Rollup merge of #121208 - nnethercote:delayed_bug-to-bug, r=lcnr

Convert `delayed_bug`s to `bug`s.

I have a suspicion that quite a few delayed bug paths are impossible to reach, so I did an experiment.

I converted every `delayed_bug` to a `bug`, ran the full test suite, then converted back every `bug` that was hit. A surprising number were never hit.

This is too dangerous to merge. Increased coverage (fuzzing or a crater run) would likely hit more cases. But it might be useful for people to look at and think about which paths are genuinely unreachable.

r? `@ghost`

compiler/rustc_trait_selection/src/traits/const_evaluatable.rs

@@ -62,14 +62,11 @@ pub fn is_const_evaluatable<'tcx>(
 
         match unexpanded_ct.kind() {
             ty::ConstKind::Expr(_) => {
-                // FIXME(generic_const_exprs): we have a `ConstKind::Expr` which is fully concrete,
-                // but currently it is not possible to evaluate `ConstKind::Expr` so we are unable
-                // to tell if it is evaluatable or not. For now we just ICE until this is
-                // implemented.
-                Err(NotConstEvaluatable::Error(tcx.dcx().span_delayed_bug(
-                    span,
-                    "evaluating `ConstKind::Expr` is not currently supported",
-                )))
+                // FIXME(generic_const_exprs): we have a fully concrete `ConstKind::Expr`, but
+                // haven't implemented evaluating `ConstKind::Expr` yet, so we are unable to tell
+                // if it is evaluatable or not. As this is unreachable for now, we can simple ICE
+                // here.
+                tcx.dcx().span_bug(span, "evaluating `ConstKind::Expr` is not currently supported");
             }
             ty::ConstKind::Unevaluated(uv) => {
                 let concrete = infcx.const_eval_resolve(param_env, uv, Some(span));

compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs

@@ -3313,7 +3313,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         expected_trait_ref.self_ty().error_reported()?;
 
         let Some(found_trait_ty) = found_trait_ref.self_ty().no_bound_vars() else {
-            return Err(self.dcx().delayed_bug("bound vars outside binder"));
+            self.dcx().bug("bound vars outside binder");
         };
 
         let found_did = match *found_trait_ty.kind() {

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -172,7 +172,9 @@ fn do_normalize_predicates<'tcx>(
     // the normalized predicates.
     let errors = infcx.resolve_regions(&outlives_env);
     if !errors.is_empty() {
-        tcx.dcx().span_delayed_bug(
+        // @lcnr: Let's still ICE here for now. I want a test case
+        // for that.
+        tcx.dcx().span_bug(
             span,
             format!("failed region resolution while normalizing {elaborated_env:?}: {errors:?}"),
         );

compiler/rustc_trait_selection/src/traits/outlives_bounds.rs

@@ -100,7 +100,7 @@ fn implied_outlives_bounds<'a, 'tcx>(
 
         let errors = ocx.select_all_or_error();
         if !errors.is_empty() {
-            infcx.dcx().span_delayed_bug(
+            infcx.dcx().span_bug(
                 span,
                 "implied_outlives_bounds failed to solve obligations from instantiation",
             );

compiler/rustc_trait_selection/src/traits/project.rs

@@ -645,11 +645,9 @@ pub fn compute_inherent_assoc_ty_args<'a, 'b, 'tcx>(
     match selcx.infcx.at(&cause, param_env).eq(DefineOpaqueTypes::No, impl_ty, self_ty) {
         Ok(mut ok) => obligations.append(&mut ok.obligations),
         Err(_) => {
-            tcx.dcx().span_delayed_bug(
+            tcx.dcx().span_bug(
                 cause.span,
-                format!(
-                    "{self_ty:?} was a subtype of {impl_ty:?} during selection but now it is not"
-                ),
+                format!("{self_ty:?} was equal to {impl_ty:?} during selection but now it is not"),
             );
         }
     }
@@ -1194,7 +1192,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
                     obligation.cause.span,
                     format!("Cannot project an associated type from `{impl_source:?}`"),
                 );
-                return Err(());
+                return Err(())
             }
         };
 

compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs

@@ -190,10 +190,9 @@ where
                 }
             }
             if !progress {
-                return Err(infcx.dcx().span_delayed_bug(
-                    span,
-                    format!("ambiguity processing {obligations:?} from {self:?}"),
-                ));
+                infcx
+                    .dcx()
+                    .span_bug(span, format!("ambiguity processing {obligations:?} from {self:?}"));
             }
         }