Change how `force-warn` lint diagnostics are recorded.

`is_force_warn` is only possible for diagnostics with `Level::Warning`,
but it is currently stored in `Diagnostic::code`, which every diagnostic
has.

This commit:
- removes the boolean `DiagnosticId::Lint::is_force_warn` field;
- adds a `ForceWarning` variant to `Level`.

Benefits:
- The common `Level::Warning` case now has no arguments, replacing
  lots of `Warning(None)` occurrences.
- `rustc_session::lint::Level` and `rustc_errors::Level` are more
  similar, both having `ForceWarning` and `Warning`.

12 files changed, 45 insertions, 53 deletions

diff --git a/compiler/rustc_builtin_macros/src/test.rs b/compiler/rustc_builtin_macros/src/test.rs
index 298bdc557ab..4d44e340ae1 100644
--- a/compiler/rustc_builtin_macros/src/test.rs
+++ b/compiler/rustc_builtin_macros/src/test.rs
@@ -394,7 +394,7 @@ fn not_testable_error(cx: &ExtCtxt<'_>, attr_sp: Span, item: Option<&ast::Item>)
     let level = match item.map(|i| &i.kind) {
         // These were a warning before #92959 and need to continue being that to avoid breaking
         // stable user code (#94508).
-        Some(ast::ItemKind::MacCall(_)) => Level::Warning(None),
+        Some(ast::ItemKind::MacCall(_)) => Level::Warning,
         _ => Level::Error,
     };
     let mut err = DiagnosticBuilder::<()>::new(dcx, level, msg);
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index deffb10c759..a912ef9e755 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -417,7 +417,7 @@ fn report_inline_asm(
     }
     let level = match level {
         llvm::DiagnosticLevel::Error => Level::Error,
-        llvm::DiagnosticLevel::Warning => Level::Warning(None),
+        llvm::DiagnosticLevel::Warning => Level::Warning,
         llvm::DiagnosticLevel::Note | llvm::DiagnosticLevel::Remark => Level::Note,
     };
     cgcx.diag_emitter.inline_asm_error(cookie as u32, msg, level, source);
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index 6c066e61a58..8e835039970 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -1847,14 +1847,9 @@ impl SharedEmitterMain {
                     dcx.emit_diagnostic(d);
                 }
                 Ok(SharedEmitterMessage::InlineAsmError(cookie, msg, level, source)) => {
-                    let err_level = match level {
-                        Level::Error => Level::Error,
-                        Level::Warning(_) => Level::Warning(None),
-                        Level::Note => Level::Note,
-                        _ => bug!("Invalid inline asm diagnostic level"),
-                    };
+                    assert!(matches!(level, Level::Error | Level::Warning | Level::Note));
                     let msg = msg.strip_prefix("error: ").unwrap_or(&msg).to_string();
-                    let mut err = DiagnosticBuilder::<()>::new(sess.dcx(), err_level, msg);
+                    let mut err = DiagnosticBuilder::<()>::new(sess.dcx(), level, msg);
 
                     // If the cookie is 0 then we don't have span information.
                     if cookie != 0 {
diff --git a/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs b/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs
index 5c0e210f147..97f2efa7874 100644
--- a/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs
+++ b/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs
@@ -87,7 +87,7 @@ fn source_string(file: Lrc<SourceFile>, line: &Line) -> String {
 fn annotation_type_for_level(level: Level) -> AnnotationType {
     match level {
         Level::Bug | Level::DelayedBug | Level::Fatal | Level::Error => AnnotationType::Error,
-        Level::Warning(_) => AnnotationType::Warning,
+        Level::ForceWarning(_) | Level::Warning => AnnotationType::Warning,
         Level::Note | Level::OnceNote => AnnotationType::Note,
         Level::Help | Level::OnceHelp => AnnotationType::Help,
         // FIXME(#59346): Not sure how to map this level
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index 701c1c02ab0..d8d6922a1bc 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -152,7 +152,6 @@ pub enum DiagnosticId {
         name: String,
         /// Indicates whether this lint should show up in cargo's future breakage report.
         has_future_breakage: bool,
-        is_force_warn: bool,
     },
 }
 
