Remove an Option and instead eagerly create error lifetimes

Author: oli-obk

compiler/rustc_hir_analysis/src/collect.rs

@@ -18,7 +18,7 @@ use rustc_ast::Recovered;
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
 use rustc_data_structures::unord::UnordMap;
-use rustc_errors::{Applicability, Diag, ErrorGuaranteed, StashKey};
+use rustc_errors::{struct_span_code_err, Applicability, Diag, ErrorGuaranteed, StashKey, E0228};
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -378,8 +378,29 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
         false
     }
 
-    fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
-        None
+    fn re_infer(
+        &self,
+        _: Option<&ty::GenericParamDef>,
+        span: Span,
+        object_lifetime_default: bool,
+    ) -> ty::Region<'tcx> {
+        if object_lifetime_default {
+            // We will have already emitted an error E0106 complaining about a
+            // missing named lifetime in `&dyn Trait`, so we elide this one.
+            let e = struct_span_code_err!(
+                self.tcx().dcx(),
+                span,
+                E0228,
+                "the lifetime bound for this object type cannot be deduced \
+                from context; please supply an explicit bound"
+            )
+            .emit();
+            self.set_tainted_by_errors(e);
+            ty::Region::new_error(self.tcx(), e)
+        } else {
+            // This indicates an illegal lifetime in a non-assoc-trait position
+            ty::Region::new_error_with_message(self.tcx(), span, "unelided lifetime in signature")
+        }
     }
 
     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -96,8 +96,14 @@ pub trait HirTyLowerer<'tcx> {
     fn allow_infer(&self) -> bool;
 
     /// Returns the region to use when a lifetime is omitted (and not elided).
-    fn re_infer(&self, param: Option<&ty::GenericParamDef>, span: Span)
-    -> Option<ty::Region<'tcx>>;
+    ///
+    /// The `borrowed` argument states whether this lifetime is from a reference.
+    fn re_infer(
+        &self,
+        param: Option<&ty::GenericParamDef>,
+        span: Span,
+        object_lifetime_default: bool,
+    ) -> ty::Region<'tcx>;
 
     /// Returns the type to use when a type is omitted.
     fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx>;
@@ -292,21 +298,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
             Some(rbv::ResolvedArg::Error(guar)) => ty::Region::new_error(tcx, guar),
 
-            None => {
-                self.re_infer(def, lifetime.ident.span).unwrap_or_else(|| {
-                    debug!(?lifetime, "unelided lifetime in signature");
-
-                    // This indicates an illegal lifetime
-                    // elision. `resolve_lifetime` should have
-                    // reported an error in this case -- but if
-                    // not, let's error out.
-                    ty::Region::new_error_with_message(
-                        tcx,
-                        lifetime.ident.span,
-                        "unelided lifetime in signature",
-                    )
-                })
-            }
+            None => self.re_infer(def, lifetime.ident.span, false),
         }
     }
 
@@ -501,20 +493,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             ) -> ty::GenericArg<'tcx> {
                 let tcx = self.lowerer.tcx();
                 match param.kind {
-                    GenericParamDefKind::Lifetime => self
-                        .lowerer
-                        .re_infer(Some(param), self.span)
-                        .unwrap_or_else(|| {
-                            debug!(?param, "unelided lifetime in signature");
-
-                            // This indicates an illegal lifetime in a non-assoc-trait position
-                            ty::Region::new_error_with_message(
-                                tcx,
-                                self.span,
-                                "unelided lifetime in signature",
-                            )
-                        })
-                        .into(),
+                    GenericParamDefKind::Lifetime => {
+                        self.lowerer.re_infer(Some(param), self.span, false).into()
+                    }
                     GenericParamDefKind::Type { has_default, .. } => {
                         if !infer_args && has_default {
                             // No type parameter provided, but a default exists.

compiler/rustc_hir_analysis/src/hir_ty_lowering/object_safety.rs

@@ -327,24 +327,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 if tcx.named_bound_var(lifetime.hir_id).is_some() {
                     self.lower_lifetime(lifetime, None)
                 } else {
-                    self.re_infer(None, span).unwrap_or_else(|| {
-                        let err = struct_span_code_err!(
-                            tcx.dcx(),
-                            span,
-                            E0228,
-                            "the lifetime bound for this object type cannot be deduced \
-                             from context; please supply an explicit bound"
-                        );
-                        let e = if borrowed {
-                            // We will have already emitted an error E0106 complaining about a
-                            // missing named lifetime in `&dyn Trait`, so we elide this one.
-                            err.delay_as_bug()
-                        } else {
-                            err.emit()
-                        };
-                        self.set_tainted_by_errors(e);
-                        ty::Region::new_error(tcx, e)
-                    })
+                    self.re_infer(None, span, !borrowed)
                 }
             })
         };

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -1321,7 +1321,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let tcx = self.fcx.tcx();
                 match param.kind {
                     GenericParamDefKind::Lifetime => {
-                        self.fcx.re_infer(Some(param), self.span).unwrap().into()
+                        self.fcx.re_infer(Some(param), self.span, false).into()
                     }
                     GenericParamDefKind::Type { has_default, .. } => {
                         if !infer_args && has_default {

compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs

@@ -226,12 +226,17 @@ impl<'a, 'tcx> HirTyLowerer<'tcx> for FnCtxt<'a, 'tcx> {
         true
     }
 
-    fn re_infer(&self, def: Option<&ty::GenericParamDef>, span: Span) -> Option<ty::Region<'tcx>> {
+    fn re_infer(
+        &self,
+        def: Option<&ty::GenericParamDef>,
+        span: Span,
+        _object_lifetime_default: bool,
+    ) -> ty::Region<'tcx> {
         let v = match def {
             Some(def) => infer::RegionParameterDefinition(span, def.name),
             None => infer::MiscVariable(span),
         };
-        Some(self.next_region_var(v))
+        self.next_region_var(v)
     }
 
     fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {

tests/ui/lifetimes/unusual-rib-combinations.rs

@@ -26,5 +26,6 @@ fn d<const C: S>() {}
 trait Foo<'a> {}
 struct Bar<const N: &'a (dyn for<'a> Foo<'a>)>;
 //~^ ERROR the type of const parameters must not depend on other generic parameters
+//~| ERROR `&dyn for<'a> Foo<'a>` is forbidden as the type of a const generic parameter
 
 fn main() {}

tests/ui/lifetimes/unusual-rib-combinations.stderr

@@ -61,7 +61,19 @@ help: add `#![feature(adt_const_params)]` to the crate attributes to enable more
 LL + #![feature(adt_const_params)]
    |
 
-error: aborting due to 8 previous errors
+error: `&dyn for<'a> Foo<'a>` is forbidden as the type of a const generic parameter
+  --> $DIR/unusual-rib-combinations.rs:27:21
+   |
+LL | struct Bar<const N: &'a (dyn for<'a> Foo<'a>)>;
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
+   |
+LL + #![feature(adt_const_params)]
+   |
+
+error: aborting due to 9 previous errors
 
 Some errors have detailed explanations: E0106, E0214, E0308, E0770.
 For more information about an error, try `rustc --explain E0106`.