Revert "Rollup merge of #136274 - compiler-errors:sized-wf, r=lcnr"

This reverts commit a8ecb79, reversing
changes made to 40c4e05.

(cherry picked from commit 9ea587e)

Author: compiler-errors

Diff for: compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1110,7 +1110,6 @@ fn check_associated_item(
                 let ty = tcx.type_of(item.def_id).instantiate_identity();
                 let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
                 wfcx.register_wf_obligation(span, loc, ty.into());
-                check_sized_if_body(wfcx, item.def_id.expect_local(), ty, Some(span));
                 Ok(())
             }
             ty::AssocKind::Fn => {
@@ -1235,7 +1234,7 @@ fn check_type_defn<'tcx>(
                     ),
                     wfcx.param_env,
                     ty,
-                    tcx.require_lang_item(LangItem::Sized, Some(hir_ty.span)),
+                    tcx.require_lang_item(LangItem::Sized, None),
                 );
             }
 
@@ -1360,7 +1359,7 @@ fn check_item_type(
                 ),
                 wfcx.param_env,
                 item_ty,
-                tcx.require_lang_item(LangItem::Sized, Some(ty_span)),
+                tcx.require_lang_item(LangItem::Sized, None),
             );
         }
 
@@ -1690,36 +1689,6 @@ fn check_fn_or_method<'tcx>(
             );
         }
     }
-
-    // If the function has a body, additionally require that the return type is sized.
-    check_sized_if_body(
-        wfcx,
-        def_id,
-        sig.output(),
-        match hir_decl.output {
-            hir::FnRetTy::Return(ty) => Some(ty.span),
-            hir::FnRetTy::DefaultReturn(_) => None,
-        },
-    );
-}
-
-fn check_sized_if_body<'tcx>(
-    wfcx: &WfCheckingCtxt<'_, 'tcx>,
-    def_id: LocalDefId,
-    ty: Ty<'tcx>,
-    maybe_span: Option<Span>,
-) {
-    let tcx = wfcx.tcx();
-    if let Some(body) = tcx.hir().maybe_body_owned_by(def_id) {
-        let span = maybe_span.unwrap_or(body.value.span);
-
-        wfcx.register_bound(
-            ObligationCause::new(span, def_id, traits::ObligationCauseCode::SizedReturnType),
-            wfcx.param_env,
-            ty,
-            tcx.require_lang_item(LangItem::Sized, Some(span)),
-        );
-    }
 }
 
 /// The `arbitrary_self_types_pointers` feature implies `arbitrary_self_types`.

Diff for: compiler/rustc_hir_typeck/src/check.rs

@@ -117,17 +117,22 @@ pub(super) fn check_fn<'a, 'tcx>(
 
     fcx.typeck_results.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
 
-    // We checked the root's ret ty during wfcheck, but not the child.
-    if fcx.tcx.is_typeck_child(fn_def_id.to_def_id()) {
-        let return_or_body_span = match decl.output {
-            hir::FnRetTy::DefaultReturn(_) => body.value.span,
-            hir::FnRetTy::Return(ty) => ty.span,
-        };
+    let return_or_body_span = match decl.output {
+        hir::FnRetTy::DefaultReturn(_) => body.value.span,
+        hir::FnRetTy::Return(ty) => ty.span,
+    };
 
+    fcx.require_type_is_sized(
+        declared_ret_ty,
+        return_or_body_span,
+        ObligationCauseCode::SizedReturnType,
+    );
+    // We checked the root's signature during wfcheck, but not the child.
+    if fcx.tcx.is_typeck_child(fn_def_id.to_def_id()) {
         fcx.require_type_is_sized(
             declared_ret_ty,
             return_or_body_span,
-            ObligationCauseCode::SizedReturnType,
+            ObligationCauseCode::WellFormed(None),
         );
     }
 

Diff for: compiler/rustc_hir_typeck/src/lib.rs

@@ -186,6 +186,8 @@ fn typeck_with_inspect<'tcx>(
         let wf_code = ObligationCauseCode::WellFormed(Some(WellFormedLoc::Ty(def_id)));
         fcx.register_wf_obligation(expected_type.into(), body.value.span, wf_code);
 
+        fcx.require_type_is_sized(expected_type, body.value.span, ObligationCauseCode::ConstSized);
+
         // Gather locals in statics (because of block expressions).
         GatherLocalsVisitor::new(&fcx).visit_body(body);
 

Diff for: compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -707,6 +707,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         };
 
         self.note_obligation_cause(&mut err, &obligation);
+        self.point_at_returns_when_relevant(&mut err, &obligation);
         err.emit()
     }
 }
@@ -809,6 +810,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     "Async",
                 );
                 self.note_obligation_cause(&mut err, &obligation);
+                self.point_at_returns_when_relevant(&mut err, &obligation);
                 return Some(err.emit());
             }
         }
@@ -854,6 +856,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     "",
                 );
                 self.note_obligation_cause(&mut err, &obligation);
+                self.point_at_returns_when_relevant(&mut err, &obligation);
                 return Some(err.emit());
             }
 
