Replace diagnostic plugins with macro_rules

32 files changed, 87 insertions, 351 deletions

diff --git a/src/librustc/error_codes.rs b/src/librustc/error_codes.rs
index bde0fdf3b8e..eee33846139 100644
--- a/src/librustc/error_codes.rs
+++ b/src/librustc/error_codes.rs
@@ -2184,11 +2184,7 @@ Examples of erroneous code:
 static X: u32 = 42;
 ```
 "##,
-
-}
-
-
-register_diagnostics! {
+;
 //  E0006, // merged with E0005
 //  E0101, // replaced with E0282
 //  E0102, // replaced with E0282
diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index 368f5bb64fe..c5d2b2d7e7f 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -88,8 +88,6 @@ mod tests;
 #[macro_use]
 mod macros;
 
-// N.B., this module needs to be declared first so diagnostics are
-// registered before they are used.
 pub mod error_codes;
 
 #[macro_use]
@@ -143,6 +141,3 @@ pub mod util {
 
 // Allows macros to refer to this crate as `::rustc`
 extern crate self as rustc;
-
-// Build the diagnostics array at the end so that the metadata includes error use sites.
-__build_diagnostic_array! { librustc, DIAGNOSTICS }
diff --git a/src/librustc_codegen_llvm/error_codes.rs b/src/librustc_codegen_llvm/error_codes.rs
index c6b5dc03a6f..042e51ed2ba 100644
--- a/src/librustc_codegen_llvm/error_codes.rs
+++ b/src/librustc_codegen_llvm/error_codes.rs
@@ -1,4 +1,4 @@
-register_long_diagnostics! {
+register_diagnostics! {
 
 E0511: r##"
 Invalid monomorphization of an intrinsic function was used. Erroneous code
diff --git a/src/librustc_codegen_llvm/lib.rs b/src/librustc_codegen_llvm/lib.rs
index 2fd78885bd0..f032d0ff046 100644
--- a/src/librustc_codegen_llvm/lib.rs
+++ b/src/librustc_codegen_llvm/lib.rs
@@ -256,7 +256,7 @@ impl CodegenBackend for LlvmCodegenBackend {
     }
 
     fn diagnostics(&self) -> &[(&'static str, &'static str)] {
-        &DIAGNOSTICS
+        &error_codes::DIAGNOSTICS
     }
 
     fn target_features(&self, sess: &Session) -> Vec<Symbol> {
@@ -425,5 +425,3 @@ impl Drop for ModuleLlvm {
         }
     }
 }
-
-__build_diagnostic_array! { librustc_codegen_llvm, DIAGNOSTICS }
diff --git a/src/librustc_codegen_ssa/error_codes.rs b/src/librustc_codegen_ssa/error_codes.rs
index 8d46dcb7c09..8ff41c275a8 100644
--- a/src/librustc_codegen_ssa/error_codes.rs
+++ b/src/librustc_codegen_ssa/error_codes.rs
@@ -1,4 +1,4 @@
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 
 E0668: r##"
 Malformed inline assembly rejected by LLVM.
diff --git a/src/librustc_codegen_ssa/lib.rs b/src/librustc_codegen_ssa/lib.rs
index 68640abb043..0f98310722e 100644
--- a/src/librustc_codegen_ssa/lib.rs
+++ b/src/librustc_codegen_ssa/lib.rs
@@ -35,8 +35,6 @@ use rustc_data_structures::svh::Svh;
 use rustc::middle::cstore::{LibSource, CrateSource, NativeLibrary};
 use syntax_pos::symbol::Symbol;
 
-// N.B., this module needs to be declared first so diagnostics are
-// registered before they are used.
 mod error_codes;
 
 pub mod common;
@@ -158,5 +156,3 @@ pub struct CodegenResults {
     pub linker_info: back::linker::LinkerInfo,
     pub crate_info: CrateInfo,
 }
-
-__build_diagnostic_array! { librustc_codegen_ssa, DIAGNOSTICS }
diff --git a/src/librustc_interface/passes.rs b/src/librustc_interface/passes.rs
index 24b44964e4f..bd9b240e24e 100644
--- a/src/librustc_interface/passes.rs
+++ b/src/librustc_interface/passes.rs
@@ -34,7 +34,7 @@ use rustc_privacy;
 use rustc_resolve::{Resolver, ResolverArenas};
 use rustc_traits;
 use rustc_typeck as typeck;
-use syntax::{self, ast, diagnostics, visit};
+use syntax::{self, ast, visit};
 use syntax::early_buffered_lints::BufferedEarlyLint;
 use syntax::ext::base::{NamedSyntaxExtension, ExtCtxt};
 use syntax::mut_visit::MutVisitor;
@@ -292,18 +292,7 @@ pub fn register_plugins<'a>(
 
     time(sess, "plugin registration", || {
         if sess.features_untracked().rustc_diagnostic_macros {
-            registry.register_macro(
-                "__diagnostic_used",
-                diagnostics::plugin::expand_diagnostic_used,
-            );
-            registry.register_macro(
-                "__register_diagnostic",
-                diagnostics::plugin::expand_register_diagnostic,
-            );
-            registry.register_macro(
-                "__build_diagnostic_array",
-                diagnostics::plugin::expand_build_diagnostic_array,
-            );
+            // FIXME: remove feature gate
         }
 
         for registrar in registrars {
diff --git a/src/librustc_interface/util.rs b/src/librustc_interface/util.rs
index f007a0cf2ab..9eaf7b77716 100644
--- a/src/librustc_interface/util.rs
+++ b/src/librustc_interface/util.rs
@@ -43,17 +43,17 @@ use std::{thread, panic};
 
