give FutureIncompatibilityReason variants more explicit names

compiler/rustc_errors/src/diagnostic.rs

@@ -151,7 +151,12 @@ impl fmt::Display for DiagnosticLocation {
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
 pub enum DiagnosticId {
     Error(String),
-    Lint { name: String, has_future_breakage: bool, is_force_warn: bool },
+    Lint {
+        name: String,
+        /// Indicates whether this lint should show up in cargo's future breakage report.
+        has_future_breakage: bool,
+        is_force_warn: bool,
+    },
 }
 
 /// A "sub"-diagnostic attached to a parent diagnostic.
@@ -301,6 +306,7 @@ impl Diagnostic {
         }
     }
 
+    /// Indicates whether this diagnostic should show up in cargo's future breakage report.
     pub fn has_future_breakage(&self) -> bool {
         match self.code {
             Some(DiagnosticId::Lint { has_future_breakage, .. }) => has_future_breakage,

compiler/rustc_lint_defs/src/builtin.rs

@@ -1017,7 +1017,7 @@ declare_lint! {
     "raw pointers must be aligned before dereferencing",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #68585 <https://github.com/rust-lang/rust/issues/104616>",
-        reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
     };
 }
 
@@ -1387,7 +1387,7 @@ declare_lint! {
     "trait-object types were treated as different depending on marker-trait order",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #56484 <https://github.com/rust-lang/rust/issues/56484>",
-        reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
     };
 }
 
@@ -2006,7 +2006,7 @@ declare_lint! {
     "detects proc macro derives using inaccessible names from parent modules",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #83583 <https://github.com/rust-lang/rust/issues/83583>",
-        reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
     };
 }
 
@@ -2618,7 +2618,7 @@ declare_lint! {
     "a C-like enum implementing Drop is cast",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #73333 <https://github.com/rust-lang/rust/issues/73333>",
-        reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
     };
 }
 
@@ -2976,7 +2976,7 @@ declare_lint! {
     "trailing semicolon in macro body used as expression",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #79813 <https://github.com/rust-lang/rust/issues/79813>",
-        reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
     };
 }
 
@@ -3709,7 +3709,7 @@ declare_lint! {
     "detects usage of old versions of certain proc-macro crates",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #83125 <https://github.com/rust-lang/rust/issues/83125>",
-        reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
     };
 }
 
@@ -4222,7 +4222,7 @@ declare_lint! {
     "impl method assumes more implied bounds than its corresponding trait method",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #105572 <https://github.com/rust-lang/rust/issues/105572>",
-        reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
     };
 }
 
@@ -4254,7 +4254,7 @@ declare_lint! {
     "`[u8]` or `str` used in a packed struct with `derive`",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #107457 <https://github.com/rust-lang/rust/issues/107457>",
-        reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
     };
     report_in_external_macro
 }
@@ -4483,7 +4483,7 @@ declare_lint! {
     Warn,
     "detects certain glob imports that require reporting an ambiguity error",
     @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseError,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
         reference: "issue #114095 <https://github.com/rust-lang/rust/issues/114095>",
     };
 }
@@ -4568,7 +4568,7 @@ declare_lint! {
     Warn,
     "elided lifetimes cannot be used in associated constants in impls",
     @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseError,
+        reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
         reference: "issue #115010 <https://github.com/rust-lang/rust/issues/115010>",
     };
 }

compiler/rustc_lint_defs/src/lib.rs

@@ -347,12 +347,18 @@ pub struct FutureIncompatibleInfo {
 /// The reason for future incompatibility
 #[derive(Copy, Clone, Debug)]
 pub enum FutureIncompatibilityReason {
-    /// This will be an error in a future release
+    /// This will be an error in a future release for all editions
-    /// for all editions
+    ///
-    FutureReleaseError,
+    /// This will *not* show up in cargo's future breakage report.
+    /// The warning will hence only be seen in local crates, not in dependencies.
+    FutureReleaseErrorDontReportInDeps,
     /// This will be an error in a future release, and
     /// Cargo should create a report even for dependencies
-    FutureReleaseErrorReportNow,
+    ///
+    /// This is the *only* reason that will make future incompatibility warnings show up in cargo's
+    /// reports. All other future incompatibility warnings are not visible when they occur in a
+    /// dependency.
+    FutureReleaseErrorReportInDeps,
     /// Code that changes meaning in some way in a
     /// future release.
     FutureReleaseSemanticsChange,
@@ -380,7 +386,7 @@ impl FutureIncompatibleInfo {
     pub const fn default_fields_for_macro() -> Self {
         FutureIncompatibleInfo {
             reference: "",
-            reason: FutureIncompatibilityReason::FutureReleaseError,
+            reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
             explain_reason: true,
         }
     }

compiler/rustc_middle/src/lint.rs

@@ -314,7 +314,10 @@ pub fn struct_lint_level(
             // Default allow lints trigger too often for testing.
             sess.opts.unstable_opts.future_incompat_test && lint.default_level != Level::Allow,
             |incompat| {
-                matches!(incompat.reason, FutureIncompatibilityReason::FutureReleaseErrorReportNow)
+                matches!(
+                    incompat.reason,
+                    FutureIncompatibilityReason::FutureReleaseErrorReportInDeps
+                )
             },
         );
 
@@ -404,8 +407,8 @@ pub fn struct_lint_level(
 
         if let Some(future_incompatible) = future_incompatible {
             let explanation = match future_incompatible.reason {
-                FutureIncompatibilityReason::FutureReleaseError
+                FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps
-                | FutureIncompatibilityReason::FutureReleaseErrorReportNow => {
+                | FutureIncompatibilityReason::FutureReleaseErrorReportInDeps => {
                     "this was previously accepted by the compiler but is being phased out; \
                          it will become a hard error in a future release!"
                         .to_owned()