diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index 8321f7fde503f..444f7877689fc 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -1981,11 +1981,7 @@ impl SharedEmitter {
 }
 
 impl Emitter for SharedEmitter {
-    fn emit_diagnostic(
-        &mut self,
-        mut diag: rustc_errors::DiagInner,
-        _registry: &rustc_errors::registry::Registry,
-    ) {
+    fn emit_diagnostic(&mut self, mut diag: rustc_errors::DiagInner) {
         // Check that we aren't missing anything interesting when converting to
         // the cut-down local `DiagInner`.
         assert!(!diag.span.has_span_labels());
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index 3b9ca5ff7288c..2999848979f33 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -34,7 +34,6 @@ use rustc_data_structures::profiling::{
 };
 pub use rustc_errors::catch_fatal_errors;
 use rustc_errors::emitter::stderr_destination;
-use rustc_errors::registry::Registry;
 use rustc_errors::translation::Translator;
 use rustc_errors::{ColorConfig, DiagCtxt, ErrCode, PResult, markdown};
 use rustc_feature::find_gated_cfg;
@@ -197,10 +196,6 @@ impl Callbacks for TimePassesCallbacks {
     }
 }
 
-pub fn diagnostics_registry() -> Registry {
-    Registry::new(rustc_errors::codes::DIAGNOSTICS)
-}
-
 /// This is the primary entry point for rustc.
 pub fn run_compiler(at_args: &[String], callbacks: &mut (dyn Callbacks + Send)) {
     let mut default_early_dcx = EarlyDiagCtxt::new(ErrorOutputType::default());
@@ -228,7 +223,7 @@ pub fn run_compiler(at_args: &[String], callbacks: &mut (dyn Callbacks + Send))
     let ice_file = ice_path_with_config(Some(&sopts.unstable_opts)).clone();
 
     if let Some(ref code) = matches.opt_str("explain") {
-        handle_explain(&default_early_dcx, diagnostics_registry(), code, sopts.color);
+        handle_explain(&default_early_dcx, code, sopts.color);
         return;
     }
 
@@ -255,7 +250,6 @@ pub fn run_compiler(at_args: &[String], callbacks: &mut (dyn Callbacks + Send))
         override_queries: None,
         extra_symbols: Vec::new(),
         make_codegen_backend: None,
-        registry: diagnostics_registry(),
         using_internal_features: &USING_INTERNAL_FEATURES,
     };
 
@@ -455,12 +449,12 @@ pub enum Compilation {
     Continue,
 }
 
-fn handle_explain(early_dcx: &EarlyDiagCtxt, registry: Registry, code: &str, color: ColorConfig) {
+fn handle_explain(early_dcx: &EarlyDiagCtxt, code: &str, color: ColorConfig) {
     // Allow "E0123" or "0123" form.
     let upper_cased_code = code.to_ascii_uppercase();
     if let Ok(code) = upper_cased_code.trim_prefix('E').parse::<u32>()
         && code <= ErrCode::MAX_AS_U32
-        && let Ok(description) = registry.try_find_description(ErrCode::from_u32(code))
+        && let Ok(description) = rustc_errors::codes::try_find_description(ErrCode::from_u32(code))
     {
         let mut is_in_code_block = false;
         let mut text = String::new();
diff --git a/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs b/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs
index 9bb3189739582..bdd3266adb66d 100644
--- a/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs
+++ b/compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs
@@ -27,7 +27,6 @@ use crate::emitter::{
     ConfusionType, Destination, MAX_SUGGESTIONS, OutputTheme, detect_confusion_type, is_different,
     normalize_whitespace, should_show_source_code,
 };
-use crate::registry::Registry;
 use crate::translation::{Translator, to_fluent_args};
 use crate::{
     CodeSuggestion, DiagInner, DiagMessage, Emitter, ErrCode, Level, MultiSpan, Style, Subdiag,
@@ -73,7 +72,7 @@ impl Debug for AnnotateSnippetEmitter {
 
 impl Emitter for AnnotateSnippetEmitter {
     /// The entry point for the diagnostics generation
-    fn emit_diagnostic(&mut self, mut diag: DiagInner, _registry: &Registry) {
+    fn emit_diagnostic(&mut self, mut diag: DiagInner) {
         let fluent_args = to_fluent_args(diag.args.iter());
 
