Make unstable library feature errors translatable

Translation is in an awkward position, but this provides a similar
interface for both errors and soft-unstable lints, and enables the use
of `DiagSymbolList` for simplifying error message construction.

Author: dianne

compiler/rustc_lint/src/context/diagnostics.rs

@@ -382,8 +382,9 @@ pub(super) fn decorate_lint(sess: &Session, diagnostic: BuiltinLintDiag, diag: &
         BuiltinLintDiag::MacroRuleNeverUsed(n, name) => {
             lints::MacroRuleNeverUsed { n: n + 1, name }.decorate_lint(diag);
         }
-        BuiltinLintDiag::UnstableFeature(msg) => {
-            lints::UnstableFeature { msg }.decorate_lint(diag);
+        BuiltinLintDiag::SoftUnstableMacro { feature, reason } => {
+            rustc_middle::error::SoftUnstableLibraryFeature::new(feature, reason)
+                .decorate_lint(diag);
         }
         BuiltinLintDiag::AvoidUsingIntelSyntax => {
             lints::AvoidIntelSyntax.decorate_lint(diag);

compiler/rustc_lint/src/lints.rs

@@ -2408,16 +2408,6 @@ pub(crate) struct MacroRuleNeverUsed {
     pub name: Symbol,
 }
 
-pub(crate) struct UnstableFeature {
-    pub msg: DiagMessage,
-}
-
-impl<'a> LintDiagnostic<'a, ()> for UnstableFeature {
-    fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, ()>) {
-        diag.primary_message(self.msg);
-    }
-}
-
 #[derive(LintDiagnostic)]
 #[diag(lint_avoid_intel_syntax)]
 pub(crate) struct AvoidIntelSyntax;

compiler/rustc_lint_defs/src/lib.rs

@@ -9,7 +9,7 @@ use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::stable_hasher::{
     HashStable, StableCompare, StableHasher, ToStableHashKey,
 };
-use rustc_error_messages::{DiagMessage, MultiSpan};
+use rustc_error_messages::MultiSpan;
 use rustc_hir::def::Namespace;
 use rustc_hir::{HashStableContext, HirId, MissingLifetimeKind};
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
@@ -720,7 +720,10 @@ pub enum BuiltinLintDiag {
     MacroIsPrivate(Ident),
     UnusedMacroDefinition(Symbol),
     MacroRuleNeverUsed(usize, Symbol),
-    UnstableFeature(DiagMessage),
+    SoftUnstableMacro {
+        feature: Symbol,
+        reason: Option<Symbol>,
+    },
     AvoidUsingIntelSyntax,
     AvoidUsingAttSyntax,
     IncompleteInclude,

compiler/rustc_middle/messages.ftl

@@ -102,6 +102,15 @@ middle_type_length_limit = reached the type-length limit while instantiating `{$
 middle_unknown_layout =
     the type `{$ty}` has an unknown layout
 
+middle_unstable_library_feature =
+    use of unstable library {$count ->
+        [one] feature
+        *[other] features
+    } {$features}{STREQ($reason, "") ->
+        [true] {""}
+        *[false] : {$reason}
+    }
+
 middle_values_too_big =
     values of the type `{$ty}` are too big for the target architecture
 middle_written_to_path = the full type name has been written to '{$path}'

compiler/rustc_middle/src/error.rs

@@ -2,8 +2,8 @@ use std::fmt;
 use std::path::PathBuf;
 
 use rustc_errors::codes::*;
-use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage};
-use rustc_macros::{Diagnostic, Subdiagnostic};
+use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, DiagSymbolList};
+use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_span::{Span, Symbol};
 
