diff --git a/compiler/rustc_expand/src/errors.rs b/compiler/rustc_expand/src/errors.rs
index 6c5732f497f8a..d74b1787d83c8 100644
--- a/compiler/rustc_expand/src/errors.rs
+++ b/compiler/rustc_expand/src/errors.rs
@@ -545,6 +545,49 @@ mod metavar_exprs {
         pub span: Span,
         pub key: MacroRulesNormalizedIdent,
     }
+
+    #[derive(Diagnostic)]
+    #[diag(r#"`${"{"}concat(..){"}"}` is not generating a valid identifier"#)]
+    pub(crate) struct ConcatInvalidIdent {
+        #[primary_span]
+        pub span: Span,
+        #[subdiagnostic]
+        pub reason: InvalidIdentReason,
+    }
+
+    #[derive(Subdiagnostic)]
+    pub(crate) enum InvalidIdentReason {
+        #[note(r#"this `${"{"}concat(..){"}"}` invocation generated an empty ident"#)]
+        Empty,
+        #[note(r#"this `${"{"}concat(..){"}"}` invocation generated `{$symbol}`, but {$start} is neither '_' nor XID_Start"#)]
+        #[note(
+            "see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers"
+        )]
+        InvalidStart { symbol: Symbol, start: char },
+        #[note(r#"this `${"{"}concat(..){"}"}` invocation generated `{$symbol}`, but {$not_continue} is not XID_Continue"#)]
+        #[note(
+            "see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers"
+        )]
+        InvalidContinue { symbol: Symbol, not_continue: char },
+    }
+
+    impl InvalidIdentReason {
+        pub(crate) fn new(symbol: Symbol) -> Self {
+            let mut chars = symbol.as_str().chars();
+            if let Some(start) = chars.next() {
+                if rustc_lexer::is_id_start(start) {
+                    let not_continue = chars
+                        .find(|c| !rustc_lexer::is_id_continue(*c))
+                        .expect("InvalidIdentReason: cannot find invalid ident reason");
+                    InvalidIdentReason::InvalidContinue { symbol, not_continue }
+                } else {
+                    InvalidIdentReason::InvalidStart { symbol, start }
+                }
+            } else {
+                InvalidIdentReason::Empty
+            }
+        }
+    }
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_expand/src/mbe/transcribe.rs b/compiler/rustc_expand/src/mbe/transcribe.rs
index 7152ffcd9f309..c56c5569f9a5b 100644
--- a/compiler/rustc_expand/src/mbe/transcribe.rs
+++ b/compiler/rustc_expand/src/mbe/transcribe.rs
@@ -18,9 +18,10 @@ use rustc_span::{
 use smallvec::{SmallVec, smallvec};
 
 use crate::errors::{
-    CountRepetitionMisplaced, MacroVarStillRepeating, MetaVarsDifSeqMatchers, MustRepeatOnce,
-    MveUnrecognizedVar, NoRepeatableVar, NoSyntaxVarsExprRepeat, VarNoTypo,
-    VarTypoSuggestionRepeatable, VarTypoSuggestionUnrepeatable, VarTypoSuggestionUnrepeatableLabel,
+    ConcatInvalidIdent, CountRepetitionMisplaced, InvalidIdentReason, MacroVarStillRepeating,
+    MetaVarsDifSeqMatchers, MustRepeatOnce, MveUnrecognizedVar, NoRepeatableVar,
+    NoSyntaxVarsExprRepeat, VarNoTypo, VarTypoSuggestionRepeatable, VarTypoSuggestionUnrepeatable,
+    VarTypoSuggestionUnrepeatableLabel,
 };
 use crate::mbe::macro_parser::NamedMatch;
 use crate::mbe::macro_parser::NamedMatch::*;
@@ -656,10 +657,10 @@ fn metavar_expr_concat<'tx>(
     let symbol = nfc_normalize(&concatenated);
     let concatenated_span = tscx.visited_dspan(dspan);
     if !rustc_lexer::is_ident(symbol.as_str()) {
-        return Err(dcx.struct_span_err(
-            concatenated_span,
-            "`${concat(..)}` is not generating a valid identifier",
-        ));
+        return Err(dcx.create_err(ConcatInvalidIdent {
+            span: concatenated_span,
+            reason: InvalidIdentReason::new(symbol),
+        }));
     }
     tscx.psess.symbol_gallery.insert(symbol, concatenated_span);
 