         if self.track_diagnostics && diag.span.has_primary_spans() && !diag.span.is_dummy() {
diff --git a/compiler/rustc_errors/src/codes.rs b/compiler/rustc_errors/src/codes.rs
index 924924f285eb4..c1e7b7c184c11 100644
--- a/compiler/rustc_errors/src/codes.rs
+++ b/compiler/rustc_errors/src/codes.rs
@@ -5,6 +5,9 @@
 //!   long description text.
 
 use std::fmt;
+use std::sync::LazyLock;
+
+use rustc_data_structures::fx::FxHashMap;
 
 rustc_index::newtype_index! {
     #[max = 9999] // Because all error codes have four digits.
@@ -27,15 +30,28 @@ macro_rules! define_error_code_constants_and_diagnostics_table {
         $(
             pub const ${concat(E, $num)}: $crate::ErrCode = $crate::ErrCode::from_u32($num);
         )*
-        pub static DIAGNOSTICS: &[($crate::ErrCode, &str)] = &[
-            $( (
-                ${concat(E, $num)},
-                include_str!(
-                    concat!("../../rustc_error_codes/src/error_codes/E", stringify!($num), ".md")
-                )
-            ), )*
-        ];
+        static DIAGNOSTICS: LazyLock<FxHashMap<ErrCode, &'static str>> = LazyLock::new(|| {
+            [
+                $( (
+                    ${concat(E, $num)},
+                    include_str!(
+                        concat!("../../rustc_error_codes/src/error_codes/E", stringify!($num), ".md")
+                    )
+                ), )*
+            ]
+            .iter()
+            .copied()
+            .collect()
+        });
     )
 }
 
 rustc_error_codes::error_codes!(define_error_code_constants_and_diagnostics_table);
+
+#[derive(Debug)]
+pub struct InvalidErrorCode;
+
+/// Returns `InvalidErrorCode` if the code requested does not exist.
+pub fn try_find_description(code: ErrCode) -> Result<&'static str, InvalidErrorCode> {
+    DIAGNOSTICS.get(&code).copied().ok_or(InvalidErrorCode)
+}
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 3433db1e07042..4ceb5cf06f938 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -24,7 +24,6 @@ use rustc_span::source_map::SourceMap;
 use rustc_span::{FileName, SourceFile, Span};
 use tracing::{debug, warn};
 
-use crate::registry::Registry;
 use crate::timings::TimingRecord;
 use crate::translation::Translator;
 use crate::{
@@ -54,7 +53,7 @@ pub type DynEmitter = dyn Emitter + DynSend;
 /// Emitter trait for emitting errors and other structured information.
 pub trait Emitter {
     /// Emit a structured diagnostic.
-    fn emit_diagnostic(&mut self, diag: DiagInner, registry: &Registry);
+    fn emit_diagnostic(&mut self, diag: DiagInner);
 
     /// Emit a notification that an artifact has been output.
     /// Currently only supported for the JSON format.
@@ -66,7 +65,7 @@ pub trait Emitter {
 
     /// Emit a report about future breakage.
     /// Currently only supported for the JSON format.
-    fn emit_future_breakage_report(&mut self, _diags: Vec<DiagInner>, _registry: &Registry) {}
+    fn emit_future_breakage_report(&mut self, _diags: Vec<DiagInner>) {}
 
     /// Emit list of unused externs.
     /// Currently only supported for the JSON format.
@@ -380,9 +379,9 @@ impl Emitter for EmitterWithNote {
         None
     }
 
-    fn emit_diagnostic(&mut self, mut diag: DiagInner, registry: &Registry) {
+    fn emit_diagnostic(&mut self, mut diag: DiagInner) {
         diag.sub(Level::Note, self.note.clone(), MultiSpan::new());
-        self.emitter.emit_diagnostic(diag, registry);
+        self.emitter.emit_diagnostic(diag);
     }
 
     fn translator(&self) -> &Translator {
@@ -399,7 +398,7 @@ impl Emitter for SilentEmitter {
         None
     }
 