 pub fn diagnostics_registry() -> Registry {
     let mut all_errors = Vec::new();
-    all_errors.extend_from_slice(&rustc::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_typeck::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_resolve::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_privacy::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_typeck::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_resolve::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_privacy::error_codes::DIAGNOSTICS);
     // FIXME: need to figure out a way to get these back in here
     // all_errors.extend_from_slice(get_codegen_backend(sess).diagnostics());
-    all_errors.extend_from_slice(&rustc_metadata::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_passes::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_plugin::DIAGNOSTICS);
-    all_errors.extend_from_slice(&rustc_mir::DIAGNOSTICS);
-    all_errors.extend_from_slice(&syntax::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_metadata::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_passes::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_plugin::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_mir::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&syntax::error_codes::DIAGNOSTICS);
 
     Registry::new(&all_errors)
 }
diff --git a/src/librustc_lint/error_codes.rs b/src/librustc_lint/error_codes.rs
index d7c39b780bf..ea2e1d9ecc5 100644
--- a/src/librustc_lint/error_codes.rs
+++ b/src/librustc_lint/error_codes.rs
@@ -1,5 +1,4 @@
-use syntax::register_diagnostics;
-
-register_diagnostics! {
+syntax::register_diagnostics! {
+;
     E0721, // `await` keyword
 }
diff --git a/src/librustc_metadata/error_codes.rs b/src/librustc_metadata/error_codes.rs
index 4d2c0291ad3..cd8e95e6c3a 100644
--- a/src/librustc_metadata/error_codes.rs
+++ b/src/librustc_metadata/error_codes.rs
@@ -1,6 +1,4 @@
-use syntax::{register_diagnostics, register_long_diagnostics};
-
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 E0454: r##"
 A link name was given with an empty name. Erroneous code example:
 
@@ -84,10 +82,7 @@ You need to link your code to the relevant crate in order to be able to use it
 (through Cargo or the `-L` option of rustc example). Plugins are crates as
 well, and you link to them the same way.
 "##,
-
-}
-
-register_diagnostics! {
+;
     E0456, // plugin `..` is not available for triple `..`
     E0457, // plugin `..` only found in rlib format, but must be available...
     E0514, // metadata version mismatch
diff --git a/src/librustc_metadata/lib.rs b/src/librustc_metadata/lib.rs
index c96d02d9b37..3ab7d372461 100644
--- a/src/librustc_metadata/lib.rs
+++ b/src/librustc_metadata/lib.rs
@@ -23,7 +23,7 @@ extern crate rustc;
 #[macro_use]
 extern crate rustc_data_structures;
 
-mod error_codes;
+pub mod error_codes;
 
 mod index;
 mod encoder;
@@ -68,5 +68,3 @@ pub fn validate_crate_name(
         sess.unwrap().abort_if_errors();
     }
 }
-
-__build_diagnostic_array! { librustc_metadata, DIAGNOSTICS }
diff --git a/src/librustc_mir/error_codes.rs b/src/librustc_mir/error_codes.rs
index 86c263a447b..74b3eff0906 100644
--- a/src/librustc_mir/error_codes.rs
+++ b/src/librustc_mir/error_codes.rs
@@ -1,4 +1,4 @@
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 
 
 E0001: r##"
@@ -2448,9 +2448,9 @@ information.
 
 There are some known bugs that trigger this message.
 "##,
-}
 
-register_diagnostics! {
+;
+
 //  E0298, // cannot compare constants
 //  E0299, // mismatched types between arms
 //  E0471, // constant evaluation error (in pattern)
diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs
index cccf7b9545b..7a5db4fc19d 100644
--- a/src/librustc_mir/lib.rs
+++ b/src/librustc_mir/lib.rs
@@ -32,7 +32,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #[macro_use] extern crate rustc_data_structures;
 #[macro_use] extern crate syntax;
 
-mod error_codes;
+pub mod error_codes;
 
 mod borrow_check;
 mod build;
@@ -62,5 +62,3 @@ pub fn provide(providers: &mut Providers<'_>) {
     };
     providers.type_name = interpret::type_name;
 }
-
-__build_diagnostic_array! { librustc_mir, DIAGNOSTICS }
diff --git a/src/librustc_passes/error_codes.rs b/src/librustc_passes/error_codes.rs
index a30cd8a627f..af07c790e2a 100644
--- a/src/librustc_passes/error_codes.rs
+++ b/src/librustc_passes/error_codes.rs
@@ -1,6 +1,4 @@
-use syntax::{register_diagnostics, register_long_diagnostics};
-
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 /*
 E0014: r##"
 Constants can only be initialized by a constant value or, in a future
@@ -320,10 +318,8 @@ async fn foo() {}
 ```
 
