Auto merge of #99217 - lcnr:implied-bounds-pre-norm, r=lcnr

consider unnormalized types for implied bounds

extracted, and slightly modified, from #98900

The idea here is that generally, rustc is split into things which can assume its inputs are well formed[^1], and things which have verify that themselves.

Generally most predicates should only deal with well formed inputs, e.g. a `&'a &'b (): Trait` predicate should be able to assume that `'b: 'a` holds. Normalization can loosen wf requirements (see #91068) and must therefore not be used in places which still have to check well formedness. The only such place should hopefully be `WellFormed` predicates

fixes #87748 and #98543

r? `@jackh726` cc `@rust-lang/types`

[^1]: These places may still encounter non-wf inputs and have to deal with them without causing an ICE as we may check for well formedness out of order.

20 files changed, 178 insertions, 76 deletions

diff --git a/src/test/ui/associated-types/issue-59324.rs b/src/test/ui/associated-types/issue-59324.rs
index 162f9e00edd..9e68e9e7751 100644
--- a/src/test/ui/associated-types/issue-59324.rs
+++ b/src/test/ui/associated-types/issue-59324.rs
@@ -15,9 +15,9 @@ pub trait ThriftService<Bug: NotFoo>:
 {
     fn get_service(
     //~^ ERROR the trait bound `Bug: Foo` is not satisfied
+    //~| ERROR the trait bound `Bug: Foo` is not satisfied
         &self,
     ) -> Self::AssocType;
-    //~^ the trait bound `Bug: Foo` is not satisfied
 }
 
 fn with_factory<H>(factory: dyn ThriftService<()>) {}
diff --git a/src/test/ui/associated-types/issue-59324.stderr b/src/test/ui/associated-types/issue-59324.stderr
index a84b599b52b..dd5ec7175b5 100644
--- a/src/test/ui/associated-types/issue-59324.stderr
+++ b/src/test/ui/associated-types/issue-59324.stderr
@@ -20,7 +20,7 @@ LL | |
 LL | |
 LL | |     Service<AssocType = <Bug as Foo>::OnlyFoo>
 ...  |
-LL | |
+LL | |     ) -> Self::AssocType;
 LL | | }
    | |_^ the trait `Foo` is not implemented for `Bug`
    |
@@ -34,6 +34,7 @@ error[E0277]: the trait bound `Bug: Foo` is not satisfied
    |
 LL | /     fn get_service(
 LL | |
+LL | |
 LL | |         &self,
 LL | |     ) -> Self::AssocType;
    | |_________________________^ the trait `Foo` is not implemented for `Bug`
@@ -50,10 +51,10 @@ LL | fn with_factory<H>(factory: dyn ThriftService<()>) {}
    |                             ^^^^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `()`
 
 error[E0277]: the trait bound `Bug: Foo` is not satisfied
-  --> $DIR/issue-59324.rs:19:10
+  --> $DIR/issue-59324.rs:16:8
    |
-LL |     ) -> Self::AssocType;
-   |          ^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `Bug`
+LL |     fn get_service(
+   |        ^^^^^^^^^^^ the trait `Foo` is not implemented for `Bug`
    |
 help: consider further restricting this bound
    |
diff --git a/src/test/ui/fn/implied-bounds-unnorm-associated-type-2.rs b/src/test/ui/fn/implied-bounds-unnorm-associated-type-2.rs
index 5a92bcd37b6..5d924555625 100644
--- a/src/test/ui/fn/implied-bounds-unnorm-associated-type-2.rs
+++ b/src/test/ui/fn/implied-bounds-unnorm-associated-type-2.rs
@@ -1,4 +1,4 @@
-// check-pass
+// check-fail
 
 trait Trait {
     type Type;
@@ -17,6 +17,7 @@ where
 
 fn g<'a, 'b>() {
     f::<'a, 'b>(());
+    //~^ ERROR lifetime may not live long enough
 }
 