 use crate::ty::Ty;
@@ -164,3 +164,40 @@ pub struct TypeLengthLimit {
     pub path: PathBuf,
     pub type_length: usize,
 }
+
+#[derive(Diagnostic)]
+#[diag(middle_unstable_library_feature, code = E0658)]
+pub struct UnstableLibraryFeatureError {
+    #[primary_span]
+    pub span: Span,
+    pub features: DiagSymbolList,
+    pub count: usize,
+    pub reason: String,
+}
+
+impl UnstableLibraryFeatureError {
+    pub fn new(feature: Symbol, reason: Option<Symbol>, span: Span) -> Self {
+        let SoftUnstableLibraryFeature { features, count, reason } =
+            SoftUnstableLibraryFeature::new(feature, reason);
+        UnstableLibraryFeatureError { span, features, count, reason }
+    }
+}
+
+/// Lint diagnostic for soft_unstable
+#[derive(LintDiagnostic)]
+#[diag(middle_unstable_library_feature)]
+pub struct SoftUnstableLibraryFeature {
+    pub features: DiagSymbolList,
+    pub count: usize,
+    pub reason: String,
+}
+
+impl SoftUnstableLibraryFeature {
+    pub fn new(feature: Symbol, reason: Option<Symbol>) -> Self {
+        SoftUnstableLibraryFeature {
+            features: vec![feature].into(),
+            count: 1,
+            reason: reason.map_or(String::new(), |r| r.to_string()),
+        }
+    }
+}

compiler/rustc_middle/src/lib.rs

@@ -48,6 +48,7 @@
 #![feature(if_let_guard)]
 #![feature(intra_doc_pointers)]
 #![feature(iter_from_coroutine)]
+#![feature(iter_intersperse)]
 #![feature(let_chains)]
 #![feature(macro_metavar_expr)]
 #![feature(min_specialization)]

compiler/rustc_middle/src/middle/stability.rs

@@ -18,12 +18,13 @@ use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_session::Session;
 use rustc_session::lint::builtin::{DEPRECATED, DEPRECATED_IN_FUTURE, SOFT_UNSTABLE};
 use rustc_session::lint::{BuiltinLintDiag, DeprecatedSinceKind, Level, Lint, LintBuffer};
-use rustc_session::parse::feature_err_issues;
+use rustc_session::parse::add_feature_diagnostics_for_issues;
 use rustc_span::Span;
 use rustc_span::symbol::{Symbol, sym};
 use tracing::debug;
 
 pub use self::StabilityLevel::*;
+use crate::error::{SoftUnstableLibraryFeature, UnstableLibraryFeatureError};
 use crate::ty::{self, TyCtxt};
 
 #[derive(PartialEq, Clone, Copy, Debug)]
@@ -107,25 +108,23 @@ pub fn report_unstable(
     reason: Option<Symbol>,
     issue: Option<NonZero<u32>>,
     suggestion: Option<(Span, String, String, Applicability)>,
-    is_soft: bool,
     span: Span,
-    soft_handler: impl FnOnce(&'static Lint, Span, String),
 ) {
-    let msg = match reason {
-        Some(r) => format!("use of unstable library feature `{feature}`: {r}"),
-        None => format!("use of unstable library feature `{feature}`"),
-    };
-
-    if is_soft {
-        soft_handler(SOFT_UNSTABLE, span, msg)
-    } else {
-        let issues = Vec::from_iter(issue);
-        let mut err = feature_err_issues(sess, &[feature], span, GateIssues::Library(issues), msg);
-        if let Some((inner_types, msg, sugg, applicability)) = suggestion {
-            err.span_suggestion(inner_types, msg, sugg, applicability);
-        }
-        err.emit();
+    let features = vec![feature];
+
+    let mut err = sess.dcx().create_err(UnstableLibraryFeatureError::new(feature, reason, span));
+    add_feature_diagnostics_for_issues(
+        &mut err,
+        sess,
+        &features,
+        GateIssues::Library(Vec::from_iter(issue)),
+        false,
+        None,
+    );
+    if let Some((inner_types, msg, sugg, applicability)) = suggestion {
+        err.span_suggestion(inner_types, msg, sugg, applicability);
     }
+    err.emit();
 }
 