 Switch to the Rust 2018 edition to use `async fn`.
-"##
-}
-
-register_diagnostics! {
+"##,
+;
     E0226, // only a single explicit lifetime bound is permitted
     E0472, // asm! is unsupported on this target
     E0561, // patterns aren't allowed in function pointer types
diff --git a/src/librustc_passes/lib.rs b/src/librustc_passes/lib.rs
index 5614b570b92..2070f306112 100644
--- a/src/librustc_passes/lib.rs
+++ b/src/librustc_passes/lib.rs
@@ -18,7 +18,7 @@ extern crate rustc;
 
 use rustc::ty::query::Providers;
 
-mod error_codes;
+pub mod error_codes;
 
 pub mod ast_validation;
 pub mod rvalue_promotion;
@@ -26,8 +26,6 @@ pub mod hir_stats;
 pub mod layout_test;
 pub mod loops;
 
-__build_diagnostic_array! { librustc_passes, DIAGNOSTICS }
-
 pub fn provide(providers: &mut Providers<'_>) {
     rvalue_promotion::provide(providers);
     loops::provide(providers);
diff --git a/src/librustc_plugin/error_codes.rs b/src/librustc_plugin/error_codes.rs
index b5f6a8d905d..7b3f01c0ee1 100644
--- a/src/librustc_plugin/error_codes.rs
+++ b/src/librustc_plugin/error_codes.rs
@@ -1,9 +1,4 @@
-use syntax::{register_diagnostics, register_long_diagnostics};
-
-register_long_diagnostics! {
-
-}
-
-register_diagnostics! {
-    E0498  // malformed plugin attribute
+syntax::register_diagnostics! {
+;
+    E0498,  // malformed plugin attribute
 }
diff --git a/src/librustc_plugin/lib.rs b/src/librustc_plugin/lib.rs
index 952bc9fff6a..1cf01d481e4 100644
--- a/src/librustc_plugin/lib.rs
+++ b/src/librustc_plugin/lib.rs
@@ -60,9 +60,7 @@
 
 pub use registry::Registry;
 
