Auto merge of rust-lang#117002 - matthiaskrgr:rollup-xbnc95q, r=matthiaskrgr

Rollup of 5 pull requests

Successful merges:

 - rust-lang#116911 (Suggest relaxing implicit `type Assoc: Sized;` bound)
 - rust-lang#116961 (Typo suggestion to change bindings with leading underscore)
 - rust-lang#116964 (Add stable Instance::body() and RustcInternal trait)
 - rust-lang#116992 (Mention the syntax for `use` on `mod foo;` if `foo` doesn't exist)
 - rust-lang#116995 (Point at assoc fn definition on type param divergence)

Failed merges:

 - rust-lang#116974 (coverage: Fix inconsistent handling of function signature spans)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_expand/messages.ftl

@@ -86,6 +86,7 @@ expand_module_circular =
 expand_module_file_not_found =
     file not found for module `{$name}`
     .help = to create the module `{$name}`, create file "{$default_path}" or "{$secondary_path}"
+    .note = if there is a `mod {$name}` elsewhere in the crate already, import it with `use crate::...` instead
 
 expand_module_in_block =
     cannot declare a non-inline module inside a block unless it has a path attribute

compiler/rustc_expand/src/errors.rs

@@ -350,6 +350,7 @@ pub(crate) struct ModuleInBlockName {
 #[derive(Diagnostic)]
 #[diag(expand_module_file_not_found, code = "E0583")]
 #[help]
+#[note]
 pub(crate) struct ModuleFileNotFound {
     #[primary_span]
     pub span: Span,

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -1557,38 +1557,24 @@ fn compare_number_of_generics<'tcx>(
                 DiagnosticId::Error("E0049".into()),
             );
 
-            let mut suffix = None;
-
+            let msg =
+                format!("expected {trait_count} {kind} parameter{}", pluralize!(trait_count),);
             if let Some(spans) = trait_spans {
                 let mut spans = spans.iter();
                 if let Some(span) = spans.next() {
-                    err.span_label(
-                        *span,
-                        format!(
-                            "expected {} {} parameter{}",
-                            trait_count,
-                            kind,
-                            pluralize!(trait_count),
-                        ),
-                    );
+                    err.span_label(*span, msg);
                 }
                 for span in spans {
                     err.span_label(*span, "");
                 }
             } else {
-                suffix = Some(format!(", expected {trait_count}"));
+                err.span_label(tcx.def_span(trait_.def_id), msg);
             }
 
             if let Some(span) = span {
                 err.span_label(
                     span,
-                    format!(
-                        "found {} {} parameter{}{}",
-                        impl_count,
-                        kind,
-                        pluralize!(impl_count),
-                        suffix.unwrap_or_default(),
-                    ),
+                    format!("found {} {} parameter{}", impl_count, kind, pluralize!(impl_count),),
                 );
             }
 

compiler/rustc_resolve/src/diagnostics.rs

@@ -1511,17 +1511,30 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 ),
             );
         }
+
+        let (span, sugg, post) = if let SuggestionTarget::SimilarlyNamed = suggestion.target
+            && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
+            && let Some(span) = suggestion.span
+            && let Some(candidate) = suggestion.candidate.as_str().strip_prefix("_")
+            && snippet == candidate
+        {
+            // When the suggested binding change would be from `x` to `_x`, suggest changing the
+            // original binding definition instead. (#60164)
+            (span, snippet, ", consider changing it")
+        } else {
+            (span, suggestion.candidate.to_string(), "")
+        };
         let msg = match suggestion.target {
             SuggestionTarget::SimilarlyNamed => format!(
-                "{} {} with a similar name exists",
+                "{} {} with a similar name exists{post}",
                 suggestion.res.article(),
                 suggestion.res.descr()
             ),
             SuggestionTarget::SingleItem => {
                 format!("maybe you meant this {}", suggestion.res.descr())
             }
         };
-        err.span_suggestion(span, msg, suggestion.candidate, Applicability::MaybeIncorrect);
+        err.span_suggestion(span, msg, sugg, Applicability::MaybeIncorrect);
         true
     }
 

