Rollup merge of #114594 - compiler-errors:new-solver-resolve-aliases, r=lcnr

Structurally normalize weak and inherent in new solver

It seems pretty obvious to me that we should be normalizing weak and inherent aliases too, since they can always be normalized. This PR still leaves open the question of what to do with opaques, though 💀

**Also**, we need to structurally resolve the target of a coercion, for the UI test to work.

r? `@lcnr`

11 files changed, 58 insertions, 53 deletions

diff --git a/compiler/rustc_hir_analysis/src/autoderef.rs b/compiler/rustc_hir_analysis/src/autoderef.rs
index c07ac35cba3..39db295044e 100644
--- a/compiler/rustc_hir_analysis/src/autoderef.rs
+++ b/compiler/rustc_hir_analysis/src/autoderef.rs
@@ -74,7 +74,7 @@ impl<'a, 'tcx> Iterator for Autoderef<'a, 'tcx> {
             // we have some type like `&<Ty as Trait>::Assoc`, since users of
             // autoderef expect this type to have been structurally normalized.
             if self.infcx.next_trait_solver()
-                && let ty::Alias(ty::Projection, _) = ty.kind()
+                && let ty::Alias(ty::Projection | ty::Inherent | ty::Weak, _) = ty.kind()
             {
                 let (normalized_ty, obligations) = self.structurally_normalize(ty)?;
                 self.state.obligations.extend(obligations);
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index fa6bad84376..b2b3f435505 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -1012,6 +1012,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         cause: Option<ObligationCause<'tcx>>,
     ) -> RelateResult<'tcx, Ty<'tcx>> {
         let source = self.try_structurally_resolve_type(expr.span, expr_ty);
+        let target = self.try_structurally_resolve_type(
+            cause.as_ref().map_or(expr.span, |cause| cause.span),
+            target,
+        );
         debug!("coercion::try({:?}: {:?} -> {:?})", expr, source, target);
 
         let cause =
@@ -1097,8 +1101,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     where
         E: AsCoercionSite,
     {
-        let prev_ty = self.resolve_vars_with_obligations(prev_ty);
-        let new_ty = self.resolve_vars_with_obligations(new_ty);
+        let prev_ty = self.try_structurally_resolve_type(cause.span, prev_ty);
+        let new_ty = self.try_structurally_resolve_type(new.span, new_ty);
         debug!(
             "coercion::try_find_coercion_lub({:?}, {:?}, exprs={:?} exprs)",
             prev_ty,
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index 1433c67d55d..322d726a89d 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -1474,7 +1474,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let ty = self.resolve_vars_with_obligations(ty);
 
         if self.next_trait_solver()
-            && let ty::Alias(ty::Projection, _) = ty.kind()
+            && let ty::Alias(ty::Projection | ty::Inherent | ty::Weak, _) = ty.kind()
         {
             match self
                 .at(&self.misc(sp), self.param_env)
diff --git a/compiler/rustc_trait_selection/src/traits/structural_normalize.rs b/compiler/rustc_trait_selection/src/traits/structural_normalize.rs
index 84746eba3ec..d3c4dc45923 100644
--- a/compiler/rustc_trait_selection/src/traits/structural_normalize.rs
+++ b/compiler/rustc_trait_selection/src/traits/structural_normalize.rs
@@ -22,7 +22,9 @@ impl<'tcx> StructurallyNormalizeExt<'tcx> for At<'_, 'tcx> {
         assert!(!ty.is_ty_var(), "should have resolved vars before calling");
 
         if self.infcx.next_trait_solver() {
-            while let ty::Alias(ty::Projection, projection_ty) = *ty.kind() {
+            while let ty::Alias(ty::Projection | ty::Inherent | ty::Weak, projection_ty) =
+                *ty.kind()
+            {
                 let new_infer_ty = self.infcx.next_ty_var(TypeVariableOrigin {
                     kind: TypeVariableOriginKind::NormalizeProjectionType,
                     span: self.cause.span,
diff --git a/tests/ui/for/issue-20605.next.stderr b/tests/ui/for/issue-20605.next.stderr
index d55efedfcbe..0955efdbb73 100644
--- a/tests/ui/for/issue-20605.next.stderr
+++ b/tests/ui/for/issue-20605.next.stderr
@@ -34,12 +34,6 @@ error: the type `&mut <dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIte
 LL |     for item in *things { *item = 0 }
    |                 ^^^^^^^
 
-error[E0614]: type `<<dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter as Iterator>::Item` cannot be dereferenced
-  --> $DIR/issue-20605.rs:5:27
-   |
-LL |     for item in *things { *item = 0 }
-   |                           ^^^^^
-
 error[E0277]: the size for values of type `<<dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter as Iterator>::Item` cannot be known at compilation time
   --> $DIR/issue-20605.rs:5:9
    |
@@ -66,6 +60,12 @@ LL |     for item in *things { *item = 0 }
 note: required by a bound in `None`
   --> $SRC_DIR/core/src/option.rs:LL:COL
 
+error[E0614]: type `<<dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter as Iterator>::Item` cannot be dereferenced
+  --> $DIR/issue-20605.rs:5:27
+   |
+LL |     for item in *things { *item = 0 }
+   |                           ^^^^^
+
 error: aborting due to 9 previous errors
 
