fix fn/const items implied bounds and wf check (rebase)

compiler/rustc_borrowck/src/type_check/free_region_relations.rs

@@ -1,5 +1,6 @@
 use rustc_data_structures::frozen::Frozen;
 use rustc_data_structures::transitive_relation::{TransitiveRelation, TransitiveRelationBuilder};
+use rustc_hir::def::DefKind;
 use rustc_infer::infer::canonical::QueryRegionConstraints;
 use rustc_infer::infer::outlives;
 use rustc_infer::infer::outlives::env::RegionBoundPairs;
@@ -195,7 +196,9 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
 
     #[instrument(level = "debug", skip(self))]
     pub(crate) fn create(mut self) -> CreateResult<'tcx> {
-        let span = self.infcx.tcx.def_span(self.universal_regions.defining_ty.def_id());
+        let tcx = self.infcx.tcx;
+        let defining_ty_def_id = self.universal_regions.defining_ty.def_id().expect_local();
+        let span = tcx.def_span(defining_ty_def_id);
 
         // Insert the facts we know from the predicates. Why? Why not.
         let param_env = self.param_env;
@@ -275,6 +278,26 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
             normalized_inputs_and_output.push(norm_ty);
         }
 
+        // Add implied bounds from impl header.
+        if matches!(tcx.def_kind(defining_ty_def_id), DefKind::AssocFn | DefKind::AssocConst) {
+            for &(ty, _) in tcx.assumed_wf_types(tcx.local_parent(defining_ty_def_id)) {
+                let Ok(TypeOpOutput { output: norm_ty, constraints: c, .. }) = self
+                    .param_env
+                    .and(type_op::normalize::Normalize::new(ty))
+                    .fully_perform(self.infcx, span)
+                else {
+                    tcx.dcx().span_delayed_bug(span, format!("failed to normalize {ty:?}"));
+                    continue;
+                };
+                constraints.extend(c);
+
+                // We currently add implied bounds from the normalized ty only.
+                // This is more conservative and matches wfcheck behavior.
+                let c = self.add_implied_bounds(norm_ty);
+                constraints.extend(c);
+            }
+        }
+
         for c in constraints {
             self.push_region_constraints(c, span);
         }

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -406,6 +406,16 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                     instantiated_predicates,
                     locations,
                 );
+
+                assert!(!matches!(
+                    tcx.impl_of_method(def_id).map(|imp| tcx.def_kind(imp)),
+                    Some(DefKind::Impl { of_trait: true })
+                ));
+                self.cx.prove_predicates(
+                    args.types().map(|ty| ty::ClauseKind::WellFormed(ty.into())),
+                    locations,
+                    ConstraintCategory::Boring,
+                );
             }
         }
     }

compiler/rustc_trait_selection/src/traits/query/type_op/ascribe_user_type.rs

@@ -63,13 +63,16 @@ fn relate_mir_and_user_ty<'tcx>(
     user_ty: Ty<'tcx>,
 ) -> Result<(), NoSolution> {
     let cause = ObligationCause::dummy_with_span(span);
+    ocx.register_obligation(Obligation::new(
+        ocx.infcx.tcx,
+        cause.clone(),
+        param_env,
+        ty::ClauseKind::WellFormed(user_ty.into()),
+    ));
+
     let user_ty = ocx.normalize(&cause, param_env, user_ty);
     ocx.eq(&cause, param_env, mir_ty, user_ty)?;
 
-    // FIXME(#104764): We should check well-formedness before normalization.
-    let predicate =
-        ty::Binder::dummy(ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(user_ty.into())));
-    ocx.register_obligation(Obligation::new(ocx.infcx.tcx, cause, param_env, predicate));
     Ok(())
 }
 
@@ -113,31 +116,38 @@ fn relate_mir_and_user_args<'tcx>(
         ocx.register_obligation(Obligation::new(tcx, cause, param_env, instantiated_predicate));
     }
 
