don't prove WC when projecting from param-env

If the param-env tells you that, forall 'a, `T::Item<'a> = u32`,
we can believe it.

Author: nikomatsakis

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1951,7 +1951,7 @@ fn confirm_param_env_candidate<'cx, 'tcx>(
     match infcx.at(cause, param_env).eq(cache_projection, obligation_projection) {
         Ok(InferOk { value: _, obligations }) => {
             nested_obligations.extend(obligations);
-            assoc_ty_own_obligations(selcx, obligation, &mut nested_obligations);
+            // NDM assoc_ty_own_obligations(selcx, obligation, &mut nested_obligations);
             // FIXME(associated_const_equality): Handle consts here as well? Maybe this progress type should just take
             // a term instead.
             Progress { term: cache_entry.term, obligations: nested_obligations }

compiler/rustc_typeck/src/check/compare_method.rs

@@ -222,8 +222,11 @@ fn compare_predicate_entailment<'tcx>(
         let impl_m_own_bounds = impl_m_predicates.instantiate_own(tcx, impl_to_placeholder_substs);
         for (predicate, span) in iter::zip(impl_m_own_bounds.predicates, impl_m_own_bounds.spans) {
             let normalize_cause = traits::ObligationCause::misc(span, impl_m_hir_id);
+            debug!("predicate before normalization: {:?}", predicate);
             let traits::Normalized { value: predicate, obligations } =
                 traits::normalize(&mut selcx, param_env, normalize_cause, predicate);
+            debug!("predicate after normalization: {:?}", predicate);
+            debug!("normalization obligations: {:#?}", obligations);
 
             inh.register_predicates(obligations);
             let cause = ObligationCause::new(

src/test/ui/feature-gates/feature-gate-generic_associated_types.rs

@@ -3,8 +3,11 @@ use std::ops::Deref;
 trait PointerFamily<U> {
     type Pointer<T>: Deref<Target = T>;
     //~^ ERROR generic associated types are unstable
-    type Pointer2<T>: Deref<Target = T> where T: Clone, U: Clone;
-    //~^ ERROR generic associated types are unstable
+    type Pointer2<T>: Deref<Target = T>
+    where
+        T: Clone,
+        U: Clone;
+    //~^^^^ ERROR generic associated types are unstable
     //~| ERROR where clauses on associated types are unstable
 }
 
@@ -15,12 +18,13 @@ impl PointerFamily<u32> for Foo {
     //~^ ERROR generic associated types are unstable
     type Pointer2<U32> = Box<U32>;
     //~^ ERROR generic associated types are unstable
-    //~| ERROR the trait bound `U32: Clone` is not satisfied
 }
 
 trait Bar {
-    type Assoc where Self: Sized;
-    //~^ ERROR where clauses on associated types are unstable
+    type Assoc
+    where
+        Self: Sized;
+    //~^^^ ERROR where clauses on associated types are unstable
 }
 
 impl Bar for Foo {

src/test/ui/feature-gates/feature-gate-generic_associated_types.stderr

@@ -10,23 +10,29 @@ LL |     type Pointer<T>: Deref<Target = T>;
 error[E0658]: generic associated types are unstable
   --> $DIR/feature-gate-generic_associated_types.rs:6:5
    |
-LL |     type Pointer2<T>: Deref<Target = T> where T: Clone, U: Clone;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | /     type Pointer2<T>: Deref<Target = T>
+LL | |     where
+LL | |         T: Clone,
+LL | |         U: Clone;
+   | |_________________^
    |
    = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information
    = help: add `#![feature(generic_associated_types)]` to the crate attributes to enable
 
 error[E0658]: where clauses on associated types are unstable
   --> $DIR/feature-gate-generic_associated_types.rs:6:5
    |
-LL |     type Pointer2<T>: Deref<Target = T> where T: Clone, U: Clone;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | /     type Pointer2<T>: Deref<Target = T>
+LL | |     where
+LL | |         T: Clone,
+LL | |         U: Clone;
+   | |_________________^
    |
    = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information
    = help: add `#![feature(generic_associated_types)]` to the crate attributes to enable
 
 error[E0658]: generic associated types are unstable
-  --> $DIR/feature-gate-generic_associated_types.rs:14:5
+  --> $DIR/feature-gate-generic_associated_types.rs:17:5
    |
 LL |     type Pointer<Usize> = Box<Usize>;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -35,7 +41,7 @@ LL |     type Pointer<Usize> = Box<Usize>;
    = help: add `#![feature(generic_associated_types)]` to the crate attributes to enable
 