-mod error_codes;
+pub mod error_codes;
 pub mod registry;
 pub mod load;
 pub mod build;
-
-__build_diagnostic_array! { librustc_plugin, DIAGNOSTICS }
diff --git a/src/librustc_privacy/error_codes.rs b/src/librustc_privacy/error_codes.rs
index 70a799d426a..67066466f1d 100644
--- a/src/librustc_privacy/error_codes.rs
+++ b/src/librustc_privacy/error_codes.rs
@@ -1,4 +1,4 @@
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 
 E0445: r##"
 A private trait was used on a public type parameter bound. Erroneous code
@@ -154,8 +154,5 @@ let f = Bar::Foo::new(); // ok!
 ```
 "##,
 
-}
-
-register_diagnostics! {
 //  E0450, moved into resolve
 }
diff --git a/src/librustc_privacy/lib.rs b/src/librustc_privacy/lib.rs
index 146058963b6..28ef3b794ba 100644
--- a/src/librustc_privacy/lib.rs
+++ b/src/librustc_privacy/lib.rs
@@ -31,7 +31,7 @@ use syntax_pos::Span;
 use std::{cmp, fmt, mem};
 use std::marker::PhantomData;
 
-mod error_codes;
+pub mod error_codes;
 
 ////////////////////////////////////////////////////////////////////////////////
 /// Generic infrastructure used to implement specific visitors below.
@@ -2035,5 +2035,3 @@ fn check_private_in_public(tcx: TyCtxt<'_>, krate: CrateNum) {
     };
     krate.visit_all_item_likes(&mut DeepVisitor::new(&mut visitor));
 }
-
-__build_diagnostic_array! { librustc_privacy, DIAGNOSTICS }
diff --git a/src/librustc_resolve/error_codes.rs b/src/librustc_resolve/error_codes.rs
index 1faaf97e981..adbff67cc8d 100644
--- a/src/librustc_resolve/error_codes.rs
+++ b/src/librustc_resolve/error_codes.rs
@@ -1,9 +1,7 @@
-use syntax::{register_diagnostics, register_long_diagnostics};
-
 // Error messages for EXXXX errors.  Each message should start and end with a
 // new line, and be wrapped to 80 characters.  In vim you can `:set tw=80` and
 // use `gq` to wrap paragraphs. Use `:set tw=0` to disable.
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 
 E0128: r##"
 Type parameter defaults can only use parameters that occur before them.
@@ -1662,10 +1660,7 @@ fn const_id<T, const N: T>() -> T { // error: const parameter
 }
 ```
 "##,
-
-}
-
-register_diagnostics! {
+;
 //  E0153, unused error code
 //  E0157, unused error code
 //  E0257,
diff --git a/src/librustc_resolve/late.rs b/src/librustc_resolve/late.rs
index e15d02a9f7e..4570bbbe339 100644
--- a/src/librustc_resolve/late.rs
+++ b/src/librustc_resolve/late.rs
@@ -286,18 +286,18 @@ impl<'a> PathSource<'a> {
     }
 
     fn error_code(self, has_unexpected_resolution: bool) -> &'static str {
-        __diagnostic_used!(E0404);
-        __diagnostic_used!(E0405);
-        __diagnostic_used!(E0412);
-        __diagnostic_used!(E0422);
-        __diagnostic_used!(E0423);
-        __diagnostic_used!(E0425);
-        __diagnostic_used!(E0531);
-        __diagnostic_used!(E0532);
-        __diagnostic_used!(E0573);
-        __diagnostic_used!(E0574);
-        __diagnostic_used!(E0575);
-        __diagnostic_used!(E0576);
+        syntax::diagnostic_used!(E0404);
+        syntax::diagnostic_used!(E0405);
+        syntax::diagnostic_used!(E0412);
+        syntax::diagnostic_used!(E0422);
+        syntax::diagnostic_used!(E0423);
+        syntax::diagnostic_used!(E0425);
+        syntax::diagnostic_used!(E0531);
+        syntax::diagnostic_used!(E0532);
+        syntax::diagnostic_used!(E0573);
+        syntax::diagnostic_used!(E0574);
+        syntax::diagnostic_used!(E0575);
+        syntax::diagnostic_used!(E0576);
         match (self, has_unexpected_resolution) {
             (PathSource::Trait(_), true) => "E0404",
             (PathSource::Trait(_), false) => "E0405",
diff --git a/src/librustc_resolve/late/diagnostics.rs b/src/librustc_resolve/late/diagnostics.rs
index a822fa049ca..0c86d8494fd 100644
--- a/src/librustc_resolve/late/diagnostics.rs
+++ b/src/librustc_resolve/late/diagnostics.rs
@@ -113,7 +113,7 @@ impl<'a> LateResolutionVisitor<'a, '_> {
 
         // Emit special messages for unresolved `Self` and `self`.
         if is_self_type(path, ns) {
-            __diagnostic_used!(E0411);
+            syntax::diagnostic_used!(E0411);
             err.code(DiagnosticId::Error("E0411".into()));
             err.span_label(span, format!("`Self` is only available in impls, traits, \
                                           and type definitions"));
@@ -122,7 +122,7 @@ impl<'a> LateResolutionVisitor<'a, '_> {
         if is_self_value(path, ns) {
             debug!("smart_resolve_path_fragment: E0424, source={:?}", source);
 
-            __diagnostic_used!(E0424);
+            syntax::diagnostic_used!(E0424);
             err.code(DiagnosticId::Error("E0424".into()));
             err.span_label(span, match source {
                 PathSource::Pat => {
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index 875ae449d94..6ba08ccef03 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -67,9 +67,7 @@ use macros::{LegacyBinding, LegacyScope};
 
 type Res = def::Res<NodeId>;
 
