Auto merge of #53900 - davidtwco:issue-53771, r=nikomatsakis

NLL regresses diagnostic for impl-trait/static-return-lifetime-infered.rs

Fixes #53771.

r? @nikomatsakis
cc @pnkfelix @estebank

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

@@ -56,9 +56,9 @@ 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.is_suitable_region(sup)?;
+        let anon_reg_sup = self.tcx.is_suitable_region(sup)?;
 
-        let anon_reg_sub = self.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;

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

@@ -36,7 +36,7 @@ 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.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) {

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

@@ -33,23 +33,23 @@ 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.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.is_suitable_region(sup).unwrap(),
+                self.tcx.is_suitable_region(sup).unwrap(),
             )
-        } else if self.is_named_region(sup) && self.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.is_suitable_region(sub).unwrap(),
+                self.tcx.is_suitable_region(sub).unwrap(),
             )
         } else {
             return None; // inapplicable

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

@@ -27,9 +27,9 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
                     sup_origin,
                     sup_r,
                 ) => {
-                    let anon_reg_sup = self.is_suitable_region(sup_r)?;
+                    let anon_reg_sup = self.tcx.is_suitable_region(sup_r)?;
                     if sub_r == &RegionKind::ReStatic &&
-                        self.is_return_type_impl_trait(anon_reg_sup.def_id)
+                        self.tcx.return_type_impl_trait(anon_reg_sup.def_id).is_some()
                     {
                         let sp = var_origin.span();
                         let return_sp = sub_origin.span();

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

@@ -15,7 +15,6 @@ use hir;
 use infer::error_reporting::nice_region_error::NiceRegionError;
 use ty::{self, Region, Ty};
 use hir::def_id::DefId;
-use hir::Node;
 use syntax_pos::Span;
 
 // The struct contains the information about the anonymous region
@@ -35,18 +34,6 @@ pub(super) struct AnonymousArgInfo<'tcx> {
     pub is_first: bool,
 }
 
-// This struct contains information regarding the
-// Refree((FreeRegion) corresponding to lifetime conflict
-#[derive(Debug)]
-pub(super) struct FreeRegionInfo {
-    // def id corresponding to FreeRegion
-    pub def_id: DefId,
-    // the bound region corresponding to FreeRegion
-    pub boundregion: ty::BoundRegion,
-    // checks if bound region is in Impl Item
-    pub is_impl_item: bool,
-}
-
 impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
     // This method walks the Type of the function body arguments using
     // `fold_regions()` function and returns the
@@ -122,36 +109,6 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
         }
     }
 
-    // This method returns the DefId and the BoundRegion corresponding to the given region.
-    pub(super) fn is_suitable_region(&self, region: Region<'tcx>) -> Option<FreeRegionInfo> {
-        let (suitable_region_binding_scope, bound_region) = match *region {
-            ty::ReFree(ref free_region) => (free_region.scope, free_region.bound_region),
-            ty::ReEarlyBound(ref ebr) => (
-                self.tcx.parent_def_id(ebr.def_id).unwrap(),
-                ty::BoundRegion::BrNamed(ebr.def_id, ebr.name),
-            ),
-            _ => return None, // not a free region
-        };
-
-        let node_id = self.tcx
-            .hir
-            .as_local_node_id(suitable_region_binding_scope)
-            .unwrap();
-        let is_impl_item = match self.tcx.hir.find(node_id) {
-            Some(Node::Item(..)) | Some(Node::TraitItem(..)) => false,
-            Some(Node::ImplItem(..)) => {
-                self.is_bound_region_in_impl_item(suitable_region_binding_scope)
-            }
-            _ => return None,
-        };
-
-        return Some(FreeRegionInfo {
-            def_id: suitable_region_binding_scope,
-            boundregion: bound_region,
-            is_impl_item: is_impl_item,
-        });
-    }
-
     // Here, we check for the case where the anonymous region
     // is in the return type.
     // FIXME(#42703) - Need to handle certain cases here.
@@ -176,22 +133,6 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
         None
     }
 
-    pub(super) fn is_return_type_impl_trait(
-        &self,
-        scope_def_id: DefId,
-    ) -> bool {
-        let ret_ty = self.tcx.type_of(scope_def_id);
-        match ret_ty.sty {
-            ty::FnDef(_, _) => {
-                let sig = ret_ty.fn_sig(self.tcx);
-                let output = self.tcx.erase_late_bound_regions(&sig.output());
-                return output.is_impl_trait();
-            }
-            _ => {}
-        }
-        false
-    }
-
     // Here we check for the case where anonymous region
     // corresponds to self and if yes, we display E0312.
     // FIXME(#42700) - Need to format self properly to
@@ -203,24 +144,4 @@ impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
                 .map(|i| i.method_has_self_argument) == Some(true)
     }
 