-    fn emit_diagnostic(&mut self, _diag: DiagInner, _registry: &Registry) {}
+    fn emit_diagnostic(&mut self, _diag: DiagInner) {}
 
     fn translator(&self) -> &Translator {
         &self.translator
diff --git a/compiler/rustc_errors/src/json.rs b/compiler/rustc_errors/src/json.rs
index 85801245bea90..310a64745bad6 100644
--- a/compiler/rustc_errors/src/json.rs
+++ b/compiler/rustc_errors/src/json.rs
@@ -31,7 +31,6 @@ use crate::emitter::{
     ColorConfig, Destination, Emitter, HumanReadableErrorType, OutputTheme, TimingEvent,
     should_show_source_code,
 };
-use crate::registry::Registry;
 use crate::timings::{TimingRecord, TimingSection};
 use crate::translation::{Translator, to_fluent_args};
 use crate::{CodeSuggestion, MultiSpan, SpanLabel, Subdiag, Suggestions, TerminalUrl};
@@ -107,8 +106,8 @@ enum EmitTyped<'a> {
 }
 
 impl Emitter for JsonEmitter {
-    fn emit_diagnostic(&mut self, diag: crate::DiagInner, registry: &Registry) {
-        let data = Diagnostic::from_errors_diagnostic(diag, self, registry);
+    fn emit_diagnostic(&mut self, diag: crate::DiagInner) {
+        let data = Diagnostic::from_errors_diagnostic(diag, self);
         let result = self.emit(EmitTyped::Diagnostic(data));
         if let Err(e) = result {
             panic!("failed to print diagnostics: {e:?}");
@@ -139,7 +138,7 @@ impl Emitter for JsonEmitter {
         }
     }
 
-    fn emit_future_breakage_report(&mut self, diags: Vec<crate::DiagInner>, registry: &Registry) {
+    fn emit_future_breakage_report(&mut self, diags: Vec<crate::DiagInner>) {
         let data: Vec<FutureBreakageItem<'_>> = diags
             .into_iter()
             .map(|mut diag| {
@@ -153,7 +152,7 @@ impl Emitter for JsonEmitter {
                 }
                 FutureBreakageItem {
                     diagnostic: EmitTyped::Diagnostic(Diagnostic::from_errors_diagnostic(
-                        diag, self, registry,
+                        diag, self,
                     )),
                 }
             })
@@ -307,11 +306,7 @@ struct UnusedExterns<'a> {
 
 impl Diagnostic {
     /// Converts from `rustc_errors::DiagInner` to `Diagnostic`.
-    fn from_errors_diagnostic(
-        diag: crate::DiagInner,
-        je: &JsonEmitter,
-        registry: &Registry,
-    ) -> Diagnostic {
+    fn from_errors_diagnostic(diag: crate::DiagInner, je: &JsonEmitter) -> Diagnostic {
         let args = to_fluent_args(diag.args.iter());
         let sugg_to_diag = |sugg: &CodeSuggestion| {
             let translated_message =
@@ -351,7 +346,7 @@ impl Diagnostic {
         let code = if let Some(code) = diag.code {
             Some(DiagnosticCode {
                 code: code.to_string(),
-                explanation: registry.try_find_description(code).ok(),
+                explanation: crate::codes::try_find_description(code).ok(),
             })
         } else if let Some(IsLint { name, .. }) = &diag.is_lint {
             Some(DiagnosticCode { code: name.to_string(), explanation: None })
@@ -388,7 +383,7 @@ impl Diagnostic {
             .ui_testing(je.ui_testing)
             .ignored_directories_in_source_blocks(je.ignored_directories_in_source_blocks.clone())
             .theme(if je.json_rendered.unicode { OutputTheme::Unicode } else { OutputTheme::Ascii })
-            .emit_diagnostic(diag, registry);
+            .emit_diagnostic(diag);
 
         let buf = Arc::try_unwrap(buf.0).unwrap().into_inner().unwrap();
         let buf = String::from_utf8(buf).unwrap();
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 68d825a4514a9..6730fbae35e21 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -71,7 +71,6 @@ use rustc_span::{DUMMY_SP, Span};
 use tracing::debug;
 
