Auto merge of #107290 - Dylan-DPC:rollup-tovojhr, r=Dylan-DPC

Rollup of 9 pull requests

Successful merges:

 - #105552 (Add help message about function pointers)
 - #106583 (Suggest coercion of `Result` using `?`)
 - #106767 (Allow setting CFG_DISABLE_UNSTABLE_FEATURES to 0)
 - #106823 (Allow fmt::Arguments::as_str() to return more Some(_).)
 - #107166 (rustc_metadata: Support non-`Option` nullable values in metadata tables)
 - #107213 (Add suggestion to remove if in let..else block)
 - #107223 (`sub_ptr()` is equivalent to `usize::try_from().unwrap_unchecked()`, not `usize::from().unwrap_unchecked()`)
 - #107227 (`new_outside_solver` ->  `evaluate_root_goal`)
 - #107232 (rustdoc: simplify settings popover DOM, CSS, JS)

Failed merges:

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

compiler/rustc_error_messages/locales/en-US/parse.ftl

@@ -238,6 +238,7 @@ parse_const_let_mutually_exclusive = `const` and `let` are mutually exclusive
 
 parse_invalid_expression_in_let_else = a `{$operator}` expression cannot be directly assigned in `let...else`
 parse_invalid_curly_in_let_else = right curly brace `{"}"}` before `else` in a `let...else` statement not allowed
+parse_extra_if_in_let_else = remove the `if` if you meant to write a `let...else` statement
 
 parse_compound_assignment_expression_in_let = can't reassign to an uninitialized variable
     .suggestion = initialize the variable

compiler/rustc_feature/src/lib.rs

@@ -83,7 +83,8 @@ impl UnstableFeatures {
     /// Otherwise, only `RUSTC_BOOTSTRAP=1` will work.
     pub fn from_environment(krate: Option<&str>) -> Self {
         // `true` if this is a feature-staged build, i.e., on the beta or stable channel.
-        let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
+        let disable_unstable_features =
+            option_env!("CFG_DISABLE_UNSTABLE_FEATURES").map(|s| s != "0").unwrap_or(false);
         // Returns whether `krate` should be counted as unstable
         let is_unstable_crate = |var: &str| {
             krate.map_or(false, |name| var.split(',').any(|new_krate| new_krate == name))

compiler/rustc_hir_typeck/src/coercion.rs

@@ -1613,12 +1613,14 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
                 if visitor.ret_exprs.len() > 0 && let Some(expr) = expression {
                     self.note_unreachable_loop_return(&mut err, &expr, &visitor.ret_exprs);
                 }
+
                 let reported = err.emit_unless(unsized_return);
 
                 self.final_ty = Some(fcx.tcx.ty_error_with_guaranteed(reported));
             }
         }
     }
+
     fn note_unreachable_loop_return(
         &self,
         err: &mut Diagnostic,

compiler/rustc_hir_typeck/src/demand.rs

@@ -59,7 +59,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             || self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
             || self.suggest_clone_for_ref(err, expr, expr_ty, expected)
             || self.suggest_into(err, expr, expr_ty, expected)
-            || self.suggest_floating_point_literal(err, expr, expected);
+            || self.suggest_floating_point_literal(err, expr, expected)
+            || self.note_result_coercion(err, expr, expected, expr_ty);
         if !suggested {
             self.point_at_expr_source_of_inferred_type(err, expr, expr_ty, expected);
         }
@@ -81,7 +82,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self.annotate_expected_due_to_let_ty(err, expr, error);
         self.emit_type_mismatch_suggestions(err, expr, expr_ty, expected, expected_ty_expr, error);
         self.note_type_is_not_clone(err, expected, expr_ty, expr);
-        self.note_need_for_fn_pointer(err, expected, expr_ty);
         self.note_internal_mutation_in_method(err, expr, expected, expr_ty);
         self.check_for_range_as_method_call(err, expr, expr_ty, expected);
         self.check_for_binding_assigned_block_without_tail_expression(err, expr, expr_ty, expected);
@@ -697,6 +697,56 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         );
     }
 