 fn deprecation_lint(is_in_effect: bool) -> &'static Lint {
@@ -592,26 +591,23 @@ impl<'tcx> TyCtxt<'tcx> {
         allow_unstable: AllowUnstable,
         unmarked: impl FnOnce(Span, DefId),
     ) -> bool {
-        let soft_handler = |lint, span, msg: String| {
-            self.node_span_lint(lint, id.unwrap_or(hir::CRATE_HIR_ID), span, |lint| {
-                lint.primary_message(msg);
-            })
-        };
         let eval_result =
             self.eval_stability_allow_unstable(def_id, id, span, method_span, allow_unstable);
         let is_allowed = matches!(eval_result, EvalResult::Allow);
         match eval_result {
             EvalResult::Allow => {}
-            EvalResult::Deny { feature, reason, issue, suggestion, is_soft } => report_unstable(
-                self.sess,
-                feature,
-                reason,
-                issue,
-                suggestion,
-                is_soft,
-                span,
-                soft_handler,
-            ),
+            EvalResult::Deny { feature, reason, issue, suggestion, is_soft } => {
+                if is_soft {
+                    self.emit_node_span_lint(
+                        SOFT_UNSTABLE,
+                        id.unwrap_or(hir::CRATE_HIR_ID),
+                        span,
+                        SoftUnstableLibraryFeature::new(feature, reason),
+                    );
+                } else {
+                    report_unstable(self.sess, feature, reason, issue, suggestion, span);
+                }
+            }
             EvalResult::Unmarked => unmarked(span, def_id),
         }
 

compiler/rustc_middle/src/ty/context.rs

@@ -2965,22 +2965,22 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         diag: &mut Diag<'_, E>,
         hir_id: Option<HirId>,
-        features: impl IntoIterator<Item = (String, Symbol)>,
+        featuresets: impl IntoIterator<Item = (String, impl std::fmt::Display)>,
     ) {
         if !self.sess.is_nightly_build() {
             return;
         }
 
         let span = hir_id.and_then(|id| self.crate_level_attribute_injection_span(id));
-        for (desc, feature) in features {
+        for (desc, features) in featuresets {
             // FIXME: make this string translatable
             let msg =
-                format!("add `#![feature({feature})]` to the crate attributes to enable{desc}");
+                format!("add `#![feature({features})]` to the crate attributes to enable{desc}");
             if let Some(span) = span {
                 diag.span_suggestion_verbose(
                     span,
                     msg,
-                    format!("#![feature({feature})]\n"),
+                    format!("#![feature({features})]\n"),
                     Applicability::MaybeIncorrect,
                 );
             } else {

compiler/rustc_resolve/src/macros.rs

@@ -1009,28 +1009,26 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     |feature| self.tcx.features().enabled(feature) || span.allows_unstable(feature);
                 let allowed_by_implication = implied_by.is_some_and(|feature| is_allowed(feature));
                 if !is_allowed(feature) && !allowed_by_implication {
-                    let lint_buffer = &mut self.lint_buffer;
-                    let soft_handler = |lint, span, msg: String| {
-                        lint_buffer.buffer_lint(
-                            lint,
+                    if is_soft {
+                        self.lint_buffer.buffer_lint(
+                            SOFT_UNSTABLE,
                             node_id,
                             span,
-                            BuiltinLintDiag::UnstableFeature(
-                                // FIXME make this translatable
-                                msg.into(),
-                            ),
-                        )
-                    };
-                    stability::report_unstable(
-                        self.tcx.sess,
-                        feature,
-                        reason.to_opt_reason(),
-                        issue,
-                        None,
-                        is_soft,
-                        span,
-                        soft_handler,
-                    );
+                            BuiltinLintDiag::SoftUnstableMacro {
+                                feature,
+                                reason: reason.to_opt_reason(),
+                            },
+                        );
+                    } else {
+                        stability::report_unstable(
+                            self.tcx.sess,
+                            feature,
+                            reason.to_opt_reason(),
+                            issue,
+                            None,
+                            span,
+                        );
+                    }
                 }
             }
         }