@@ -248,7 +247,8 @@ impl Diagnostic {
                 true
             }
 
-            Level::Warning(_)
+            Level::ForceWarning(_)
+            | Level::Warning
             | Level::Note
             | Level::OnceNote
             | Level::Help
@@ -262,7 +262,7 @@ impl Diagnostic {
         &mut self,
         unstable_to_stable: &FxIndexMap<LintExpectationId, LintExpectationId>,
     ) {
-        if let Level::Expect(expectation_id) | Level::Warning(Some(expectation_id)) =
+        if let Level::Expect(expectation_id) | Level::ForceWarning(Some(expectation_id)) =
             &mut self.level
         {
             if expectation_id.is_stable() {
@@ -292,8 +292,11 @@ impl Diagnostic {
     }
 
     pub(crate) fn is_force_warn(&self) -> bool {
-        match self.code {
-            Some(DiagnosticId::Lint { is_force_warn, .. }) => is_force_warn,
+        match self.level {
+            Level::ForceWarning(_) => {
+                assert!(self.is_lint);
+                true
+            }
             _ => false,
         }
     }
@@ -472,7 +475,7 @@ impl Diagnostic {
     /// Add a warning attached to this diagnostic.
     #[rustc_lint_diagnostics]
     pub fn warn(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self {
-        self.sub(Level::Warning(None), msg, MultiSpan::new());
+        self.sub(Level::Warning, msg, MultiSpan::new());
         self
     }
 
@@ -484,7 +487,7 @@ impl Diagnostic {
         sp: S,
         msg: impl Into<SubdiagnosticMessage>,
     ) -> &mut Self {
-        self.sub(Level::Warning(None), msg, sp.into());
+        self.sub(Level::Warning, msg, sp.into());
         self
     }
 
diff --git a/compiler/rustc_errors/src/json.rs b/compiler/rustc_errors/src/json.rs
index 52fcb50e9fb..87bf9c23456 100644
--- a/compiler/rustc_errors/src/json.rs
+++ b/compiler/rustc_errors/src/json.rs
@@ -198,7 +198,7 @@ impl Emitter for JsonEmitter {
             .into_iter()
             .map(|mut diag| {
                 if diag.level == crate::Level::Allow {
-                    diag.level = crate::Level::Warning(None);
+                    diag.level = crate::Level::Warning;
                 }
                 FutureBreakageItem {
                     diagnostic: EmitTyped::Diagnostic(Diagnostic::from_errors_diagnostic(
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index d27fe8779f4..f64a5d65fcf 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -738,7 +738,7 @@ impl DiagCtxt {
     #[rustc_lint_diagnostics]
     #[track_caller]
     pub fn struct_warn(&self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'_, ()> {
-        DiagnosticBuilder::new(self, Warning(None), msg)
+        DiagnosticBuilder::new(self, Warning, msg)
     }
 
     /// Construct a builder at the `Allow` level with the `msg`.
@@ -1005,7 +1005,7 @@ impl DiagCtxt {
             (0, 0) => return,
             (0, _) => inner
                 .emitter
-                .emit_diagnostic(&Diagnostic::new(Warning(None), DiagnosticMessage::Str(warnings))),
+                .emit_diagnostic(&Diagnostic::new(Warning, DiagnosticMessage::Str(warnings))),
             (_, 0) => {
                 inner.emit_diagnostic(Diagnostic::new(Fatal, errors));
             }
@@ -1094,7 +1094,7 @@ impl DiagCtxt {
         &'a self,
         warning: impl IntoDiagnostic<'a, ()>,
     ) -> DiagnosticBuilder<'a, ()> {
-        warning.into_diagnostic(self, Warning(None))
+        warning.into_diagnostic(self, Warning)
     }
 
     #[track_caller]
@@ -1304,10 +1304,7 @@ impl DiagCtxtInner {
             self.fulfilled_expectations.insert(expectation_id.normalize());
         }
 
-        if matches!(diagnostic.level, Warning(_))
-            && !self.flags.can_emit_warnings
-            && !diagnostic.is_force_warn()
-        {
+        if diagnostic.level == Warning && !self.flags.can_emit_warnings {
             if diagnostic.has_future_breakage() {
                 (*TRACK_DIAGNOSTIC)(diagnostic, &mut |_| {});
             }
@@ -1359,7 +1356,7 @@ impl DiagCtxtInner {
                 self.emitter.emit_diagnostic(&diagnostic);
                 if diagnostic.is_error() {
                     self.deduplicated_err_count += 1;
-                } else if let Warning(_) = diagnostic.level {
+                } else if matches!(diagnostic.level, ForceWarning(_) | Warning) {
                     self.deduplicated_warn_count += 1;
                 }
             }
@@ -1562,14 +1559,17 @@ pub enum Level {
     /// Its `EmissionGuarantee` is `ErrorGuaranteed`.
     Error,
 
