Rollup merge of #145747 - joshtriplett:builtin-diag-dyn, r=jdonszelmann

Refactor lint buffering to avoid requiring a giant enum

Lint buffering currently relies on a giant enum `BuiltinLintDiag` containing all the lints that might potentially get buffered. In addition to being an unwieldy enum in a central crate, this also makes `rustc_lint_defs` a build bottleneck: it depends on various types from various crates (with a steady pressure to add more), and many crates depend on it.

Having all of these variants in a separate crate also prevents detecting when a variant becomes unused, which we can do with a dedicated type defined and used in the same crate.

Refactor this to use a dyn trait, to allow using `LintDiagnostic` types directly.

Because the existing `BuiltinLintDiag` requires some additional types in order to decorate some variants, which are only available later in `rustc_lint`, use an enum `DecorateDiagCompat` to handle both the `dyn LintDiagnostic` case and the `BuiltinLintDiag` case.

---

With the infrastructure in place, use it to migrate three of the enum variants to use `LintDiagnostic` directly, as a proof of concept and to demonstrate that the net result is a reduction in code size and a removal of a boilerplate-heavy layer of indirection.

Also remove an unused `BuiltinLintDiag` variant.

1 files changed, 0 insertions, 101 deletions

diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index a1e26bf1503..6c509734626 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -1,7 +1,6 @@
 #![allow(rustc::untranslatable_diagnostic)]
 use std::num::NonZero;
 
-use rustc_abi::ExternAbi;
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagArgValue, DiagMessage, DiagStyledString, ElidedLifetimeInPathSubdiag,
@@ -816,80 +815,6 @@ pub(crate) enum InvalidReferenceCastingDiag<'tcx> {
     },
 }
 
-// hidden_unicode_codepoints.rs
-#[derive(LintDiagnostic)]
-#[diag(lint_hidden_unicode_codepoints)]
-#[note]
-pub(crate) struct HiddenUnicodeCodepointsDiag<'a> {
-    pub label: &'a str,
-    pub count: usize,
-    #[label]
-    pub span_label: Span,
-    #[subdiagnostic]
-    pub labels: Option<HiddenUnicodeCodepointsDiagLabels>,
-    #[subdiagnostic]
-    pub sub: HiddenUnicodeCodepointsDiagSub,
-}
-
-pub(crate) struct HiddenUnicodeCodepointsDiagLabels {
-    pub spans: Vec<(char, Span)>,
-}
-
-impl Subdiagnostic for HiddenUnicodeCodepointsDiagLabels {
-    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
-        for (c, span) in self.spans {
-            diag.span_label(span, format!("{c:?}"));
-        }
-    }
-}
-
-pub(crate) enum HiddenUnicodeCodepointsDiagSub {
-    Escape { spans: Vec<(char, Span)> },
-    NoEscape { spans: Vec<(char, Span)> },
-}
-
-// Used because of multiple multipart_suggestion and note
-impl Subdiagnostic for HiddenUnicodeCodepointsDiagSub {
-    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
-        match self {
-            HiddenUnicodeCodepointsDiagSub::Escape { spans } => {
-                diag.multipart_suggestion_with_style(
-                    fluent::lint_suggestion_remove,
-                    spans.iter().map(|(_, span)| (*span, "".to_string())).collect(),
-                    Applicability::MachineApplicable,
-                    SuggestionStyle::HideCodeAlways,
-                );
-                diag.multipart_suggestion(
-                    fluent::lint_suggestion_escape,
-                    spans
-                        .into_iter()
-                        .map(|(c, span)| {
-                            let c = format!("{c:?}");
-                            (span, c[1..c.len() - 1].to_string())
-                        })
-                        .collect(),
-                    Applicability::MachineApplicable,
-                );
-            }
-            HiddenUnicodeCodepointsDiagSub::NoEscape { spans } => {
-                // FIXME: in other suggestions we've reversed the inner spans of doc comments. We
-                // should do the same here to provide the same good suggestions as we do for
-                // literals above.
-                diag.arg(
-                    "escaped",
-                    spans
-                        .into_iter()
-                        .map(|(c, _)| format!("{c:?}"))
-                        .collect::<Vec<String>>()
-                        .join(", "),
-                );
-                diag.note(fluent::lint_suggestion_remove);
-                diag.note(fluent::lint_no_suggestion_note_escape);
-            }
-        }
-    }
-}
-
 // map_unit_fn.rs
 #[derive(LintDiagnostic)]
 #[diag(lint_map_unit_fn)]
@@ -2567,16 +2492,6 @@ pub(crate) mod unexpected_cfg_value {
 }
 
 #[derive(LintDiagnostic)]
-#[diag(lint_unexpected_builtin_cfg)]
-#[note(lint_controlled_by)]
-#[note(lint_incoherent)]
-pub(crate) struct UnexpectedBuiltinCfg {
-    pub(crate) cfg: String,
-    pub(crate) cfg_name: Symbol,
-    pub(crate) controlled_by: &'static str,
-}
-
-#[derive(LintDiagnostic)]
 #[diag(lint_macro_use_deprecated)]
 #[help]
 pub(crate) struct MacroUseDeprecated;
@@ -2690,14 +2605,6 @@ pub(crate) struct IllFormedAttributeInput {
 }
 
 #[derive(LintDiagnostic)]
-pub(crate) enum InnerAttributeUnstable {
-    #[diag(lint_inner_macro_attribute_unstable)]
-    InnerMacroAttribute,
-    #[diag(lint_custom_inner_attribute_unstable)]
-    CustomInnerAttribute,
-}
-
-#[derive(LintDiagnostic)]
 #[diag(lint_unknown_diagnostic_attribute)]
 pub(crate) struct UnknownDiagnosticAttribute {
     #[subdiagnostic]
@@ -2890,14 +2797,6 @@ pub(crate) struct PatternsInFnsWithoutBodySub {
 }
 
 #[derive(LintDiagnostic)]
-#[diag(lint_extern_without_abi)]
-pub(crate) struct MissingAbi {
-    #[suggestion(code = "extern {default_abi}", applicability = "machine-applicable")]
-    pub span: Span,
-    pub default_abi: ExternAbi,
-}
-
-#[derive(LintDiagnostic)]
 #[diag(lint_legacy_derive_helpers)]
 pub(crate) struct LegacyDeriveHelpers {
     #[label]