compiler/rustc_smir/src/rustc_internal/internal.rs

@@ -0,0 +1,61 @@
+//! Module containing the translation from stable mir constructs to the rustc counterpart.
+//!
+//! This module will only include a few constructs to allow users to invoke internal rustc APIs
+//! due to incomplete stable coverage.
+
+// Prefer importing stable_mir over internal rustc constructs to make this file more readable.
+use crate::rustc_smir::{MaybeStable, Tables};
+use rustc_middle::ty::{self as rustc_ty, Ty as InternalTy};
+use stable_mir::ty::{Const, GenericArgKind, GenericArgs, Region, Ty};
+use stable_mir::DefId;
+
+use super::RustcInternal;
+
+impl<'tcx> RustcInternal<'tcx> for DefId {
+    type T = rustc_span::def_id::DefId;
+    fn internal(&self, tables: &mut Tables<'tcx>) -> Self::T {
+        tables.def_ids[*self]
+    }
+}
+
+impl<'tcx> RustcInternal<'tcx> for GenericArgs {
+    type T = rustc_ty::GenericArgsRef<'tcx>;
+    fn internal(&self, tables: &mut Tables<'tcx>) -> Self::T {
+        tables.tcx.mk_args_from_iter(self.0.iter().map(|arg| arg.internal(tables)))
+    }
+}
+
+impl<'tcx> RustcInternal<'tcx> for GenericArgKind {
+    type T = rustc_ty::GenericArg<'tcx>;
+    fn internal(&self, tables: &mut Tables<'tcx>) -> Self::T {
+        match self {
+            GenericArgKind::Lifetime(reg) => reg.internal(tables).into(),
+            GenericArgKind::Type(ty) => ty.internal(tables).into(),
+            GenericArgKind::Const(cnst) => cnst.internal(tables).into(),
+        }
+    }
+}
+
+impl<'tcx> RustcInternal<'tcx> for Region {
+    type T = rustc_ty::Region<'tcx>;
+    fn internal(&self, _tables: &mut Tables<'tcx>) -> Self::T {
+        todo!()
+    }
+}
+
+impl<'tcx> RustcInternal<'tcx> for Ty {
+    type T = InternalTy<'tcx>;
+    fn internal(&self, tables: &mut Tables<'tcx>) -> Self::T {
+        match tables.types[self.0] {
+            MaybeStable::Stable(_) => todo!(),
+            MaybeStable::Rustc(ty) => ty,
+        }
+    }
+}
+
+impl<'tcx> RustcInternal<'tcx> for Const {
+    type T = rustc_ty::Const<'tcx>;
+    fn internal(&self, _tables: &mut Tables<'tcx>) -> Self::T {
+        todo!()
+    }
+}

compiler/rustc_smir/src/rustc_internal/mod.rs

@@ -20,6 +20,8 @@ use std::fmt::Debug;
 use std::hash::Hash;
 use std::ops::{ControlFlow, Index};
 
+mod internal;
+
 impl<'tcx> Index<stable_mir::DefId> for Tables<'tcx> {
     type Output = DefId;
 
@@ -231,3 +233,11 @@ impl<K: PartialEq + Hash + Eq, V: Copy + Debug + PartialEq + IndexedVal> Index<V
         k
     }
 }
+
+/// Trait used to translate a stable construct to its rustc counterpart.
+///
+/// This is basically a mirror of [crate::rustc_smir::Stable].
+pub(crate) trait RustcInternal<'tcx> {
+    type T;
+    fn internal(&self, tables: &mut Tables<'tcx>) -> Self::T;
+}

compiler/rustc_smir/src/rustc_smir/builder.rs

@@ -0,0 +1,55 @@
+//! Logic required to produce a monomorphic stable body.
+//!
+//! We first retrieve and monomorphize the rustc body representation, i.e., we generate a
+//! monomorphic body using internal representation.
+//! After that, we convert the internal representation into a stable one.
+use crate::rustc_smir::{Stable, Tables};
+use rustc_middle::mir;
+use rustc_middle::mir::visit::MutVisitor;
+use rustc_middle::ty::{self, Ty, TyCtxt};
+
+/// Builds a monomorphic body for a given instance.
+pub struct BodyBuilder<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    instance: ty::Instance<'tcx>,
+}
+
+impl<'tcx> BodyBuilder<'tcx> {
+    pub fn new(tcx: TyCtxt<'tcx>, instance: ty::Instance<'tcx>) -> Self {
+        BodyBuilder { tcx, instance }
+    }
+
+    pub fn build(mut self, tables: &mut Tables<'tcx>) -> stable_mir::mir::Body {
+        let mut body = self.tcx.instance_mir(self.instance.def).clone();
+        let generics = self.tcx.generics_of(self.instance.def_id());
+        if generics.requires_monomorphization(self.tcx) {
+            self.visit_body(&mut body);
+        }
+        body.stable(tables)
+    }
+
+    fn monomorphize<T>(&self, value: T) -> T
+    where
+        T: ty::TypeFoldable<TyCtxt<'tcx>>,
+    {
+        self.instance.instantiate_mir_and_normalize_erasing_regions(
+            self.tcx,
+            ty::ParamEnv::reveal_all(),
+            ty::EarlyBinder::bind(value),
+        )
+    }
+}
+
+impl<'tcx> MutVisitor<'tcx> for BodyBuilder<'tcx> {
+    fn visit_ty_const(&mut self, ct: &mut ty::Const<'tcx>, _location: mir::Location) {
+        *ct = self.monomorphize(*ct);
+    }
+
+    fn visit_ty(&mut self, ty: &mut Ty<'tcx>, _: mir::visit::TyContext) {
+        *ty = self.monomorphize(*ty);
+    }
+
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+}