-    /// A warning about the code being compiled. Does not prevent compilation from finishing.
+    /// A `force-warn` lint warning about the code being compiled. Does not prevent compilation
+    /// from finishing.
     ///
-    /// This [`LintExpectationId`] is used for expected lint diagnostics, which should
-    /// also emit a warning due to the `force-warn` flag. In all other cases this should
-    /// be `None`.
+    /// The [`LintExpectationId`] is used for expected lint diagnostics. In all other cases this
+    /// should be `None`.
+    ForceWarning(Option<LintExpectationId>),
+
+    /// A warning about the code being compiled. Does not prevent compilation from finishing.
     ///
     /// Its `EmissionGuarantee` is `()`.
-    Warning(Option<LintExpectationId>),
+    Warning,
 
     /// A message giving additional context. Rare, because notes are more commonly attached to other
     /// diagnostics such as errors.
@@ -1622,7 +1622,7 @@ impl Level {
             Bug | DelayedBug | Fatal | Error => {
                 spec.set_fg(Some(Color::Red)).set_intense(true);
             }
-            Warning(_) => {
+            ForceWarning(_) | Warning => {
                 spec.set_fg(Some(Color::Yellow)).set_intense(cfg!(windows));
             }
             Note | OnceNote => {
@@ -1641,7 +1641,7 @@ impl Level {
         match self {
             Bug | DelayedBug => "error: internal compiler error",
             Fatal | Error => "error",
-            Warning(_) => "warning",
+            ForceWarning(_) | Warning => "warning",
             Note | OnceNote => "note",
             Help | OnceHelp => "help",
             FailureNote => "failure-note",
@@ -1655,7 +1655,7 @@ impl Level {
 
     pub fn get_expectation_id(&self) -> Option<LintExpectationId> {
         match self {
-            Expect(id) | Warning(Some(id)) => Some(*id),
+            Expect(id) | ForceWarning(Some(id)) => Some(*id),
             _ => None,
         }
     }
diff --git a/compiler/rustc_expand/src/proc_macro_server.rs b/compiler/rustc_expand/src/proc_macro_server.rs
index 0053f550318..6392894fea2 100644
--- a/compiler/rustc_expand/src/proc_macro_server.rs
+++ b/compiler/rustc_expand/src/proc_macro_server.rs
@@ -380,7 +380,7 @@ impl ToInternal<rustc_errors::Level> for Level {
     fn to_internal(self) -> rustc_errors::Level {
         match self {
             Level::Error => rustc_errors::Level::Error,
-            Level::Warning => rustc_errors::Level::Warning(None),
+            Level::Warning => rustc_errors::Level::Warning,
             Level::Note => rustc_errors::Level::Note,
             Level::Help => rustc_errors::Level::Help,
             _ => unreachable!("unknown proc_macro::Level variant: {:?}", self),
diff --git a/compiler/rustc_middle/src/lint.rs b/compiler/rustc_middle/src/lint.rs
index 212e831e106..c5e4dfaf19e 100644
--- a/compiler/rustc_middle/src/lint.rs
+++ b/compiler/rustc_middle/src/lint.rs
@@ -312,8 +312,9 @@ pub fn struct_lint_level(
                 // create a `DiagnosticBuilder` and continue as we would for warnings.
                 rustc_errors::Level::Expect(expect_id)
             }
-            Level::ForceWarn(Some(expect_id)) => rustc_errors::Level::Warning(Some(expect_id)),
-            Level::Warn | Level::ForceWarn(None) => rustc_errors::Level::Warning(None),
+            Level::ForceWarn(Some(expect_id)) => rustc_errors::Level::ForceWarning(Some(expect_id)),
+            Level::ForceWarn(None) => rustc_errors::Level::ForceWarning(None),
+            Level::Warn => rustc_errors::Level::Warning,
             Level::Deny | Level::Forbid => rustc_errors::Level::Error,
         };
         let mut err = DiagnosticBuilder::new(sess.dcx(), err_level, "");
@@ -350,22 +351,19 @@ pub fn struct_lint_level(
         // suppressed the lint due to macros.
         err.primary_message(msg);
 
+        let name = lint.name_lower();
+        err.code(DiagnosticId::Lint { name, has_future_breakage });
+
         // Lint diagnostics that are covered by the expect level will not be emitted outside
         // the compiler. It is therefore not necessary to add any information for the user.
         // This will therefore directly call the decorate function which will in turn emit
         // the `Diagnostic`.
         if let Level::Expect(_) = level {
-            let name = lint.name_lower();
-            err.code(DiagnosticId::Lint { name, has_future_breakage, is_force_warn: false });
             decorate(&mut err);
             err.emit();
             return;
         }
 