 use crate::emitter::TimingEvent;
-use crate::registry::Registry;
 use crate::timings::TimingRecord;
 
 pub mod annotate_snippet_emitter_writer;
@@ -84,7 +83,6 @@ pub mod error;
 pub mod json;
 mod lock;
 pub mod markdown;
-pub mod registry;
 #[cfg(test)]
 mod tests;
 pub mod timings;
@@ -299,8 +297,6 @@ impl<'a> std::ops::Deref for DiagCtxtHandle<'a> {
 struct DiagCtxtInner {
     flags: DiagCtxtFlags,
 
-    registry: Registry,
-
     /// The error guarantees from all emitted errors. The length gives the error count.
     err_guars: Vec<ErrorGuaranteed>,
     /// The error guarantee from all emitted lint errors. The length gives the
@@ -482,11 +478,6 @@ impl DiagCtxt {
         self
     }
 
-    pub fn with_registry(mut self, registry: Registry) -> Self {
-        self.inner.get_mut().registry = registry;
-        self
-    }
-
     pub fn new(emitter: Box<DynEmitter>) -> Self {
         Self { inner: Lock::new(DiagCtxtInner::new(emitter)) }
     }
@@ -539,7 +530,6 @@ impl DiagCtxt {
         let mut inner = self.inner.borrow_mut();
         let DiagCtxtInner {
             flags: _,
-            registry: _,
             err_guars,
             lint_err_guars,
             delayed_bugs,
@@ -813,7 +803,7 @@ impl<'a> DiagCtxtHandle<'a> {
                 .emitted_diagnostic_codes
                 .iter()
                 .filter_map(|&code| {
-                    if inner.registry.try_find_description(code).is_ok() {
+                    if crate::codes::try_find_description(code).is_ok() {
                         Some(code.to_string())
                     } else {
                         None
@@ -885,7 +875,7 @@ impl<'a> DiagCtxtHandle<'a> {
         let inner = &mut *self.inner.borrow_mut();
         let diags = std::mem::take(&mut inner.future_breakage_diagnostics);
         if !diags.is_empty() {
-            inner.emitter.emit_future_breakage_report(diags, &inner.registry);
+            inner.emitter.emit_future_breakage_report(diags);
         }
     }
 
@@ -1186,7 +1176,6 @@ impl DiagCtxtInner {
     fn new(emitter: Box<DynEmitter>) -> Self {
         Self {
             flags: DiagCtxtFlags { can_emit_warnings: true, ..Default::default() },
-            registry: Registry::new(&[]),
             err_guars: Vec::new(),
             lint_err_guars: Vec::new(),
             delayed_bugs: Vec::new(),
@@ -1362,7 +1351,7 @@ impl DiagCtxtInner {
                 }
                 self.has_printed = true;
 
-                self.emitter.emit_diagnostic(diagnostic, &self.registry);
+                self.emitter.emit_diagnostic(diagnostic);
             }
 
             if is_error {
diff --git a/compiler/rustc_errors/src/registry.rs b/compiler/rustc_errors/src/registry.rs
deleted file mode 100644
index baca7700d90e2..0000000000000
--- a/compiler/rustc_errors/src/registry.rs
+++ /dev/null
@@ -1,23 +0,0 @@
-use rustc_data_structures::fx::FxHashMap;
-
-use crate::ErrCode;
-
-#[derive(Debug)]
-pub struct InvalidErrorCode;
-
-#[derive(Clone)]
-pub struct Registry {
-    long_descriptions: FxHashMap<ErrCode, &'static str>,
-}
-
-impl Registry {
-    pub fn new(long_descriptions: &[(ErrCode, &'static str)]) -> Registry {
-        Registry { long_descriptions: long_descriptions.iter().copied().collect() }
-    }
-
-    /// Returns `InvalidErrorCode` if the code requested does not exist in the
-    /// registry.
-    pub fn try_find_description(&self, code: ErrCode) -> Result<&'static str, InvalidErrorCode> {
-        self.long_descriptions.get(&code).copied().ok_or(InvalidErrorCode)
-    }
-}
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 276fa5db7798a..d3244acef2c1f 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -7,7 +7,6 @@ use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::jobserver::{self, Proxy};
 use rustc_data_structures::stable_hasher::StableHasher;
-use rustc_errors::registry::Registry;
 use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed};
 use rustc_lint::LintStore;
 use rustc_middle::ty;
@@ -374,9 +373,6 @@ pub struct Config {
     pub make_codegen_backend:
         Option<Box<dyn FnOnce(&config::Options, &Target) -> Box<dyn CodegenBackend> + Send>>,
 
