Use a dedicated type instead of a reference for the diagnostic context

This paves the way for tracking more state (e.g. error tainting) in the diagnostic context handle

compiler/rustc_expand/src/base.rs

@@ -12,7 +12,7 @@ use rustc_ast::{self as ast, AttrVec, Attribute, HasAttrs, Item, NodeId, PatKind
 use rustc_attr::{self as attr, Deprecation, Stability};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::sync::{self, Lrc};
-use rustc_errors::{DiagCtxt, ErrorGuaranteed, PResult};
+use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed, PResult};
 use rustc_feature::Features;
 use rustc_lint_defs::{BufferedEarlyLint, RegisteredTools};
 use rustc_parse::{parser::Parser, MACRO_ARGUMENTS};
@@ -1135,7 +1135,7 @@ impl<'a> ExtCtxt<'a> {
         }
     }
 
-    pub fn dcx(&self) -> &'a DiagCtxt {
+    pub fn dcx(&self) -> DiagCtxtHandle<'a> {
         self.sess.dcx()
     }
 
@@ -1256,7 +1256,7 @@ pub fn resolve_path(sess: &Session, path: impl Into<PathBuf>, span: Span) -> PRe
 }
 
 pub fn parse_macro_name_and_helper_attrs(
-    dcx: &rustc_errors::DiagCtxt,
+    dcx: DiagCtxtHandle<'_>,
     attr: &Attribute,
     macro_type: &str,
 ) -> Option<(Symbol, Vec<Symbol>)> {

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, Diag, DiagCtxt, DiagMessage};
+use rustc_errors::{Applicability, Diag, DiagCtxtHandle, DiagMessage};
 use rustc_macros::Subdiagnostic;
 use rustc_parse::parser::{Parser, Recovery};
 use rustc_span::source_map::SourceMap;
@@ -324,7 +324,12 @@ enum ExplainDocComment {
     },
 }
 
-pub(super) fn annotate_doc_comment(dcx: &DiagCtxt, err: &mut Diag<'_>, sm: &SourceMap, span: Span) {
+pub(super) fn annotate_doc_comment(
+    dcx: DiagCtxtHandle<'_>,
+    err: &mut Diag<'_>,
+    sm: &SourceMap,
+    span: Span,
+) {
     if let Ok(src) = sm.span_to_snippet(span) {
         if src.starts_with("///") || src.starts_with("/**") {
             err.subdiagnostic(dcx, ExplainDocComment::Outer { span });

compiler/rustc_expand/src/mbe/transcribe.rs

@@ -10,7 +10,7 @@ use rustc_ast::token::IdentIsRaw;
 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
 use rustc_ast::tokenstream::{DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree};
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::{pluralize, Diag, DiagCtxt, PResult};
+use rustc_errors::{pluralize, Diag, DiagCtxtHandle, PResult};
 use rustc_parse::parser::ParseNtResult;
 use rustc_session::parse::ParseSess;
 use rustc_span::hygiene::{LocalExpnId, Transparency};
@@ -571,7 +571,7 @@ fn lockstep_iter_size(
 /// * `[ $( ${count(foo, 1)} ),* ]` will return an error because `${count(foo, 1)}` is
 ///   declared inside a single repetition and the index `1` implies two nested repetitions.
 fn count_repetitions<'a>(
-    dcx: &'a DiagCtxt,
+    dcx: DiagCtxtHandle<'a>,
     depth_user: usize,
     mut matched: &NamedMatch,
     repeats: &[(usize, usize)],
@@ -632,7 +632,7 @@ fn count_repetitions<'a>(
 
 /// Returns a `NamedMatch` item declared on the LHS given an arbitrary [Ident]
 fn matched_from_ident<'ctx, 'interp, 'rslt>(
-    dcx: &'ctx DiagCtxt,
+    dcx: DiagCtxtHandle<'ctx>,
     ident: Ident,
     interp: &'interp FxHashMap<MacroRulesNormalizedIdent, NamedMatch>,
 ) -> PResult<'ctx, &'rslt NamedMatch>
@@ -646,7 +646,7 @@ where
 
 /// Used by meta-variable expressions when an user input is out of the actual declared bounds. For
 /// example, index(999999) in an repetition of only three elements.
-fn out_of_bounds_err<'a>(dcx: &'a DiagCtxt, max: usize, span: Span, ty: &str) -> Diag<'a> {
+fn out_of_bounds_err<'a>(dcx: DiagCtxtHandle<'a>, max: usize, span: Span, ty: &str) -> Diag<'a> {
     let msg = if max == 0 {
         format!(
             "meta-variable expression `{ty}` with depth parameter \
@@ -662,7 +662,7 @@ fn out_of_bounds_err<'a>(dcx: &'a DiagCtxt, max: usize, span: Span, ty: &str) ->
 }
 
 fn transcribe_metavar_expr<'a>(
-    dcx: &'a DiagCtxt,
+    dcx: DiagCtxtHandle<'a>,
     expr: &MetaVarExpr,
     interp: &FxHashMap<MacroRulesNormalizedIdent, NamedMatch>,
     marker: &mut Marker,
@@ -730,7 +730,7 @@ fn transcribe_metavar_expr<'a>(
 
 /// Extracts an identifier that can be originated from a `$var:ident` variable or from a token tree.
 fn extract_ident<'a>(
-    dcx: &'a DiagCtxt,
+    dcx: DiagCtxtHandle<'a>,
     ident: Ident,
     interp: &FxHashMap<MacroRulesNormalizedIdent, NamedMatch>,
 ) -> PResult<'a, String> {