@@ -869,6 +872,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     kind: expected_kind.as_str(),
                 });
                 self.note_obligation_cause(&mut err, &obligation);
+                self.point_at_returns_when_relevant(&mut err, &obligation);
                 return Some(err.emit());
             }
         }
@@ -2829,6 +2833,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         err.span_note(self.tcx.def_span(def_id), "opaque type is declared here");
 
         self.note_obligation_cause(&mut err, &obligation);
+        self.point_at_returns_when_relevant(&mut err, &obligation);
         self.dcx().try_steal_replace_and_emit_err(self.tcx.def_span(def_id), StashKey::Cycle, err)
     }
 

Diff for: compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs

@@ -185,6 +185,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             suggest_increasing_limit,
         );
         self.note_obligation_cause(&mut err, &obligation);
+        self.point_at_returns_when_relevant(&mut err, &obligation);
         err.emit()
     }
 }

Diff for: compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

@@ -1765,7 +1765,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         };
 
         err.code(E0746);
-        err.primary_message("return type cannot be a trait object without pointer indirection");
+        err.primary_message("return type cannot have an unboxed trait object");
         err.children.clear();
 
         let span = obligation.cause.span;
@@ -1781,13 +1781,25 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         } else {
             ("dyn ", span.shrink_to_lo())
         };
-
-        err.span_suggestion_verbose(
-            impl_span,
-            "consider returning an `impl Trait` instead of a `dyn Trait`",
-            "impl ",
-            Applicability::MaybeIncorrect,
-        );
+        let alternatively = if visitor
+            .returns
+            .iter()
+            .map(|expr| self.typeck_results.as_ref().unwrap().expr_ty_adjusted_opt(expr))
+            .collect::<FxHashSet<_>>()
+            .len()
+            <= 1
+        {
+            err.span_suggestion_verbose(
+                impl_span,
+                "consider returning an `impl Trait` instead of a `dyn Trait`",
+                "impl ",
+                Applicability::MaybeIncorrect,
+            );
+            "alternatively, "
+        } else {
+            err.help("if there were a single returned type, you could use `impl Trait` instead");
+            ""
+        };
 
         let mut sugg = vec![
             (span.shrink_to_lo(), format!("Box<{pre}")),
@@ -1819,7 +1831,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
 
         err.multipart_suggestion(
             format!(
-                "alternatively, box the return type, and wrap all of the returned values in \
+                "{alternatively}box the return type, and wrap all of the returned values in \
                  `Box::new`",
             ),
             sugg,
@@ -1829,6 +1841,41 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         true
     }
 
+    pub(super) fn point_at_returns_when_relevant(
+        &self,
+        err: &mut Diag<'_>,
+        obligation: &PredicateObligation<'tcx>,
+    ) {
+        match obligation.cause.code().peel_derives() {
+            ObligationCauseCode::SizedReturnType => {}
+            _ => return,
+        }
+
+        let hir = self.tcx.hir();
+        let node = self.tcx.hir_node_by_def_id(obligation.cause.body_id);
+        if let hir::Node::Item(hir::Item {
+            kind: hir::ItemKind::Fn { body: body_id, .. }, ..
+        }) = node
+        {
+            let body = hir.body(*body_id);
+            // Point at all the `return`s in the function as they have failed trait bounds.
+            let mut visitor = ReturnsVisitor::default();
+            visitor.visit_body(body);
+            let typeck_results = self.typeck_results.as_ref().unwrap();
+            for expr in &visitor.returns {
+                if let Some(returned_ty) = typeck_results.node_type_opt(expr.hir_id) {
+                    let ty = self.resolve_vars_if_possible(returned_ty);
+                    if ty.references_error() {
+                        // don't print out the [type error] here
+                        err.downgrade_to_delayed_bug();
+                    } else {
+                        err.span_label(expr.span, format!("this returned value is of type `{ty}`"));
+                    }
+                }
+            }
+        }
+    }
+
     pub(super) fn report_closure_arg_mismatch(
         &self,
         span: Span,

Diff for: tests/crashes/134355.rs

@@ -0,0 +1,6 @@
+//@ known-bug: #134355
+
+//@compile-flags: --crate-type=lib
+fn digit() -> str {
+    return { i32::MIN };
+}

Diff for: tests/rustdoc-json/primitives/primitive_impls.rs

@@ -1,14 +1,11 @@
-#![feature(no_core, lang_items)]
+#![feature(no_core)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]
 #![no_core]
 #![rustc_coherence_is_core]
 
 //@ set impl_i32 = "$.index[*][?(@.docs=='Only core can do this')].id"
 
-#[lang = "sized"]
-trait Sized {}
-
 /// Only core can do this
 impl i32 {
     //@ set identity = "$.index[*][?(@.docs=='Do Nothing')].id"

Diff for: tests/rustdoc-ui/custom_code_classes_in_docs-warning3.rs

@@ -2,12 +2,9 @@
 // feature.
 
