Handle normalization failure in struct_tail_erasing_lifetimes

Fixes an ICE that occurred when the struct in question has an error

Author: gurry

compiler/rustc_middle/src/ty/util.rs

@@ -190,7 +190,20 @@ impl<'tcx> TyCtxt<'tcx> {
         param_env: ty::ParamEnv<'tcx>,
     ) -> Ty<'tcx> {
         let tcx = self;
-        tcx.struct_tail_with_normalize(ty, |ty| tcx.normalize_erasing_regions(param_env, ty), || {})
+        tcx.struct_tail_with_normalize(
+            ty,
+            |ty| match tcx.try_normalize_erasing_regions(param_env, ty) {
+                Ok(ty) => ty,
+                Err(_e) => {
+                    if let Some(guar) = tcx.dcx().has_errors() {
+                        Ty::new_error(tcx, guar)
+                    } else {
+                        bug!("normalization failed, but no errors reported");
+                    }
+                }
+            },
+            || {},
+        )
     }
 
     /// Returns the deeply last field of nested structures, or the same type if

tests/crashes/113272.rs tests/ui/structs/ice-struct-tail-normalization-113272.rs

@@ -1,9 +1,10 @@
-//@ known-bug: #113272
 trait Trait {
     type RefTarget;
 }
 
 impl Trait for () where Missing: Trait {}
+//~^ ERROR cannot find type `Missing` in this scope
+//~| ERROR not all trait items implemented, missing: `RefTarget`
 
 struct Other {
     data: <() as Trait>::RefTarget,
@@ -12,5 +13,6 @@ struct Other {
 fn main() {
     unsafe {
         std::mem::transmute::<Option<()>, Option<&Other>>(None);
+//~^ ERROR cannot transmute between types of different sizes, or dependently-sized types
     }
 }

tests/ui/structs/ice-struct-tail-normalization-113272.stderr

@@ -0,0 +1,28 @@
+error[E0412]: cannot find type `Missing` in this scope
+  --> $DIR/ice-struct-tail-normalization-113272.rs:5:25
+   |
+LL | impl Trait for () where Missing: Trait {}
+   |                         ^^^^^^^ not found in this scope
+
+error[E0046]: not all trait items implemented, missing: `RefTarget`
+  --> $DIR/ice-struct-tail-normalization-113272.rs:5:1
+   |
+LL |     type RefTarget;
+   |     -------------- `RefTarget` from trait
+...
+LL | impl Trait for () where Missing: Trait {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `RefTarget` in implementation
+
+error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
+  --> $DIR/ice-struct-tail-normalization-113272.rs:15:9
+   |
+LL |         std::mem::transmute::<Option<()>, Option<&Other>>(None);
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: source type: `Option<()>` (8 bits)
+   = note: target type: `Option<&Other>` (unable to determine layout for `Other` because `<() as Trait>::RefTarget` cannot be normalized)
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0046, E0412, E0512.
+For more information about an error, try `rustc --explain E0046`.