Rollup of 9 pull requests

compiler/rustc_ast_lowering/src/lib.rs

@@ -1310,9 +1310,13 @@ impl<'hir, R: ResolverAstLoweringExt<'hir>> LoweringContext<'_, 'hir, R> {
                 }
                 GenericArg::Type(self.lower_ty_alloc(ty, itctx).try_as_ambig_ty().unwrap())
             }
-            ast::GenericArg::Const(ct) => GenericArg::Const(
-                self.lower_anon_const_to_const_arg_and_alloc(ct).try_as_ambig_ct().unwrap(),
-            ),
+            ast::GenericArg::Const(ct) => {
+                let ct = self.lower_anon_const_to_const_arg_and_alloc(ct);
+                match ct.try_as_ambig_ct() {
+                    Some(ct) => GenericArg::Const(ct),
+                    None => GenericArg::Infer(hir::InferArg { hir_id: ct.hir_id, span: ct.span }),
+                }
+            }
         }
     }
 

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -737,6 +737,23 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
             TokenTree::Token(token, spacing) => {
                 let token_str = self.token_to_string_ext(token, convert_dollar_crate);
                 self.word(token_str);
+                // Emit hygiene annotations for identity-bearing tokens,
+                // matching how print_ident() and print_lifetime() call ann_post().
+                match token.kind {
+                    token::Ident(name, _) => {
+                        self.ann_post(Ident::new(name, token.span));
+                    }
+                    token::NtIdent(ident, _) => {
+                        self.ann_post(ident);
+                    }
+                    token::Lifetime(name, _) => {
+                        self.ann_post(Ident::new(name, token.span));
+                    }
+                    token::NtLifetime(ident, _) => {
+                        self.ann_post(ident);
+                    }
+                    _ => {}
+                }
                 if let token::DocComment(..) = token.kind {
                     self.hardbreak()
                 }

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -374,10 +374,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         self.body
     }
 
-    fn unsized_feature_enabled(&self) -> bool {
-        self.tcx().features().unsized_fn_params()
-    }
-
     /// Equate the inferred type and the annotated type for user type annotations
     #[instrument(skip(self), level = "debug")]
     fn check_user_type_annotations(&mut self) {
@@ -660,7 +656,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                     );
                 }
 
-                if !self.unsized_feature_enabled() {
+                if !self.tcx().features().unsized_fn_params() {
                     let trait_ref = ty::TraitRef::new(
                         tcx,
                         tcx.require_lang_item(LangItem::Sized, self.last_span),
@@ -936,9 +932,10 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             }
         }
 
-        // When `unsized_fn_params` is enabled, only function calls
-        // and nullary ops are checked in `check_call_dest`.
-        if !self.unsized_feature_enabled() {
+        // When `unsized_fn_params` is enabled, this is checked in `check_call_dest`,
+        // and `hir_typeck` still forces all non-argument locals to be sized (i.e., we don't
+        // fully re-check what was already checked on HIR).
+        if !self.tcx().features().unsized_fn_params() {
             match self.body.local_kind(local) {
                 LocalKind::ReturnPointer | LocalKind::Arg => {
                     // return values of normal functions are required to be
@@ -1953,8 +1950,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             }
 
             // When `unsized_fn_params` is not enabled,
-            // this check is done at `check_local`.
-            if self.unsized_feature_enabled() {
+            // this check is done at `visit_local_decl`.
+            if self.tcx().features().unsized_fn_params() {
                 let span = term.source_info.span;
                 self.ensure_place_sized(dest_ty, span);
             }

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -2874,6 +2874,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         span: Span,
     ) -> Const<'tcx> {
         let tcx = self.tcx();
+
+        let ty = if !ty.has_infer() { Some(ty) } else { None };
+
         if let LitKind::Err(guar) = *kind {
             return ty::Const::new_error(tcx, guar);
         }
@@ -2905,16 +2908,20 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         };
 
         let lit_input = match expr.kind {
-            hir::ExprKind::Lit(lit) => Some(LitToConstInput { lit: lit.node, ty, neg: false }),
+            hir::ExprKind::Lit(lit) => {
+                Some(LitToConstInput { lit: lit.node, ty: Some(ty), neg: false })
+            }
             hir::ExprKind::Unary(hir::UnOp::Neg, expr) => match expr.kind {
-                hir::ExprKind::Lit(lit) => Some(LitToConstInput { lit: lit.node, ty, neg: true }),
+                hir::ExprKind::Lit(lit) => {
+                    Some(LitToConstInput { lit: lit.node, ty: Some(ty), neg: true })
+                }
                 _ => None,
             },
             _ => None,
         };
 
         lit_input.and_then(|l| {
-            if const_lit_matches_ty(tcx, &l.lit, l.ty, l.neg) {
+            if const_lit_matches_ty(tcx, &l.lit, ty, l.neg) {
                 tcx.at(expr.span)
                     .lit_to_const(l)
                     .map(|value| ty::Const::new_value(tcx, value.valtree, value.ty))

compiler/rustc_lint/src/for_loops_over_fallibles.rs

@@ -49,6 +49,11 @@ impl<'tcx> LateLintPass<'tcx> for ForLoopsOverFallibles {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
         let Some((pat, arg)) = extract_for_loop(expr) else { return };
 