 error[E0658]: generic associated types are unstable
-  --> $DIR/feature-gate-generic_associated_types.rs:16:5
+  --> $DIR/feature-gate-generic_associated_types.rs:19:5
    |
 LL |     type Pointer2<U32> = Box<U32>;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -44,35 +50,25 @@ LL |     type Pointer2<U32> = Box<U32>;
    = help: add `#![feature(generic_associated_types)]` to the crate attributes to enable
 
 error[E0658]: where clauses on associated types are unstable
-  --> $DIR/feature-gate-generic_associated_types.rs:22:5
+  --> $DIR/feature-gate-generic_associated_types.rs:24:5
    |
-LL |     type Assoc where Self: Sized;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | /     type Assoc
+LL | |     where
+LL | |         Self: Sized;
+   | |____________________^
    |
    = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information
    = help: add `#![feature(generic_associated_types)]` to the crate attributes to enable
 
 error[E0658]: where clauses on associated types are unstable
-  --> $DIR/feature-gate-generic_associated_types.rs:27:5
+  --> $DIR/feature-gate-generic_associated_types.rs:31:5
    |
 LL |     type Assoc = Foo where Self: Sized;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information
    = help: add `#![feature(generic_associated_types)]` to the crate attributes to enable
 
-error[E0277]: the trait bound `U32: Clone` is not satisfied
-  --> $DIR/feature-gate-generic_associated_types.rs:16:26
-   |
-LL |     type Pointer2<U32> = Box<U32>;
-   |                          ^^^^^^^^ the trait `Clone` is not implemented for `U32`
-   |
-help: consider restricting type parameter `U32`
-   |
-LL |     type Pointer2<U32: std::clone::Clone> = Box<U32>;
-   |                      +++++++++++++++++++
-
-error: aborting due to 8 previous errors
+error: aborting due to 7 previous errors
 
-Some errors have detailed explanations: E0277, E0658.
-For more information about an error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0658`.

src/test/ui/generic-associated-types/bugs/issue-87755.rs

@@ -1,14 +1,13 @@
-// check-fail
-// known-bug: #87755
-
-// This should pass.
+// check-pass
 
 #![feature(generic_associated_types)]
 
 use std::fmt::Debug;
 
 trait Foo {
-    type Ass where Self::Ass: Debug;
+    type Ass
+    where
+        Self::Ass: Debug;
 }
 
 #[derive(Debug)]

src/test/ui/generic-associated-types/bugs/issue-87755.stderr

@@ -1,4 +1,6 @@
 // Regression test from https://github.com/rust-lang/rust/pull/98109
+//
+// check-pass
 
 #![feature(generic_associated_types)]
 
@@ -13,10 +15,6 @@ where
     for<'a> T: Get<Value<'a> = ()>,
 {
     || {
-        //~^ `T` does not live long enough
-        //
-        // FIXME(#98437). This regressed at some point and
-        // probably should work.
         let _x = x;
     };
 }

src/test/ui/generic-associated-types/collectivity-regression.rs

@@ -1,18 +1,13 @@
-// revisions: base extended
-//[base] check-fail
-//[extended] check-pass
+// check-pass
 
 #![feature(generic_associated_types)]
-#![cfg_attr(extended, feature(generic_associated_types_extended))]
-#![cfg_attr(extended, allow(incomplete_features))]
 
 pub trait FromLendingIterator<A>: Sized {
     fn from_iter<T: for<'x> LendingIterator<Item<'x> = A>>(iter: T) -> Self;
 }
 
 impl<A> FromLendingIterator<A> for Vec<A> {
     fn from_iter<I: for<'x> LendingIterator<Item<'x> = A>>(mut iter: I) -> Self {
-        //[base]~^ impl has stricter
         let mut v = vec![];
         while let Some(item) = iter.next() {
             v.push(item);

src/test/ui/generic-associated-types/collectivity-regression.stderr

@@ -1,18 +1,13 @@
-// revisions: base extended
-//[base] check-fail
-//[extended] check-pass
+// check-pass
 
 #![feature(generic_associated_types)]
-#![cfg_attr(extended, feature(generic_associated_types_extended))]
-#![cfg_attr(extended, allow(incomplete_features))]
 
 pub trait FromLendingIterator<A>: Sized {
     fn from_iter<T: for<'x> LendingIterator<Item<'x> = A>>(iter: T) -> Self;
 }
 
 impl<A> FromLendingIterator<A> for Vec<A> {
     fn from_iter<I: for<'x> LendingIterator<Item<'x> = A>>(mut iter: I) -> Self {
-        //[base]~^ impl has stricter
         let mut v = vec![];
         while let Some(item) = iter.next() {
             v.push(item);