-// N.B., this module needs to be declared first so diagnostics are
-// registered before they are used.
-mod error_codes;
+pub mod error_codes;
 mod diagnostics;
 mod late;
 mod macros;
@@ -2817,5 +2815,3 @@ impl CrateLint {
         }
     }
 }
-
-__build_diagnostic_array! { librustc_resolve, DIAGNOSTICS }
diff --git a/src/librustc_typeck/error_codes.rs b/src/librustc_typeck/error_codes.rs
index 4d960b416ff..e11dcfafb8f 100644
--- a/src/librustc_typeck/error_codes.rs
+++ b/src/librustc_typeck/error_codes.rs
@@ -1,6 +1,6 @@
 // ignore-tidy-filelength
 
-register_long_diagnostics! {
+syntax::register_diagnostics! {
 
 E0023: r##"
 A pattern used to match against an enum variant must provide a sub-pattern for
@@ -4870,10 +4870,7 @@ fn foo_recursive(n: usize) -> Pin<Box<dyn Future<Output = ()>>> {
 The `Box<...>` ensures that the result is of known size,
 and the pin is required to keep it in the same place in memory.
 "##,
-
-}  // (end of detailed error messages)
-
-register_diagnostics! {
+;
 //  E0035, merged into E0087/E0089
 //  E0036, merged into E0087/E0089
 //  E0068,
diff --git a/src/librustc_typeck/lib.rs b/src/librustc_typeck/lib.rs
index 9d9a9d9b559..91c7522280a 100644
--- a/src/librustc_typeck/lib.rs
+++ b/src/librustc_typeck/lib.rs
@@ -78,9 +78,7 @@ This API is completely unstable and subject to change.
 
 #[macro_use] extern crate rustc;
 
-// N.B., this module needs to be declared first so diagnostics are
-// registered before they are used.
-mod error_codes;
+pub mod error_codes;
 
 mod astconv;
 mod check;
@@ -389,5 +387,3 @@ pub fn hir_trait_to_predicates<'tcx>(
 
     bounds
 }
-
-__build_diagnostic_array! { librustc_typeck, DIAGNOSTICS }
diff --git a/src/librustc_typeck/structured_errors.rs b/src/librustc_typeck/structured_errors.rs
index 3e3eab8cf4c..273a36edc56 100644
--- a/src/librustc_typeck/structured_errors.rs
+++ b/src/librustc_typeck/structured_errors.rs
@@ -48,7 +48,7 @@ impl<'tcx> StructuredDiagnostic<'tcx> for VariadicError<'tcx> {
     fn session(&self) -> &Session { self.sess }
 
     fn code(&self) -> DiagnosticId {
-        __diagnostic_used!(E0617);
+        syntax::diagnostic_used!(E0617);
         DiagnosticId::Error("E0617".to_owned())
     }
 
@@ -104,7 +104,7 @@ impl<'tcx> StructuredDiagnostic<'tcx> for SizedUnsizedCastError<'tcx> {
     fn session(&self) -> &Session { self.sess }
 
     fn code(&self) -> DiagnosticId {
-        __diagnostic_used!(E0607);
+        syntax::diagnostic_used!(E0607);
         DiagnosticId::Error("E0607".to_owned())
     }
 
diff --git a/src/libsyntax/diagnostics/macros.rs b/src/libsyntax/diagnostics/macros.rs
index b754d083376..c95c5bd5d02 100644
--- a/src/libsyntax/diagnostics/macros.rs
+++ b/src/libsyntax/diagnostics/macros.rs
@@ -1,13 +1,14 @@
 #[macro_export]
-macro_rules! register_diagnostic {
-    ($code:tt, $description:tt) => (__register_diagnostic! { $code, $description });
-    ($code:tt) => (__register_diagnostic! { $code })
+macro_rules! diagnostic_used {
+    ($code:ident) => (
+        let _ = crate::error_codes::$code;
+    )
 }
 
