Silence some follow-up errors [1/x]

compiler/rustc_hir/src/hir.rs

@@ -2405,6 +2405,39 @@ impl<'hir> Ty<'hir> {
         my_visitor.visit_ty(self);
         my_visitor.0
     }
+
+    /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
+    /// use inference to provide suggestions for the appropriate type if possible.
+    pub fn is_suggestable_infer_ty(&self) -> bool {
+        fn are_suggestable_generic_args(generic_args: &[GenericArg<'_>]) -> bool {
+            generic_args.iter().any(|arg| match arg {
+                GenericArg::Type(ty) => ty.is_suggestable_infer_ty(),
+                GenericArg::Infer(_) => true,
+                _ => false,
+            })
+        }
+        debug!(?self);
+        match &self.kind {
+            TyKind::Infer => true,
+            TyKind::Slice(ty) => ty.is_suggestable_infer_ty(),
+            TyKind::Array(ty, length) => {
+                ty.is_suggestable_infer_ty() || matches!(length, ArrayLen::Infer(_, _))
+            }
+            TyKind::Tup(tys) => tys.iter().any(Self::is_suggestable_infer_ty),
+            TyKind::Ptr(mut_ty) | TyKind::Ref(_, mut_ty) => mut_ty.ty.is_suggestable_infer_ty(),
+            TyKind::OpaqueDef(_, generic_args, _) => are_suggestable_generic_args(generic_args),
+            TyKind::Path(QPath::TypeRelative(ty, segment)) => {
+                ty.is_suggestable_infer_ty() || are_suggestable_generic_args(segment.args().args)
+            }
+            TyKind::Path(QPath::Resolved(ty_opt, Path { segments, .. })) => {
+                ty_opt.is_some_and(Self::is_suggestable_infer_ty)
+                    || segments
+                        .iter()
+                        .any(|segment| are_suggestable_generic_args(segment.args().args))
+            }
+            _ => false,
+        }
+    }
 }
 
 /// Not represented directly in the AST; referred to by name through a `ty_path`.
@@ -2735,14 +2768,23 @@ pub enum FnRetTy<'hir> {
     Return(&'hir Ty<'hir>),
 }
 
-impl FnRetTy<'_> {
+impl<'hir> FnRetTy<'hir> {
     #[inline]
     pub fn span(&self) -> Span {
         match *self {
             Self::DefaultReturn(span) => span,
             Self::Return(ref ty) => ty.span,
         }
     }
+
+    pub fn get_infer_ret_ty(&self) -> Option<&'hir Ty<'hir>> {
+        if let Self::Return(ty) = self {
+            if ty.is_suggestable_infer_ty() {
+                return Some(*ty);
+            }
+        }
+        None
+    }
 }
 
 /// Represents `for<...>` binder before a closure

compiler/rustc_hir_analysis/src/collect.rs

@@ -642,7 +642,7 @@ fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
             tcx.ensure().generics_of(def_id);
             tcx.ensure().type_of(def_id);
             tcx.ensure().predicates_of(def_id);
-            if !is_suggestable_infer_ty(ty) {
+            if !ty.is_suggestable_infer_ty() {
                 let mut visitor = HirPlaceholderCollector::default();
                 visitor.visit_item(it);
                 placeholder_type_error(tcx, None, visitor.0, false, None, it.kind.descr());
@@ -674,7 +674,7 @@ fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
         hir::TraitItemKind::Const(ty, body_id) => {
             tcx.ensure().type_of(def_id);
             if !tcx.dcx().has_stashed_diagnostic(ty.span, StashKey::ItemNoType)
-                && !(is_suggestable_infer_ty(ty) && body_id.is_some())
+                && !(ty.is_suggestable_infer_ty() && body_id.is_some())
             {
                 // Account for `const C: _;`.
                 let mut visitor = HirPlaceholderCollector::default();
@@ -726,7 +726,7 @@ fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
         }
         hir::ImplItemKind::Const(ty, _) => {
             // Account for `const T: _ = ..;`
-            if !is_suggestable_infer_ty(ty) {
+            if !ty.is_suggestable_infer_ty() {
                 let mut visitor = HirPlaceholderCollector::default();
                 visitor.visit_impl_item(impl_item);
                 placeholder_type_error(tcx, None, visitor.0, false, None, "associated constant");
@@ -1054,48 +1054,6 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::TraitDef {
     }
 }
 
-fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
-    generic_args.iter().any(|arg| match arg {
-        hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
-        hir::GenericArg::Infer(_) => true,
-        _ => false,
-    })
-}
-
-/// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
-/// use inference to provide suggestions for the appropriate type if possible.
-fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
-    debug!(?ty);
-    use hir::TyKind::*;
-    match &ty.kind {
-        Infer => true,
-        Slice(ty) => is_suggestable_infer_ty(ty),
-        Array(ty, length) => {
-            is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
-        }
-        Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
-        Ptr(mut_ty) | Ref(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
-        OpaqueDef(_, generic_args, _) => are_suggestable_generic_args(generic_args),
-        Path(hir::QPath::TypeRelative(ty, segment)) => {
-            is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
-        }
-        Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
-            ty_opt.is_some_and(is_suggestable_infer_ty)
-                || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
-        }
-        _ => false,
-    }
-}
-
-pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
-    if let hir::FnRetTy::Return(ty) = output {
-        if is_suggestable_infer_ty(ty) {
-            return Some(*ty);
-        }
-    }
-    None
-}
-
 #[instrument(level = "debug", skip(tcx))]
 fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<ty::PolyFnSig<'_>> {
     use rustc_hir::Node::*;
@@ -1188,7 +1146,7 @@ fn infer_return_ty_for_fn_sig<'tcx>(
 ) -> ty::PolyFnSig<'tcx> {
     let hir_id = tcx.local_def_id_to_hir_id(def_id);
 
-    match get_infer_ret_ty(&sig.decl.output) {
+    match sig.decl.output.get_infer_ret_ty() {
         Some(ty) => {
             let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
             // Typeck doesn't expect erased regions to be returned from `type_of`.

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -9,8 +9,8 @@ use rustc_middle::ty::{self, ImplTraitInTraitData, IsSuggestable, Ty, TyCtxt, Ty
 use rustc_span::symbol::Ident;
 use rustc_span::{Span, DUMMY_SP};
 
+use super::bad_placeholder;
 use super::ItemCtxt;
-use super::{bad_placeholder, is_suggestable_infer_ty};
 pub use opaque::test_opaque_hidden_types;
 
 mod opaque;
@@ -368,7 +368,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
             }
             TraitItemKind::Const(ty, body_id) => body_id
                 .and_then(|body_id| {
-                    is_suggestable_infer_ty(ty).then(|| {
+                    ty.is_suggestable_infer_ty().then(|| {
                         infer_placeholder_type(
                             tcx,
                             def_id,
@@ -392,7 +392,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
                 Ty::new_fn_def(tcx, def_id.to_def_id(), args)
             }
             ImplItemKind::Const(ty, body_id) => {
-                if is_suggestable_infer_ty(ty) {
+                if ty.is_suggestable_infer_ty() {
                     infer_placeholder_type(
                         tcx,
                         def_id,
@@ -416,7 +416,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
 
         Node::Item(item) => match item.kind {
             ItemKind::Static(ty, .., body_id) => {
-                if is_suggestable_infer_ty(ty) {
+                if ty.is_suggestable_infer_ty() {
                     infer_placeholder_type(
                         tcx,
                         def_id,
@@ -430,7 +430,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
                 }
             }
             ItemKind::Const(ty, _, body_id) => {
-                if is_suggestable_infer_ty(ty) {
+                if ty.is_suggestable_infer_ty() {
                     infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident, "constant")
                 } else {
                     icx.to_ty(ty)
@@ -603,6 +603,8 @@ fn infer_placeholder_type<'a>(
             }
 
             err.emit();
+            // diagnostic stashing loses the information of whether something is a hard error.
+            Ty::new_error_with_message(tcx, span, "ItemNoType is a hard error")
         }
         None => {
             let mut diag = bad_placeholder(tcx, vec![span], kind);
@@ -623,15 +625,9 @@ fn infer_placeholder_type<'a>(
                 }
             }
 