 fn main() {}
diff --git a/src/test/ui/fn/implied-bounds-unnorm-associated-type-2.stderr b/src/test/ui/fn/implied-bounds-unnorm-associated-type-2.stderr
new file mode 100644
index 00000000000..0c3df04eabc
--- /dev/null
+++ b/src/test/ui/fn/implied-bounds-unnorm-associated-type-2.stderr
@@ -0,0 +1,17 @@
+error: lifetime may not live long enough
+  --> $DIR/implied-bounds-unnorm-associated-type-2.rs:19:5
+   |
+LL | fn g<'a, 'b>() {
+   |      --  -- lifetime `'b` defined here
+   |      |
+   |      lifetime `'a` defined here
+LL |     f::<'a, 'b>(());
+   |     ^^^^^^^^^^^^^^^ requires that `'b` must outlive `'a`
+   |
+   = help: consider adding the following bound: `'b: 'a`
+   = note: requirement occurs because of a function pointer to `f`
+   = note: the function `f` is invariant over the parameter `'a`
+   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/fn/implied-bounds-unnorm-associated-type-3.rs b/src/test/ui/fn/implied-bounds-unnorm-associated-type-3.rs
index dc25ac08613..888f74cf6b3 100644
--- a/src/test/ui/fn/implied-bounds-unnorm-associated-type-3.rs
+++ b/src/test/ui/fn/implied-bounds-unnorm-associated-type-3.rs
@@ -1,6 +1,4 @@
-// check-fail
-// See issue #91899. If we treat unnormalized args as WF, `Self` can also be a
-// source of unsoundness.
+// check-pass
 
 pub trait Yokeable<'a>: 'static {
     type Output: 'a;
@@ -17,7 +15,6 @@ pub trait ZeroCopyFrom<C: ?Sized>: for<'a> Yokeable<'a> {
 
 impl<T> ZeroCopyFrom<[T]> for &'static [T] {
     fn zero_copy_from<'b>(cart: &'b [T]) -> &'b [T] {
-        //~^ the parameter
         cart
     }
 }
diff --git a/src/test/ui/fn/implied-bounds-unnorm-associated-type-3.stderr b/src/test/ui/fn/implied-bounds-unnorm-associated-type-3.stderr
deleted file mode 100644
index 95cf4fb168f..00000000000
--- a/src/test/ui/fn/implied-bounds-unnorm-associated-type-3.stderr
+++ /dev/null
@@ -1,14 +0,0 @@
-error[E0310]: the parameter type `T` may not live long enough
-  --> $DIR/implied-bounds-unnorm-associated-type-3.rs:19:5
-   |
-LL |     fn zero_copy_from<'b>(cart: &'b [T]) -> &'b [T] {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `[T]` will meet its required lifetime bounds
-   |
-help: consider adding an explicit lifetime bound...
-   |
-LL | impl<T: 'static> ZeroCopyFrom<[T]> for &'static [T] {
-   |       +++++++++
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0310`.
diff --git a/src/test/ui/fn/implied-bounds-unnorm-associated-type-4.rs b/src/test/ui/fn/implied-bounds-unnorm-associated-type-4.rs
new file mode 100644
index 00000000000..12859252c87
--- /dev/null
+++ b/src/test/ui/fn/implied-bounds-unnorm-associated-type-4.rs
@@ -0,0 +1,24 @@
+// A regression test for #98543
+
+trait Trait {
+    type Type;
+}
+
+impl<T> Trait for T {
+    type Type = ();
+}
+
+fn f<'a, 'b>(s: &'b str, _: <&'a &'b () as Trait>::Type) -> &'a str
+where
+    &'a &'b (): Trait, // <- adding this bound is the change from #91068
+{
+    s
+}
+
+fn main() {