+    // Now prove the well-formedness of `def_id` with `substs`.
+    // Note for some items, proving the WF of `ty` is not sufficient because the
+    // well-formedness of an item may depend on the WF of gneneric args not present in the
+    // item's type. Currently this is true for associated consts, e.g.:
+    // ```rust
+    // impl<T> MyTy<T> {
+    //     const CONST: () = { /* arbitrary code that depends on T being WF */ };
+    // }
+    // ```
+    for arg in args {
+        ocx.register_obligation(Obligation::new(
+            tcx,
+            cause.clone(),
+            param_env,
+            ty::ClauseKind::WellFormed(arg),
+        ));
+    }
+
     if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
+        ocx.register_obligation(Obligation::new(
+            tcx,
+            cause.clone(),
+            param_env,
+            ty::ClauseKind::WellFormed(self_ty.into()),
+        ));
+
         let self_ty = ocx.normalize(&cause, param_env, self_ty);
         let impl_self_ty = tcx.type_of(impl_def_id).instantiate(tcx, args);
         let impl_self_ty = ocx.normalize(&cause, param_env, impl_self_ty);
 
         ocx.eq(&cause, param_env, self_ty, impl_self_ty)?;
-        let predicate = ty::Binder::dummy(ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(
-            impl_self_ty.into(),
-        )));
-        ocx.register_obligation(Obligation::new(tcx, cause.clone(), param_env, predicate));
     }
 
-    // In addition to proving the predicates, we have to
-    // prove that `ty` is well-formed -- this is because
-    // the WF of `ty` is predicated on the args being
-    // well-formed, and we haven't proven *that*. We don't
-    // want to prove the WF of types from  `args` directly because they
-    // haven't been normalized.
-    //
-    // FIXME(nmatsakis): Well, perhaps we should normalize
-    // them?  This would only be relevant if some input
-    // type were ill-formed but did not appear in `ty`,
-    // which...could happen with normalization...
-    let predicate =
-        ty::Binder::dummy(ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(ty.into())));
-    ocx.register_obligation(Obligation::new(tcx, cause, param_env, predicate));
     Ok(())
 }

compiler/rustc_trait_selection/src/traits/query/type_op/prove_predicate.rs

@@ -30,6 +30,23 @@ impl<'tcx> super::QueryTypeOp<'tcx> for ProvePredicate<'tcx> {
             }
         }
 
+        if let ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(arg)) =
+            key.value.predicate.kind().skip_binder()
+        {
+            match arg.as_type()?.kind() {
+                ty::Param(_)
+                | ty::Bool
+                | ty::Char
+                | ty::Int(_)
+                | ty::Float(_)
+                | ty::Str
+                | ty::Uint(_) => {
+                    return Some(());
+                }
+                _ => {}
+            }
+        }
+
         None
     }
 

tests/ui/borrowck/fn-item-check-trait-ref.rs

@@ -0,0 +1,15 @@
+// The method `assert_static` should be callable only for static values,
+// because the impl has an implied bound `where T: 'static`.
+
+// check-fail
+
+trait AnyStatic<Witness>: Sized {
+    fn assert_static(self) {}
+}
+
+impl<T> AnyStatic<&'static T> for T {}
+
+fn main() {
+    (&String::new()).assert_static();
+    //~^ ERROR temporary value dropped while borrowed
+}

tests/ui/borrowck/fn-item-check-trait-ref.stderr

@@ -0,0 +1,12 @@
+error[E0716]: temporary value dropped while borrowed
+  --> $DIR/fn-item-check-trait-ref.rs:13:7
+   |
+LL |     (&String::new()).assert_static();
+   |     --^^^^^^^^^^^^^------------------ 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`.

tests/ui/borrowck/fn-item-check-type-params.rs

@@ -0,0 +1,57 @@
+// Regression test for #104005.
+//
+// Previously, different borrowck implementations used to disagree here.
+// The status of each is documented on `fn test_*`.
+
+// check-fail
+
+use std::fmt::Display;
+
+trait Displayable {
+    fn display(self) -> Box<dyn Display>;
+}
+
+impl<T: Display> Displayable for (T, Option<&'static T>) {
+    fn display(self) -> Box<dyn Display> {
+        Box::new(self.0)
+    }
+}
+
+fn extend_lt<T, U>(val: T) -> Box<dyn Display>
+where
+    (T, Option<U>): Displayable,
+{
+    Displayable::display((val, None))
+}
+
+// AST: fail
+// HIR: pass
+// MIR: pass
+pub fn test_call<'a>(val: &'a str) {
+    extend_lt(val);
+    //~^ ERROR borrowed data escapes outside of function
+}
+
+// AST: fail
+// HIR: fail
+// MIR: pass
+pub fn test_coercion<'a>() {
+    let _: fn(&'a str) -> _ = extend_lt;
+    //~^ ERROR lifetime may not live long enough
+}
+
+// AST: fail
+// HIR: fail
+// MIR: fail
+pub fn test_arg() {
+    fn want<I, O>(_: I, _: impl Fn(I) -> O) {}
+    want(&String::new(), extend_lt);
+    //~^ ERROR temporary value dropped while borrowed
+}
+
+// An exploit of the unsoundness.
+fn main() {
+    let val = extend_lt(&String::from("blah blah blah"));
+    //~^ ERROR temporary value dropped while borrowed
+    println!("{}", val);
+}