 #[macro_export]
 macro_rules! span_fatal {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.span_fatal_with_code(
             $span,
             &format!($($message)*),
@@ -19,7 +20,7 @@ macro_rules! span_fatal {
 #[macro_export]
 macro_rules! span_err {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.span_err_with_code(
             $span,
             &format!($($message)*),
@@ -31,7 +32,7 @@ macro_rules! span_err {
 #[macro_export]
 macro_rules! span_warn {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.span_warn_with_code(
             $span,
             &format!($($message)*),
@@ -43,7 +44,7 @@ macro_rules! span_warn {
 #[macro_export]
 macro_rules! struct_err {
     ($session:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.struct_err_with_code(
             &format!($($message)*),
             $crate::errors::DiagnosticId::Error(stringify!($code).to_owned()),
@@ -54,7 +55,7 @@ macro_rules! struct_err {
 #[macro_export]
 macro_rules! span_err_or_warn {
     ($is_warning:expr, $session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         if $is_warning {
             $session.span_warn_with_code(
                 $span,
@@ -74,7 +75,7 @@ macro_rules! span_err_or_warn {
 #[macro_export]
 macro_rules! struct_span_fatal {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.struct_span_fatal_with_code(
             $span,
             &format!($($message)*),
@@ -86,7 +87,7 @@ macro_rules! struct_span_fatal {
 #[macro_export]
 macro_rules! struct_span_err {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.struct_span_err_with_code(
             $span,
             &format!($($message)*),
@@ -98,7 +99,7 @@ macro_rules! struct_span_err {
 #[macro_export]
 macro_rules! stringify_error_code {
     ($code:ident) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $crate::errors::DiagnosticId::Error(stringify!($code).to_owned())
     })
 }
@@ -117,7 +118,7 @@ macro_rules! type_error_struct {
 #[macro_export]
 macro_rules! struct_span_warn {
     ($session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         $session.struct_span_warn_with_code(
             $span,
             &format!($($message)*),
@@ -129,7 +130,7 @@ macro_rules! struct_span_warn {
 #[macro_export]
 macro_rules! struct_span_err_or_warn {
     ($is_warning:expr, $session:expr, $span:expr, $code:ident, $($message:tt)*) => ({
-        __diagnostic_used!($code);
+        $crate::diagnostic_used!($code);
         if $is_warning {
             $session.struct_span_warn_with_code(
                 $span,
@@ -169,20 +170,22 @@ macro_rules! help {
 
 #[macro_export]
 macro_rules! register_diagnostics {
-    ($($code:tt),*) => (
-        $($crate::register_diagnostic! { $code })*
+    ($($ecode:ident: $message:expr,)*) => (
+        $crate::register_diagnostics!{$($ecode:$message,)* ;}
     );
-    ($($code:tt),*,) => (
-        $($crate::register_diagnostic! { $code })*
-    )
-}
 
