diff --git a/compiler/rustc_expand/src/lib.rs b/compiler/rustc_expand/src/lib.rs
index f77eac2b068c2..efed41de23a89 100644
--- a/compiler/rustc_expand/src/lib.rs
+++ b/compiler/rustc_expand/src/lib.rs
@@ -1,6 +1,7 @@
#![feature(crate_visibility_modifier)]
#![feature(decl_macro)]
#![feature(destructuring_assignment)]
+#![feature(format_args_capture)]
#![feature(iter_zip)]
#![feature(proc_macro_diagnostic)]
#![feature(proc_macro_internals)]
diff --git a/compiler/rustc_expand/src/mbe/macro_parser.rs b/compiler/rustc_expand/src/mbe/macro_parser.rs
index 1aed42a24e2b3..a7434d73abe68 100644
--- a/compiler/rustc_expand/src/mbe/macro_parser.rs
+++ b/compiler/rustc_expand/src/mbe/macro_parser.rs
@@ -85,6 +85,7 @@ use smallvec::{smallvec, SmallVec};
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::sync::Lrc;
+use rustc_span::symbol::Ident;
use std::borrow::Cow;
use std::collections::hash_map::Entry::{Occupied, Vacant};
use std::mem;
@@ -615,7 +616,11 @@ fn inner_parse_loop<'root, 'tt>(
/// Use the given sequence of token trees (`ms`) as a matcher. Match the token
/// stream from the given `parser` against it and return the match.
-pub(super) fn parse_tt(parser: &mut Cow<'_, Parser<'_>>, ms: &[TokenTree]) -> NamedParseResult {
+pub(super) fn parse_tt(
+ parser: &mut Cow<'_, Parser<'_>>,
+ ms: &[TokenTree],
+ macro_name: Ident,
+) -> NamedParseResult {
// A queue of possible matcher positions. We initialize it with the matcher position in which
// the "dot" is before the first token of the first token tree in `ms`. `inner_parse_loop` then
// processes all of these possible matcher positions and produces possible next positions into
@@ -711,7 +716,7 @@ pub(super) fn parse_tt(parser: &mut Cow<'_, Parser<'_>>, ms: &[TokenTree]) -> Na
return Error(
parser.token.span,
format!(
- "local ambiguity: multiple parsing options: {}",
+ "local ambiguity when calling macro `{macro_name}`: multiple parsing options: {}",
match next_items.len() {
0 => format!("built-in NTs {}.", nts),
1 => format!("built-in NTs {} or 1 other option.", nts),
diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs
index 6608573d720a8..abad190b072ab 100644
--- a/compiler/rustc_expand/src/mbe/macro_rules.rs
+++ b/compiler/rustc_expand/src/mbe/macro_rules.rs
@@ -245,7 +245,7 @@ fn generic_extension<'cx>(
// are not recorded. On the first `Success(..)`ful matcher, the spans are merged.
let mut gated_spans_snapshot = mem::take(&mut *sess.gated_spans.spans.borrow_mut());
- match parse_tt(&mut Cow::Borrowed(&parser), lhs_tt) {
+ match parse_tt(&mut Cow::Borrowed(&parser), lhs_tt, name) {
Success(named_matches) => {
// The matcher was `Success(..)`ful.
// Merge the gated spans from parsing the matcher with the pre-existing ones.
@@ -338,7 +338,7 @@ fn generic_extension<'cx>(
_ => continue,
};
if let Success(_) =
- parse_tt(&mut Cow::Borrowed(&parser_from_cx(sess, arg.clone())), lhs_tt)
+ parse_tt(&mut Cow::Borrowed(&parser_from_cx(sess, arg.clone())), lhs_tt, name)
{
if comma_span.is_dummy() {
err.note("you might be missing a comma");
@@ -432,7 +432,7 @@ pub fn compile_declarative_macro(
];
let parser = Parser::new(&sess.parse_sess, body, true, rustc_parse::MACRO_ARGUMENTS);
- let argument_map = match parse_tt(&mut Cow::Borrowed(&parser), &argument_gram) {
+ let argument_map = match parse_tt(&mut Cow::Borrowed(&parser), &argument_gram, def.ident) {
Success(m) => m,
Failure(token, msg) => {
let s = parse_failure_msg(&token);
diff --git a/src/test/ui/macros/local-ambiguity-multiple-parsing-options.stderr b/src/test/ui/macros/local-ambiguity-multiple-parsing-options.stderr
index 0ae56c422213c..68b278fd3c886 100644
--- a/src/test/ui/macros/local-ambiguity-multiple-parsing-options.stderr
+++ b/src/test/ui/macros/local-ambiguity-multiple-parsing-options.stderr
@@ -1,10 +1,10 @@
-error: local ambiguity: multiple parsing options: built-in NTs ident ('i') or ident ('j').
+error: local ambiguity when calling macro `ambiguity`: multiple parsing options: built-in NTs ident ('i') or ident ('j').
--> $DIR/local-ambiguity-multiple-parsing-options.rs:7:12
|
LL | ambiguity!(error);
| ^^^^^
-error: local ambiguity: multiple parsing options: built-in NTs ident ('i') or ident ('j').
+error: local ambiguity when calling macro `ambiguity`: multiple parsing options: built-in NTs ident ('i') or ident ('j').
--> $DIR/local-ambiguity-multiple-parsing-options.rs:8:12
|
LL | ambiguity!(error);