diff --git a/tests/ui/macros/metavar-expressions/concat-trace-errors.rs b/tests/ui/macros/metavar-expressions/concat-trace-errors.rs
index 45407f5e86d56..284c84378e4ab 100644
--- a/tests/ui/macros/metavar-expressions/concat-trace-errors.rs
+++ b/tests/ui/macros/metavar-expressions/concat-trace-errors.rs
@@ -16,18 +16,28 @@ macro_rules! post_expansion {
     ($a:literal) => {
         const _: () = ${concat("hi", $a, "bye")};
         //~^ ERROR is not generating a valid identifier
+        //~| NOTE this `${concat(..)}` invocation generated `hi!bye`, but '!' is not XID_Continue
+        //~| NOTE see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
     }
 }
 
 post_expansion!("!");
+//~^ NOTE in this expansion of post_expansion!
+//~| NOTE in this expansion of post_expansion!
+//~| NOTE in this expansion of post_expansion!
 
 macro_rules! post_expansion_many {
     ($a:ident, $b:ident, $c:ident, $d:literal, $e:ident) => {
         const _: () = ${concat($a, $b, $c, $d, $e)};
         //~^ ERROR is not generating a valid identifier
+        //~| NOTE this `${concat(..)}` invocation generated `abc.de`, but '.' is not XID_Continue
+        //~| NOTE see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
     }
 }
 
 post_expansion_many!(a, b, c, ".d", e);
+//~^ NOTE in this expansion of post_expansion_many!
+//~| NOTE in this expansion of post_expansion_many!
+//~| NOTE in this expansion of post_expansion_many!
 
 fn main() {}
diff --git a/tests/ui/macros/metavar-expressions/concat-trace-errors.stderr b/tests/ui/macros/metavar-expressions/concat-trace-errors.stderr
index dac8b58a15ce2..a6fc67d415d9c 100644
--- a/tests/ui/macros/metavar-expressions/concat-trace-errors.stderr
+++ b/tests/ui/macros/metavar-expressions/concat-trace-errors.stderr
@@ -7,10 +7,12 @@ LL |         const _: () = ${concat("hi", $a, "bye")};
 LL | post_expansion!("!");
    | -------------------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `hi!bye`, but '!' is not XID_Continue
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `post_expansion` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-trace-errors.rs:26:24
+  --> $DIR/concat-trace-errors.rs:31:24
    |
 LL |         const _: () = ${concat($a, $b, $c, $d, $e)};
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -18,6 +20,8 @@ LL |         const _: () = ${concat($a, $b, $c, $d, $e)};
 LL | post_expansion_many!(a, b, c, ".d", e);
    | -------------------------------------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `abc.de`, but '.' is not XID_Continue
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `post_expansion_many` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 2 previous errors
diff --git a/tests/ui/macros/metavar-expressions/concat-usage-errors.rs b/tests/ui/macros/metavar-expressions/concat-usage-errors.rs
index 277ad240b1bf2..c82c9b92da9fc 100644
--- a/tests/ui/macros/metavar-expressions/concat-usage-errors.rs
+++ b/tests/ui/macros/metavar-expressions/concat-usage-errors.rs
@@ -1,4 +1,5 @@
 //@ edition: 2021
+//@ dont-require-annotations: NOTE
 
 #![feature(macro_metavar_expr_concat)]
 
@@ -43,6 +44,7 @@ macro_rules! starting_number {
     ($ident:ident) => {{
         let ${concat("1", $ident)}: () = ();
         //~^ ERROR `${concat(..)}` is not generating a valid identifier
+        //~| NOTE this `${concat(..)}` invocation generated `1_abc`, but '1' is neither '_' nor XID_Start
     }};
 }
 