-#[macro_export]
-macro_rules! register_long_diagnostics {
-    ($($code:tt: $description:tt),*) => (
-        $($crate::register_diagnostic! { $code, $description })*
-    );
-    ($($code:tt: $description:tt),*,) => (
-        $($crate::register_diagnostic! { $code, $description })*
+    ($($ecode:ident: $message:expr,)* ; $($code:ident,)*) => (
+        pub static DIAGNOSTICS: &[(&str, &str)] = &[
+            $( (stringify!($ecode), $message), )*
+        ];
+
+        $(
+            #[deny(unused)]
+            pub(crate) const $ecode: &str = $message;
+        )*
+        $(
+            #[deny(unused)]
+            pub(crate) const $code: () = ();
+        )*
     )
 }
diff --git a/src/libsyntax/diagnostics/plugin.rs b/src/libsyntax/diagnostics/plugin.rs
deleted file mode 100644
index 5de39c8d14d..00000000000
--- a/src/libsyntax/diagnostics/plugin.rs
+++ /dev/null
@@ -1,185 +0,0 @@
-use std::collections::BTreeMap;
-
-use crate::ast::{self, Ident, Name};
-use crate::source_map;
-use crate::ext::base::{ExtCtxt, MacEager, MacResult};
-use crate::parse::token::{self, Token};
-use crate::ptr::P;
-use crate::symbol::kw;
-use crate::tokenstream::{TokenTree, TokenStream};
-
-use smallvec::smallvec;
-use syntax_pos::Span;
-
-pub use errors::*;
-
-// Maximum width of any line in an extended error description (inclusive).
-const MAX_DESCRIPTION_WIDTH: usize = 80;
-
-/// Error information type.
-pub struct ErrorInfo {
-    pub description: Option<Name>,
-    pub use_site: Option<Span>
-}
-
-/// Mapping from error codes to metadata.
-pub type ErrorMap = BTreeMap<Name, ErrorInfo>;
-
-pub fn expand_diagnostic_used<'cx>(ecx: &'cx mut ExtCtxt<'_>,
-                                   span: Span,
-                                   tts: TokenStream)
-                                   -> Box<dyn MacResult+'cx> {
-    assert_eq!(tts.len(), 1);
-    let code = match tts.into_trees().next() {
-        Some(TokenTree::Token(Token { kind: token::Ident(code, _), .. })) => code,
-        _ => unreachable!()
-    };
-
-    ecx.parse_sess.registered_diagnostics.with_lock(|diagnostics| {
-        match diagnostics.get_mut(&code) {
-            // Previously used errors.
-            Some(&mut ErrorInfo { description: _, use_site: Some(previous_span) }) => {
-                ecx.struct_span_warn(span, &format!(
-                    "diagnostic code {} already used", code
-                )).span_note(previous_span, "previous invocation")
-                  .emit();
-            }
-            // Newly used errors.
-            Some(ref mut info) => {
-                info.use_site = Some(span);
-            }
-            // Unregistered errors.
-            None => {
-                ecx.span_err(span, &format!(
-                    "used diagnostic code {} not registered", code
-                ));
-            }
-        }
-    });
-    MacEager::expr(ecx.expr_tuple(span, Vec::new()))
-}
-
-pub fn expand_register_diagnostic<'cx>(ecx: &'cx mut ExtCtxt<'_>,
-                                       span: Span,
-                                       tts: TokenStream)
-                                       -> Box<dyn MacResult+'cx> {
-    assert!(tts.len() == 1 || tts.len() == 3);
-    let mut cursor = tts.into_trees();
-    let code = match cursor.next() {
-        Some(TokenTree::Token(Token { kind: token::Ident(code, _), .. })) => code,
-        _ => unreachable!()
-    };
-    let description = match  (cursor.next(), cursor.next()) {
-        (None, None) => None,
-        (
-            Some(TokenTree::Token(Token { kind: token::Comma, .. })),
-            Some(TokenTree::Token(Token { kind: token::Literal(token::Lit { symbol, .. }), ..}))
-        ) => {
-            Some(symbol)
-        },
-        _ => unreachable!()
-    };
-
-    // Check that the description starts and ends with a newline and doesn't
-    // overflow the maximum line width.
-    description.map(|raw_msg| {
-        let msg = raw_msg.as_str();
-        if !msg.starts_with("\n") || !msg.ends_with("\n") {
-            ecx.span_err(span, &format!(
-                "description for error code {} doesn't start and end with a newline",
-                code
-            ));
-        }
-
-        // URLs can be unavoidably longer than the line limit, so we allow them.
-        // Allowed format is: `[name]: https://www.rust-lang.org/`
-        let is_url = |l: &str| l.starts_with("[") && l.contains("]:") && l.contains("http");
-
-        if msg.lines().any(|line| line.len() > MAX_DESCRIPTION_WIDTH && !is_url(line)) {
-            ecx.span_err(span, &format!(
-                "description for error code {} contains a line longer than {} characters.\n\
-                 if you're inserting a long URL use the footnote style to bypass this check.",
-                code, MAX_DESCRIPTION_WIDTH
-            ));
-        }
-    });
-    // Add the error to the map.
-    ecx.parse_sess.registered_diagnostics.with_lock(|diagnostics| {
-        let info = ErrorInfo {
-            description,
-            use_site: None
-        };
-        if diagnostics.insert(code, info).is_some() {
-            ecx.span_err(span, &format!(
-                "diagnostic code {} already registered", code
-            ));
-        }
-    });
-
-    MacEager::items(smallvec![])
-}
-
-pub fn expand_build_diagnostic_array<'cx>(ecx: &'cx mut ExtCtxt<'_>,
-                                          span: Span,
-                                          tts: TokenStream)
-                                          -> Box<dyn MacResult+'cx> {
-    assert_eq!(tts.len(), 3);
-    let ident = match tts.into_trees().nth(2) {
-        // DIAGNOSTICS ident.
-        Some(TokenTree::Token(Token { kind: token::Ident(name, _), span }))
-        => Ident::new(name, span),
-        _ => unreachable!()
-    };
-
-    // Construct the output expression.
-    let (count, expr) =
-        ecx.parse_sess.registered_diagnostics.with_lock(|diagnostics| {
-            let descriptions: Vec<P<ast::Expr>> =
-                diagnostics.iter().filter_map(|(&code, info)| {
-                    info.description.map(|description| {
-                        ecx.expr_tuple(span, vec![
-                            ecx.expr_str(span, code),
-                            ecx.expr_str(span, description)
-                        ])
-                    })
-                }).collect();
-            (descriptions.len(), ecx.expr_vec(span, descriptions))
-        });
-
-    let static_ = ecx.lifetime(span, Ident::with_dummy_span(kw::StaticLifetime));
-    let ty_str = ecx.ty_rptr(
-        span,
-        ecx.ty_ident(span, ecx.ident_of("str")),
-        Some(static_),
-        ast::Mutability::Immutable,
-    );
-
-    let ty = ecx.ty(
-        span,
-        ast::TyKind::Array(
-            ecx.ty(
-                span,
-                ast::TyKind::Tup(vec![ty_str.clone(), ty_str])
-            ),
-            ast::AnonConst {
-                id: ast::DUMMY_NODE_ID,
-                value: ecx.expr_usize(span, count),
-            },
-        ),
-    );
-
-    MacEager::items(smallvec![
-        P(ast::Item {
-            ident,
-            attrs: Vec::new(),
-            id: ast::DUMMY_NODE_ID,
-            node: ast::ItemKind::Const(
-                ty,
-                expr,
-            ),
-            vis: source_map::respan(span.shrink_to_lo(), ast::VisibilityKind::Public),
-            span,
-            tokens: None,
-        })
-    ])
-}
diff --git a/src/libsyntax/error_codes.rs b/src/libsyntax/error_codes.rs
index 76b2575bfd6..9925dd8ada0 100644
--- a/src/libsyntax/error_codes.rs
+++ b/src/libsyntax/error_codes.rs
@@ -421,9 +421,8 @@ Delete the offending feature attribute, or add it to the list of allowed
 features in the `-Z allow_features` flag.
 "##,
 