-    /// Registry of diagnostics codes.
-    pub registry: Registry,
-
     /// The inner atomic value is set to true when a feature marked as `internal` is
     /// enabled. Makes it so that "please report a bug" is hidden, as ICEs with
     /// internal features are wontfix, and they are usually the cause of the ICEs.
@@ -464,7 +460,6 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
                     temps_dir,
                 },
                 bundle,
-                config.registry,
                 config.locale_resources,
                 config.lint_caps,
                 target,
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index b0272d726bc38..4241af244941e 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -6,8 +6,8 @@ use std::sync::atomic::AtomicBool;
 
 use rustc_abi::Align;
 use rustc_data_structures::profiling::TimePassesFormat;
+use rustc_errors::ColorConfig;
 use rustc_errors::emitter::HumanReadableErrorType;
-use rustc_errors::{ColorConfig, registry};
 use rustc_hir::attrs::{CollapseMacroDebuginfo, NativeLibKind};
 use rustc_session::config::{
     AnnotateMoves, AutoDiff, BranchProtection, CFGuard, Cfg, CoverageLevel, CoverageOptions,
@@ -72,7 +72,6 @@ where
             sessopts,
             io,
             None,
-            registry::Registry::new(&[]),
             vec![],
             Default::default(),
             target,
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index 27d6efb8b5490..b141aada43bb9 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -963,7 +963,6 @@ pub fn build_session(
     sopts: config::Options,
     io: CompilerIO,
     fluent_bundle: Option<Arc<rustc_errors::FluentBundle>>,
-    registry: rustc_errors::registry::Registry,
     fluent_resources: Vec<&'static str>,
     driver_lint_caps: FxHashMap<lint::LintId, lint::Level>,
     target: Target,
@@ -992,9 +991,8 @@ pub fn build_session(
     let source_map = rustc_span::source_map::get_source_map().unwrap();
     let emitter = default_emitter(&sopts, Arc::clone(&source_map), translator);
 
-    let mut dcx = DiagCtxt::new(emitter)
-        .with_flags(sopts.unstable_opts.dcx_flags(can_emit_warnings))
-        .with_registry(registry);
+    let mut dcx =
+        DiagCtxt::new(emitter).with_flags(sopts.unstable_opts.dcx_flags(can_emit_warnings));
     if let Some(ice_file) = ice_file {
         dcx = dcx.with_ice_file(ice_file);
     }
diff --git a/src/doc/rustc-dev-guide/examples/rustc-interface-example.rs b/src/doc/rustc-dev-guide/examples/rustc-interface-example.rs
index 360f70c8e865a..fe9895d778fd3 100644
--- a/src/doc/rustc-dev-guide/examples/rustc-interface-example.rs
+++ b/src/doc/rustc-dev-guide/examples/rustc-interface-example.rs
@@ -4,14 +4,12 @@
 
 extern crate rustc_driver;
 extern crate rustc_error_codes;
-extern crate rustc_errors;
 extern crate rustc_hash;
 extern crate rustc_hir;
 extern crate rustc_interface;
 extern crate rustc_session;
 extern crate rustc_span;
 
-use rustc_errors::registry;
 use rustc_hash::FxHashMap;
 use rustc_session::config;
 