@@ -56,6 +58,8 @@ macro_rules! starting_invalid_unicode {
     ($ident:ident) => {{
         let ${concat("\u{00BD}", $ident)}: () = ();
         //~^ ERROR `${concat(..)}` is not generating a valid identifier
+        //~| NOTE this `${concat(..)}` invocation generated `\u{00BD}_abc`, but '\' is neither '_' nor XID_Start
+        //~| NOTE see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
     }};
 }
 
@@ -75,6 +79,7 @@ macro_rules! ending_invalid_unicode {
     ($ident:ident) => {{
         let ${concat($ident, "\u{00BD}")}: () = ();
         //~^ ERROR `${concat(..)}` is not generating a valid identifier
+        //~| NOTE this `${concat(..)}` invocation generated `_abc\u{00BD}`, but '\' is not XID_Continue
     }};
 }
 
@@ -82,6 +87,7 @@ macro_rules! empty {
     () => {{
         let ${concat("", "")}: () = ();
         //~^ ERROR `${concat(..)}` is not generating a valid identifier
+        //~| NOTE this `${concat(..)}` invocation generated an empty ident
     }};
 }
 
@@ -130,6 +136,8 @@ macro_rules! bad_literal_string {
         //~| ERROR `${concat(..)}` is not generating a valid identifier
         //~| ERROR `${concat(..)}` is not generating a valid identifier
         //~| ERROR `${concat(..)}` is not generating a valid identifier
+        //~| NOTE this `${concat(..)}` invocation generated `_foo🤷`, but '🤷' is not XID_Continue
+        //~| NOTE this `${concat(..)}` invocation generated `_foo-1`, but '-' is not XID_Continue
     }
 }
 
diff --git a/tests/ui/macros/metavar-expressions/concat-usage-errors.stderr b/tests/ui/macros/metavar-expressions/concat-usage-errors.stderr
index c124b76cb781a..2ba81551289df 100644
--- a/tests/ui/macros/metavar-expressions/concat-usage-errors.stderr
+++ b/tests/ui/macros/metavar-expressions/concat-usage-errors.stderr
@@ -1,131 +1,131 @@
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:7:10
+  --> $DIR/concat-usage-errors.rs:8:10
    |
 LL |         ${concat()}
    |          ^^^^^^^^^^
 
 error: `concat` must have at least two elements
-  --> $DIR/concat-usage-errors.rs:10:11
+  --> $DIR/concat-usage-errors.rs:11:11
    |
 LL |         ${concat(aaaa)}
    |           ^^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:13:10
+  --> $DIR/concat-usage-errors.rs:14:10
    |
 LL |         ${concat(aaaa,)}
    |          ^^^^^^^^^^^^^^^
 
 error: expected comma
-  --> $DIR/concat-usage-errors.rs:18:10
+  --> $DIR/concat-usage-errors.rs:19:10
    |
 LL |         ${concat(aaaa aaaa)}
    |          ^^^^^^^^^^^^^^^^^^^
 
 error: `concat` must have at least two elements
-  --> $DIR/concat-usage-errors.rs:21:11
+  --> $DIR/concat-usage-errors.rs:22:11
    |
 LL |         ${concat($ex)}
    |           ^^^^^^
 