 #![deny(warnings)]
-#![feature(no_core, lang_items)]
+#![feature(no_core)]
 #![no_core]
 
-#[lang = "sized"]
-trait Sized {}
-
 /// ```{class="}
 /// main;
 /// ```

Diff for: tests/rustdoc-ui/custom_code_classes_in_docs-warning3.stderr

@@ -1,5 +1,5 @@
 error: unclosed quote string `"`
-  --> $DIR/custom_code_classes_in_docs-warning3.rs:11:1
+  --> $DIR/custom_code_classes_in_docs-warning3.rs:8:1
    |
 LL | / /// ```{class="}
 LL | | /// main;
@@ -17,7 +17,7 @@ LL | #![deny(warnings)]
    = note: `#[deny(rustdoc::invalid_codeblock_attributes)]` implied by `#[deny(warnings)]`
 
 error: unclosed quote string `"`
-  --> $DIR/custom_code_classes_in_docs-warning3.rs:11:1
+  --> $DIR/custom_code_classes_in_docs-warning3.rs:8:1
    |
 LL | / /// ```{class="}
 LL | | /// main;

Diff for: tests/rustdoc/cfg_doc_reexport.rs

@@ -1,12 +1,9 @@
 #![feature(doc_cfg)]
-#![feature(no_core, lang_items)]
+#![feature(no_core)]
 
 #![crate_name = "foo"]
 #![no_core]
 
-#[lang = "sized"]
-trait Sized {}
-
 //@ has 'foo/index.html'
 //@ has - '//dt/*[@class="stab portability"]' 'foobar'
 //@ has - '//dt/*[@class="stab portability"]' 'bar'

Diff for: tests/rustdoc/cross-crate-primitive-doc.rs

@@ -2,12 +2,9 @@
 //@ compile-flags: --extern-html-root-url=primitive_doc=../ -Z unstable-options
 //@ only-linux
 
-#![feature(no_core, lang_items)]
+#![feature(no_core)]
 #![no_core]
 
-#[lang = "sized"]
-trait Sized {}
-
 extern crate primitive_doc;
 
 //@ has 'cross_crate_primitive_doc/fn.foo.html' '//a[@href="../primitive_doc/primitive.usize.html"]' 'usize'

Diff for: tests/rustdoc/intra-doc/no-doc-primitive.rs

@@ -6,13 +6,8 @@
 #![rustc_coherence_is_core]
 #![crate_type = "rlib"]
 
-
 //@ has no_doc_primitive/index.html
 //! A [`char`] and its [`char::len_utf8`].
-
-#[lang = "sized"]
-trait Sized {}
-
 impl char {
     pub fn len_utf8(self) -> usize {
         42

Diff for: tests/rustdoc/reexport-trait-from-hidden-111064-2.rs

@@ -1,11 +1,8 @@
 // Regression test for <https://github.com/rust-lang/rust/issues/111064>.
-#![feature(no_core, lang_items)]
+#![feature(no_core)]
 #![no_core]
 #![crate_name = "foo"]
 
-#[lang = "sized"]
-trait Sized {}
-
 //@ files "foo" "['sidebar-items.js', 'all.html', 'hidden', 'index.html', 'struct.Bar.html', \
 //        'visible']"
 //@ files "foo/hidden" "['inner']"

Diff for: tests/rustdoc/safe-intrinsic.rs

@@ -1,13 +1,10 @@
 #![feature(intrinsics)]
-#![feature(no_core, lang_items)]
+#![feature(no_core)]
 #![feature(rustc_attrs)]
 
 #![no_core]
 #![crate_name = "foo"]
 
-#[lang = "sized"]
-trait Sized {}
-
 //@ has 'foo/fn.abort.html'
 //@ has - '//pre[@class="rust item-decl"]' 'pub fn abort() -> !'
 #[rustc_intrinsic]

Diff for: tests/ui/associated-consts/issue-58022.stderr

@@ -1,3 +1,12 @@
+error[E0790]: cannot refer to the associated constant on trait without specifying the corresponding `impl` type
+  --> $DIR/issue-58022.rs:4:25
+   |
+LL |     const SIZE: usize;
+   |     ------------------ `Foo::SIZE` defined here
+LL |
+LL |     fn new(slice: &[u8; Foo::SIZE]) -> Self;
+   |                         ^^^^^^^^^ cannot refer to the associated constant of trait
+
 error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
   --> $DIR/issue-58022.rs:13:41
    |
@@ -12,15 +21,6 @@ LL | pub struct Bar<T: ?Sized>(T);
    |            ^^^
    = note: the return type of a function must have a statically known size
 
-error[E0790]: cannot refer to the associated constant on trait without specifying the corresponding `impl` type
-  --> $DIR/issue-58022.rs:4:25
-   |
-LL |     const SIZE: usize;
-   |     ------------------ `Foo::SIZE` defined here
-LL |
-LL |     fn new(slice: &[u8; Foo::SIZE]) -> Self;
-   |                         ^^^^^^^^^ cannot refer to the associated constant of trait
-
 error[E0423]: expected function, tuple struct or tuple variant, found trait `Foo`
   --> $DIR/issue-58022.rs:15:9
    |