-            diag.emit();
+            Ty::new_error(tcx, diag.emit())
         }
     }
-
-    // Typeck doesn't expect erased regions to be returned from `type_of`.
-    tcx.fold_regions(ty, |r, _| match *r {
-        ty::ReErased => tcx.lifetimes.re_static,
-        _ => r,
-    })
 }
 
 fn check_feature_inherent_assoc_ty(tcx: TyCtxt<'_>, span: Span) {

compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs

@@ -134,6 +134,21 @@ impl TaitConstraintLocator<'_> {
             debug!("no constraint: no typeck results");
             return;
         }
+
+        if let Some(hir_sig) = self.tcx.hir_node_by_def_id(item_def_id).fn_decl() {
+            if hir_sig.output.get_infer_ret_ty().is_some() {
+                let guar = self.tcx.dcx().span_delayed_bug(
+                    hir_sig.output.span(),
+                    "inferring return types and opaque types do not mix well",
+                );
+                self.found = Some(ty::OpaqueHiddenType {
+                    span: DUMMY_SP,
+                    ty: Ty::new_error(self.tcx, guar),
+                });
+                return;
+            }
+        }
+
         // Calling `mir_borrowck` can lead to cycle errors through
         // const-checking, avoid calling it if we don't have to.
         // ```rust

compiler/rustc_hir_typeck/src/lib.rs

@@ -181,7 +181,7 @@ fn typeck_with_fallback<'tcx>(
     let mut fcx = FnCtxt::new(&inh, param_env, def_id);
 
     if let Some(hir::FnSig { header, decl, .. }) = fn_sig {
-        let fn_sig = if rustc_hir_analysis::collect::get_infer_ret_ty(&decl.output).is_some() {
+        let fn_sig = if decl.output.get_infer_ret_ty().is_some() {
             fcx.astconv().ty_of_fn(id, header.unsafety, header.abi, decl, None, None)
         } else {
             tcx.fn_sig(def_id).instantiate_identity()

tests/ui/type-alias-impl-trait/issue-77179.rs

@@ -6,9 +6,7 @@ type Pointer<T> = impl std::ops::Deref<Target = T>;
 
 fn test() -> Pointer<_> {
     //~^ ERROR: the placeholder `_` is not allowed within types
-    //~| ERROR: non-defining opaque type use in defining scope
     Box::new(1)
-    //~^ ERROR expected generic type parameter, found `i32`
 }
 
 fn main() {

tests/ui/type-alias-impl-trait/issue-77179.stderr

@@ -7,28 +7,6 @@ LL | fn test() -> Pointer<_> {
    |              |       not allowed in type signatures
    |              help: replace with the correct return type: `Pointer<i32>`
 
-error[E0792]: non-defining opaque type use in defining scope
-  --> $DIR/issue-77179.rs:7:14
-   |
-LL | fn test() -> Pointer<_> {
-   |              ^^^^^^^^^^ argument `i32` is not a generic parameter
-   |
-note: for this opaque type
-  --> $DIR/issue-77179.rs:5:19
-   |
-LL | type Pointer<T> = impl std::ops::Deref<Target = T>;
-   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error[E0792]: expected generic type parameter, found `i32`
-  --> $DIR/issue-77179.rs:10:5
-   |
-LL | type Pointer<T> = impl std::ops::Deref<Target = T>;
-   |              - this generic parameter must be used with a generic type parameter
-...
-LL |     Box::new(1)
-   |     ^^^^^^^^^^^
-
-error: aborting due to 3 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0121, E0792.
-For more information about an error, try `rustc --explain E0121`.
+For more information about this error, try `rustc --explain E0121`.