 error: expected comma
-  --> $DIR/concat-usage-errors.rs:27:10
+  --> $DIR/concat-usage-errors.rs:28:10
    |
 LL |         ${concat($ex, aaaa 123)}
    |          ^^^^^^^^^^^^^^^^^^^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:30:10
+  --> $DIR/concat-usage-errors.rs:31:10
    |
 LL |         ${concat($ex, aaaa,)}
    |          ^^^^^^^^^^^^^^^^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:90:26
+  --> $DIR/concat-usage-errors.rs:96:26
    |
 LL |         let ${concat(_a, 'b')}: () = ();
    |                          ^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:93:26
+  --> $DIR/concat-usage-errors.rs:99:26
    |
 LL |         let ${concat(_a, 1)}: () = ();
    |                          ^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:95:26
+  --> $DIR/concat-usage-errors.rs:101:26
    |
 LL |         let ${concat(_a, 1.5)}: () = ();
    |                          ^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:97:26
+  --> $DIR/concat-usage-errors.rs:103:26
    |
 LL |         let ${concat(_a, c"hi")}: () = ();
    |                          ^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:99:26
+  --> $DIR/concat-usage-errors.rs:105:26
    |
 LL |         let ${concat(_a, b"hi")}: () = ();
    |                          ^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:101:26
+  --> $DIR/concat-usage-errors.rs:107:26
    |
 LL |         let ${concat(_a, b'b')}: () = ();
    |                          ^^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:103:26
+  --> $DIR/concat-usage-errors.rs:109:26
    |
 LL |         let ${concat(_a, b'b')}: () = ();
    |                          ^^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:106:30
+  --> $DIR/concat-usage-errors.rs:112:30
    |
 LL |         let ${concat($ident, 'b')}: () = ();
    |                              ^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:108:30
+  --> $DIR/concat-usage-errors.rs:114:30
    |
 LL |         let ${concat($ident, 1)}: () = ();
    |                              ^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:110:30
+  --> $DIR/concat-usage-errors.rs:116:30
    |
 LL |         let ${concat($ident, 1.5)}: () = ();
    |                              ^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:112:30
+  --> $DIR/concat-usage-errors.rs:118:30
    |
 LL |         let ${concat($ident, c"hi")}: () = ();
    |                              ^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:114:30
+  --> $DIR/concat-usage-errors.rs:120:30
    |
 LL |         let ${concat($ident, b"hi")}: () = ();
    |                              ^^^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:116:30
+  --> $DIR/concat-usage-errors.rs:122:30
    |
 LL |         let ${concat($ident, b'b')}: () = ();
    |                              ^^^^
 
 error: expected identifier or string literal
-  --> $DIR/concat-usage-errors.rs:118:30
+  --> $DIR/concat-usage-errors.rs:124:30
    |
 LL |         let ${concat($ident, b'b')}: () = ();
    |                              ^^^^
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/concat-usage-errors.rs:24:19
+  --> $DIR/concat-usage-errors.rs:25:19
    |
 LL |         ${concat($ex, aaaa)}
    |                   ^^
@@ -133,13 +133,13 @@ LL |         ${concat($ex, aaaa)}
    = note: currently only string and integer literals are supported
 
