Auto merge of #120576 - nnethercote:merge-Diagnostic-DiagnosticBuilder, r=davidtwco

Overhaul `Diagnostic` and `DiagnosticBuilder`

Implements the first part of https://github.com/rust-lang/compiler-team/issues/722, which moves functionality and use away from `Diagnostic`, onto `DiagnosticBuilder`.

Likely follow-ups:
- Move things around, because this PR was written to minimize diff size, so some things end up in sub-optimal places. E.g. `DiagnosticBuilder` has impls in both `diagnostic.rs` and `diagnostic_builder.rs`.
- Rename `Diagnostic` as `DiagInner` and `DiagnosticBuilder` as `Diag`.

r? `@davidtwco`

compiler/rustc_expand/src/base.rs

@@ -1176,6 +1176,8 @@ impl<'a> ExtCtxt<'a> {
         for (span, notes) in self.expansions.iter() {
             let mut db = self.dcx().create_note(errors::TraceMacro { span: *span });
             for note in notes {
+                // FIXME: make this translatable
+                #[allow(rustc::untranslatable_diagnostic)]
                 db.note(note.clone());
             }
             db.emit();

compiler/rustc_expand/src/config.rs

@@ -384,6 +384,7 @@ impl<'a> StripUnconfigured<'a> {
             );
 
             if attr.is_doc_comment() {
+                #[allow(rustc::untranslatable_diagnostic)]
                 err.help("`///` is for documentation comments. For a plain comment, use `//`.");
             }
 

compiler/rustc_expand/src/mbe/diagnostics.rs

@@ -7,7 +7,7 @@ use crate::mbe::{
 use rustc_ast::token::{self, Token, TokenKind};
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast_pretty::pprust;
-use rustc_errors::{Applicability, DiagCtxt, Diagnostic, DiagnosticBuilder, DiagnosticMessage};
+use rustc_errors::{Applicability, DiagCtxt, DiagnosticBuilder, DiagnosticMessage};
 use rustc_parse::parser::{Parser, Recovery};
 use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::Ident;
@@ -285,7 +285,11 @@ pub(super) fn emit_frag_parse_err(
     e.emit();
 }
 
-pub(crate) fn annotate_err_with_kind(err: &mut Diagnostic, kind: AstFragmentKind, span: Span) {
+pub(crate) fn annotate_err_with_kind(
+    err: &mut DiagnosticBuilder<'_>,
+    kind: AstFragmentKind,
+    span: Span,
+) {
     match kind {
         AstFragmentKind::Ty => {
             err.span_label(span, "this macro call doesn't expand to a type");
@@ -313,7 +317,7 @@ enum ExplainDocComment {
 
 pub(super) fn annotate_doc_comment(
     dcx: &DiagCtxt,
-    err: &mut Diagnostic,
+    err: &mut DiagnosticBuilder<'_>,
     sm: &SourceMap,
     span: Span,
 ) {

compiler/rustc_expand/src/proc_macro_server.rs

@@ -10,7 +10,7 @@ use rustc_ast::util::literal::escape_byte_str_symbol;
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
-use rustc_errors::{ErrorGuaranteed, MultiSpan, PResult};
+use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed, MultiSpan, PResult};
 use rustc_parse::lexer::nfc_normalize;
 use rustc_parse::parse_stream_from_source_str;
 use rustc_session::parse::ParseSess;
@@ -509,13 +509,14 @@ impl server::FreeFunctions for Rustc<'_, '_> {
     }
 
     fn emit_diagnostic(&mut self, diagnostic: Diagnostic<Self::Span>) {
-        let mut diag =
-            rustc_errors::Diagnostic::new(diagnostic.level.to_internal(), diagnostic.message);
+        let message = rustc_errors::DiagnosticMessage::from(diagnostic.message);
+        let mut diag: DiagnosticBuilder<'_, rustc_errors::ErrorGuaranteed> =
+            DiagnosticBuilder::new(&self.sess().dcx, diagnostic.level.to_internal(), message);
         diag.span(MultiSpan::from_spans(diagnostic.spans));
         for child in diagnostic.children {
             diag.sub(child.level.to_internal(), child.message, MultiSpan::from_spans(child.spans));
         }
-        self.sess().dcx.emit_diagnostic(diag);
+        diag.emit();
     }
 }