Rollup merge of #97023 - cjgillot:uniform-anon, r=estebank

Diagnose anonymous lifetimes errors more uniformly between async and regular fns

Async fns and regular fns are desugared differently.  For the former, we create a generic parameter at HIR level.  For the latter, we just create an anonymous region for typeck.

I plan to migrate regular fns to the async fn desugaring.

Before that, this PR attempts to merge the diagnostics for both cases.

r? ```@estebank```

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -567,15 +567,17 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         let lifetime =
             self.try_match_adt_and_generic_args(substs, needle_fr, args, search_stack)?;
         match lifetime.name {
-            hir::LifetimeName::Param(_)
+            hir::LifetimeName::Param(hir::ParamName::Plain(_) | hir::ParamName::Error)
             | hir::LifetimeName::Error
-            | hir::LifetimeName::Static
-            | hir::LifetimeName::Underscore => {
+            | hir::LifetimeName::Static => {
                 let lifetime_span = lifetime.span;
                 Some(RegionNameHighlight::MatchedAdtAndSegment(lifetime_span))
             }
 
-            hir::LifetimeName::ImplicitObjectLifetimeDefault | hir::LifetimeName::Implicit => {
+            hir::LifetimeName::Param(hir::ParamName::Fresh(_))
+            | hir::LifetimeName::ImplicitObjectLifetimeDefault
+            | hir::LifetimeName::Implicit
+            | hir::LifetimeName::Underscore => {
                 // In this case, the user left off the lifetime; so
                 // they wrote something like:
                 //

compiler/rustc_hir/src/hir.rs

@@ -131,6 +131,17 @@ impl LifetimeName {
         }
     }
 
+    pub fn is_anonymous(&self) -> bool {
+        match *self {
+            LifetimeName::ImplicitObjectLifetimeDefault
+            | LifetimeName::Implicit
+            | LifetimeName::Underscore
+            | LifetimeName::Param(ParamName::Fresh(_))
+            | LifetimeName::Error => true,
+            LifetimeName::Static | LifetimeName::Param(_) => false,
+        }
+    }
+
     pub fn is_elided(&self) -> bool {
         match self {
             LifetimeName::ImplicitObjectLifetimeDefault

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -72,7 +72,7 @@ use rustc_middle::ty::{
     subst::{GenericArgKind, Subst, SubstsRef},
     Binder, EarlyBinder, List, Region, Ty, TyCtxt, TypeFoldable,
 };
-use rustc_span::{sym, BytePos, DesugaringKind, Pos, Span};
+use rustc_span::{sym, symbol::kw, BytePos, DesugaringKind, Pos, Span};
 use rustc_target::spec::abi;
 use std::ops::ControlFlow;
 use std::{cmp, fmt, iter};
@@ -161,35 +161,45 @@ fn msg_span_from_early_bound_and_free_regions<'tcx>(
             {
                 sp = param.span;
             }
-            (format!("the lifetime `{}` as defined here", br.name), sp)
+            let text = if br.has_name() {
+                format!("the lifetime `{}` as defined here", br.name)
+            } else {
+                format!("the anonymous lifetime as defined here")
+            };
+            (text, sp)
         }
-        ty::ReFree(ty::FreeRegion {
-            bound_region: ty::BoundRegionKind::BrNamed(_, name), ..
-        }) => {
-            let mut sp = sm.guess_head_span(tcx.def_span(scope));
-            if let Some(param) =
-                tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(name))
+        ty::ReFree(ref fr) => {
+            if !fr.bound_region.is_named()
+                && let Some((ty, _)) = find_anon_type(tcx, region, &fr.bound_region)
             {
-                sp = param.span;
-            }
-            (format!("the lifetime `{}` as defined here", name), sp)
-        }
-        ty::ReFree(ref fr) => match fr.bound_region {
-            ty::BrAnon(idx) => {
-                if let Some((ty, _)) = find_anon_type(tcx, region, &fr.bound_region) {
-                    ("the anonymous lifetime defined here".to_string(), ty.span)
-                } else {
-                    (
+                ("the anonymous lifetime defined here".to_string(), ty.span)
+            } else {
+                match fr.bound_region {
+                    ty::BoundRegionKind::BrNamed(_, name) => {
+                        let mut sp = sm.guess_head_span(tcx.def_span(scope));
+                        if let Some(param) =
+                            tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(name))
+                        {
+                            sp = param.span;
+                        }
+                        let text = if name == kw::UnderscoreLifetime {
+                            format!("the anonymous lifetime as defined here")
+                        } else {
+                            format!("the lifetime `{}` as defined here", name)
+                        };
+                        (text, sp)
+                    }
+                    ty::BrAnon(idx) => (
                         format!("the anonymous lifetime #{} defined here", idx + 1),
-                        tcx.def_span(scope),
-                    )
+                        tcx.def_span(scope)
+                    ),
+                    _ => (
+                        format!("the lifetime `{}` as defined here", region),
+                        sm.guess_head_span(tcx.def_span(scope)),
+                    ),
                 }
             }
-            _ => (
-                format!("the lifetime `{}` as defined here", region),
-                sm.guess_head_span(tcx.def_span(scope)),
-            ),
-        },
+        }
         _ => bug!(),
     }
 }
@@ -2552,7 +2562,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 ty::ReEarlyBound(ty::EarlyBoundRegion { name, .. })
                 | ty::ReFree(ty::FreeRegion { bound_region: ty::BrNamed(_, name), .. }),
                 _,
-            ) => {
+            ) if name != kw::UnderscoreLifetime => {
                 // Does the required lifetime have a nice name we can print?
                 let mut err = struct_span_err!(
                     self.tcx.sess,

