Auto merge of #100765 - Xiretza:session-diagnostic-unification, r=compiler-errors

Kind-less SessionDiagnostic derive

From #100730 (comment):

> Hm, maybe we should expose some `sess.struct_$SOMETHING` (like `struct_diagnostic`?) that is generic over `EmissionGuarantee`, then make the `SessionDiagnostic` derive generic, i.e.
>
> ```rust
> impl<'tcx> SessionDiagnostic for UnusedGenericParams {
>   fn into_diagnostic<T: EmissionGuarantee>( .. ) -> DiagnosticBuilder<'tcx, T> {
>     let mut diag = sess.struct_diagnostic(rustc_errors:..);
>     ..
>   }
> }
> ```

Discussed [on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/147480-t-compiler.2Fwg-diagnostics/topic/.23100717.20translation.20-.20kind-less.20derive).

Author: bors

compiler/rustc_borrowck/src/session_diagnostics.rs

@@ -3,7 +3,7 @@ use rustc_middle::ty::Ty;
 use rustc_span::Span;
 
 #[derive(SessionDiagnostic)]
-#[error(borrowck::move_unsized, code = "E0161")]
+#[diag(borrowck::move_unsized, code = "E0161")]
 pub(crate) struct MoveUnsized<'tcx> {
     pub ty: Ty<'tcx>,
     #[primary_span]
@@ -12,7 +12,7 @@ pub(crate) struct MoveUnsized<'tcx> {
 }
 
 #[derive(SessionDiagnostic)]
-#[error(borrowck::higher_ranked_lifetime_error)]
+#[diag(borrowck::higher_ranked_lifetime_error)]
 pub(crate) struct HigherRankedLifetimeError {
     #[subdiagnostic]
     pub cause: Option<HigherRankedErrorCause>,
@@ -29,14 +29,14 @@ pub(crate) enum HigherRankedErrorCause {
 }
 
 #[derive(SessionDiagnostic)]
-#[error(borrowck::higher_ranked_subtype_error)]
+#[diag(borrowck::higher_ranked_subtype_error)]
 pub(crate) struct HigherRankedSubtypeError {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(borrowck::generic_does_not_live_long_enough)]
+#[diag(borrowck::generic_does_not_live_long_enough)]
 pub(crate) struct GenericDoesNotLiveLongEnough {
     pub kind: String,
     #[primary_span]

compiler/rustc_builtin_macros/src/cfg.rs

@@ -36,15 +36,15 @@ pub fn expand_cfg(
 }
 
 #[derive(SessionDiagnostic)]
-#[error(builtin_macros::requires_cfg_pattern)]
+#[diag(builtin_macros::requires_cfg_pattern)]
 struct RequiresCfgPattern {
     #[primary_span]
     #[label]
     span: Span,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(builtin_macros::expected_one_cfg_pattern)]
+#[diag(builtin_macros::expected_one_cfg_pattern)]
 struct OneCfgPattern {
     #[primary_span]
     span: Span,

compiler/rustc_const_eval/src/errors.rs

@@ -3,7 +3,7 @@ use rustc_macros::SessionDiagnostic;
 use rustc_span::Span;
 
 #[derive(SessionDiagnostic)]
-#[error(const_eval::unstable_in_stable)]
+#[diag(const_eval::unstable_in_stable)]
 pub(crate) struct UnstableInStable {
     pub gate: String,
     #[primary_span]
@@ -22,14 +22,14 @@ pub(crate) struct UnstableInStable {
 }
 
 #[derive(SessionDiagnostic)]
-#[error(const_eval::thread_local_access, code = "E0625")]
+#[diag(const_eval::thread_local_access, code = "E0625")]
 pub(crate) struct NonConstOpErr {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(const_eval::static_access, code = "E0013")]
+#[diag(const_eval::static_access, code = "E0013")]
 #[help]
 pub(crate) struct StaticAccessErr {
     #[primary_span]
@@ -41,7 +41,7 @@ pub(crate) struct StaticAccessErr {
 }
 
 #[derive(SessionDiagnostic)]
-#[error(const_eval::raw_ptr_to_int)]
+#[diag(const_eval::raw_ptr_to_int)]
 #[note]
 #[note(const_eval::note2)]
 pub(crate) struct RawPtrToIntErr {
@@ -50,38 +50,38 @@ pub(crate) struct RawPtrToIntErr {
 }
 
 #[derive(SessionDiagnostic)]
-#[error(const_eval::raw_ptr_comparison)]
+#[diag(const_eval::raw_ptr_comparison)]
 #[note]
 pub(crate) struct RawPtrComparisonErr {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(const_eval::panic_non_str)]
+#[diag(const_eval::panic_non_str)]
 pub(crate) struct PanicNonStrErr {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(const_eval::mut_deref, code = "E0658")]
+#[diag(const_eval::mut_deref, code = "E0658")]
 pub(crate) struct MutDerefErr {
     #[primary_span]
     pub span: Span,
     pub kind: ConstContext,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(const_eval::transient_mut_borrow, code = "E0658")]
+#[diag(const_eval::transient_mut_borrow, code = "E0658")]
 pub(crate) struct TransientMutBorrowErr {
     #[primary_span]
     pub span: Span,
     pub kind: ConstContext,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(const_eval::transient_mut_borrow_raw, code = "E0658")]
+#[diag(const_eval::transient_mut_borrow_raw, code = "E0658")]
 pub(crate) struct TransientMutBorrowErrRaw {
     #[primary_span]
     pub span: Span,