+    pub(crate) fn note_result_coercion(
+        &self,
+        err: &mut Diagnostic,
+        expr: &hir::Expr<'tcx>,
+        expected: Ty<'tcx>,
+        found: Ty<'tcx>,
+    ) -> bool {
+        let ty::Adt(e, substs_e) = expected.kind() else { return false; };
+        let ty::Adt(f, substs_f) = found.kind() else { return false; };
+        if e.did() != f.did() {
+            return false;
+        }
+        if Some(e.did()) != self.tcx.get_diagnostic_item(sym::Result) {
+            return false;
+        }
+        let map = self.tcx.hir();
+        if let Some(hir::Node::Expr(expr)) = map.find_parent(expr.hir_id)
+            && let hir::ExprKind::Ret(_) = expr.kind
+        {
+            // `return foo;`
+        } else if map.get_return_block(expr.hir_id).is_some() {
+            // Function's tail expression.
+        } else {
+            return false;
+        }
+        let e = substs_e.type_at(1);
+        let f = substs_f.type_at(1);
+        if self
+            .infcx
+            .type_implements_trait(
+                self.tcx.get_diagnostic_item(sym::Into).unwrap(),
+                [f, e],
+                self.param_env,
+            )
+            .must_apply_modulo_regions()
+        {
+            err.multipart_suggestion(
+                "use `?` to coerce and return an appropriate `Err`, and wrap the resulting value \
+                 in `Ok` so the expression remains of type `Result`",
+                vec![
+                    (expr.span.shrink_to_lo(), "Ok(".to_string()),
+                    (expr.span.shrink_to_hi(), "?)".to_string()),
+                ],
+                Applicability::MaybeIncorrect,
+            );
+            return true;
+        }
+        false
+    }
+
     /// If the expected type is an enum (Issue #55250) with any variants whose
     /// sole field is of the found type, suggest such variants. (Issue #42764)
     fn suggest_compatible_variants(

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -926,43 +926,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    pub(in super::super) fn note_need_for_fn_pointer(
-        &self,
-        err: &mut Diagnostic,
-        expected: Ty<'tcx>,
-        found: Ty<'tcx>,
-    ) {
-        let (sig, did, substs) = match (&expected.kind(), &found.kind()) {
-            (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
-                let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1);
-                let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2);
-                if sig1 != sig2 {
-                    return;
-                }
-                err.note(
-                    "different `fn` items always have unique types, even if their signatures are \
-                     the same",
-                );
-                (sig1, *did1, substs1)
-            }
-            (ty::FnDef(did, substs), ty::FnPtr(sig2)) => {
-                let sig1 = self.tcx.bound_fn_sig(*did).subst(self.tcx, substs);
-                if sig1 != *sig2 {
-                    return;
-                }
-                (sig1, *did, substs)
-            }
-            _ => return,
-        };
-        err.help(&format!("change the expected type to be function pointer `{}`", sig));
-        err.help(&format!(
-            "if the expected type is due to type inference, cast the expected `fn` to a function \
-             pointer: `{} as {}`",
-            self.tcx.def_path_str_with_substs(did, substs),
-            sig
-        ));
-    }
-
     // Instantiates the given path, which must refer to an item with the given
     // number of type parameters and type.
     #[instrument(skip(self, span), level = "debug")]

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -1841,6 +1841,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 self.suggest_as_ref_where_appropriate(span, &exp_found, diag);
                 self.suggest_accessing_field_where_appropriate(cause, &exp_found, diag);
                 self.suggest_await_on_expect_found(cause, span, &exp_found, diag);
+                self.suggest_function_pointers(cause, span, &exp_found, diag);
             }
         }
 
@@ -2585,7 +2586,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
     /// with the other type. A TyVar inference type is compatible with any type, and an IntVar or
     /// FloatVar inference type are compatible with themselves or their concrete types (Int and
     /// Float types, respectively). When comparing two ADTs, these rules apply recursively.
-    pub fn same_type_modulo_infer(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
+    pub fn same_type_modulo_infer<T: relate::Relate<'tcx>>(&self, a: T, b: T) -> bool {
         let (a, b) = self.resolve_vars_if_possible((a, b));
         SameTypeModuloInfer(self).relate(a, b).is_ok()
     }

compiler/rustc_infer/src/infer/error_reporting/suggest.rs

@@ -8,7 +8,7 @@ use rustc_middle::traits::{
     StatementAsExpression,
 };
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::{self as ty, Ty, TypeVisitable};
+use rustc_middle::ty::{self as ty, IsSuggestable, Ty, TypeVisitable};
 use rustc_span::{sym, BytePos, Span};
 
 use crate::errors::SuggAddLetForLetChains;
@@ -351,6 +351,82 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         }
     }
 
