Auto merge of #60714 - varkor:existential-global-lift-ice, r=oli-obk

Fix ICE with un-feature-gated existential type

Fixes #60371.

r? @oli-obk

src/librustc_typeck/check/writeback.rs

@@ -611,26 +611,33 @@ impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
  }
  }
 
- let new = ty::ResolvedOpaqueTy {
- concrete_type: definition_ty,
- substs: self.tcx().lift_to_global(&opaque_defn.substs).unwrap(),
- };
-
- let old = self.tables
- .concrete_existential_types
- .insert(def_id, new);
- if let Some(old) = old {
- if old.concrete_type != definition_ty || old.substs != opaque_defn.substs {
- span_bug!(
- span,
- "visit_opaque_types tried to write \
- different types for the same existential type: {:?}, {:?}, {:?}, {:?}",
- def_id,
- definition_ty,
- opaque_defn,
- old,
- );
+ if let Some(substs) = self.tcx().lift_to_global(&opaque_defn.substs) {
+ let new = ty::ResolvedOpaqueTy {
+ concrete_type: definition_ty,
+ substs,
+ };
+
+ let old = self.tables
+ .concrete_existential_types
+ .insert(def_id, new);
+ if let Some(old) = old {
+ if old.concrete_type != definition_ty || old.substs != opaque_defn.substs {
+ span_bug!(
+ span,
+ "visit_opaque_types tried to write \
+ different types for the same existential type: {:?}, {:?}, {:?}, {:?}",
+ def_id,
+ definition_ty,
+ opaque_defn,
+ old,
+ );
+ }
  }
+ } else {
+ self.tcx().sess.delay_span_bug(
+ span,
+ "cannot lift `opaque_defn` substs to global type context",
+ );
  }
  }
  }

src/test/ui/existential-type/issue-60371.rs

@@ -0,0 +1,15 @@
+trait Bug {
+ type Item: Bug;
+
+ const FUN: fn() -> Self::Item;
+}
+
+impl Bug for &() {
+ existential type Item: Bug; //~ ERROR existential types are unstable
+ //~^ ERROR the trait bound `(): Bug` is not satisfied
+ //~^^ ERROR could not find defining uses
+
+ const FUN: fn() -> Self::Item = || ();
+}
+
+fn main() {}

src/test/ui/existential-type/issue-60371.stderr

@@ -0,0 +1,29 @@
+error[E0658]: existential types are unstable
+ --> $DIR/issue-60371.rs:8:5
+ |
+LL | existential type Item: Bug;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: for more information, see https://github.com/rust-lang/rust/issues/34511
+ = help: add #![feature(existential_type)] to the crate attributes to enable
+
+error[E0277]: the trait bound `(): Bug` is not satisfied
+ --> $DIR/issue-60371.rs:8:5
+ |
+LL | existential type Item: Bug;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Bug` is not implemented for `()`
+ |
+ = help: the following implementations were found:
+ <&() as Bug>
+ = note: the return type of a function must have a statically known size
+
+error: could not find defining uses
+ --> $DIR/issue-60371.rs:8:5
+ |
+LL | existential type Item: Bug;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0277, E0658.
+For more information about an error, try `rustc --explain E0277`.