Do not ICE on invalid input

Author: estebank

compiler/rustc_trait_selection/src/traits/object_safety.rs

@@ -463,10 +463,17 @@ fn virtual_call_violation_for_method<'tcx>(
 
             let param_env = tcx.param_env(method.def_id);
 
-            let abi_of_ty = |ty: Ty<'tcx>| -> &Abi {
+            let abi_of_ty = |ty: Ty<'tcx>| -> Option<&Abi> {
                 match tcx.layout_of(param_env.and(ty)) {
-                    Ok(layout) => &layout.abi,
-                    Err(err) => bug!("error: {}\n while computing layout for type {:?}", err, ty),
+                    Ok(layout) => Some(&layout.abi),
+                    Err(err) => {
+                        // #78372
+                        tcx.sess.delay_span_bug(
+                            tcx.def_span(method.def_id),
+                            &format!("error: {}\n while computing layout for type {:?}", err, ty),
+                        );
+                        None
+                    }
                 }
             };
 
@@ -475,7 +482,7 @@ fn virtual_call_violation_for_method<'tcx>(
                 receiver_for_self_ty(tcx, receiver_ty, tcx.mk_unit(), method.def_id);
 
             match abi_of_ty(unit_receiver_ty) {
-                &Abi::Scalar(..) => (),
+                Some(Abi::Scalar(..)) => (),
                 abi => {
                     tcx.sess.delay_span_bug(
                         tcx.def_span(method.def_id),
@@ -495,13 +502,12 @@ fn virtual_call_violation_for_method<'tcx>(
                 receiver_for_self_ty(tcx, receiver_ty, trait_object_ty, method.def_id);
 
             match abi_of_ty(trait_object_receiver) {
-                &Abi::ScalarPair(..) => (),
+                Some(Abi::ScalarPair(..)) => (),
                 abi => {
                     tcx.sess.delay_span_bug(
                         tcx.def_span(method.def_id),
                         &format!(
-                            "receiver when `Self = {}` should have a ScalarPair ABI; \
-                                 found {:?}",
+                            "receiver when `Self = {}` should have a ScalarPair ABI; found {:?}",
                             trait_object_ty, abi
                         ),
                     );

src/test/ui/issues/issue-78372.rs

@@ -0,0 +1,14 @@
+use std::ops::DispatchFromDyn; //~ ERROR use of unstable library feature 'dispatch_from_dyn'
+struct Smaht<T, MISC>(PhantomData); //~ ERROR cannot find type `PhantomData` in this scope
+impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {} //~ ERROR cannot find type `U` in this scope
+//~^ ERROR cannot find type `MISC` in this scope
+//~| ERROR use of unstable library feature 'dispatch_from_dyn'
+//~| ERROR the trait `DispatchFromDyn` may only be implemented for a coercion between structures
+//~| ERROR type parameter `T` must be covered by another type when it appears before the first
+trait Foo: X<u32> {}
+trait X<T> {
+    fn foo(self: Smaht<Self, T>);
+}
+trait Marker {}
+impl Marker for dyn Foo {}
+fn main() {}

src/test/ui/issues/issue-78372.stderr

@@ -0,0 +1,62 @@
+error[E0412]: cannot find type `PhantomData` in this scope
+  --> $DIR/issue-78372.rs:2:23
+   |
+LL | struct Smaht<T, MISC>(PhantomData);
+   |                       ^^^^^^^^^^^ not found in this scope
+   |
+help: consider importing this struct
+   |
+LL | use std::marker::PhantomData;
+   |
+
+error[E0412]: cannot find type `U` in this scope
+  --> $DIR/issue-78372.rs:3:31
+   |
+LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
+   |      -                        ^ help: a type parameter with a similar name exists: `T`
+   |      |
+   |      similarly named type parameter `T` defined here
+
+error[E0412]: cannot find type `MISC` in this scope
+  --> $DIR/issue-78372.rs:3:34
+   |
+LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
+   |       -                          ^^^^ not found in this scope
+   |       |
+   |       help: you might be missing a type parameter: `, MISC`
+
+error[E0658]: use of unstable library feature 'dispatch_from_dyn'
+  --> $DIR/issue-78372.rs:1:5
+   |
+LL | use std::ops::DispatchFromDyn;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(dispatch_from_dyn)]` to the crate attributes to enable
+
+error[E0658]: use of unstable library feature 'dispatch_from_dyn'
+  --> $DIR/issue-78372.rs:3:9
+   |
+LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(dispatch_from_dyn)]` to the crate attributes to enable
+
+error[E0378]: the trait `DispatchFromDyn` may only be implemented for a coercion between structures
+  --> $DIR/issue-78372.rs:3:1
+   |
+LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0210]: type parameter `T` must be covered by another type when it appears before the first local type (`Smaht<[type error], [type error]>`)
+  --> $DIR/issue-78372.rs:3:6
+   |
+LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
+   |      ^ type parameter `T` must be covered by another type when it appears before the first local type (`Smaht<[type error], [type error]>`)
+   |
+   = note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local, and no uncovered type parameters appear before that first local type
+   = note: in this case, 'before' refers to the following order: `impl<..> ForeignTrait<T1, ..., Tn> for T0`, where `T0` is the first and `Tn` is the last
+
+error: aborting due to 7 previous errors
+
+Some errors have detailed explanations: E0210, E0378, E0412, E0658.
+For more information about an error, try `rustc --explain E0210`.