+    pub(super) fn suggest_function_pointers(
+        &self,
+        cause: &ObligationCause<'tcx>,
+        span: Span,
+        exp_found: &ty::error::ExpectedFound<Ty<'tcx>>,
+        diag: &mut Diagnostic,
+    ) {
+        debug!("suggest_function_pointers(cause={:?}, exp_found={:?})", cause, exp_found);
+        let ty::error::ExpectedFound { expected, found } = exp_found;
+        let expected_inner = expected.peel_refs();
+        let found_inner = found.peel_refs();
+        if !expected_inner.is_fn() || !found_inner.is_fn() {
+            return;
+        }
+        match (&expected_inner.kind(), &found_inner.kind()) {
+            (ty::FnPtr(sig), ty::FnDef(did, substs)) => {
+                let expected_sig = &(self.normalize_fn_sig)(*sig);
+                let found_sig =
+                    &(self.normalize_fn_sig)(self.tcx.bound_fn_sig(*did).subst(self.tcx, substs));
+
+                let fn_name = self.tcx.def_path_str_with_substs(*did, substs);
+
+                if !self.same_type_modulo_infer(*found_sig, *expected_sig)
+                    || !sig.is_suggestable(self.tcx, true)
+                    || ty::util::is_intrinsic(self.tcx, *did)
+                {
+                    return;
+                }
+
+                let (msg, sugg) = match (expected.is_ref(), found.is_ref()) {
+                    (true, false) => {
+                        let msg = "consider using a reference";
+                        let sug = format!("&{fn_name}");
+                        (msg, sug)
+                    }
+                    (false, true) => {
+                        let msg = "consider removing the reference";
+                        let sug = format!("{fn_name}");
+                        (msg, sug)
+                    }
+                    (true, true) => {
+                        diag.note("fn items are distinct from fn pointers");
+                        let msg = "consider casting to a fn pointer";
+                        let sug = format!("&({fn_name} as {sig})");
+                        (msg, sug)
+                    }
+                    (false, false) => {
+                        diag.note("fn items are distinct from fn pointers");
+                        let msg = "consider casting to a fn pointer";
+                        let sug = format!("{fn_name} as {sig}");
+                        (msg, sug)
+                    }
+                };
+                diag.span_suggestion(span, msg, &sugg, Applicability::MaybeIncorrect);
+            }
+            (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
+                let expected_sig =
+                    &(self.normalize_fn_sig)(self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1));
+                let found_sig =
+                    &(self.normalize_fn_sig)(self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2));
+
+                if self.same_type_modulo_infer(*found_sig, *expected_sig) {
+                    diag.note(
+                    "different fn items have unique types, even if their signatures are the same",
+                    );
+                }
+            }
+            (ty::FnDef(_, _), ty::FnPtr(_)) => {
+                diag.note("fn items are distinct from fn pointers");
+            }
+            _ => {
+                return;
+            }
+        };
+    }
+
     pub fn should_suggest_as_ref(&self, expected: Ty<'tcx>, found: Ty<'tcx>) -> Option<&str> {
         if let (ty::Adt(exp_def, exp_substs), ty::Ref(_, found_ty, _)) =
             (expected.kind(), found.kind())

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -985,7 +985,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
         let vis = self.get_visibility(id);
         let span = self.get_span(id, sess);
         let macro_rules = match kind {
-            DefKind::Macro(..) => self.root.tables.macro_rules.get(self, id).is_some(),
+            DefKind::Macro(..) => self.root.tables.is_macro_rules.get(self, id),
             _ => false,
         };
 