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -84,6 +84,13 @@ pub trait EmissionGuarantee: Sized {
     /// of `Self` without actually performing the emission.
     #[track_caller]
     fn diagnostic_builder_emit_producing_guarantee(db: &mut DiagnosticBuilder<'_, Self>) -> Self;
+
+    /// Creates a new `DiagnosticBuilder` that will return this type of guarantee.
+    #[track_caller]
+    fn make_diagnostic_builder(
+        handler: &Handler,
+        msg: impl Into<DiagnosticMessage>,
+    ) -> DiagnosticBuilder<'_, Self>;
 }
 
 /// Private module for sealing the `IsError` helper trait.
@@ -166,6 +173,15 @@ impl EmissionGuarantee for ErrorGuaranteed {
             }
         }
     }
+
+    fn make_diagnostic_builder(
+        handler: &Handler,
+        msg: impl Into<DiagnosticMessage>,
+    ) -> DiagnosticBuilder<'_, Self> {
+        DiagnosticBuilder::new_guaranteeing_error::<_, { Level::Error { lint: false } }>(
+            handler, msg,
+        )
+    }
 }
 
 impl<'a> DiagnosticBuilder<'a, ()> {
@@ -208,6 +224,13 @@ impl EmissionGuarantee for () {
             DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => {}
         }
     }
+
+    fn make_diagnostic_builder(
+        handler: &Handler,
+        msg: impl Into<DiagnosticMessage>,
+    ) -> DiagnosticBuilder<'_, Self> {
+        DiagnosticBuilder::new(handler, Level::Warning(None), msg)
+    }
 }
 
 impl<'a> DiagnosticBuilder<'a, !> {
@@ -247,6 +270,13 @@ impl EmissionGuarantee for ! {
         // Then fatally error, returning `!`
         crate::FatalError.raise()
     }
+
+    fn make_diagnostic_builder(
+        handler: &Handler,
+        msg: impl Into<DiagnosticMessage>,
+    ) -> DiagnosticBuilder<'_, Self> {
+        DiagnosticBuilder::new_fatal(handler, msg)
+    }
 }
 
 /// In general, the `DiagnosticBuilder` uses deref to allow access to

compiler/rustc_errors/src/lib.rs

@@ -641,6 +641,15 @@ impl Handler {
         self.inner.borrow_mut().emit_stashed_diagnostics()
     }
 
+    /// Construct a builder with the `msg` at the level appropriate for the specific `EmissionGuarantee`.
+    #[rustc_lint_diagnostics]
+    pub fn struct_diagnostic<G: EmissionGuarantee>(
+        &self,
+        msg: impl Into<DiagnosticMessage>,
+    ) -> DiagnosticBuilder<'_, G> {
+        G::make_diagnostic_builder(self, msg)
+    }
+
     /// Construct a builder at the `Warning` level at the given `span` and with the `msg`.
     ///
     /// Attempting to `.emit()` the builder will only emit if either:

compiler/rustc_expand/src/errors.rs

@@ -3,44 +3,44 @@ use rustc_span::symbol::MacroRulesNormalizedIdent;
 use rustc_span::Span;
 
 #[derive(SessionDiagnostic)]
-#[error(expand::expr_repeat_no_syntax_vars)]
+#[diag(expand::expr_repeat_no_syntax_vars)]
 pub(crate) struct NoSyntaxVarsExprRepeat {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(expand::must_repeat_once)]
+#[diag(expand::must_repeat_once)]
 pub(crate) struct MustRepeatOnce {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(expand::count_repetition_misplaced)]
+#[diag(expand::count_repetition_misplaced)]
 pub(crate) struct CountRepetitionMisplaced {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(expand::meta_var_expr_unrecognized_var)]
+#[diag(expand::meta_var_expr_unrecognized_var)]
 pub(crate) struct MetaVarExprUnrecognizedVar {
     #[primary_span]
     pub span: Span,
     pub key: MacroRulesNormalizedIdent,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(expand::var_still_repeating)]
+#[diag(expand::var_still_repeating)]
 pub(crate) struct VarStillRepeating {
     #[primary_span]
     pub span: Span,
     pub ident: MacroRulesNormalizedIdent,
 }
 
 #[derive(SessionDiagnostic)]
-#[error(expand::meta_var_dif_seq_matchers)]
+#[diag(expand::meta_var_dif_seq_matchers)]
 pub(crate) struct MetaVarsDifSeqMatchers {
     #[primary_span]
     pub span: Span,

compiler/rustc_interface/src/passes.rs

@@ -265,7 +265,7 @@ impl LintStoreExpand for LintStoreExpandImpl<'_> {
 }
 
 #[derive(SessionDiagnostic)]
-#[error(interface::ferris_identifier)]
+#[diag(interface::ferris_identifier)]
 struct FerrisIdentifier {
     #[primary_span]
     spans: Vec<Span>,
@@ -274,7 +274,7 @@ struct FerrisIdentifier {
 }
 
 #[derive(SessionDiagnostic)]
-#[error(interface::emoji_identifier)]
+#[diag(interface::emoji_identifier)]
 struct EmojiIdentifier {
     #[primary_span]
     spans: Vec<Span>,

compiler/rustc_lint/src/types.rs

@@ -1546,7 +1546,7 @@ impl InvalidAtomicOrdering {
 
         if matches!(fail_ordering, sym::Release | sym::AcqRel) {
             #[derive(LintDiagnostic)]
-            #[lint(lint::atomic_ordering_invalid)]
+            #[diag(lint::atomic_ordering_invalid)]
             #[help]
             struct InvalidAtomicOrderingDiag {
                 method: Symbol,