Stop using `String` for error codes.

Error codes are integers, but `String` is used everywhere to represent
them. Gross!

This commit introduces `ErrCode`, an integral newtype for error codes,
replacing `String`. It also introduces a constant for every error code,
e.g. `E0123`, and removes the `error_code!` macro. The constants are
imported wherever used with `use rustc_errors::codes::*`.

With the old code, we have three different ways to specify an error code
at a use point:
```
error_code!(E0123)  // macro call

struct_span_code_err!(dcx, span, E0123, "msg");  // bare ident arg to macro call

\#[diag(name, code = "E0123")]  // string
struct Diag;
```

With the new code, they all use the `E0123` constant.
```
E0123  // constant

struct_span_code_err!(dcx, span, E0123, "msg");  // constant

\#[diag(name, code = E0123)]  // constant
struct Diag;
```

The commit also changes the structure of the error code definitions:
- `rustc_error_codes` now just defines a higher-order macro listing the
  used error codes and nothing else.
- Because that's now the only thing in the `rustc_error_codes` crate, I
  moved it into the `lib.rs` file and removed the `error_codes.rs` file.
- `rustc_errors` uses that macro to define everything, e.g. the error
  code constants and the `DIAGNOSTIC_TABLES`. This is in its new
  `codes.rs` file.

1 files changed, 14 insertions, 14 deletions

diff --git a/compiler/rustc_metadata/src/errors.rs b/compiler/rustc_metadata/src/errors.rs
index 27c26d31781..d17bf0cf708 100644
--- a/compiler/rustc_metadata/src/errors.rs
+++ b/compiler/rustc_metadata/src/errors.rs
@@ -4,7 +4,7 @@ use std::{
 };
 
 use rustc_errors::{
-    error_code, DiagCtxt, DiagnosticBuilder, EmissionGuarantee, IntoDiagnostic, Level,
+    codes::*, DiagCtxt, DiagnosticBuilder, EmissionGuarantee, IntoDiagnostic, Level,
 };
 use rustc_macros::Diagnostic;
 use rustc_session::config;
@@ -122,7 +122,7 @@ pub struct WasmImportForm {
 }
 
 #[derive(Diagnostic)]
-#[diag(metadata_empty_link_name, code = "E0454")]
+#[diag(metadata_empty_link_name, code = E0454)]
 pub struct EmptyLinkName {
     #[primary_span]
     #[label]
@@ -130,21 +130,21 @@ pub struct EmptyLinkName {
 }
 
 #[derive(Diagnostic)]
-#[diag(metadata_link_framework_apple, code = "E0455")]
+#[diag(metadata_link_framework_apple, code = E0455)]
 pub struct LinkFrameworkApple {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(metadata_framework_only_windows, code = "E0455")]
+#[diag(metadata_framework_only_windows, code = E0455)]
 pub struct FrameworkOnlyWindows {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(metadata_unknown_link_kind, code = "E0458")]
+#[diag(metadata_unknown_link_kind, code = E0458)]
 pub struct UnknownLinkKind<'a> {
     #[primary_span]
     #[label]
@@ -239,7 +239,7 @@ pub struct IncompatibleWasmLink {
 }
 
 #[derive(Diagnostic)]
-#[diag(metadata_link_requires_name, code = "E0459")]
+#[diag(metadata_link_requires_name, code = E0459)]
 pub struct LinkRequiresName {
     #[primary_span]
     #[label]
@@ -502,7 +502,7 @@ impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for MultipleCandidates {
         let mut diag = DiagnosticBuilder::new(dcx, level, fluent::metadata_multiple_candidates);
         diag.arg("crate_name", self.crate_name);
         diag.arg("flavor", self.flavor);
-        diag.code(error_code!(E0464));
+        diag.code(E0464);
         diag.span(self.span);
         for (i, candidate) in self.candidates.iter().enumerate() {
             diag.note(format!("candidate #{}: {}", i + 1, candidate.display()));
@@ -512,7 +512,7 @@ impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for MultipleCandidates {
 }
 
 #[derive(Diagnostic)]
-#[diag(metadata_symbol_conflicts_current, code = "E0519")]
+#[diag(metadata_symbol_conflicts_current, code = E0519)]
 pub struct SymbolConflictsCurrent {
     #[primary_span]
     pub span: Span,
@@ -537,7 +537,7 @@ pub struct DlError {
 }
 
 #[derive(Diagnostic)]
-#[diag(metadata_newer_crate_version, code = "E0460")]
+#[diag(metadata_newer_crate_version, code = E0460)]
 #[note]
 #[note(metadata_found_crate_versions)]
 pub struct NewerCrateVersion {
@@ -549,7 +549,7 @@ pub struct NewerCrateVersion {
 }
 
 #[derive(Diagnostic)]
-#[diag(metadata_no_crate_with_triple, code = "E0461")]
+#[diag(metadata_no_crate_with_triple, code = E0461)]
 #[note(metadata_found_crate_versions)]
 pub struct NoCrateWithTriple<'a> {
     #[primary_span]
@@ -561,7 +561,7 @@ pub struct NoCrateWithTriple<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(metadata_found_staticlib, code = "E0462")]
+#[diag(metadata_found_staticlib, code = E0462)]
 #[note(metadata_found_crate_versions)]
 #[help]
 pub struct FoundStaticlib {
@@ -573,7 +573,7 @@ pub struct FoundStaticlib {
 }
 
 #[derive(Diagnostic)]
-#[diag(metadata_incompatible_rustc, code = "E0514")]
+#[diag(metadata_incompatible_rustc, code = E0514)]
 #[note(metadata_found_crate_versions)]
 #[help]
 pub struct IncompatibleRustc {
@@ -598,7 +598,7 @@ impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for InvalidMetadataFiles {
         let mut diag = DiagnosticBuilder::new(dcx, level, fluent::metadata_invalid_meta_files);
         diag.arg("crate_name", self.crate_name);
         diag.arg("add_info", self.add_info);
-        diag.code(error_code!(E0786));
+        diag.code(E0786);
         diag.span(self.span);
         for crate_rejection in self.crate_rejections {
             diag.note(crate_rejection);
@@ -627,7 +627,7 @@ impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for CannotFindCrate {
         diag.arg("current_crate", self.current_crate);
         diag.arg("add_info", self.add_info);
         diag.arg("locator_triple", self.locator_triple.triple());
-        diag.code(error_code!(E0463));
+        diag.code(E0463);
         diag.span(self.span);
         if (self.crate_name == sym::std || self.crate_name == sym::core)
             && self.locator_triple != TargetTriple::from_triple(config::host_triple())