diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 6232c875ee81e..f77f53a131090 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -94,8 +94,7 @@ mod styled_buffer;
 mod tests;
 pub mod translation;
 
-pub type PErr<'a> = Diag<'a>;
-pub type PResult<'a, T> = Result<T, PErr<'a>>;
+pub type PResult<'a, T> = Result<T, Diag<'a>>;
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
diff --git a/compiler/rustc_parse/src/lexer/tokentrees.rs b/compiler/rustc_parse/src/lexer/tokentrees.rs
index c6c9eb3b0b263..ee38f16d4ecd5 100644
--- a/compiler/rustc_parse/src/lexer/tokentrees.rs
+++ b/compiler/rustc_parse/src/lexer/tokentrees.rs
@@ -1,7 +1,7 @@
 use rustc_ast::token::{self, Delimiter, Token};
 use rustc_ast::tokenstream::{DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree};
 use rustc_ast_pretty::pprust::token_to_string;
-use rustc_errors::{Applicability, PErr};
+use rustc_errors::{Applicability, Diag};
 use rustc_span::symbol::kw;
 
 use super::diagnostics::{report_suspicious_mismatch_block, same_indentation_level};
@@ -14,7 +14,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
     pub(super) fn lex_token_trees(
         &mut self,
         is_delimited: bool,
-    ) -> (Spacing, TokenStream, Result<(), Vec<PErr<'psess>>>) {
+    ) -> (Spacing, TokenStream, Result<(), Vec<Diag<'psess>>>) {
         // Move past the opening delimiter.
         let open_spacing = self.bump_minimal();
 
@@ -56,7 +56,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
         }
     }
 
-    fn eof_err(&mut self) -> PErr<'psess> {
+    fn eof_err(&mut self) -> Diag<'psess> {
         let msg = "this file contains an unclosed delimiter";
         let mut err = self.dcx().struct_span_err(self.token.span, msg);
 
@@ -98,7 +98,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
     fn lex_token_tree_open_delim(
         &mut self,
         open_delim: Delimiter,
-    ) -> Result<TokenTree, Vec<PErr<'psess>>> {
+    ) -> Result<TokenTree, Vec<Diag<'psess>>> {
         // The span for beginning of the delimited section.
         let pre_span = self.token.span;
 
@@ -250,8 +250,8 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
     fn unclosed_delim_err(
         &mut self,
         tts: TokenStream,
-        mut errs: Vec<PErr<'psess>>,
-    ) -> Vec<PErr<'psess>> {
+        mut errs: Vec<Diag<'psess>>,
+    ) -> Vec<Diag<'psess>> {
         // If there are unclosed delims, see if there are diff markers and if so, point them
         // out instead of complaining about the unclosed delims.
         let mut parser = Parser::new(self.psess, tts, None);
@@ -308,7 +308,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
         errs
     }
 
-    fn close_delim_err(&mut self, delim: Delimiter) -> PErr<'psess> {
+    fn close_delim_err(&mut self, delim: Delimiter) -> Diag<'psess> {
         // An unexpected closing delimiter (i.e., there is no matching opening delimiter).
         let token_str = token_to_string(&self.token);
         let msg = format!("unexpected closing delimiter: `{token_str}`");
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 34131e3af6e2c..e5edf605d823e 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -16,7 +16,7 @@ use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::{
-    Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, FatalError, PErr, PResult, Subdiagnostic,
+    Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, FatalError, PResult, Subdiagnostic,
     Suggestions, pluralize,
 };
 use rustc_session::errors::ExprParenthesesNeeded;
@@ -2132,7 +2132,7 @@ impl<'a> Parser<'a> {
         &mut self,
         delim: Delimiter,
         lo: Span,
-        err: PErr<'a>,
+        err: Diag<'a>,
     ) -> P<Expr> {
         let guar = err.emit();
         // Recover from parse error, callers expect the closing delim to be consumed.
@@ -3014,7 +3014,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Check for exclusive ranges written as `..<`
-    pub(crate) fn maybe_err_dotdotlt_syntax(&self, maybe_lt: Token, mut err: PErr<'a>) -> PErr<'a> {
+    pub(crate) fn maybe_err_dotdotlt_syntax(&self, maybe_lt: Token, mut err: Diag<'a>) -> Diag<'a> {
         if maybe_lt == token::Lt
             && (self.expected_tokens.contains(&TokenType::Token(token::Gt))
                 || matches!(self.token.kind, token::Literal(..)))