+        // Do not put suggestions for external macros.
+        if pat.span.from_expansion() {
+            return;
+        }
+
         let arg_span = arg.span.source_callsite();
 
         let ty = cx.typeck_results().expr_ty(arg);
@@ -77,6 +82,8 @@ impl<'tcx> LateLintPass<'tcx> for ForLoopsOverFallibles {
         };
 
         let sub = if let Some(recv) = extract_iterator_next_call(cx, arg)
+            && recv.span.can_be_used_for_suggestions()
+            && recv.span.between(arg_span.shrink_to_hi()).can_be_used_for_suggestions()
             && let Ok(recv_snip) = cx.sess().source_map().span_to_snippet(recv.span)
         {
             ForLoopsOverFalliblesLoopSub::RemoveNext {

compiler/rustc_middle/src/ty/consts/lit.rs

@@ -10,7 +10,10 @@ pub struct LitToConstInput<'tcx> {
     /// The absolute value of the resultant constant.
     pub lit: LitKind,
     /// The type of the constant.
-    pub ty: Ty<'tcx>,
+    ///
+    /// `None` is used by const generics when the type of the constant is unknown, e.g.
+    /// if there are inference variables
+    pub ty: Option<Ty<'tcx>>,
     /// If the constant is negative.
     pub neg: bool,
 }

compiler/rustc_mir_build/src/builder/expr/as_constant.rs

@@ -50,7 +50,8 @@ pub(crate) fn as_constant_inner<'tcx>(
 
     match *kind {
         ExprKind::Literal { lit, neg } => {
-            let const_ = lit_to_mir_constant(tcx, LitToConstInput { lit: lit.node, ty, neg });
+            let const_ =
+                lit_to_mir_constant(tcx, LitToConstInput { lit: lit.node, ty: Some(ty), neg });
 
             ConstOperand { span, user_ty: None, const_ }
         }
@@ -109,6 +110,8 @@ pub(crate) fn as_constant_inner<'tcx>(
 fn lit_to_mir_constant<'tcx>(tcx: TyCtxt<'tcx>, lit_input: LitToConstInput<'tcx>) -> Const<'tcx> {
     let LitToConstInput { lit, ty, neg } = lit_input;
 
+    let ty = ty.expect("type of literal must be known at this point");
+
     if let Err(guar) = ty.error_reported() {
         return Const::Ty(Ty::new_error(tcx, guar), ty::Const::new_error(tcx, guar));
     }

compiler/rustc_mir_build/src/thir/constant.rs

@@ -31,25 +31,27 @@ pub(crate) fn lit_to_const<'tcx>(
             .unwrap_or_else(|| bug!("expected to create ScalarInt from uint {:?}", result))
     };
 
