Rollup merge of #125750 - compiler-errors:expect, r=lcnr

Align `Term` methods with `GenericArg` methods, add `Term::expect_*`

* `Term::ty` -> `Term::as_type`.
* `Term::ct` -> `Term::as_const`.
* Adds `Term::expect_type` and `Term::expect_const`, and uses them in favor of `.ty().unwrap()`, etc.

I could also shorten these to `as_ty` and then do `GenericArg::as_ty` as well, but I do think the `as_` is important to signal that this is a conversion method, and not a getter, like `Const::ty` is.

r? types

compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs

@@ -726,7 +726,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReplaceProjectionWith<'_, 'tcx> {
                     )
                     .expect("expected to be able to unify goal projection with dyn's projection"),
             );
-            proj.term.ty().unwrap()
+            proj.term.expect_type()
         } else {
             ty.super_fold_with(self)
         }

compiler/rustc_trait_selection/src/solve/normalizes_to/opaque_types.rs

@@ -17,7 +17,7 @@ impl<'tcx> EvalCtxt<'_, InferCtxt<'tcx>> {
     ) -> QueryResult<'tcx> {
         let tcx = self.interner();
         let opaque_ty = goal.predicate.alias;
-        let expected = goal.predicate.term.ty().expect("no such thing as an opaque const");
+        let expected = goal.predicate.term.as_type().expect("no such thing as an opaque const");
 
         match (goal.param_env.reveal(), self.solver_mode()) {
             (Reveal::UserFacing, SolverMode::Normal) => {

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -553,7 +553,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
     }
 
     fn is_self_referential_projection(&self, p: ty::PolyProjectionPredicate<'tcx>) -> bool {
-        if let Some(ty) = p.term().skip_binder().ty() {
+        if let Some(ty) = p.term().skip_binder().as_type() {
             matches!(ty.kind(), ty::Alias(ty::Projection, proj) if proj == &p.skip_binder().projection_term.expect_ty(self.tcx))
         } else {
             false

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

@@ -1112,7 +1112,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                                 {
                                     Some((
                                         DefIdOrName::DefId(def_id),
-                                        pred.kind().rebind(proj.term.ty().unwrap()),
+                                        pred.kind().rebind(proj.term.expect_type()),
                                         pred.kind().rebind(args.as_slice()),
                                     ))
                                 } else {
@@ -1129,7 +1129,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             {
                                 Some((
                                     DefIdOrName::Name("trait object"),
-                                    pred.rebind(proj.term.ty().unwrap()),
+                                    pred.rebind(proj.term.expect_type()),
                                     pred.rebind(args.as_slice()),
                                 ))
                             } else {
@@ -1157,7 +1157,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             {
                                 Some((
                                     name,
-                                    pred.kind().rebind(proj.term.ty().unwrap()),
+                                    pred.kind().rebind(proj.term.expect_type()),
                                     pred.kind().rebind(args.as_slice()),
                                 ))
                             } else {
@@ -3840,7 +3840,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     })
                 } else if let Some(where_pred) = where_pred.as_projection_clause()
                     && let Some(failed_pred) = failed_pred.as_projection_clause()
-                    && let Some(found) = failed_pred.skip_binder().term.ty()
+                    && let Some(found) = failed_pred.skip_binder().term.as_type()
                 {
                     type_diffs = vec![Sorts(ty::error::ExpectedFound {
                         expected: where_pred

compiler/rustc_trait_selection/src/traits/normalize.rs

@@ -259,7 +259,7 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
                     obligations.len = ?self.obligations.len(),
                     "AssocTypeNormalizer: normalized type"
                 );
-                normalized_ty.ty().unwrap()
+                normalized_ty.expect_type()
             }
 
             ty::Projection => {
@@ -289,7 +289,7 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
                 )
                 .ok()
                 .flatten()
-                .map(|term| term.ty().unwrap())
+                .map(|term| term.expect_type())
                 .map(|normalized_ty| {
                     PlaceholderReplacer::replace_placeholders(
                         infcx,

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -946,7 +946,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 // since we don't actually use them.
                 &mut vec![],
             )
-            .ty()
+            .as_type()
             .unwrap();
 
             if let ty::Dynamic(data, ..) = ty.kind() { data.principal() } else { None }

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -286,7 +286,7 @@ fn extend_cause_with_original_assoc_item_obligation<'tcx>(
             // implemented, but rather from a "second order" obligation, where an associated
             // type has a projection coming from another associated type.
             // See `tests/ui/traits/assoc-type-in-superbad.rs` for an example.
-            if let Some(term_ty) = proj.term.ty()
+            if let Some(term_ty) = proj.term.as_type()
                 && let Some(impl_item_span) = ty_to_impl_span(term_ty)
             {
                 cause.span = impl_item_span;