Avoid repetition on “use of unstable library feature 'rustc_private'”

src/librustc/middle/stability.rs

@@ -18,8 +18,9 @@ use hir::def::Def;
 use hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefId, LOCAL_CRATE};
 use ty::{self, TyCtxt};
 use middle::privacy::AccessLevels;
+use session::DiagnosticMessageId;
 use syntax::symbol::Symbol;
-use syntax_pos::{Span, DUMMY_SP};
+use syntax_pos::{Span, MultiSpan, DUMMY_SP};
 use syntax::ast;
 use syntax::ast::{NodeId, Attribute};
 use syntax::feature_gate::{GateIssue, emit_feature_err, find_lang_feature_accepted_version};
@@ -597,8 +598,29 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                                            feature.as_str(), &r),
                     None => format!("use of unstable library feature '{}'", &feature)
                 };
-                emit_feature_err(&self.sess.parse_sess, &feature.as_str(), span,
-                                 GateIssue::Library(Some(issue)), &msg);
+
+
+                let msp: MultiSpan = span.into();
+                let cm = &self.sess.parse_sess.codemap();
+                let span_key = msp.primary_span().and_then(|sp: Span|
+                    if sp != DUMMY_SP {
+                        let file = cm.lookup_char_pos(sp.lo()).file;
+                        if file.name.starts_with("<") && file.name.ends_with(" macros>") {
+                            None
+                        } else {
+                            Some(span)
+                        }
+                    } else {
+                        None
+                    }
+                );
+
+                let error_id = (DiagnosticMessageId::StabilityId(issue), span_key, msg.clone());
+                let fresh = self.sess.one_time_diagnostics.borrow_mut().insert(error_id);
+                if fresh {
+                    emit_feature_err(&self.sess.parse_sess, &feature.as_str(), span,
+                                     GateIssue::Library(Some(issue)), &msg);
+                }
             }
             Some(_) => {
                 // Stable APIs are always ok to call and deprecated APIs are

src/librustc/session/mod.rs

@@ -75,10 +75,10 @@ pub struct Session {
     pub working_dir: (String, bool),
     pub lint_store: RefCell<lint::LintStore>,
     pub buffered_lints: RefCell<Option<lint::LintBuffer>>,
-    /// Set of (LintId, Option<Span>, message) tuples tracking lint
+    /// Set of (DiagnosticId, Option<Span>, message) tuples tracking
     /// (sub)diagnostics that have been set once, but should not be set again,
-    /// in order to avoid redundantly verbose output (Issue #24690).
-    pub one_time_diagnostics: RefCell<FxHashSet<(lint::LintId, Option<Span>, String)>>,
+    /// in order to avoid redundantly verbose output (Issue #24690, #44953).
+    pub one_time_diagnostics: RefCell<FxHashSet<(DiagnosticMessageId, Option<Span>, String)>>,
     pub plugin_llvm_passes: RefCell<Vec<String>>,
     pub plugin_attributes: RefCell<Vec<(String, AttributeType)>>,
     pub crate_types: RefCell<Vec<config::CrateType>>,
@@ -164,6 +164,13 @@ enum DiagnosticBuilderMethod {
     // add more variants as needed to support one-time diagnostics
 }
 
+/// Diagnostic message id - used in order to avoid emitting the same message more than once
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum DiagnosticMessageId {
+    LintId(lint::LintId),
+    StabilityId(u32)
+}
+
 impl Session {
     pub fn local_crate_disambiguator(&self) -> CrateDisambiguator {
         match *self.crate_disambiguator.borrow() {
@@ -360,7 +367,7 @@ impl Session {
                 do_method()
             },
             _ => {
-                let lint_id = lint::LintId::of(lint);
+                let lint_id = DiagnosticMessageId::LintId(lint::LintId::of(lint));
                 let id_span_message = (lint_id, span, message.to_owned());
                 let fresh = self.one_time_diagnostics.borrow_mut().insert(id_span_message);
                 if fresh {