+    let x = String::from("Hello World!");
+    let y = f(&x, ());
+    drop(x);
+    //~^ ERROR cannot move out of `x` because it is borrowed
+    println!("{}", y);
+}
diff --git a/src/test/ui/fn/implied-bounds-unnorm-associated-type-4.stderr b/src/test/ui/fn/implied-bounds-unnorm-associated-type-4.stderr
new file mode 100644
index 00000000000..fcbaa91d19f
--- /dev/null
+++ b/src/test/ui/fn/implied-bounds-unnorm-associated-type-4.stderr
@@ -0,0 +1,14 @@
+error[E0505]: cannot move out of `x` because it is borrowed
+  --> $DIR/implied-bounds-unnorm-associated-type-4.rs:21:10
+   |
+LL |     let y = f(&x, ());
+   |               -- borrow of `x` occurs here
+LL |     drop(x);
+   |          ^ move out of `x` occurs here
+LL |
+LL |     println!("{}", y);
+   |                    - borrow later used here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0505`.
diff --git a/src/test/ui/fn/implied-bounds-unnorm-associated-type-5.rs b/src/test/ui/fn/implied-bounds-unnorm-associated-type-5.rs
new file mode 100644
index 00000000000..2a9a6a8cc6c
--- /dev/null
+++ b/src/test/ui/fn/implied-bounds-unnorm-associated-type-5.rs
@@ -0,0 +1,23 @@
+trait Trait<'a>: 'a {
+    type Type;
+}
+
+// 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
+    type Type = ();
+}
+
+fn f<'a, 'b>(s: &'b str, _: <&'b () as Trait<'a>>::Type) -> &'a str
+where
+    &'b (): Trait<'a>,
+{
+    s
+}
+
+fn main() {
+    let x = String::from("Hello World!");
+    let y = f(&x, ());
+    drop(x);
+    println!("{}", y);
+}
diff --git a/src/test/ui/fn/implied-bounds-unnorm-associated-type-5.stderr b/src/test/ui/fn/implied-bounds-unnorm-associated-type-5.stderr
new file mode 100644
index 00000000000..458756a3dcd
--- /dev/null
+++ b/src/test/ui/fn/implied-bounds-unnorm-associated-type-5.stderr
@@ -0,0 +1,19 @@
+error[E0309]: the parameter type `T` may not live long enough
+  --> $DIR/implied-bounds-unnorm-associated-type-5.rs:6:13
+   |
+LL | impl<'a, T> Trait<'a> for T {
+   |             ^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds...
+   |
+note: ...that is required by this bound
+  --> $DIR/implied-bounds-unnorm-associated-type-5.rs:1:18
+   |
+LL | trait Trait<'a>: 'a {
+   |                  ^^
+help: consider adding an explicit lifetime bound...
+   |
+LL | impl<'a, T: 'a> Trait<'a> for T {
+   |           ++++
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0309`.
diff --git a/src/test/ui/fn/implied-bounds-unnorm-associated-type.rs b/src/test/ui/fn/implied-bounds-unnorm-associated-type.rs
index 04b6f4dd84e..d58d25036c5 100644
--- a/src/test/ui/fn/implied-bounds-unnorm-associated-type.rs
+++ b/src/test/ui/fn/implied-bounds-unnorm-associated-type.rs
@@ -1,6 +1,6 @@
 // check-fail
-// See issue #91068. Types in the substs of an associated type can't be implied
-// to be WF, since they don't actually have to be constructed.
+// See issue #91068. We check that the unnormalized associated types in
+// function signatures are implied
 