-    let (valtree, valtree_ty) = match (lit, expected_ty.kind()) {
+    let (valtree, valtree_ty) = match (lit, expected_ty.map(|ty| ty.kind())) {
         (ast::LitKind::Str(s, _), _) => {
             let str_bytes = s.as_str().as_bytes();
             let valtree_ty = Ty::new_imm_ref(tcx, tcx.lifetimes.re_static, tcx.types.str_);
             (ty::ValTree::from_raw_bytes(tcx, str_bytes), valtree_ty)
         }
-        (ast::LitKind::ByteStr(byte_sym, _), ty::Ref(_, inner_ty, _))
+        (ast::LitKind::ByteStr(byte_sym, _), Some(ty::Ref(_, inner_ty, _)))
             if let ty::Slice(ty) | ty::Array(ty, _) = inner_ty.kind()
                 && let ty::Uint(UintTy::U8) = ty.kind() =>
         {
-            (ty::ValTree::from_raw_bytes(tcx, byte_sym.as_byte_str()), expected_ty)
+            (ty::ValTree::from_raw_bytes(tcx, byte_sym.as_byte_str()), expected_ty.unwrap())
         }
-        (ast::LitKind::ByteStr(byte_sym, _), ty::Slice(inner_ty) | ty::Array(inner_ty, _))
-            if tcx.features().deref_patterns()
-                && let ty::Uint(UintTy::U8) = inner_ty.kind() =>
+        (
+            ast::LitKind::ByteStr(byte_sym, _),
+            Some(ty::Slice(inner_ty) | ty::Array(inner_ty, _)),
+        ) if tcx.features().deref_patterns()
+            && let ty::Uint(UintTy::U8) = inner_ty.kind() =>
         {
             // Byte string literal patterns may have type `[u8]` or `[u8; N]` if `deref_patterns` is
             // enabled, in order to allow, e.g., `deref!(b"..."): Vec<u8>`.
-            (ty::ValTree::from_raw_bytes(tcx, byte_sym.as_byte_str()), expected_ty)
+            (ty::ValTree::from_raw_bytes(tcx, byte_sym.as_byte_str()), expected_ty.unwrap())
         }
         (ast::LitKind::ByteStr(byte_sym, _), _) => {
             let valtree = ty::ValTree::from_raw_bytes(tcx, byte_sym.as_byte_str());
@@ -79,11 +81,11 @@ pub(crate) fn lit_to_const<'tcx>(
                 trunc(if neg { u128::wrapping_neg(n.get()) } else { n.get() }, i.to_unsigned());
             (ty::ValTree::from_scalar_int(tcx, scalar_int), Ty::new_int(tcx, i))
         }
-        (ast::LitKind::Int(n, ast::LitIntType::Unsuffixed), ty::Uint(ui)) if !neg => {
+        (ast::LitKind::Int(n, ast::LitIntType::Unsuffixed), Some(ty::Uint(ui))) if !neg => {
             let scalar_int = trunc(n.get(), *ui);
             (ty::ValTree::from_scalar_int(tcx, scalar_int), Ty::new_uint(tcx, *ui))
         }
-        (ast::LitKind::Int(n, ast::LitIntType::Unsuffixed), ty::Int(i)) => {
+        (ast::LitKind::Int(n, ast::LitIntType::Unsuffixed), Some(ty::Int(i))) => {
             // Unsigned "negation" has the same bitwise effect as signed negation,
             // which gets the result we want without additional casts.
             let scalar_int =
@@ -101,7 +103,7 @@ pub(crate) fn lit_to_const<'tcx>(
             let bits = parse_float_into_scalar(n, fty, neg)?;
             (ty::ValTree::from_scalar_int(tcx, bits), Ty::new_float(tcx, fty))
         }
-        (ast::LitKind::Float(n, ast::LitFloatType::Unsuffixed), ty::Float(fty)) => {
+        (ast::LitKind::Float(n, ast::LitFloatType::Unsuffixed), Some(ty::Float(fty))) => {
             let bits = parse_float_into_scalar(n, *fty, neg)?;
             (ty::ValTree::from_scalar_int(tcx, bits), Ty::new_float(tcx, *fty))
         }

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -696,7 +696,7 @@ impl<'tcx> PatCtxt<'tcx> {
                 // patterns to `str`, and byte-string literal patterns to `[u8; N]` or `[u8]`.
 
                 let pat_ty = self.typeck_results.node_type(pat.hir_id);
-                let lit_input = LitToConstInput { lit: lit.node, ty: pat_ty, neg: *negated };
+                let lit_input = LitToConstInput { lit: lit.node, ty: Some(pat_ty), neg: *negated };
                 let constant = const_lit_matches_ty(self.tcx, &lit.node, pat_ty, *negated)
                     .then(|| self.tcx.at(expr.span).lit_to_const(lit_input))
                     .flatten()

compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs

@@ -158,6 +158,7 @@ impl UnderspecifiedArgKind {
 
 struct ClosureEraser<'a, 'tcx> {
     infcx: &'a InferCtxt<'tcx>,
+    depth: usize,
 }
 
 impl<'a, 'tcx> ClosureEraser<'a, 'tcx> {
@@ -172,7 +173,8 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for ClosureEraser<'a, 'tcx> {
     }
 
     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        match ty.kind() {
+        self.depth += 1;
+        let ty = match ty.kind() {
             ty::Closure(_, args) => {
                 // For a closure type, we turn it into a function pointer so that it gets rendered
                 // as `fn(args) -> Ret`.
@@ -233,9 +235,15 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for ClosureEraser<'a, 'tcx> {
                 // its type parameters.
                 ty.super_fold_with(self)
             }
-            // We don't have an unknown type parameter anywhere, replace with `_`.
+            // We are in the top-level type, not one of its type parameters. Name it with its
+            // parameters replaced.
+            _ if self.depth == 1 => ty.super_fold_with(self),
+            // We don't have an unknown type parameter anywhere, and we are in a type parameter.
+            // Replace with `_`.
             _ => self.new_infer(),
-        }
+        };
+        self.depth -= 1;
+        ty
     }
 