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs

@@ -12,6 +12,7 @@ use rustc_errors::{struct_span_err, Applicability, Diagnostic, ErrorGuaranteed};
 use rustc_hir as hir;
 use rustc_hir::{GenericParamKind, Ty};
 use rustc_middle::ty::Region;
+use rustc_span::symbol::kw;
 
 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
     /// Print the error message for lifetime errors when both the concerned regions are anonymous.
@@ -169,7 +170,7 @@ pub fn suggest_adding_lifetime_params<'tcx>(
         return false;
     };
 
-    if !lifetime_sub.name.is_elided() || !lifetime_sup.name.is_elided() {
+    if !lifetime_sub.name.is_anonymous() || !lifetime_sup.name.is_anonymous() {
         return false;
     };
 
@@ -188,32 +189,37 @@ pub fn suggest_adding_lifetime_params<'tcx>(
         _ => return false,
     };
 
-    let (suggestion_param_name, introduce_new) = generics
+    let suggestion_param_name = generics
         .params
         .iter()
-        .find(|p| matches!(p.kind, GenericParamKind::Lifetime { .. }))
-        .and_then(|p| tcx.sess.source_map().span_to_snippet(p.span).ok())
-        .map(|name| (name, false))
-        .unwrap_or_else(|| ("'a".to_string(), true));
-
-    let mut suggestions = vec![
-        if let hir::LifetimeName::Underscore = lifetime_sub.name {
-            (lifetime_sub.span, suggestion_param_name.clone())
+        .filter(|p| matches!(p.kind, GenericParamKind::Lifetime { .. }))
+        .map(|p| p.name.ident().name)
+        .find(|i| *i != kw::UnderscoreLifetime);
+    let introduce_new = suggestion_param_name.is_none();
+    let suggestion_param_name =
+        suggestion_param_name.map(|n| n.to_string()).unwrap_or_else(|| "'a".to_owned());
+
+    debug!(?lifetime_sup.span);
+    debug!(?lifetime_sub.span);
+    let make_suggestion = |span: rustc_span::Span| {
+        if span.is_empty() {
+            (span, format!("{}, ", suggestion_param_name))
+        } else if let Ok("&") = tcx.sess.source_map().span_to_snippet(span).as_deref() {
+            (span.shrink_to_hi(), format!("{} ", suggestion_param_name))
         } else {
-            (lifetime_sub.span.shrink_to_hi(), suggestion_param_name.clone() + " ")
-        },
-        if let hir::LifetimeName::Underscore = lifetime_sup.name {
-            (lifetime_sup.span, suggestion_param_name.clone())
-        } else {
-            (lifetime_sup.span.shrink_to_hi(), suggestion_param_name.clone() + " ")
-        },
-    ];
+            (span, suggestion_param_name.clone())
+        }
+    };
+    let mut suggestions =
+        vec![make_suggestion(lifetime_sub.span), make_suggestion(lifetime_sup.span)];
 
     if introduce_new {
-        let new_param_suggestion = match &generics.params {
-            [] => (generics.span, format!("<{}>", suggestion_param_name)),
-            [first, ..] => (first.span.shrink_to_lo(), format!("{}, ", suggestion_param_name)),
-        };
+        let new_param_suggestion =
+            if let Some(first) = generics.params.iter().find(|p| !p.name.ident().span.is_empty()) {
+                (first.span.shrink_to_lo(), format!("{}, ", suggestion_param_name))
+            } else {
+                (generics.span, format!("<{}>", suggestion_param_name))
+            };
 
         suggestions.push(new_param_suggestion);
     }

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs

@@ -4,6 +4,7 @@ use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
 use rustc_middle::ty;
+use rustc_span::symbol::kw;
 