@@ -1283,7 +1283,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
     fn get_macro(self, id: DefIndex, sess: &Session) -> ast::MacroDef {
         match self.def_kind(id) {
             DefKind::Macro(_) => {
-                let macro_rules = self.root.tables.macro_rules.get(self, id).is_some();
+                let macro_rules = self.root.tables.is_macro_rules.get(self, id);
                 let body =
                     self.root.tables.macro_definition.get(self, id).unwrap().decode((self, sess));
                 ast::MacroDef { macro_rules, body: ast::ptr::P(body) }
@@ -1595,11 +1595,11 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
     }
 
     fn get_attr_flags(self, index: DefIndex) -> AttrFlags {
-        self.root.tables.attr_flags.get(self, index).unwrap_or(AttrFlags::empty())
+        self.root.tables.attr_flags.get(self, index)
     }
 
     fn get_is_intrinsic(self, index: DefIndex) -> bool {
-        self.root.tables.is_intrinsic.get(self, index).is_some()
+        self.root.tables.is_intrinsic.get(self, index)
     }
 }
 

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -226,12 +226,7 @@ provide! { tcx, def_id, other, cdata,
     deduced_param_attrs => { table }
     is_type_alias_impl_trait => {
         debug_assert_eq!(tcx.def_kind(def_id), DefKind::OpaqueTy);
-        cdata
-            .root
-            .tables
-            .is_type_alias_impl_trait
-            .get(cdata, def_id.index)
-            .is_some()
+        cdata.root.tables.is_type_alias_impl_trait.get(cdata, def_id.index)
     }
     collect_return_position_impl_trait_in_trait_tys => {
         Ok(cdata

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -483,7 +483,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         self.lazy(DefPathHashMapRef::BorrowedFromTcx(self.tcx.def_path_hash_to_def_index_map()))
     }
 
-    fn encode_source_map(&mut self) -> LazyTable<u32, LazyValue<rustc_span::SourceFile>> {
+    fn encode_source_map(&mut self) -> LazyTable<u32, Option<LazyValue<rustc_span::SourceFile>>> {
         let source_map = self.tcx.sess.source_map();
         let all_source_files = source_map.files();
 
@@ -1130,7 +1130,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             attr_flags |= AttrFlags::IS_DOC_HIDDEN;
         }
         if !attr_flags.is_empty() {
-            self.tables.attr_flags.set(def_id.local_def_index, attr_flags);
+            self.tables.attr_flags.set_nullable(def_id.local_def_index, attr_flags);
         }
     }
 
@@ -1387,7 +1387,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         if impl_item.kind == ty::AssocKind::Fn {
             record!(self.tables.fn_sig[def_id] <- tcx.fn_sig(def_id));
             if tcx.is_intrinsic(def_id) {
-                self.tables.is_intrinsic.set(def_id.index, ());
+                self.tables.is_intrinsic.set_nullable(def_id.index, true);
             }
         }
     }
@@ -1519,7 +1519,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             }
             hir::ItemKind::Macro(ref macro_def, _) => {
                 if macro_def.macro_rules {
-                    self.tables.macro_rules.set(def_id.index, ());
+                    self.tables.is_macro_rules.set_nullable(def_id.index, true);
                 }
                 record!(self.tables.macro_definition[def_id] <- &*macro_def.body);
             }
@@ -1529,7 +1529,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             hir::ItemKind::OpaqueTy(ref opaque) => {
                 self.encode_explicit_item_bounds(def_id);
                 if matches!(opaque.origin, hir::OpaqueTyOrigin::TyAlias) {
-                    self.tables.is_type_alias_impl_trait.set(def_id.index, ());
+                    self.tables.is_type_alias_impl_trait.set_nullable(def_id.index, true);
                 }
             }
             hir::ItemKind::Enum(..) => {
@@ -1636,7 +1636,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         if let hir::ItemKind::Fn(..) = item.kind {
             record!(self.tables.fn_sig[def_id] <- tcx.fn_sig(def_id));
             if tcx.is_intrinsic(def_id) {
-                self.tables.is_intrinsic.set(def_id.index, ());
+                self.tables.is_intrinsic.set_nullable(def_id.index, true);
             }
         }
         if let hir::ItemKind::Impl { .. } = item.kind {
@@ -2038,7 +2038,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
         }
         if let hir::ForeignItemKind::Fn(..) = nitem.kind {
             if tcx.is_intrinsic(def_id) {
-                self.tables.is_intrinsic.set(def_id.index, ());
+                self.tables.is_intrinsic.set_nullable(def_id.index, true);
             }
         }
     }