compiler/rustc_smir/src/rustc_smir/mod.rs

@@ -7,7 +7,7 @@
 //!
 //! For now, we are developing everything inside `rustc`, thus, we keep this module private.
 
-use crate::rustc_internal::IndexMap;
+use crate::rustc_internal::{IndexMap, RustcInternal};
 use crate::rustc_smir::hir::def::DefKind;
 use crate::rustc_smir::stable_mir::ty::{BoundRegion, EarlyBoundRegion, Region};
 use rustc_hir as hir;
@@ -26,6 +26,7 @@ use stable_mir::{self, opaque, Context, Filename};
 use tracing::debug;
 
 mod alloc;
+mod builder;
 
 impl<'tcx> Context for Tables<'tcx> {
     fn local_crate(&self) -> stable_mir::Crate {
@@ -171,8 +172,9 @@ impl<'tcx> Context for Tables<'tcx> {
         }
     }
 
-    fn instance_body(&mut self, _def: InstanceDef) -> Body {
-        todo!("Monomorphize the body")
+    fn instance_body(&mut self, def: InstanceDef) -> Body {
+        let instance = self.instances[def];
+        builder::BodyBuilder::new(self.tcx, instance).build(self)
     }
 
     fn instance_ty(&mut self, def: InstanceDef) -> stable_mir::ty::Ty {
@@ -195,9 +197,21 @@ impl<'tcx> Context for Tables<'tcx> {
         let def_id = self[def_id];
         let generics = self.tcx.generics_of(def_id);
         let result = generics.requires_monomorphization(self.tcx);
-        println!("req {result}: {def_id:?}");
         result
     }
+
+    fn resolve_instance(
+        &mut self,
+        def: stable_mir::ty::FnDef,
+        args: &stable_mir::ty::GenericArgs,
+    ) -> Option<stable_mir::mir::mono::Instance> {
+        let def_id = def.0.internal(self);
+        let args_ref = args.internal(self);
+        match Instance::resolve(self.tcx, ParamEnv::reveal_all(), def_id, args_ref) {
+            Ok(Some(instance)) => Some(instance.stable(self)),
+            Ok(None) | Err(_) => None,
+        }
+    }
 }
 
 #[derive(Clone)]

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

@@ -2665,6 +2665,29 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                             // Check for foreign traits being reachable.
                             self.tcx.visible_parent_map(()).get(&def_id).is_some()
                         };
+                        if Some(def_id) == self.tcx.lang_items().sized_trait()
+                            && let Some(hir::Node::TraitItem(hir::TraitItem {
+                                ident,
+                                kind: hir::TraitItemKind::Type(bounds, None),
+                                ..
+                            })) = tcx.hir().get_if_local(item_def_id)
+                            // Do not suggest relaxing if there is an explicit `Sized` obligation.
+                            && !bounds.iter()
+                                .filter_map(|bound| bound.trait_ref())
+                                .any(|tr| tr.trait_def_id() == self.tcx.lang_items().sized_trait())
+                        {
+                            let (span, separator) = if let [.., last] = bounds {
+                                (last.span().shrink_to_hi(), " +")
+                            } else {
+                                (ident.span.shrink_to_hi(), ":")
+                            };
+                            err.span_suggestion_verbose(
+                                span,
+                                "consider relaxing the implicit `Sized` restriction",
+                                format!("{separator} ?Sized"),
+                                Applicability::MachineApplicable,
+                            );
+                        }
                         if let DefKind::Trait = tcx.def_kind(item_def_id)
                             && !visible_item
                         {

compiler/stable_mir/src/error.rs

@@ -4,6 +4,7 @@
 //! - [CompilerError]: This represents errors that can be raised when invoking the compiler.
 //! - [Error]: Generic error that represents the reason why a request that could not be fulfilled.
 
+use std::convert::From;
 use std::fmt::{Debug, Display, Formatter};
 use std::{error, fmt};
 
@@ -31,6 +32,12 @@ impl Error {
     }
 }
 
+impl From<&str> for Error {
+    fn from(value: &str) -> Self {
+        Self(value.into())
+    }
+}
+
 impl Display for Error {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         Display::fmt(&self.0, f)