-        let name = lint.name_lower();
-        let is_force_warn = matches!(level, Level::ForceWarn(_));
-        err.code(DiagnosticId::Lint { name, has_future_breakage, is_force_warn });
-
         if let Some(future_incompatible) = future_incompatible {
             let explanation = match future_incompatible.reason {
                 FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps
diff --git a/compiler/rustc_session/src/parse.rs b/compiler/rustc_session/src/parse.rs
index 439fa18b7fa..598178c3c2a 100644
--- a/compiler/rustc_session/src/parse.rs
+++ b/compiler/rustc_session/src/parse.rs
@@ -143,11 +143,7 @@ pub fn feature_warn_issue(
     // Decorate this as a future-incompatibility lint as in rustc_middle::lint::struct_lint_level
     let lint = UNSTABLE_SYNTAX_PRE_EXPANSION;
     let future_incompatible = lint.future_incompatible.as_ref().unwrap();
-    err.code(DiagnosticId::Lint {
-        name: lint.name_lower(),
-        has_future_breakage: false,
-        is_force_warn: false,
-    });
+    err.code(DiagnosticId::Lint { name: lint.name_lower(), has_future_breakage: false });
     err.warn(lint.desc);
     err.note(format!("for more information, see {}", future_incompatible.reference));
 
diff --git a/src/tools/miri/src/diagnostics.rs b/src/tools/miri/src/diagnostics.rs
index 819d2018a15..bf3284df596 100644
--- a/src/tools/miri/src/diagnostics.rs
+++ b/src/tools/miri/src/diagnostics.rs
@@ -455,7 +455,7 @@ pub fn report_msg<'tcx>(
     let sess = machine.tcx.sess;
     let level = match diag_level {
         DiagLevel::Error => Level::Error,
-        DiagLevel::Warning => Level::Warning(None),
+        DiagLevel::Warning => Level::Warning,
         DiagLevel::Note => Level::Note,
     };
     let mut err = DiagnosticBuilder::<()>::new(sess.dcx(), level, title);
diff --git a/src/tools/rustfmt/src/parse/session.rs b/src/tools/rustfmt/src/parse/session.rs
index 2663f16b8e8..f4fb5073dfd 100644
--- a/src/tools/rustfmt/src/parse/session.rs
+++ b/src/tools/rustfmt/src/parse/session.rs
@@ -446,7 +446,7 @@ mod tests {
                 Some(ignore_list),
             );
             let span = MultiSpan::from_span(mk_sp(BytePos(0), BytePos(1)));
-            let non_fatal_diagnostic = build_diagnostic(DiagnosticLevel::Warning(None), Some(span));
+            let non_fatal_diagnostic = build_diagnostic(DiagnosticLevel::Warning, Some(span));
             emitter.emit_diagnostic(&non_fatal_diagnostic);
             assert_eq!(num_emitted_errors.load(Ordering::Acquire), 0);
             assert_eq!(can_reset_errors.load(Ordering::Acquire), true);
@@ -470,7 +470,7 @@ mod tests {
                 None,
             );
             let span = MultiSpan::from_span(mk_sp(BytePos(0), BytePos(1)));
-            let non_fatal_diagnostic = build_diagnostic(DiagnosticLevel::Warning(None), Some(span));
+            let non_fatal_diagnostic = build_diagnostic(DiagnosticLevel::Warning, Some(span));
             emitter.emit_diagnostic(&non_fatal_diagnostic);
             assert_eq!(num_emitted_errors.load(Ordering::Acquire), 1);
             assert_eq!(can_reset_errors.load(Ordering::Acquire), false);
@@ -507,8 +507,8 @@ mod tests {
             );
             let bar_span = MultiSpan::from_span(mk_sp(BytePos(0), BytePos(1)));
             let foo_span = MultiSpan::from_span(mk_sp(BytePos(21), BytePos(22)));
-            let bar_diagnostic = build_diagnostic(DiagnosticLevel::Warning(None), Some(bar_span));
-            let foo_diagnostic = build_diagnostic(DiagnosticLevel::Warning(None), Some(foo_span));
+            let bar_diagnostic = build_diagnostic(DiagnosticLevel::Warning, Some(bar_span));
+            let foo_diagnostic = build_diagnostic(DiagnosticLevel::Warning, Some(foo_span));
             let fatal_diagnostic = build_diagnostic(DiagnosticLevel::Fatal, None);
             emitter.emit_diagnostic(&bar_diagnostic);
             emitter.emit_diagnostic(&foo_diagnostic);