-    // Here we check if the bound region is in Impl Item.
-    pub(super) fn is_bound_region_in_impl_item(
-        &self,
-        suitable_region_binding_scope: DefId,
-    ) -> bool {
-        let container_id = self.tcx
-            .associated_item(suitable_region_binding_scope)
-            .container
-            .id();
-        if self.tcx.impl_trait_ref(container_id).is_some() {
-            // For now, we do not try to target impls of traits. This is
-            // because this message is going to suggest that the user
-            // change the fn signature, but they may not be free to do so,
-            // since the signature must match the trait.
-            //
-            // FIXME(#42706) -- in some cases, we could do better here.
-            return true;
-        }
-        false
-    }
 }

src/librustc/ty/context.rs

@@ -17,7 +17,7 @@ use session::Session;
 use session::config::{BorrowckMode, OutputFilenames};
 use session::config::CrateType;
 use middle;
-use hir::{TraitCandidate, HirId, ItemLocalId};
+use hir::{TraitCandidate, HirId, ItemLocalId, Node};
 use hir::def::{Def, Export};
 use hir::def_id::{CrateNum, DefId, DefIndex, LOCAL_CRATE};
 use hir::map as hir_map;
@@ -872,6 +872,18 @@ impl<'tcx> CommonTypes<'tcx> {
     }
 }
 
+// This struct contains information regarding the `ReFree(FreeRegion)` corresponding to a lifetime
+// conflict.
+#[derive(Debug)]
+pub struct FreeRegionInfo {
+    // def id corresponding to FreeRegion
+    pub def_id: DefId,
+    // the bound region corresponding to FreeRegion
+    pub boundregion: ty::BoundRegion,
+    // checks if bound region is in Impl Item
+    pub is_impl_item: bool,
+}
+
 /// The central data structure of the compiler. It stores references
 /// to the various **arenas** and also houses the results of the
 /// various **compiler queries** that have been performed. See the
@@ -1571,6 +1583,74 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             }
         })
     }
+
+    // This method returns the DefId and the BoundRegion corresponding to the given region.
+    pub fn is_suitable_region(&self, region: Region<'tcx>) -> Option<FreeRegionInfo> {
+        let (suitable_region_binding_scope, bound_region) = match *region {
+            ty::ReFree(ref free_region) => (free_region.scope, free_region.bound_region),
+            ty::ReEarlyBound(ref ebr) => (
+                self.parent_def_id(ebr.def_id).unwrap(),
+                ty::BoundRegion::BrNamed(ebr.def_id, ebr.name),
+            ),
+            _ => return None, // not a free region
+        };
+
+        let node_id = self.hir
+            .as_local_node_id(suitable_region_binding_scope)
+            .unwrap();
+        let is_impl_item = match self.hir.find(node_id) {
+            Some(Node::Item(..)) | Some(Node::TraitItem(..)) => false,
+            Some(Node::ImplItem(..)) => {
+                self.is_bound_region_in_impl_item(suitable_region_binding_scope)
+            }
+            _ => return None,
+        };
+
+        return Some(FreeRegionInfo {
+            def_id: suitable_region_binding_scope,
+            boundregion: bound_region,
+            is_impl_item: is_impl_item,
+        });
+    }
+
+    pub fn return_type_impl_trait(
+        &self,
+        scope_def_id: DefId,
+    ) -> Option<Ty<'tcx>> {
+        let ret_ty = self.type_of(scope_def_id);
+        match ret_ty.sty {
+            ty::FnDef(_, _) => {
+                let sig = ret_ty.fn_sig(*self);
+                let output = self.erase_late_bound_regions(&sig.output());
+                if output.is_impl_trait() {
+                    Some(output)
+                } else {
+                    None
+                }
+            }
+            _ => None
+        }
+    }
+
+    // Here we check if the bound region is in Impl Item.
+    pub fn is_bound_region_in_impl_item(
+        &self,
+        suitable_region_binding_scope: DefId,
+    ) -> bool {
+        let container_id = self.associated_item(suitable_region_binding_scope)
+            .container
+            .id();
+        if self.impl_trait_ref(container_id).is_some() {
+            // For now, we do not try to target impls of traits. This is
+            // because this message is going to suggest that the user
+            // change the fn signature, but they may not be free to do so,
+            // since the signature must match the trait.
+            //
+            // FIXME(#42706) -- in some cases, we could do better here.
+            return true;
+        }
+        false
+    }
 }
 
 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {

src/librustc/ty/mod.rs

@@ -80,7 +80,7 @@ pub use self::sty::TyKind::*;
 pub use self::binding::BindingMode;
 pub use self::binding::BindingMode::*;
 
-pub use self::context::{TyCtxt, GlobalArenas, AllArenas, tls, keep_local};
+pub use self::context::{TyCtxt, FreeRegionInfo, GlobalArenas, AllArenas, tls, keep_local};
 pub use self::context::{Lift, TypeckTables};
 
 pub use self::instance::{Instance, InstanceDef};