Enforce supertrait outlives obligations hold when confirming impl

Author: compiler-errors

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -27,6 +27,7 @@ use crate::traits::project::ProjectAndUnifyResult;
 use crate::traits::project::ProjectionCacheKeyExt;
 use crate::traits::ProjectionCacheKey;
 use crate::traits::Unimplemented;
+use hir::def::DefKind;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_errors::{Diag, EmissionGuarantee};
@@ -35,6 +36,7 @@ use rustc_hir::def_id::DefId;
 use rustc_infer::infer::BoundRegionConversionTime;
 use rustc_infer::infer::BoundRegionConversionTime::HigherRankedType;
 use rustc_infer::infer::DefineOpaqueTypes;
+use rustc_infer::traits::util::elaborate;
 use rustc_infer::traits::TraitObligation;
 use rustc_middle::dep_graph::dep_kinds;
 use rustc_middle::dep_graph::DepNodeIndex;
@@ -2795,6 +2797,34 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
             });
         }
 
+        if matches!(self.tcx().def_kind(def_id), DefKind::Impl { of_trait: true })
+            && let Some(header) = self.tcx().impl_trait_header(def_id)
+        {
+            let trait_clause: ty::Clause<'tcx> =
+                header.trait_ref.instantiate(self.tcx(), args).to_predicate(self.tcx());
+            for clause in elaborate(self.tcx(), [trait_clause]) {
+                if matches!(
+                    clause.kind().skip_binder(),
+                    ty::ClauseKind::TypeOutlives(..) | ty::ClauseKind::RegionOutlives(..)
+                ) {
+                    let clause = normalize_with_depth_to(
+                        self,
+                        param_env,
+                        cause.clone(),
+                        recursion_depth,
+                        clause,
+                        &mut obligations,
+                    );
+                    obligations.push(Obligation {
+                        cause: cause.clone(),
+                        recursion_depth,
+                        param_env,
+                        predicate: clause.as_predicate(),
+                    });
+                }
+            }
+        }
+
         obligations
     }
 }

tests/ui/fn/implied-bounds-unnorm-associated-type-5.rs

@@ -5,6 +5,7 @@ trait Trait<'a>: 'a {
 // if the `T: 'a` bound gets implied we would probably get ub here again
 impl<'a, T> Trait<'a> for T {
     //~^ ERROR the parameter type `T` may not live long enough
+    //~| ERROR the parameter type `T` may not live long enough
     type Type = ();
 }
 

tests/ui/fn/implied-bounds-unnorm-associated-type-5.stderr

@@ -16,8 +16,21 @@ help: consider adding an explicit lifetime bound
 LL | impl<'a, T: 'a> Trait<'a> for T {
    |           ++++
 
+error[E0309]: the parameter type `T` may not live long enough
+  --> $DIR/implied-bounds-unnorm-associated-type-5.rs:6:27
+   |
+LL | impl<'a, T> Trait<'a> for T {
+   |      --                   ^ ...so that the type `T` will meet its required lifetime bounds
+   |      |
+   |      the parameter type `T` must be valid for the lifetime `'a` as defined here...
+   |
+help: consider adding an explicit lifetime bound
+   |
+LL | impl<'a, T: 'a> Trait<'a> for T {
+   |           ++++
+
 error[E0505]: cannot move out of `x` because it is borrowed
-  --> $DIR/implied-bounds-unnorm-associated-type-5.rs:21:10
+  --> $DIR/implied-bounds-unnorm-associated-type-5.rs:22:10
    |
 LL |     let x = String::from("Hello World!");
    |         - binding `x` declared here
@@ -34,7 +47,7 @@ LL -     let y = f(&x, ());
 LL +     let y = f(x.clone(), ());
    |
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 Some errors have detailed explanations: E0309, E0505.
 For more information about an error, try `rustc --explain E0309`.

tests/ui/static/static-lifetime.rs

@@ -1,6 +1,7 @@
 pub trait Arbitrary: Sized + 'static {}
 
 impl<'a, A: Clone> Arbitrary for ::std::borrow::Cow<'a, A> {} //~ ERROR lifetime bound
+//~^ ERROR cannot infer an appropriate lifetime for lifetime parameter `'a`
 
 fn main() {
 }

tests/ui/static/static-lifetime.stderr

@@ -11,6 +11,32 @@ LL | impl<'a, A: Clone> Arbitrary for ::std::borrow::Cow<'a, A> {}
    |      ^^
    = note: but lifetime parameter must outlive the static lifetime
 
-error: aborting due to 1 previous error
+error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements
+  --> $DIR/static-lifetime.rs:3:34
+   |
+LL | impl<'a, A: Clone> Arbitrary for ::std::borrow::Cow<'a, A> {}
+   |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: first, the lifetime cannot outlive the lifetime `'a` as defined here...
+  --> $DIR/static-lifetime.rs:3:6
+   |
+LL | impl<'a, A: Clone> Arbitrary for ::std::borrow::Cow<'a, A> {}
+   |      ^^
+note: ...so that the types are compatible
+  --> $DIR/static-lifetime.rs:3:34
+   |
+LL | impl<'a, A: Clone> Arbitrary for ::std::borrow::Cow<'a, A> {}
+   |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: expected `<Cow<'a, A> as Arbitrary>`
+              found `<Cow<'_, A> as Arbitrary>`
+   = note: but, the lifetime must be valid for the static lifetime...
+note: ...so that the declared lifetime parameter bounds are satisfied
+  --> $DIR/static-lifetime.rs:3:34
+   |
+LL | impl<'a, A: Clone> Arbitrary for ::std::borrow::Cow<'a, A> {}
+   |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0478`.
+Some errors have detailed explanations: E0478, E0495.
+For more information about an error, try `rustc --explain E0478`.

tests/ui/wf/wf-in-where-clause-static.rs

@@ -1,10 +1,3 @@
-//@ check-pass
-//@ known-bug: #98117
-
-// Should fail. Functions are responsible for checking the well-formedness of
-// their own where clauses, so this should fail and require an explicit bound
-// `T: 'static`.
-
 use std::fmt::Display;
 
 trait Static: 'static {}
@@ -19,5 +12,6 @@ where
 
 fn main() {
     let s = foo(&String::from("blah blah blah"));
+    //~^ ERROR temporary value dropped while borrowed
     println!("{}", s);
 }

tests/ui/wf/wf-in-where-clause-static.stderr

@@ -0,0 +1,12 @@
+error[E0716]: temporary value dropped while borrowed
+  --> $DIR/wf-in-where-clause-static.rs:14:18
+   |
+LL |     let s = foo(&String::from("blah blah blah"));
+   |             -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-- temporary value is freed at the end of this statement
+   |             |    |
+   |             |    creates a temporary value which is freed while still in use
+   |             argument requires that borrow lasts for `'static`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0716`.