Buffer and migrate nice region errors

src/librustc/infer/error_reporting/nice_region_error/mod.rs

@@ -1,9 +1,10 @@
 use crate::infer::InferCtxt;
 use crate::infer::lexical_region_resolve::RegionResolutionError;
 use crate::infer::lexical_region_resolve::RegionResolutionError::*;
-use syntax::source_map::Span;
 use crate::ty::{self, TyCtxt};
 use crate::util::common::ErrorReported;
+use errors::DiagnosticBuilder;
+use syntax::source_map::Span;
 
 mod different_lifetimes;
 mod find_anon_type;
@@ -59,7 +60,7 @@ fn tcx(&self) -> TyCtxt<'cx, 'gcx, 'tcx> {
         self.infcx.tcx
     }
 
-    pub fn try_report_from_nll(&self) -> Option<ErrorReported> {
+    pub fn try_report_from_nll(&self) -> Option<DiagnosticBuilder<'cx>> {
         // Due to the improved diagnostics returned by the MIR borrow checker, only a subset of
         // the nice region errors are required when running under the MIR borrow checker.
         self.try_report_named_anon_conflict()
@@ -68,6 +69,7 @@ pub fn try_report_from_nll(&self) -> Option<ErrorReported> {
 
     pub fn try_report(&self) -> Option<ErrorReported> {
         self.try_report_from_nll()
+            .map(|mut diag| { diag.emit(); ErrorReported })
             .or_else(|| self.try_report_anon_anon_conflict())
             .or_else(|| self.try_report_outlives_closure())
             .or_else(|| self.try_report_static_impl_trait())

src/librustc/infer/error_reporting/nice_region_error/named_anon_conflict.rs

@@ -2,13 +2,12 @@
 //! where one region is named and the other is anonymous.
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::ty;
-use crate::util::common::ErrorReported;
-use errors::Applicability;
+use errors::{Applicability, DiagnosticBuilder};
 
 impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
     /// When given a `ConcreteFailure` for a function with arguments containing a named region and
     /// an anonymous region, emit an descriptive diagnostic error.
-    pub(super) fn try_report_named_anon_conflict(&self) -> Option<ErrorReported> {
+    pub(super) fn try_report_named_anon_conflict(&self) -> Option<DiagnosticBuilder<'a>> {
         let (span, sub, sup) = self.get_regions();
 
         debug!(
@@ -96,21 +95,23 @@ pub(super) fn try_report_named_anon_conflict(&self) -> Option<ErrorReported> {
             ("parameter type".to_owned(), "type".to_owned())
         };
 
-        struct_span_err!(
+        let mut diag = struct_span_err!(
             self.tcx().sess,
             span,
             E0621,
             "explicit lifetime required in {}",
             error_var
-        ).span_suggestion(
+        );
+
+        diag.span_suggestion(
                 new_ty_span,
                 &format!("add explicit lifetime `{}` to {}", named, span_label_var),
                 new_ty.to_string(),
                 Applicability::Unspecified,
             )
-        .span_label(span, format!("lifetime `{}` required", named))
-        .emit();
-        return Some(ErrorReported);
+            .span_label(span, format!("lifetime `{}` required", named));
+
+        Some(diag)
     }
 
     // This method returns whether the given Region is Named

src/librustc/infer/error_reporting/nice_region_error/placeholder_error.rs

@@ -8,13 +8,12 @@
 use crate::ty;
 use crate::ty::error::ExpectedFound;
 use crate::ty::subst::Substs;
-use crate::util::common::ErrorReported;
 use crate::util::ppaux::RegionHighlightMode;
 
 impl NiceRegionError<'me, 'gcx, 'tcx> {
     /// When given a `ConcreteFailure` for a function with arguments containing a named region and
     /// an anonymous region, emit a descriptive diagnostic error.
-    pub(super) fn try_report_placeholder_conflict(&self) -> Option<ErrorReported> {
+    pub(super) fn try_report_placeholder_conflict(&self) -> Option<DiagnosticBuilder<'me>> {
         match &self.error {
             ///////////////////////////////////////////////////////////////////////////
             // NB. The ordering of cases in this match is very
@@ -178,7 +177,7 @@ fn try_report_placeholders_trait(
         trait_def_id: DefId,
         expected_substs: &'tcx Substs<'tcx>,
         actual_substs: &'tcx Substs<'tcx>,
-    ) -> ErrorReported {
+    ) -> DiagnosticBuilder<'me> {
         debug!(
             "try_report_placeholders_trait(\
              vid={:?}, \
@@ -295,8 +294,7 @@ fn try_report_placeholders_trait(
             any_self_ty_has_vid,
         );
 
-        err.emit();
-        ErrorReported
+        err
     }
 
     /// Add notes with details about the expected and actual trait refs, with attention to cases

src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs

@@ -244,7 +244,8 @@ pub(super) fn report_error(
         if let (Some(f), Some(o)) = (self.to_error_region(fr), self.to_error_region(outlived_fr)) {
             let tables = infcx.tcx.typeck_tables_of(mir_def_id);
             let nice = NiceRegionError::new_from_span(infcx, span, o, f, Some(tables));
-            if let Some(_error_reported) = nice.try_report_from_nll() {
+            if let Some(diag) = nice.try_report_from_nll() {
+                diag.buffer(errors_buffer);
                 return;
             }
         }