Auto merge of #57901 - lqd:issue_57362, r=nikomatsakis

Add information to higher-ranked lifetimes conflicts error messages

Make these errors go through the new "placeholder error" code path, to have self tys displayed and make them hopefully less confusing.

Should fix #57362.

r? @nikomatsakis — so we can iterate on the specific wording you wanted.

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

@@ -46,9 +46,9 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
         let (span, sub, sup) = self.get_regions();
 
         // Determine whether the sub and sup consist of both anonymous (elided) regions.
-        let anon_reg_sup = self.tcx.is_suitable_region(sup)?;
+        let anon_reg_sup = self.tcx().is_suitable_region(sup)?;
 
-        let anon_reg_sub = self.tcx.is_suitable_region(sub)?;
+        let anon_reg_sub = self.tcx().is_suitable_region(sub)?;
         let scope_def_id_sup = anon_reg_sup.def_id;
         let bregion_sup = anon_reg_sup.boundregion;
         let scope_def_id_sub = anon_reg_sub.def_id;
@@ -138,7 +138,7 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
         };
 
 
-        struct_span_err!(self.tcx.sess, span, E0623, "lifetime mismatch")
+        struct_span_err!(self.tcx().sess, span, E0623, "lifetime mismatch")
             .span_label(span_1, main_label)
             .span_label(span_2, String::new())
             .span_label(span, span_label)

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

@@ -26,10 +26,10 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
         region: Region<'tcx>,
         br: &ty::BoundRegion,
     ) -> Option<(&hir::Ty, &hir::FnDecl)> {
-        if let Some(anon_reg) = self.tcx.is_suitable_region(region) {
+        if let Some(anon_reg) = self.tcx().is_suitable_region(region) {
             let def_id = anon_reg.def_id;
-            if let Some(node_id) = self.tcx.hir().as_local_node_id(def_id) {
-                let fndecl = match self.tcx.hir().get(node_id) {
+            if let Some(node_id) = self.tcx().hir().as_local_node_id(def_id) {
+                let fndecl = match self.tcx().hir().get(node_id) {
                     Node::Item(&hir::Item {
                         node: hir::ItemKind::Fn(ref fndecl, ..),
                         ..
@@ -64,7 +64,7 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
         br: &ty::BoundRegion,
     ) -> Option<(&'gcx hir::Ty)> {
         let mut nested_visitor = FindNestedTypeVisitor {
-            tcx: self.tcx,
+            tcx: self.tcx(),
             bound_region: *br,
             found_type: None,
             current_index: ty::INNERMOST,

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

@@ -22,37 +22,41 @@ impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
 
         if let Some(tables) = self.in_progress_tables {
             let tables = tables.borrow();
-            NiceRegionError::new(self.tcx, error.clone(), Some(&tables)).try_report().is_some()
+            NiceRegionError::new(self, error.clone(), Some(&tables)).try_report().is_some()
         } else {
-            NiceRegionError::new(self.tcx, error.clone(), None).try_report().is_some()
+            NiceRegionError::new(self, error.clone(), None).try_report().is_some()
         }
     }
 }
 
 pub struct NiceRegionError<'cx, 'gcx: 'tcx, 'tcx: 'cx> {
-    tcx: TyCtxt<'cx, 'gcx, 'tcx>,
+    infcx: &'cx InferCtxt<'cx, 'gcx, 'tcx>,
     error: Option<RegionResolutionError<'tcx>>,
     regions: Option<(Span, ty::Region<'tcx>, ty::Region<'tcx>)>,
     tables: Option<&'cx ty::TypeckTables<'tcx>>,
 }
 
 impl<'cx, 'gcx, 'tcx> NiceRegionError<'cx, 'gcx, 'tcx> {
     pub fn new(
-        tcx: TyCtxt<'cx, 'gcx, 'tcx>,
+        infcx: &'cx InferCtxt<'cx, 'gcx, 'tcx>,
         error: RegionResolutionError<'tcx>,
         tables: Option<&'cx ty::TypeckTables<'tcx>>,
     ) -> Self {
-        Self { tcx, error: Some(error), regions: None, tables }
+        Self { infcx, error: Some(error), regions: None, tables }
     }
 
     pub fn new_from_span(
-        tcx: TyCtxt<'cx, 'gcx, 'tcx>,
+        infcx: &'cx InferCtxt<'cx, 'gcx, 'tcx>,
         span: Span,
         sub: ty::Region<'tcx>,
         sup: ty::Region<'tcx>,
         tables: Option<&'cx ty::TypeckTables<'tcx>>,
     ) -> Self {
-        Self { tcx, error: None, regions: Some((span, sub, sup)), tables }
+        Self { infcx, error: None, regions: Some((span, sub, sup)), tables }
+    }
+
+    fn tcx(&self) -> TyCtxt<'cx, 'gcx, 'tcx> {
+        self.infcx.tcx
     }
 
     pub fn try_report_from_nll(&self) -> Option<ErrorReported> {

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

@@ -24,23 +24,23 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
         // version new_ty of its type where the anonymous region is replaced
         // with the named one.//scope_def_id
         let (named, anon, anon_arg_info, region_info) = if self.is_named_region(sub)
-            && self.tcx.is_suitable_region(sup).is_some()
+            && self.tcx().is_suitable_region(sup).is_some()
             && self.find_arg_with_region(sup, sub).is_some()
         {
             (
                 sub,
                 sup,
                 self.find_arg_with_region(sup, sub).unwrap(),
-                self.tcx.is_suitable_region(sup).unwrap(),
+                self.tcx().is_suitable_region(sup).unwrap(),
             )
-        } else if self.is_named_region(sup) && self.tcx.is_suitable_region(sub).is_some()
+        } else if self.is_named_region(sup) && self.tcx().is_suitable_region(sub).is_some()
             && self.find_arg_with_region(sub, sup).is_some()
         {
             (
                 sup,
                 sub,
                 self.find_arg_with_region(sub, sup).unwrap(),
-                self.tcx.is_suitable_region(sub).unwrap(),
+                self.tcx().is_suitable_region(sub).unwrap(),
             )
         } else {
             return None; // inapplicable
@@ -97,7 +97,7 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
         };
 
         struct_span_err!(
-            self.tcx.sess,
+            self.tcx().sess,
             span,
             E0621,
             "explicit lifetime required in {}",

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

@@ -47,15 +47,15 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
             // closure, provide a specific message pointing this out.
             if let (&SubregionOrigin::BindingTypeIsNotValidAtDecl(ref external_span),
                     &RegionKind::ReFree(ref free_region)) = (&sub_origin, sup_region) {
-                let hir = &self.tcx.hir();
+                let hir = &self.tcx().hir();
                 if let Some(node_id) = hir.as_local_node_id(free_region.scope) {
                     if let Node::Expr(Expr {
                         node: Closure(_, _, _, closure_span, None),
                         ..
                     }) = hir.get(node_id) {
                         let sup_sp = sup_origin.span();
                         let origin_sp = origin.span();
-                        let mut err = self.tcx.sess.struct_span_err(
+                        let mut err = self.tcx().sess.struct_span_err(
                             sup_sp,
                             "borrowed data cannot be stored outside of its closure");
                         err.span_label(sup_sp, "cannot be stored outside of its closure");