Auto merge of #144157 - compiler-errors:no-witness, r=<try>

Remove the `CoroutineWitness` type

It's no longer needed, since it just always the `Coroutine` that it's contained within.

This PR reworks a bit of obligation stalling logic and dtorck constraint behavior, but otherwise it's pretty straightforward.

r? `@lcnr` or reassign (e.g. to oli, who probably would also be down to review)

Author: rust-bors[bot]

compiler/rustc_borrowck/src/lib.rs

@@ -1801,7 +1801,6 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                     | ty::Closure(_, _)
                     | ty::CoroutineClosure(_, _)
                     | ty::Coroutine(_, _)
-                    | ty::CoroutineWitness(..)
                     | ty::Never
                     | ty::Tuple(_)
                     | ty::UnsafeBinder(_)
@@ -1844,7 +1843,6 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                     | ty::FnDef(_, _)
                     | ty::FnPtr(..)
                     | ty::Dynamic(_, _, _)
-                    | ty::CoroutineWitness(..)
                     | ty::Never
                     | ty::UnsafeBinder(_)
                     | ty::Alias(_, _)

compiler/rustc_borrowck/src/type_check/input_output.rs

@@ -86,7 +86,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         // them with fresh ty vars.
                         resume_ty: next_ty_var(),
                         yield_ty: next_ty_var(),
-                        witness: next_ty_var(),
                     },
                 )
                 .args,

compiler/rustc_codegen_cranelift/src/value_and_place.rs

@@ -973,19 +973,6 @@ pub(crate) fn assert_assignable<'tcx>(
                 }
             }
         }
-        (&ty::CoroutineWitness(def_id_a, args_a), &ty::CoroutineWitness(def_id_b, args_b))
-            if def_id_a == def_id_b =>
-        {
-            let mut types_a = args_a.types();
-            let mut types_b = args_b.types();
-            loop {
-                match (types_a.next(), types_b.next()) {
-                    (Some(a), Some(b)) => assert_assignable(fx, a, b, limit - 1),
-                    (None, None) => return,
-                    (Some(_), None) | (None, Some(_)) => panic!("{:#?}/{:#?}", from_ty, to_ty),
-                }
-            }
-        }
         _ => {
             assert_eq!(
                 from_ty,

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -344,7 +344,6 @@ fn exported_generic_symbols_provider_local<'tcx>(
                 ty::FnDef(def_id, _) => *def_id,
                 ty::Coroutine(def_id, _) => *def_id,
                 ty::CoroutineClosure(def_id, _) => *def_id,
-                ty::CoroutineWitness(def_id, _) => *def_id,
                 _ => return false,
             };
             let Some(root_def_id) = root_def_id.as_local() else {

compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs

@@ -437,8 +437,7 @@ fn push_debuginfo_type_name<'tcx>(
         | ty::Infer(_)
         | ty::Placeholder(..)
         | ty::Alias(..)
-        | ty::Bound(..)
-        | ty::CoroutineWitness(..) => {
+        | ty::Bound(..) => {
             bug!(
                 "debuginfo: Trying to create type name for \
                   unexpected type: {:?}",

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -176,7 +176,6 @@ fn const_to_valtree_inner<'tcx>(
         | ty::Closure(..)
         | ty::CoroutineClosure(..)
         | ty::Coroutine(..)
-        | ty::CoroutineWitness(..)
         | ty::UnsafeBinder(_) => Err(ValTreeCreationError::NonSupportedType(ty)),
     }
 }
@@ -336,7 +335,6 @@ pub fn valtree_to_const_value<'tcx>(
         | ty::Closure(..)
         | ty::CoroutineClosure(..)
         | ty::Coroutine(..)
-        | ty::CoroutineWitness(..)
         | ty::FnPtr(..)
         | ty::Str
         | ty::Slice(_)

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -184,7 +184,6 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                     | ty::Closure(_, _)
                     | ty::CoroutineClosure(_, _)
                     | ty::Coroutine(_, _)
-                    | ty::CoroutineWitness(..)
                     | ty::UnsafeBinder(_)
                     | ty::Never
                     | ty::Tuple(_)

compiler/rustc_const_eval/src/interpret/stack.rs

@@ -499,7 +499,6 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 | ty::Char
                 | ty::Ref(..)
                 | ty::Coroutine(..)
-                | ty::CoroutineWitness(..)
                 | ty::Array(..)
                 | ty::Closure(..)
                 | ty::CoroutineClosure(..)

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -795,8 +795,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
             | ty::Placeholder(..)
             | ty::Bound(..)
             | ty::Param(..)
-            | ty::Alias(..)
-            | ty::CoroutineWitness(..) => bug!("Encountered invalid type {:?}", ty),
+            | ty::Alias(..) => bug!("Encountered invalid type {:?}", ty),
         }
     }
 

compiler/rustc_const_eval/src/util/type_name.rs

@@ -58,7 +58,6 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
 
             ty::Alias(ty::Free, _) => bug!("type_name: unexpected free alias"),
             ty::Alias(ty::Inherent, _) => bug!("type_name: unexpected inherent projection"),
-            ty::CoroutineWitness(..) => bug!("type_name: unexpected `CoroutineWitness`"),
         }
     }