 trait Trait {
     type Type;
@@ -12,12 +12,12 @@ impl<T> Trait for T {
 
 fn f<'a, 'b>(s: &'b str, _: <&'a &'b () as Trait>::Type) -> &'a str {
     s
-    //~^ ERROR lifetime may not live long enough
 }
 
 fn main() {
     let x = String::from("Hello World!");
     let y = f(&x, ());
     drop(x);
+    //~^ ERROR cannot move out of `x` because it is borrowed
     println!("{}", y);
 }
diff --git a/src/test/ui/fn/implied-bounds-unnorm-associated-type.stderr b/src/test/ui/fn/implied-bounds-unnorm-associated-type.stderr
index 8096f08385c..e35f46e4439 100644
--- a/src/test/ui/fn/implied-bounds-unnorm-associated-type.stderr
+++ b/src/test/ui/fn/implied-bounds-unnorm-associated-type.stderr
@@ -1,14 +1,14 @@
-error: lifetime may not live long enough
-  --> $DIR/implied-bounds-unnorm-associated-type.rs:14:5
+error[E0505]: cannot move out of `x` because it is borrowed
+  --> $DIR/implied-bounds-unnorm-associated-type.rs:20:10
    |
-LL | fn f<'a, 'b>(s: &'b str, _: <&'a &'b () as Trait>::Type) -> &'a str {
-   |      --  -- lifetime `'b` defined here
-   |      |
-   |      lifetime `'a` defined here
-LL |     s
-   |     ^ function was supposed to return data with lifetime `'a` but it is returning data with lifetime `'b`
-   |
-   = help: consider adding the following bound: `'b: 'a`
+LL |     let y = f(&x, ());
+   |               -- borrow of `x` occurs here
+LL |     drop(x);
+   |          ^ move out of `x` occurs here
+LL |
+LL |     println!("{}", y);
+   |                    - borrow later used here
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0505`.
diff --git a/src/test/ui/generic-associated-types/bugs/issue-87748.stderr b/src/test/ui/generic-associated-types/bugs/issue-87748.stderr
deleted file mode 100644
index ac197dfe6ff..00000000000
--- a/src/test/ui/generic-associated-types/bugs/issue-87748.stderr
+++ /dev/null
@@ -1,20 +0,0 @@
-error[E0478]: lifetime bound not satisfied
-  --> $DIR/issue-87748.rs:18:5
-   |
-LL |     fn do_sth(_: u32) {}
-   |     ^^^^^^^^^^^^^^^^^
-   |
-note: lifetime parameter instantiated with the anonymous lifetime as defined here
-  --> $DIR/issue-87748.rs:18:5
-   |
-LL |     fn do_sth(_: u32) {}
-   |     ^^^^^^^^^^^^^^^^^
-note: but lifetime parameter must outlive the anonymous lifetime as defined here
-  --> $DIR/issue-87748.rs:18:5
-   |
-LL |     fn do_sth(_: u32) {}
-   |     ^^^^^^^^^^^^^^^^^
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0478`.
diff --git a/src/test/ui/generic-associated-types/bugs/issue-87748.rs b/src/test/ui/generic-associated-types/issue-87748.rs
index a3d00ee03b1..1a1ab9bf8a4 100644
--- a/src/test/ui/generic-associated-types/bugs/issue-87748.rs
+++ b/src/test/ui/generic-associated-types/issue-87748.rs
@@ -1,13 +1,14 @@
-// check-fail
-// known-bug: #87748
+// Checks that we properly add implied bounds from unnormalized projections in
+// inputs when typechecking functions.
 
-// This should pass, but unnormalized input args aren't treated as implied.
+// check-pass
 
 #![feature(generic_associated_types)]
 
 trait MyTrait {
     type Assoc<'a, 'b> where 'b: 'a;
     fn do_sth(arg: Self::Assoc<'_, '_>);
+    fn do_sth2(arg: Self::Assoc<'_, '_>) {}
 }
 
 struct Foo;
@@ -16,8 +17,7 @@ impl MyTrait for Foo {
     type Assoc<'a, 'b> = u32 where 'b: 'a;
 
     fn do_sth(_: u32) {}
-    // fn do_sth(_: Self::Assoc<'static, 'static>) {}
-    // fn do_sth(_: Self::Assoc<'_, '_>) {}
+    fn do_sth2(_: Self::Assoc<'static, 'static>) {}
 }
 
 fn main() {}
diff --git a/src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-85455.rs b/src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-85455.rs
index 172bf218c0d..de9348f5397 100644
--- a/src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-85455.rs
+++ b/src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-85455.rs
@@ -7,7 +7,6 @@ trait SomeTrait<'a> {
 fn give_me_ice<T>() {
     callee::<fn(&()) -> <T as SomeTrait<'_>>::Associated>();
     //~^ ERROR the trait bound `for<'r> T: SomeTrait<'r>` is not satisfied [E0277]
-    //~| ERROR the trait bound `for<'r> T: SomeTrait<'r>` is not satisfied [E0277]
 }
 
 fn callee<T: Fn<(&'static (),)>>() {
diff --git a/src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-85455.stderr b/src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-85455.stderr
index ecca4b999e7..6a948a116e0 100644
--- a/src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-85455.stderr
+++ b/src/test/ui/higher-rank-trait-bounds/normalize-under-binder/issue-85455.stderr
@@ -9,17 +9,6 @@ help: consider restricting type parameter `T`
 LL | fn give_me_ice<T: for<'r> SomeTrait<'r>>() {
    |                 +++++++++++++++++++++++
 