@@ -50,8 +48,6 @@ fn main() {
         //
         // The second parameter is local providers and the third parameter is external providers.
         override_queries: None, // Option<fn(&Session, &mut ty::query::Providers<'_>, &mut ty::query::Providers<'_>)>
-        // Registry of diagnostics codes.
-        registry: registry::Registry::new(rustc_errors::codes::DIAGNOSTICS),
         make_codegen_backend: None,
         expanded_args: Vec::new(),
         ice_file: None,
diff --git a/src/doc/rustc-dev-guide/examples/rustc-interface-getting-diagnostics.rs b/src/doc/rustc-dev-guide/examples/rustc-interface-getting-diagnostics.rs
index 2512ba3c3f924..83b71b351bbc3 100644
--- a/src/doc/rustc-dev-guide/examples/rustc-interface-getting-diagnostics.rs
+++ b/src/doc/rustc-dev-guide/examples/rustc-interface-getting-diagnostics.rs
@@ -15,7 +15,7 @@ extern crate rustc_span;
 use std::sync::{Arc, Mutex};
 
 use rustc_errors::emitter::Emitter;
-use rustc_errors::registry::{self, Registry};
+use rustc_errors::registry::Registry;
 use rustc_errors::translation::Translate;
 use rustc_errors::{DiagInner, FluentBundle};
 use rustc_session::config;
@@ -76,7 +76,6 @@ fn main() {
         })),
         register_lints: None,
         override_queries: None,
-        registry: registry::Registry::new(rustc_errors::codes::DIAGNOSTICS),
         make_codegen_backend: None,
         expanded_args: Vec::new(),
         ice_file: None,
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 413163290ee30..a45175dc08f0d 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -322,7 +322,6 @@ pub(crate) fn create_config(
         }),
         extra_symbols: Vec::new(),
         make_codegen_backend: None,
-        registry: rustc_driver::diagnostics_registry(),
         ice_file: None,
         using_internal_features: &USING_INTERNAL_FEATURES,
     }
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index 6cd7d2c628d58..0605d16699fa3 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -196,7 +196,6 @@ pub(crate) fn run(dcx: DiagCtxtHandle<'_>, input: Input, options: RustdocOptions
         override_queries: None,
         extra_symbols: Vec::new(),
         make_codegen_backend: None,
-        registry: rustc_driver::diagnostics_registry(),
         ice_file: None,
         using_internal_features: &rustc_driver::USING_INTERNAL_FEATURES,
     };
diff --git a/src/librustdoc/passes/lint/check_code_block_syntax.rs b/src/librustdoc/passes/lint/check_code_block_syntax.rs
index b08533317abeb..5749b4ac081e1 100644
--- a/src/librustdoc/passes/lint/check_code_block_syntax.rs
+++ b/src/librustdoc/passes/lint/check_code_block_syntax.rs
@@ -5,7 +5,6 @@ use std::sync::Arc;
 
 use rustc_data_structures::sync::Lock;
 use rustc_errors::emitter::Emitter;
-use rustc_errors::registry::Registry;
 use rustc_errors::translation::{Translator, to_fluent_args};
 use rustc_errors::{Applicability, DiagCtxt, DiagInner};
 use rustc_parse::{source_str_to_stream, unwrap_or_emit_fatal};
@@ -150,7 +149,7 @@ struct BufferEmitter {
 }
 
 impl Emitter for BufferEmitter {
-    fn emit_diagnostic(&mut self, diag: DiagInner, _registry: &Registry) {
+    fn emit_diagnostic(&mut self, diag: DiagInner) {
         let mut buffer = self.buffer.borrow_mut();
 
         let fluent_args = to_fluent_args(diag.args.iter());
diff --git a/src/tools/error_index_generator/main.rs b/src/tools/error_index_generator/main.rs
index 97ac47918c092..c78df2b60b56d 100644
--- a/src/tools/error_index_generator/main.rs
+++ b/src/tools/error_index_generator/main.rs
@@ -1,10 +1,11 @@
 #![feature(rustc_private)]
 
 extern crate rustc_driver;
+extern crate rustc_error_codes;
+extern crate rustc_errors;
 extern crate rustc_log;
 extern crate rustc_session;
 