 Some errors have detailed explanations: E0277, E0614.
diff --git a/tests/ui/lazy-type-alias/coerce-behind-lazy.current.stderr b/tests/ui/lazy-type-alias/coerce-behind-lazy.current.stderr
new file mode 100644
index 00000000000..98b3921dec4
--- /dev/null
+++ b/tests/ui/lazy-type-alias/coerce-behind-lazy.current.stderr
@@ -0,0 +1,11 @@
+warning: the feature `lazy_type_alias` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/coerce-behind-lazy.rs:5:12
+   |
+LL | #![feature(lazy_type_alias)]
+   |            ^^^^^^^^^^^^^^^
+   |
+   = note: see issue #112792 <https://github.com/rust-lang/rust/issues/112792> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/tests/ui/lazy-type-alias/coerce-behind-lazy.next.stderr b/tests/ui/lazy-type-alias/coerce-behind-lazy.next.stderr
new file mode 100644
index 00000000000..98b3921dec4
--- /dev/null
+++ b/tests/ui/lazy-type-alias/coerce-behind-lazy.next.stderr
@@ -0,0 +1,11 @@
+warning: the feature `lazy_type_alias` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/coerce-behind-lazy.rs:5:12
+   |
+LL | #![feature(lazy_type_alias)]
+   |            ^^^^^^^^^^^^^^^
+   |
+   = note: see issue #112792 <https://github.com/rust-lang/rust/issues/112792> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+warning: 1 warning emitted
+
diff --git a/tests/ui/lazy-type-alias/coerce-behind-lazy.rs b/tests/ui/lazy-type-alias/coerce-behind-lazy.rs
new file mode 100644
index 00000000000..745eadb9625
--- /dev/null
+++ b/tests/ui/lazy-type-alias/coerce-behind-lazy.rs
@@ -0,0 +1,16 @@
+// check-pass
+// revisions: current next
+//[next] compile-flags: -Ztrait-solver=next
+
+#![feature(lazy_type_alias)]
+//~^ WARN the feature `lazy_type_alias` is incomplete
+
+use std::any::Any;
+
+type Coerce = Box<dyn Any>;
+
+fn test() -> Coerce {
+    Box::new(1)
+}
+
+fn main() {}
diff --git a/tests/ui/traits/new-solver/lazy-nested-obligations-2.rs b/tests/ui/traits/new-solver/lazy-nested-obligations-2.rs
index fd91d81cdf0..20f504928c7 100644
--- a/tests/ui/traits/new-solver/lazy-nested-obligations-2.rs
+++ b/tests/ui/traits/new-solver/lazy-nested-obligations-2.rs
@@ -1,5 +1,5 @@
 // compile-flags: -Ztrait-solver=next
-// known-bug: #95863
+// check-pass
 
 pub trait With {
     type F;
diff --git a/tests/ui/traits/new-solver/lazy-nested-obligations-2.stderr b/tests/ui/traits/new-solver/lazy-nested-obligations-2.stderr
deleted file mode 100644
index d0a4cd661b3..00000000000
--- a/tests/ui/traits/new-solver/lazy-nested-obligations-2.stderr
+++ /dev/null
@@ -1,39 +0,0 @@
-error[E0308]: mismatched types
-  --> $DIR/lazy-nested-obligations-2.rs:15:23
-   |
-LL |     let _: V<i32> = V(f);
-   |                     - ^ types differ
-   |                     |
-   |                     arguments to this struct are incorrect
-   |
-   = note: expected associated type `<i32 as With>::F`
-                      found fn item `for<'a> fn(&'a str) {f}`
-   = help: consider constraining the associated type `<i32 as With>::F` to `for<'a> fn(&'a str) {f}` or calling a method that returns `<i32 as With>::F`
-   = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
-note: tuple struct defined here
-  --> $DIR/lazy-nested-obligations-2.rs:16:16
-   |
-LL |     pub struct V<T: With>(<T as With>::F);
-   |                ^
-
-error[E0308]: mismatched types
-  --> $DIR/lazy-nested-obligations-2.rs:21:30
-   |
-LL |     let _: E3<i32> = E3::Var(f);
-   |                      ------- ^ types differ
-   |                      |
-   |                      arguments to this enum variant are incorrect
-   |
-   = note: expected associated type `<i32 as With>::F`
-                      found fn item `for<'a> fn(&'a str) {f}`
-   = help: consider constraining the associated type `<i32 as With>::F` to `for<'a> fn(&'a str) {f}` or calling a method that returns `<i32 as With>::F`
-   = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
-note: tuple variant defined here
-  --> $DIR/lazy-nested-obligations-2.rs:19:9
-   |
-LL |         Var(<T as With>::F),
-   |         ^^^
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/traits/new-solver/more-object-bound.stderr b/tests/ui/traits/new-solver/more-object-bound.stderr
index 4554b8c7473..54965dee184 100644
--- a/tests/ui/traits/new-solver/more-object-bound.stderr
+++ b/tests/ui/traits/new-solver/more-object-bound.stderr
@@ -1,8 +1,8 @@
 error[E0277]: the trait bound `dyn Trait<A = A, B = B>: Trait` is not satisfied
-  --> $DIR/more-object-bound.rs:12:17
+  --> $DIR/more-object-bound.rs:12:5
    |
 LL |     foo::<A, B, dyn Trait<A = A, B = B>>(x)
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `dyn Trait<A = A, B = B>`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `dyn Trait<A = A, B = B>`
    |
 note: required by a bound in `foo`
   --> $DIR/more-object-bound.rs:18:8