Suggest making private tuple struct field public

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -334,6 +334,15 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
         self.r.field_names.insert(def_id, field_names);
     }
 
+    fn insert_field_visibilities_local(&mut self, def_id: DefId, vdata: &ast::VariantData) {
+        let field_vis = vdata
+            .fields()
+            .iter()
+            .map(|field| field.vis.span.until(field.ident.map_or(field.ty.span, |i| i.span)))
+            .collect();
+        self.r.field_visibility_spans.insert(def_id, field_vis);
+    }
+
     fn insert_field_names_extern(&mut self, def_id: DefId) {
         let field_names =
             self.r.cstore().struct_field_names_untracked(def_id, self.r.session).collect();
@@ -737,6 +746,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
 
                 // Record field names for error reporting.
                 self.insert_field_names_local(def_id, vdata);
+                self.insert_field_visibilities_local(def_id, vdata);
 
                 // If this is a tuple or unit struct, define a name
                 // in the value namespace as well.
@@ -770,6 +780,8 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                         Res::Def(DefKind::Ctor(CtorOf::Struct, ctor_kind), ctor_def_id.to_def_id());
                     self.r.define(parent, ident, ValueNS, (ctor_res, ctor_vis, sp, expansion));
                     self.r.visibilities.insert(ctor_def_id, ctor_vis);
+                    // We need the field visibility spans also for the constructor for E0603.
+                    self.insert_field_visibilities_local(ctor_def_id.to_def_id(), vdata);
 
                     self.r
                         .struct_constructors
@@ -783,6 +795,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
 
                 // Record field names for error reporting.
                 self.insert_field_names_local(def_id, vdata);
+                self.insert_field_visibilities_local(def_id, vdata);
             }
 
             ItemKind::Trait(..) => {
@@ -1510,6 +1523,7 @@ impl<'a, 'b> Visitor<'b> for BuildReducedGraphVisitor<'a, 'b> {
 
         // Record field names for error reporting.
         self.insert_field_names_local(def_id.to_def_id(), &variant.data);
+        self.insert_field_visibilities_local(def_id.to_def_id(), &variant.data);
 
         visit::walk_variant(self, variant);
     }

compiler/rustc_resolve/src/diagnostics.rs

@@ -6,7 +6,9 @@ use rustc_ast::{self as ast, Crate, ItemKind, ModKind, NodeId, Path, CRATE_NODE_
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::struct_span_err;
-use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan};
+use rustc_errors::{
+    pluralize, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan,
+};
 use rustc_feature::BUILTIN_ATTRIBUTES;
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, CtorOf, DefKind, NonMacroAttrKind, PerNS};
@@ -1604,6 +1606,16 @@ impl<'a> Resolver<'a> {
         err.span_label(ident.span, &format!("private {}", descr));
         if let Some(span) = ctor_fields_span {
             err.span_label(span, "a constructor is private if any of the fields is private");
+            if let Res::Def(_, d) = res && let Some(fields) = self.field_visibility_spans.get(&d) {
+                err.multipart_suggestion_verbose(
+                    &format!(
+                        "consider making the field{} publicly accessible",
+                        pluralize!(fields.len())
+                    ),
+                    fields.iter().map(|span| (*span, "pub ".to_string())).collect(),
+                    Applicability::MaybeIncorrect,
+                );
+            }
         }
 
         // Print the whole import chain to make it easier to see what happens.

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -1451,6 +1451,17 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
                         .collect();
 
                     if non_visible_spans.len() > 0 {
+                        if let Some(fields) = self.r.field_visibility_spans.get(&def_id) {
+                            err.multipart_suggestion_verbose(
+                                &format!(
+                                    "consider making the field{} publicly accessible",
+                                    pluralize!(fields.len())
+                                ),
+                                fields.iter().map(|span| (*span, "pub ".to_string())).collect(),
+                                Applicability::MaybeIncorrect,
+                            );
+                        }
+
                         let mut m: MultiSpan = non_visible_spans.clone().into();
                         non_visible_spans
                             .into_iter()

compiler/rustc_resolve/src/lib.rs

@@ -881,6 +881,10 @@ pub struct Resolver<'a> {
     /// Used for hints during error reporting.
     field_names: FxHashMap<DefId, Vec<Spanned<Symbol>>>,
 
+    /// Span of the privacy modifier in fields of an item `DefId` accessible with dot syntax.
+    /// Used for hints during error reporting.
+    field_visibility_spans: FxHashMap<DefId, Vec<Span>>,
+
     /// All imports known to succeed or fail.
     determined_imports: Vec<&'a Import<'a>>,
 
@@ -1268,6 +1272,7 @@ impl<'a> Resolver<'a> {
 
             has_self: FxHashSet::default(),
             field_names: FxHashMap::default(),
+            field_visibility_spans: FxHashMap::default(),
 
             determined_imports: Vec::new(),
             indeterminate_imports: Vec::new(),

tests/ui/privacy/issue-75906.stderr

@@ -9,6 +9,10 @@ note: constructor is not visible here due to private fields
    |
 LL |     pub struct Bar(u8);
    |                    ^^ private field
+help: consider making the field publicly accessible
+   |
+LL |     pub struct Bar(pub u8);
+   |                    +++
 
 error: aborting due to previous error
 

tests/ui/privacy/issue-75907.rs

@@ -2,7 +2,7 @@
 
 mod foo {
     pub(crate) struct Foo(u8);
-    pub(crate) struct Bar(pub u8, u8, Foo);
+    pub(crate) struct Bar(pub u8, pub(in crate::foo) u8, Foo);
 
     pub(crate) fn make_bar() -> Bar {
         Bar(1, 12, Foo(10))

tests/ui/privacy/issue-75907.stderr

@@ -11,6 +11,10 @@ LL |     let Bar(x, y, Foo(z)) = make_bar();
    |                ^  ^^^^^^ private field
    |                |
    |                private field
+help: consider making the fields publicly accessible
+   |
+LL |     pub(crate) struct Bar(pub u8, pub u8, pub Foo);
+   |                           ~~~     ~~~     +++
 
 error[E0532]: cannot match against a tuple struct which contains private fields
   --> $DIR/issue-75907.rs:15:19
@@ -23,6 +27,10 @@ note: constructor is not visible here due to private fields
    |
 LL |     let Bar(x, y, Foo(z)) = make_bar();
    |                       ^ private field
+help: consider making the field publicly accessible
+   |
+LL |     pub(crate) struct Foo(pub u8);
+   |                           +++
 
 error: aborting due to 2 previous errors