-}
+;
 
-register_diagnostics! {
     E0539, // incorrect meta item
     E0540, // multiple rustc_deprecated attributes
     E0542, // missing 'since'
@@ -447,7 +446,7 @@ register_diagnostics! {
     // attribute
     E0630,
     E0693, // incorrect `repr(align)` attribute format
-    E0694, // an unknown tool name found in scoped attributes
+//  E0694, // an unknown tool name found in scoped attributes
     E0703, // invalid ABI
     E0717, // rustc_promotable without stability attribute
 }
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 1741932c1b8..75ce306df80 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -123,11 +123,8 @@ scoped_tls::scoped_thread_local!(pub static GLOBALS: Globals);
 pub mod diagnostics {
     #[macro_use]
     pub mod macros;
-    pub mod plugin;
 }
 
-// N.B., this module needs to be declared first so diagnostics are
-// registered before they are used.
 pub mod error_codes;
 
 pub mod util {
@@ -182,5 +179,3 @@ pub mod ext {
 }
 
 pub mod early_buffered_lints;
-
-__build_diagnostic_array! { libsyntax, DIAGNOSTICS }
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index b1af4806e2d..981f5f1f7b0 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -8,7 +8,6 @@ use crate::parse::parser::Parser;
 use crate::parse::parser::emit_unclosed_delims;
 use crate::parse::token::TokenKind;
 use crate::tokenstream::{TokenStream, TokenTree};
-use crate::diagnostics::plugin::ErrorMap;
 use crate::print::pprust;
 use crate::symbol::Symbol;
 
@@ -64,8 +63,6 @@ pub struct ParseSess {
     pub missing_fragment_specifiers: Lock<FxHashSet<Span>>,
     /// Places where raw identifiers were used. This is used for feature-gating raw identifiers.
     pub raw_identifier_spans: Lock<Vec<Span>>,
-    /// The registered diagnostics codes.
-    crate registered_diagnostics: Lock<ErrorMap>,
     /// Used to determine and report recursive module inclusions.
     included_mod_stack: Lock<Vec<PathBuf>>,
     source_map: Lrc<SourceMap>,
@@ -95,7 +92,6 @@ impl ParseSess {
             config: FxHashSet::default(),
             missing_fragment_specifiers: Lock::new(FxHashSet::default()),
             raw_identifier_spans: Lock::new(Vec::new()),
-            registered_diagnostics: Lock::new(ErrorMap::new()),
             included_mod_stack: Lock::new(vec![]),
             source_map,
             buffered_lints: Lock::new(vec![]),
diff --git a/src/libsyntax_ext/error_codes.rs b/src/libsyntax_ext/error_codes.rs
index 49808fc0b60..2bc990574f7 100644
--- a/src/libsyntax_ext/error_codes.rs
+++ b/src/libsyntax_ext/error_codes.rs
@@ -1,5 +1,3 @@
-use syntax::register_long_diagnostics;
-
 // Error messages for EXXXX errors.
 // Each message should start and end with a new line, and be wrapped to 80
 // characters.  In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use