tests/ui/borrowck/fn-item-check-type-params.stderr

@@ -0,0 +1,43 @@
+error[E0521]: borrowed data escapes outside of function
+  --> $DIR/fn-item-check-type-params.rs:31:5
+   |
+LL | pub fn test_call<'a>(val: &'a str) {
+   |                  --  --- `val` is a reference that is only valid in the function body
+   |                  |
+   |                  lifetime `'a` defined here
+LL |     extend_lt(val);
+   |     ^^^^^^^^^^^^^^
+   |     |
+   |     `val` escapes the function body here
+   |     argument requires that `'a` must outlive `'static`
+
+error: lifetime may not live long enough
+  --> $DIR/fn-item-check-type-params.rs:39:12
+   |
+LL | pub fn test_coercion<'a>() {
+   |                      -- lifetime `'a` defined here
+LL |     let _: fn(&'a str) -> _ = extend_lt;
+   |            ^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
+
+error[E0716]: temporary value dropped while borrowed
+  --> $DIR/fn-item-check-type-params.rs:48:11
+   |
+LL |     want(&String::new(), extend_lt);
+   |     ------^^^^^^^^^^^^^------------- 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[E0716]: temporary value dropped while borrowed
+  --> $DIR/fn-item-check-type-params.rs:54:26
+   |
+LL |     let val = extend_lt(&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 4 previous errors
+
+Some errors have detailed explanations: E0521, E0716.
+For more information about an error, try `rustc --explain E0521`.

tests/ui/higher-ranked/trait-bounds/issue-59311.rs

@@ -17,6 +17,7 @@ where
     v.t(|| {});
     //~^ ERROR: higher-ranked lifetime error
     //~| ERROR: higher-ranked lifetime error
+    //~| ERROR: higher-ranked lifetime error
 }
 
 fn main() {}

tests/ui/higher-ranked/trait-bounds/issue-59311.stderr

@@ -6,6 +6,15 @@ LL |     v.t(|| {});
    |
    = note: could not prove `{closure@$DIR/issue-59311.rs:17:9: 17:11} well-formed`
 
+error: higher-ranked lifetime error
+  --> $DIR/issue-59311.rs:17:5
+   |
+LL |     v.t(|| {});
+   |     ^^^^^^^^^^
+   |
+   = note: could not prove `{closure@$DIR/issue-59311.rs:17:9: 17:11} well-formed`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error: higher-ranked lifetime error
   --> $DIR/issue-59311.rs:17:9
    |
@@ -14,5 +23,5 @@ LL |     v.t(|| {});
    |
    = note: could not prove `for<'a> &'a V: 'b`
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 

tests/ui/implied-bounds/implied-bounds-on-trait-hierarchy.rs → tests/ui/implied-bounds/implied-bounds-on-trait-hierarchy-1.rs

@@ -1,9 +1,7 @@
-// check-pass
-// known-bug: #84591
+// issue: #84591
 
-// Should fail. Subtrait can incorrectly extend supertrait lifetimes even when
-// supertrait has weaker implied bounds than subtrait. Strongly related to
-// issue #25860.
+// Subtrait was able to incorrectly extend supertrait lifetimes even when
+// supertrait had weaker implied bounds than subtrait.
 
 trait Subtrait<T>: Supertrait {}
 trait Supertrait {
@@ -34,6 +32,7 @@ fn main() {
     {
         let x = "Hello World".to_string();
         subs_to_soup((x.as_str(), &mut d));
+        //~^ does not live long enough
     }
     println!("{}", d);
 }

tests/ui/implied-bounds/implied-bounds-on-trait-hierarchy-1.stderr

@@ -0,0 +1,16 @@
+error[E0597]: `x` does not live long enough
+  --> $DIR/implied-bounds-on-trait-hierarchy-1.rs:34:23
+   |
+LL |         let x = "Hello World".to_string();
+   |             - binding `x` declared here
+LL |         subs_to_soup((x.as_str(), &mut d));
+   |                       ^ borrowed value does not live long enough
+LL |
+LL |     }
+   |     - `x` dropped here while still borrowed
+LL |     println!("{}", d);
+   |                    - borrow later used here
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0597`.