Rollup of 6 pull requests

compiler/rustc_error_messages/src/lib.rs

@@ -216,6 +216,12 @@ impl From<Span> for MultiSpan {
     }
 }
 
+impl From<Option<Span>> for MultiSpan {
+    fn from(span: Option<Span>) -> MultiSpan {
+        MultiSpan::from_spans(span.into_iter().collect())
+    }
+}
+
 impl From<Vec<Span>> for MultiSpan {
     fn from(spans: Vec<Span>) -> MultiSpan {
         MultiSpan::from_spans(spans)

compiler/rustc_lint_defs/src/builtin.rs

@@ -137,6 +137,7 @@ pub mod hardwired {
             UNREACHABLE_PATTERNS,
             UNSAFE_ATTR_OUTSIDE_UNSAFE,
             UNSAFE_OP_IN_UNSAFE_FN,
+            UNSTABLE_IMPORTS,
             UNSTABLE_NAME_COLLISIONS,
             UNSTABLE_SYNTAX_PRE_EXPANSION,
             UNSUPPORTED_CALLING_CONVENTIONS,
@@ -5857,3 +5858,28 @@ declare_lint! {
     "`repr(C, align)` types nested inside `repr(C, packed)` types \
     do not always have a C-compatible layout",
 }
+
+declare_lint! {
+    /// The `unstable_imports` lints detects imports that go through unstable modules.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// use core::intrinsics::transmute;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Previous versions of Rust accidentally allowed certain imports through unstable modules
+    /// because stability information of modules was not correctly accounted for if the imported
+    /// item was stable itself.
+    pub UNSTABLE_IMPORTS,
+    Deny,
+    "lints on accidentally allowed unstable imports",
+    @future_incompatible = FutureIncompatibleInfo {
+        reason: fcw!(FutureReleaseError # 163160),
+        report_in_deps: true,
+    };
+}

compiler/rustc_macros/src/diagnostics/subdiagnostic.rs

@@ -315,7 +315,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
                     let binding = info.binding.binding.clone();
                     // FIXME(#100717): support `Option<Span>` on `primary_span` like in the
                     // diagnostic derive
-                    if !matches!(info.ty, FieldInnerTy::Plain(_)) {
+                    if !matches!(info.ty, FieldInnerTy::Plain(_) | FieldInnerTy::Option(_)) {
                         throw_invalid_attr!(attr, |diag| {
                             let diag = diag.note("there must be exactly one primary span");
 

compiler/rustc_passes/src/stability.rs

@@ -19,8 +19,8 @@ use rustc_hir::{
     UsePath, Variant,
 };
 use rustc_lint_defs::builtin::{
-    DEPRECATED, DUPLICATE_FEATURES, INEFFECTIVE_UNSTABLE_REEXPORTS,
-    INEFFECTIVE_UNSTABLE_TRAIT_IMPL, STABLE_FEATURES,
+    DUPLICATE_FEATURES, INEFFECTIVE_UNSTABLE_REEXPORTS, INEFFECTIVE_UNSTABLE_TRAIT_IMPL,
+    STABLE_FEATURES, UNSTABLE_IMPORTS,
 };
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::lib_features::{FeatureStability, LibFeatures};
@@ -1079,7 +1079,7 @@ impl<'tcx> Checker<'tcx> {
                             suggestion,
                         };
                         self.tcx.emit_node_span_lint(
-                            DEPRECATED,
+                            UNSTABLE_IMPORTS,
                             id,
                             method_span.unwrap_or(span),
                             diag,