     fn fold_const(&mut self, c: ty::Const<'tcx>) -> ty::Const<'tcx> {
@@ -287,7 +295,7 @@ fn ty_to_string<'tcx>(
     let ty = infcx.resolve_vars_if_possible(ty);
     // We use `fn` ptr syntax for closures, but this only works when the closure does not capture
     // anything. We also remove all type parameters that are fully known to the type system.
-    let ty = ty.fold_with(&mut ClosureEraser { infcx });
+    let ty = ty.fold_with(&mut ClosureEraser { infcx, depth: 0 });
 
     match (ty.kind(), called_method_def_id) {
         // We don't want the regular output for `fn`s because it includes its path in
@@ -467,6 +475,25 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         term: Term<'tcx>,
         error_code: TypeAnnotationNeeded,
         should_label_span: bool,
+    ) -> Diag<'a> {
+        self.emit_inference_failure_err_with_type_hint(
+            body_def_id,
+            failure_span,
+            term,
+            error_code,
+            should_label_span,
+            None,
+        )
+    }
+
+    pub fn emit_inference_failure_err_with_type_hint(
+        &self,
+        body_def_id: LocalDefId,
+        failure_span: Span,
+        term: Term<'tcx>,
+        error_code: TypeAnnotationNeeded,
+        should_label_span: bool,
+        ty: Option<Ty<'tcx>>,
     ) -> Diag<'a> {
         let term = self.resolve_vars_if_possible(term);
         let arg_data = self
@@ -479,7 +506,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             return self.bad_inference_failure_err(failure_span, arg_data, error_code);
         };
 
-        let mut local_visitor = FindInferSourceVisitor::new(self, typeck_results, term);
+        let mut local_visitor = FindInferSourceVisitor::new(self, typeck_results, term, ty);
         if let Some(body) = self.tcx.hir_maybe_body_owned_by(
             self.tcx.typeck_root_def_id(body_def_id.to_def_id()).expect_local(),
         ) {
@@ -779,10 +806,20 @@ impl<'tcx> InferSourceKind<'tcx> {
             | InferSourceKind::ClosureReturn { ty, .. } => {
                 if ty.is_closure() {
                     ("closure", closure_as_fn_str(infcx, ty), long_ty_path)
-                } else if !ty.is_ty_or_numeric_infer() {
-                    ("normal", infcx.tcx.short_string(ty, &mut long_ty_path), long_ty_path)
-                } else {
+                } else if ty.is_ty_or_numeric_infer()
+                    || ty.is_primitive()
+                    || matches!(
+                        ty.kind(),
+                        ty::Adt(_, args)
+                        if args.types().count() == 0 && args.consts().count() == 0
+                    )
+                {
+                    // `ty` is either `_`, a primitive type like `u32` or a type with no type or
+                    // const parameters. We will not mention the type in the main inference error
+                    // message.
                     ("other", String::new(), long_ty_path)
+                } else {
+                    ("normal", infcx.tcx.short_string(ty, &mut long_ty_path), long_ty_path)
                 }
             }
             // FIXME: We should be able to add some additional info here.
@@ -815,6 +852,7 @@ struct FindInferSourceVisitor<'a, 'tcx> {
     typeck_results: &'a TypeckResults<'tcx>,
 
     target: Term<'tcx>,
+    ty: Option<Ty<'tcx>>,
 
     attempt: usize,
     infer_source_cost: usize,
@@ -826,12 +864,14 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
         tecx: &'a TypeErrCtxt<'a, 'tcx>,
         typeck_results: &'a TypeckResults<'tcx>,
         target: Term<'tcx>,
+        ty: Option<Ty<'tcx>>,
     ) -> Self {
         FindInferSourceVisitor {
             tecx,
             typeck_results,
 
             target,
+            ty,
 
             attempt: 0,
             infer_source_cost: usize::MAX,
@@ -1213,7 +1253,7 @@ impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> {
     fn visit_local(&mut self, local: &'tcx LetStmt<'tcx>) {
         intravisit::walk_local(self, local);
 
-        if let Some(ty) = self.opt_node_type(local.hir_id) {
+        if let Some(mut ty) = self.opt_node_type(local.hir_id) {
             if self.generic_arg_contains_target(ty.into()) {
                 fn get_did(
                     typeck_results: &TypeckResults<'_>,
@@ -1241,7 +1281,11 @@ impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> {
                         _ => None,
                     }
                 }
-
+                if let Some(t) = self.ty
+                    && ty.has_infer()
+                {
+                    ty = t;
+                }
                 if let LocalSource::Normal = local.source
                     && local.ty.is_none()
                 {