-extern crate rustc_errors;
 use std::env;
 use std::error::Error;
 use std::fs::{self, File};
@@ -16,7 +17,22 @@ use mdbook_driver::MDBook;
 use mdbook_driver::book::{BookItem, Chapter};
 use mdbook_driver::config::Config;
 use mdbook_summary::parse_summary;
-use rustc_errors::codes::DIAGNOSTICS;
+use rustc_errors::codes::ErrCode;
+
+macro_rules! define_error_codes_table {
+    ($($num:literal,)*) => (
+        static DIAGNOSTICS: &[(ErrCode, &str)] = &[
+            $( (
+                ErrCode::from_u32($num),
+                include_str!(
+                    concat!("../../../compiler/rustc_error_codes/src/error_codes/E", stringify!($num), ".md")
+                )
+            ), )*
+        ];
+    )
+}
+
+rustc_error_codes::error_codes!(define_error_codes_table);
 
 enum OutputFormat {
     HTML,
diff --git a/src/tools/rustfmt/src/parse/session.rs b/src/tools/rustfmt/src/parse/session.rs
index 7b6ffa1e495f6..2a5c8f776427d 100644
--- a/src/tools/rustfmt/src/parse/session.rs
+++ b/src/tools/rustfmt/src/parse/session.rs
@@ -5,7 +5,6 @@ use std::sync::atomic::{AtomicBool, Ordering};
 use rustc_data_structures::sync::IntoDynSyncSend;
 use rustc_errors::annotate_snippet_emitter_writer::AnnotateSnippetEmitter;
 use rustc_errors::emitter::{DynEmitter, Emitter, SilentEmitter, stderr_destination};
-use rustc_errors::registry::Registry;
 use rustc_errors::translation::Translator;
 use rustc_errors::{ColorConfig, Diag, DiagCtxt, DiagInner, Level as DiagnosticLevel};
 use rustc_session::parse::ParseSess as RawParseSess;
@@ -41,10 +40,10 @@ struct SilentOnIgnoredFilesEmitter {
 }
 
 impl SilentOnIgnoredFilesEmitter {
-    fn handle_non_ignoreable_error(&mut self, diag: DiagInner, registry: &Registry) {
+    fn handle_non_ignoreable_error(&mut self, diag: DiagInner) {
         self.has_non_ignorable_parser_errors = true;
         self.can_reset.store(false, Ordering::Release);
-        self.emitter.emit_diagnostic(diag, registry);
+        self.emitter.emit_diagnostic(diag);
     }
 }
 
@@ -53,9 +52,9 @@ impl Emitter for SilentOnIgnoredFilesEmitter {
         None
     }
 
-    fn emit_diagnostic(&mut self, diag: DiagInner, registry: &Registry) {
+    fn emit_diagnostic(&mut self, diag: DiagInner) {
         if diag.level() == DiagnosticLevel::Fatal {
-            return self.handle_non_ignoreable_error(diag, registry);
+            return self.handle_non_ignoreable_error(diag);
         }
         if let Some(primary_span) = &diag.span.primary_span() {
             let file_name = self.source_map.span_to_filename(*primary_span);
@@ -73,7 +72,7 @@ impl Emitter for SilentOnIgnoredFilesEmitter {
                 }
             }
         }
-        self.handle_non_ignoreable_error(diag, registry);
+        self.handle_non_ignoreable_error(diag);
     }
 
     fn translator(&self) -> &Translator {
@@ -340,7 +339,7 @@ mod tests {
                 None
             }
 
-            fn emit_diagnostic(&mut self, _diag: DiagInner, _registry: &Registry) {
+            fn emit_diagnostic(&mut self, _diag: DiagInner) {
                 self.num_emitted_errors.fetch_add(1, Ordering::Release);
             }
 
