diff --git a/compiler/rustc_builtin_macros/src/asm.rs b/compiler/rustc_builtin_macros/src/asm.rs
index 76805617c93..137ac441579 100644
--- a/compiler/rustc_builtin_macros/src/asm.rs
+++ b/compiler/rustc_builtin_macros/src/asm.rs
@@ -29,7 +29,7 @@ pub struct AsmArgs {
 }
 
 fn parse_args<'a>(
-    ecx: &mut ExtCtxt<'a>,
+    ecx: &ExtCtxt<'a>,
     sp: Span,
     tts: TokenStream,
     is_global_asm: bool,
@@ -303,7 +303,7 @@ pub fn parse_asm_args<'a>(
 ///
 /// This function must be called immediately after the option token is parsed.
 /// Otherwise, the suggestion will be incorrect.
-fn err_duplicate_option(p: &mut Parser<'_>, symbol: Symbol, span: Span) {
+fn err_duplicate_option(p: &Parser<'_>, symbol: Symbol, span: Span) {
     // Tool-only output
     let full_span = if p.token.kind == token::Comma { span.to(p.token.span) } else { span };
     p.psess.dcx.emit_err(errors::AsmOptAlreadyprovided { span, symbol, full_span });
@@ -315,7 +315,7 @@ fn err_duplicate_option(p: &mut Parser<'_>, symbol: Symbol, span: Span) {
 /// This function must be called immediately after the option token is parsed.
 /// Otherwise, the error will not point to the correct spot.
 fn try_set_option<'a>(
-    p: &mut Parser<'a>,
+    p: &Parser<'a>,
     args: &mut AsmArgs,
     symbol: Symbol,
     option: ast::InlineAsmOptions,
diff --git a/compiler/rustc_builtin_macros/src/assert.rs b/compiler/rustc_builtin_macros/src/assert.rs
index 5905bdd7108..d200179f3a0 100644
--- a/compiler/rustc_builtin_macros/src/assert.rs
+++ b/compiler/rustc_builtin_macros/src/assert.rs
@@ -111,7 +111,7 @@ fn expr_if_not(
     cx.expr_if(span, cx.expr(span, ExprKind::Unary(UnOp::Not, cond)), then, els)
 }
 
-fn parse_assert<'a>(cx: &mut ExtCtxt<'a>, sp: Span, stream: TokenStream) -> PResult<'a, Assert> {
+fn parse_assert<'a>(cx: &ExtCtxt<'a>, sp: Span, stream: TokenStream) -> PResult<'a, Assert> {
     let mut parser = cx.new_parser_from_tts(stream);
 
     if parser.token == token::Eof {
diff --git a/compiler/rustc_builtin_macros/src/cfg.rs b/compiler/rustc_builtin_macros/src/cfg.rs
index 9197b9ebdf9..5dc9bbacd06 100644
--- a/compiler/rustc_builtin_macros/src/cfg.rs
+++ b/compiler/rustc_builtin_macros/src/cfg.rs
@@ -35,7 +35,7 @@ pub fn expand_cfg(
     })
 }
 
-fn parse_cfg<'a>(cx: &mut ExtCtxt<'a>, span: Span, tts: TokenStream) -> PResult<'a, ast::MetaItem> {
+fn parse_cfg<'a>(cx: &ExtCtxt<'a>, span: Span, tts: TokenStream) -> PResult<'a, ast::MetaItem> {
     let mut p = cx.new_parser_from_tts(tts);
 
     if p.token == token::Eof {
diff --git a/compiler/rustc_builtin_macros/src/cfg_accessible.rs b/compiler/rustc_builtin_macros/src/cfg_accessible.rs
index 1933b2e1fb7..98c0ca3a526 100644
--- a/compiler/rustc_builtin_macros/src/cfg_accessible.rs
+++ b/compiler/rustc_builtin_macros/src/cfg_accessible.rs
@@ -10,7 +10,7 @@ use rustc_span::Span;
 
 pub(crate) struct Expander;
 
-fn validate_input<'a>(ecx: &mut ExtCtxt<'_>, mi: &'a ast::MetaItem) -> Option<&'a ast::Path> {
+fn validate_input<'a>(ecx: &ExtCtxt<'_>, mi: &'a ast::MetaItem) -> Option<&'a ast::Path> {
     use errors::CfgAccessibleInvalid::*;
     match mi.meta_item_list() {
         None => {}
diff --git a/compiler/rustc_builtin_macros/src/concat_bytes.rs b/compiler/rustc_builtin_macros/src/concat_bytes.rs
index a2f827c5567..45fec294578 100644
--- a/compiler/rustc_builtin_macros/src/concat_bytes.rs
+++ b/compiler/rustc_builtin_macros/src/concat_bytes.rs
@@ -8,7 +8,7 @@ use crate::errors;
 
