Resolve target type of coercion

Author: compiler-errors

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,

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.

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
+

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
+

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() {}

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;

tests/ui/traits/new-solver/lazy-nested-obligations-2.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