Mark `never_type_fallback_flowing_into_unsafe` as a semantic change

...rather than a future error

3 files changed, 19 insertions, 2 deletions

diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index 7f3f31843f5..efdb4b077e9 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -4185,7 +4185,7 @@ declare_lint! {
     Warn,
     "never type fallback affecting unsafe function calls",
     @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::EditionAndFutureReleaseError(Edition::Edition2024),
+        reason: FutureIncompatibilityReason::EditionAndFutureReleaseSemanticsChange(Edition::Edition2024),
         reference: "issue #123748 <https://github.com/rust-lang/rust/issues/123748>",
     };
     @edition Edition2024 => Deny;
diff --git a/compiler/rustc_lint_defs/src/lib.rs b/compiler/rustc_lint_defs/src/lib.rs
index 1bf5d9e5098..eac4afee050 100644
--- a/compiler/rustc_lint_defs/src/lib.rs
+++ b/compiler/rustc_lint_defs/src/lib.rs
@@ -432,6 +432,17 @@ pub enum FutureIncompatibilityReason {
     /// [`EditionError`]: FutureIncompatibilityReason::EditionError
     /// [`FutureReleaseErrorDontReportInDeps`]: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps
     EditionAndFutureReleaseError(Edition),
+    /// This will change meaning in the provided edition *and* in a future
+    /// release.
+    ///
+    /// This variant a combination of [`FutureReleaseSemanticsChange`]
+    /// and [`EditionSemanticsChange`]. This is useful in rare cases when we
+    /// want to have "preview" of a breaking change in an edition, but do a
+    /// breaking change later on all editions anyway.
+    ///
+    /// [`EditionSemanticsChange`]: FutureIncompatibilityReason::EditionSemanticsChange
+    /// [`FutureReleaseSemanticsChange`]: FutureIncompatibilityReason::FutureReleaseSemanticsChange
+    EditionAndFutureReleaseSemanticsChange(Edition),
     /// A custom reason.
     ///
     /// Choose this variant if the built-in text of the diagnostic of the
@@ -446,7 +457,8 @@ impl FutureIncompatibilityReason {
         match self {
             Self::EditionError(e)
             | Self::EditionSemanticsChange(e)
-            | Self::EditionAndFutureReleaseError(e) => Some(e),
+            | Self::EditionAndFutureReleaseError(e)
+            | Self::EditionAndFutureReleaseSemanticsChange(e) => Some(e),
 
             FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps
             | FutureIncompatibilityReason::FutureReleaseErrorReportInDeps
diff --git a/compiler/rustc_middle/src/lint.rs b/compiler/rustc_middle/src/lint.rs
index 1bcdbe33286..92ba6ceee93 100644
--- a/compiler/rustc_middle/src/lint.rs
+++ b/compiler/rustc_middle/src/lint.rs
@@ -388,6 +388,11 @@ pub fn lint_level(
                          it will become a hard error in Rust {edition} and in a future release in all editions!"
                     )
                 }
+                FutureIncompatibilityReason::EditionAndFutureReleaseSemanticsChange(edition) => {
+                    format!(
+                        "this changes meaning in Rust {edition} and in a future release in all editions!"
+                    )
+                }
                 FutureIncompatibilityReason::Custom(reason) => reason.to_owned(),
             };