 /// Emits errors for literal expressions that are invalid inside and outside of an array.
 fn invalid_type_err(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     token_lit: token::Lit,
     span: Span,
     is_nested: bool,
@@ -65,7 +65,7 @@ fn invalid_type_err(
 /// Otherwise, returns `None`, and either pushes the `expr`'s span to `missing_literals` or
 /// updates `guar` accordingly.
 fn handle_array_element(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     guar: &mut Option<ErrorGuaranteed>,
     missing_literals: &mut Vec<rustc_span::Span>,
     expr: &P<rustc_ast::Expr>,
diff --git a/compiler/rustc_builtin_macros/src/edition_panic.rs b/compiler/rustc_builtin_macros/src/edition_panic.rs
index fa22e911642..bb3c83e8c0e 100644
--- a/compiler/rustc_builtin_macros/src/edition_panic.rs
+++ b/compiler/rustc_builtin_macros/src/edition_panic.rs
@@ -40,7 +40,7 @@ pub fn expand_unreachable<'cx>(
 
 fn expand<'cx>(
     mac: rustc_span::Symbol,
-    cx: &'cx mut ExtCtxt<'_>,
+    cx: &'cx ExtCtxt<'_>,
     sp: Span,
     tts: TokenStream,
 ) -> MacroExpanderResult<'cx> {
diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index 6f031f270ca..51d6058a744 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -65,7 +65,7 @@ struct MacroInput {
 /// ```text
 /// Ok((fmtstr, parsed arguments))
 /// ```
-fn parse_args<'a>(ecx: &mut ExtCtxt<'a>, sp: Span, tts: TokenStream) -> PResult<'a, MacroInput> {
+fn parse_args<'a>(ecx: &ExtCtxt<'a>, sp: Span, tts: TokenStream) -> PResult<'a, MacroInput> {
     let mut args = FormatArguments::new();
 
     let mut p = ecx.new_parser_from_tts(tts);
@@ -604,7 +604,7 @@ fn invalid_placeholder_type_error(
 }
 
 fn report_missing_placeholders(
-    ecx: &mut ExtCtxt<'_>,
+    ecx: &ExtCtxt<'_>,
     unused: Vec<(Span, bool)>,
     used: &[bool],
     args: &FormatArguments,
@@ -734,7 +734,7 @@ fn report_missing_placeholders(
 /// This function detects and reports unused format!() arguments that are
 /// redundant due to implicit captures (e.g. `format!("{x}", x)`).
 fn report_redundant_format_arguments<'a>(
-    ecx: &mut ExtCtxt<'a>,
+    ecx: &ExtCtxt<'a>,
     args: &FormatArguments,
     used: &[bool],
     placeholders: Vec<(Span, &str)>,
@@ -806,7 +806,7 @@ fn report_redundant_format_arguments<'a>(
 /// there are named arguments or numbered positional arguments in the
 /// format string.
 fn report_invalid_references(
-    ecx: &mut ExtCtxt<'_>,
+    ecx: &ExtCtxt<'_>,
     invalid_refs: &[(usize, Option<Span>, PositionUsedAs, FormatArgPositionKind)],
     template: &[FormatArgsPiece],
     fmt_span: Span,
diff --git a/compiler/rustc_builtin_macros/src/source_util.rs b/compiler/rustc_builtin_macros/src/source_util.rs
index abcdfabcaed..61a6361ae8d 100644
--- a/compiler/rustc_builtin_macros/src/source_util.rs
+++ b/compiler/rustc_builtin_macros/src/source_util.rs
@@ -234,7 +234,7 @@ pub fn expand_include_bytes(
 }
 
 fn load_binary_file(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     original_path: &Path,
     macro_span: Span,
     path_span: Span,
diff --git a/compiler/rustc_builtin_macros/src/test.rs b/compiler/rustc_builtin_macros/src/test.rs
index 81ac78dd58f..c7568f1461c 100644
--- a/compiler/rustc_builtin_macros/src/test.rs
+++ b/compiler/rustc_builtin_macros/src/test.rs
@@ -96,7 +96,7 @@ pub fn expand_bench(
 }
 
 pub fn expand_test_or_bench(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     attr_sp: Span,
     item: Annotatable,
     is_bench: bool,