-error[E0277]: the trait bound `for<'r> T: SomeTrait<'r>` is not satisfied
-  --> $DIR/issue-85455.rs:8:14
-   |
-LL |     callee::<fn(&()) -> <T as SomeTrait<'_>>::Associated>();
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'r> SomeTrait<'r>` is not implemented for `T`
-   |
-help: consider restricting type parameter `T`
-   |
-LL | fn give_me_ice<T: for<'r> SomeTrait<'r>>() {
-   |                 +++++++++++++++++++++++
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/implied-bounds/assoc-ty-wf-used-to-get-assoc-ty.rs b/src/test/ui/implied-bounds/assoc-ty-wf-used-to-get-assoc-ty.rs
new file mode 100644
index 00000000000..33b746c5edf
--- /dev/null
+++ b/src/test/ui/implied-bounds/assoc-ty-wf-used-to-get-assoc-ty.rs
@@ -0,0 +1,27 @@
+// Test for a less than ideal interaction of implied bounds and normalization.
+trait Tr {
+    type Ty;
+}
+
+impl<T: 'static> Tr for T {
+    type Ty = &'static T;
+}
+
+// `<&'a u8 as Tr>::Ty` should cause an error because `&'a u8: Tr` doesn't hold for
+// all possible 'a. However, we consider normalized types for implied bounds.
+//
+// We normalize this projection to `&'static &'a u8` and add a nested `&'a u8: 'static`
+// bound. This bound is then proven using the implied bounds for `&'static &'a u8` which
+// we only get by normalizing in the first place.
+fn test<'a>(x: &'a u8, _wf: <&'a u8 as Tr>::Ty) -> &'static u8 { x }
+
+fn main() {
+    // This works as we have 'static references due to promotion.
+    let _: &'static u8 = test(&3, &&3);
+    // This causes an error because the projection requires 'a to be 'static.
+    // It would be unsound if this compiled.
+    let x: u8 = 3;
+    let _: &'static u8 = test(&x, &&3);
+    //~^ ERROR `x` does not live long enough
+
+}
diff --git a/src/test/ui/implied-bounds/assoc-ty-wf-used-to-get-assoc-ty.stderr b/src/test/ui/implied-bounds/assoc-ty-wf-used-to-get-assoc-ty.stderr
new file mode 100644
index 00000000000..d0249e74f39
--- /dev/null
+++ b/src/test/ui/implied-bounds/assoc-ty-wf-used-to-get-assoc-ty.stderr
@@ -0,0 +1,15 @@
+error[E0597]: `x` does not live long enough
+  --> $DIR/assoc-ty-wf-used-to-get-assoc-ty.rs:24:31
+   |
+LL |     let _: &'static u8 = test(&x, &&3);
+   |                          -----^^------
+   |                          |    |
+   |                          |    borrowed value does not live long enough
+   |                          argument requires that `x` is borrowed for `'static`
+...
+LL | }
+   | - `x` dropped here while still borrowed
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0597`.
diff --git a/src/test/ui/nll/relate_tys/impl-fn-ignore-binder-via-bottom.rs b/src/test/ui/nll/relate_tys/impl-fn-ignore-binder-via-bottom.rs
index c4db6fc97dc..05e2ea047f6 100644
--- a/src/test/ui/nll/relate_tys/impl-fn-ignore-binder-via-bottom.rs
+++ b/src/test/ui/nll/relate_tys/impl-fn-ignore-binder-via-bottom.rs
@@ -30,4 +30,5 @@ fn main() {
     let _x = <fn(&())>::make_f();
     //~^ ERROR implementation of `Y` is not general enough
     //~| ERROR implementation of `Y` is not general enough
+    //~| ERROR implementation of `Y` is not general enough
 }
diff --git a/src/test/ui/nll/relate_tys/impl-fn-ignore-binder-via-bottom.stderr b/src/test/ui/nll/relate_tys/impl-fn-ignore-binder-via-bottom.stderr
index 51adfca3e79..8c47379886d 100644
--- a/src/test/ui/nll/relate_tys/impl-fn-ignore-binder-via-bottom.stderr
+++ b/src/test/ui/nll/relate_tys/impl-fn-ignore-binder-via-bottom.stderr
@@ -16,5 +16,14 @@ LL |     let _x = <fn(&())>::make_f();
    = note: `Y` would have to be implemented for the type `for<'r> fn(&'r ())`
    = note: ...but `Y` is actually implemented for the type `fn(&'0 ())`, for some specific lifetime `'0`
 
-error: aborting due to 2 previous errors
+error: implementation of `Y` is not general enough
+  --> $DIR/impl-fn-ignore-binder-via-bottom.rs:30:14
+   |
+LL |     let _x = <fn(&())>::make_f();
+   |              ^^^^^^^^^^^^^^^^^^^ implementation of `Y` is not general enough
+   |
+   = note: `Y` would have to be implemented for the type `for<'r> fn(&'r ())`
+   = note: ...but `Y` is actually implemented for the type `fn(&'0 ())`, for some specific lifetime `'0`
+
+error: aborting due to 3 previous errors