a sort key to sort a buffer of diagnostics.  By default, it is the primary span of
     /// `span` if there is one.  Otherwise, it is `DUMMY_SP`.
     pub sort_span: Span,
+
+    /// If diagnostic is from Lint, custom hash function ignores notes
+    /// otherwise hash is based on the all the fields
+    pub is_lint: bool,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
@@ -91,6 +96,7 @@ impl Diagnostic {
             children: vec![],
             suggestions: vec![],
             sort_span: DUMMY_SP,
+            is_lint: false,
         }
     }
 
@@ -558,6 +564,11 @@ impl Diagnostic {
         self
     }
 
+    pub fn set_is_lint(&mut self) -> &mut Self {
+        self.is_lint = true;
+        self
+    }
+
     pub fn code(&mut self, s: DiagnosticId) -> &mut Self {
         self.code = Some(s);
         self
@@ -617,6 +628,42 @@ impl Diagnostic {
         let sub = SubDiagnostic { level, message, span, render_span };
         self.children.push(sub);
     }
+
+    /// Fields used for Hash, and PartialEq trait
+    fn keys(
+        &self,
+    ) -> (
+        &Level,
+        &Vec<(String, Style)>,
+        &Option<DiagnosticId>,
+        &MultiSpan,
+        &Vec<CodeSuggestion>,
+        Option<&Vec<SubDiagnostic>>,
+    ) {
+        (
+            &self.level,
+            &self.message,
+            &self.code,
+            &self.span,
+            &self.suggestions,
+            (if self.is_lint { None } else { Some(&self.children) }),
+        )
+    }
+}
+
+impl Hash for Diagnostic {
+    fn hash<H>(&self, state: &mut H)
+    where
+        H: Hasher,
+    {
+        self.keys().hash(state);
+    }
+}
+
+impl PartialEq for Diagnostic {
+    fn eq(&self, other: &Self) -> bool {
+        self.keys() == other.keys()
+    }
 }
 
 impl SubDiagnostic {

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -242,6 +242,7 @@ impl<'a> DiagnosticBuilder<'a> {
         sp: S,
         msg: &str,
     ) -> &mut Self);
+    forward!(pub fn set_is_lint(&mut self,) -> &mut Self);
 
     /// See [`Diagnostic::multipart_suggestion()`].
     pub fn multipart_suggestion(