 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
     /// When given a `ConcreteFailure` for a function with parameters containing a named region and
@@ -67,7 +68,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         let is_impl_item = region_info.is_impl_item;
 
         match br {
-            ty::BrAnon(_) => {}
+            ty::BrNamed(_, kw::UnderscoreLifetime) | ty::BrAnon(_) => {}
             _ => {
                 /* not an anonymous region */
                 debug!("try_report_named_anon_conflict: not an anonymous region");

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -2177,61 +2177,47 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
         define_scoped_cx!(self);
 
         let mut region_index = self.region_index;
+        let mut next_name = |this: &Self| loop {
+            let name = name_by_region_index(region_index);
+            region_index += 1;
+            if !this.used_region_names.contains(&name) {
+                break name;
+            }
+        };
+
         // If we want to print verbosely, then print *all* binders, even if they
         // aren't named. Eventually, we might just want this as the default, but
         // this is not *quite* right and changes the ordering of some output
         // anyways.
         let (new_value, map) = if self.tcx().sess.verbose() {
             // anon index + 1 (BrEnv takes 0) -> name
-            let mut region_map: BTreeMap<u32, Symbol> = BTreeMap::default();
+            let mut region_map: FxHashMap<_, _> = Default::default();
             let bound_vars = value.bound_vars();
             for var in bound_vars {
+                let ty::BoundVariableKind::Region(var) = var else { continue };
                 match var {
-                    ty::BoundVariableKind::Region(ty::BrNamed(_, name)) => {
+                    ty::BrAnon(_) | ty::BrEnv => {
                         start_or_continue(&mut self, "for<", ", ");
+                        let name = next_name(&self);
                         do_continue(&mut self, name);
+                        region_map.insert(var, ty::BrNamed(CRATE_DEF_ID.to_def_id(), name));
                     }
-                    ty::BoundVariableKind::Region(ty::BrAnon(i)) => {
+                    ty::BrNamed(def_id, kw::UnderscoreLifetime) => {
                         start_or_continue(&mut self, "for<", ", ");
-                        let name = loop {
-                            let name = name_by_region_index(region_index);
-                            region_index += 1;
-                            if !self.used_region_names.contains(&name) {
-                                break name;
-                            }
-                        };
+                        let name = next_name(&self);
                         do_continue(&mut self, name);
-                        region_map.insert(i + 1, name);
+                        region_map.insert(var, ty::BrNamed(def_id, name));
                     }
-                    ty::BoundVariableKind::Region(ty::BrEnv) => {
+                    ty::BrNamed(_, name) => {
                         start_or_continue(&mut self, "for<", ", ");
-                        let name = loop {
-                            let name = name_by_region_index(region_index);
-                            region_index += 1;
-                            if !self.used_region_names.contains(&name) {
-                                break name;
-                            }
-                        };
                         do_continue(&mut self, name);
-                        region_map.insert(0, name);
                     }
-                    _ => continue,
                 }
             }
             start_or_continue(&mut self, "", "> ");
 
             self.tcx.replace_late_bound_regions(value.clone(), |br| {
-                let kind = match br.kind {
-                    ty::BrNamed(_, _) => br.kind,
-                    ty::BrAnon(i) => {
-                        let name = region_map[&(i + 1)];
-                        ty::BrNamed(CRATE_DEF_ID.to_def_id(), name)
-                    }
-                    ty::BrEnv => {
-                        let name = region_map[&0];
-                        ty::BrNamed(CRATE_DEF_ID.to_def_id(), name)
-                    }
-                };
+                let kind = region_map[&br.kind];
                 self.tcx.mk_region(ty::ReLateBound(
                     ty::INNERMOST,
                     ty::BoundRegion { var: br.var, kind },
@@ -2242,21 +2228,20 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
             let mut name = |br: ty::BoundRegion| {
                 start_or_continue(&mut self, "for<", ", ");
                 let kind = match br.kind {
-                    ty::BrNamed(_, name) => {
-                        do_continue(&mut self, name);
-                        br.kind
-                    }
                     ty::BrAnon(_) | ty::BrEnv => {
-                        let name = loop {
-                            let name = name_by_region_index(region_index);
-                            region_index += 1;
-                            if !self.used_region_names.contains(&name) {
-                                break name;
-                            }
-                        };
+                        let name = next_name(&self);
                         do_continue(&mut self, name);
                         ty::BrNamed(CRATE_DEF_ID.to_def_id(), name)
                     }
+                    ty::BrNamed(def_id, kw::UnderscoreLifetime) => {
+                        let name = next_name(&self);
+                        do_continue(&mut self, name);
+                        ty::BrNamed(def_id, name)
+                    }
+                    ty::BrNamed(_, name) => {
+                        do_continue(&mut self, name);
+                        br.kind
+                    }
                 };
                 tcx.mk_region(ty::ReLateBound(ty::INNERMOST, ty::BoundRegion { var: br.var, kind }))
             };