@@ -401,7 +400,6 @@ mod tests {
             let source =
                 String::from(r#"extern "system" fn jni_symbol!( funcName ) ( ... ) -> {} "#);
             source_map.new_source_file(filename(&source_map, "foo.rs"), source);
-            let registry = Registry::new(&[]);
             let mut emitter = build_emitter(
                 Arc::clone(&num_emitted_errors),
                 Arc::clone(&can_reset_errors),
@@ -410,7 +408,7 @@ mod tests {
             );
             let span = MultiSpan::from_span(mk_sp(BytePos(0), BytePos(1)));
             let fatal_diagnostic = build_diagnostic(DiagnosticLevel::Fatal, Some(span));
-            emitter.emit_diagnostic(fatal_diagnostic, &registry);
+            emitter.emit_diagnostic(fatal_diagnostic);
             assert_eq!(num_emitted_errors.load(Ordering::Acquire), 1);
             assert_eq!(can_reset_errors.load(Ordering::Acquire), false);
         }
@@ -424,7 +422,6 @@ mod tests {
             let source_map = Arc::new(SourceMap::new(FilePathMapping::empty()));
             let source = String::from(r#"pub fn bar() { 1x; }"#);
             source_map.new_source_file(filename(&source_map, "foo.rs"), source);
-            let registry = Registry::new(&[]);
             let mut emitter = build_emitter(
                 Arc::clone(&num_emitted_errors),
                 Arc::clone(&can_reset_errors),
@@ -433,7 +430,7 @@ mod tests {
             );
             let span = MultiSpan::from_span(mk_sp(BytePos(0), BytePos(1)));
             let non_fatal_diagnostic = build_diagnostic(DiagnosticLevel::Warning, Some(span));
-            emitter.emit_diagnostic(non_fatal_diagnostic, &registry);
+            emitter.emit_diagnostic(non_fatal_diagnostic);
             assert_eq!(num_emitted_errors.load(Ordering::Acquire), 0);
             assert_eq!(can_reset_errors.load(Ordering::Acquire), true);
         }
@@ -446,7 +443,6 @@ mod tests {
             let source_map = Arc::new(SourceMap::new(FilePathMapping::empty()));
             let source = String::from(r#"pub fn bar() { 1x; }"#);
             source_map.new_source_file(filename(&source_map, "foo.rs"), source);
-            let registry = Registry::new(&[]);
             let mut emitter = build_emitter(
                 Arc::clone(&num_emitted_errors),
                 Arc::clone(&can_reset_errors),
@@ -455,7 +451,7 @@ mod tests {
             );
             let span = MultiSpan::from_span(mk_sp(BytePos(0), BytePos(1)));
             let non_fatal_diagnostic = build_diagnostic(DiagnosticLevel::Warning, Some(span));
-            emitter.emit_diagnostic(non_fatal_diagnostic, &registry);
+            emitter.emit_diagnostic(non_fatal_diagnostic);
             assert_eq!(num_emitted_errors.load(Ordering::Acquire), 1);
             assert_eq!(can_reset_errors.load(Ordering::Acquire), false);
         }
@@ -474,7 +470,6 @@ mod tests {
             source_map.new_source_file(filename(&source_map, "bar.rs"), bar_source);
             source_map.new_source_file(filename(&source_map, "foo.rs"), foo_source);
             source_map.new_source_file(filename(&source_map, "fatal.rs"), fatal_source);
-            let registry = Registry::new(&[]);
             let mut emitter = build_emitter(
                 Arc::clone(&num_emitted_errors),
                 Arc::clone(&can_reset_errors),
@@ -486,9 +481,9 @@ mod tests {
             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, &registry);
-            emitter.emit_diagnostic(foo_diagnostic, &registry);
-            emitter.emit_diagnostic(fatal_diagnostic, &registry);
+            emitter.emit_diagnostic(bar_diagnostic);
+            emitter.emit_diagnostic(foo_diagnostic);
+            emitter.emit_diagnostic(fatal_diagnostic);
             assert_eq!(num_emitted_errors.load(Ordering::Acquire), 2);
             assert_eq!(can_reset_errors.load(Ordering::Acquire), false);
         }
diff --git a/tests/ui-fulldeps/run-compiler-twice.rs b/tests/ui-fulldeps/run-compiler-twice.rs
index 241d9e7efbd72..8b5e99cbee8dc 100644
--- a/tests/ui-fulldeps/run-compiler-twice.rs
+++ b/tests/ui-fulldeps/run-compiler-twice.rs
@@ -72,7 +72,6 @@ fn compile(code: String, output: PathBuf, sysroot: Sysroot, linker: Option<&Path
         override_queries: None,
         extra_symbols: Vec::new(),
         make_codegen_backend: None,
-        registry: rustc_driver::diagnostics_registry(),
         using_internal_features: &rustc_driver::USING_INTERNAL_FEATURES,
     };