 error: variable `foo` is not recognized in meta-variable expression
-  --> $DIR/concat-usage-errors.rs:37:30
+  --> $DIR/concat-usage-errors.rs:38:30
    |
 LL |         const ${concat(FOO, $foo)}: i32 = 2;
    |                              ^^^
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-usage-errors.rs:44:14
+  --> $DIR/concat-usage-errors.rs:45:14
    |
 LL |         let ${concat("1", $ident)}: () = ();
    |              ^^^^^^^^^^^^^^^^^^^^^
@@ -147,10 +147,12 @@ LL |         let ${concat("1", $ident)}: () = ();
 LL |     starting_number!(_abc);
    |     ---------------------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `1_abc`, but '1' is neither '_' nor XID_Start
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `starting_number` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-usage-errors.rs:57:14
+  --> $DIR/concat-usage-errors.rs:59:14
    |
 LL |         let ${concat("\u{00BD}", $ident)}: () = ();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -158,10 +160,12 @@ LL |         let ${concat("\u{00BD}", $ident)}: () = ();
 LL |     starting_invalid_unicode!(_abc);
    |     ------------------------------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `\u{00BD}_abc`, but '\' is neither '_' nor XID_Start
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `starting_invalid_unicode` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-usage-errors.rs:76:14
+  --> $DIR/concat-usage-errors.rs:80:14
    |
 LL |         let ${concat($ident, "\u{00BD}")}: () = ();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -169,10 +173,12 @@ LL |         let ${concat($ident, "\u{00BD}")}: () = ();
 LL |     ending_invalid_unicode!(_abc);
    |     ----------------------------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `_abc\u{00BD}`, but '\' is not XID_Continue
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `ending_invalid_unicode` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: expected pattern, found `$`
-  --> $DIR/concat-usage-errors.rs:90:13
+  --> $DIR/concat-usage-errors.rs:96:13
    |
 LL |         let ${concat(_a, 'b')}: () = ();
    |             ^ expected pattern
@@ -183,7 +189,7 @@ LL |     unsupported_literals!(_abc);
    = note: this error originates in the macro `unsupported_literals` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-usage-errors.rs:83:14
+  --> $DIR/concat-usage-errors.rs:88:14
    |
 LL |         let ${concat("", "")}: () = ();
    |              ^^^^^^^^^^^^^^^^
@@ -191,10 +197,11 @@ LL |         let ${concat("", "")}: () = ();
 LL |     empty!();
    |     -------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated an empty ident
    = note: this error originates in the macro `empty` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-usage-errors.rs:125:16
+  --> $DIR/concat-usage-errors.rs:131:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -202,10 +209,12 @@ LL |         const ${concat(_foo, $literal)}: () = ();
 LL |     bad_literal_string!("\u{00BD}");
    |     ------------------------------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `_foo\u{00BD}`, but '\' is not XID_Continue
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `bad_literal_string` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-usage-errors.rs:125:16
+  --> $DIR/concat-usage-errors.rs:131:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -213,10 +222,12 @@ LL |         const ${concat(_foo, $literal)}: () = ();
 LL |     bad_literal_string!("\x41");
    |     --------------------------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `_foo\x41`, but '\' is not XID_Continue
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `bad_literal_string` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-usage-errors.rs:125:16
+  --> $DIR/concat-usage-errors.rs:131:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -224,10 +235,12 @@ LL |         const ${concat(_foo, $literal)}: () = ();
 LL |     bad_literal_string!("🤷");
    |     ------------------------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `_foo🤷`, but '🤷' is not XID_Continue
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `bad_literal_string` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-usage-errors.rs:125:16
+  --> $DIR/concat-usage-errors.rs:131:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -235,10 +248,12 @@ LL |         const ${concat(_foo, $literal)}: () = ();
 LL |     bad_literal_string!("d[-_-]b");
    |     ------------------------------ in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `_food[-_-]b`, but '[' is not XID_Continue
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `bad_literal_string` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-usage-errors.rs:125:16
+  --> $DIR/concat-usage-errors.rs:131:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -246,10 +261,12 @@ LL |         const ${concat(_foo, $literal)}: () = ();
 LL |     bad_literal_string!("-1");
    |     ------------------------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `_foo-1`, but '-' is not XID_Continue
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `bad_literal_string` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-usage-errors.rs:125:16
+  --> $DIR/concat-usage-errors.rs:131:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -257,10 +274,12 @@ LL |         const ${concat(_foo, $literal)}: () = ();
 LL |     bad_literal_string!("1.0");
    |     -------------------------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `_foo1.0`, but '.' is not XID_Continue
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `bad_literal_string` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `${concat(..)}` is not generating a valid identifier
-  --> $DIR/concat-usage-errors.rs:125:16
+  --> $DIR/concat-usage-errors.rs:131:16
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -268,10 +287,12 @@ LL |         const ${concat(_foo, $literal)}: () = ();
 LL |     bad_literal_string!("'1'");
    |     -------------------------- in this macro invocation
    |
+   = note: this `${concat(..)}` invocation generated `_foo'1'`, but '\'' is not XID_Continue
+   = note: see <https://doc.rust-lang.org/reference/identifiers.html> for the definition of valid identifiers
    = note: this error originates in the macro `bad_literal_string` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/concat-usage-errors.rs:138:31
+  --> $DIR/concat-usage-errors.rs:146:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
@@ -279,7 +300,7 @@ LL |         const ${concat(_foo, $literal)}: () = ();
    = note: currently only string and integer literals are supported
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/concat-usage-errors.rs:138:31
+  --> $DIR/concat-usage-errors.rs:146:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
@@ -288,7 +309,7 @@ LL |         const ${concat(_foo, $literal)}: () = ();
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/concat-usage-errors.rs:138:31
+  --> $DIR/concat-usage-errors.rs:146:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
@@ -297,7 +318,7 @@ LL |         const ${concat(_foo, $literal)}: () = ();
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/concat-usage-errors.rs:138:31
+  --> $DIR/concat-usage-errors.rs:146:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
@@ -306,19 +327,19 @@ LL |         const ${concat(_foo, $literal)}: () = ();
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: floats are not supported as metavariables of `${concat(..)}`
-  --> $DIR/concat-usage-errors.rs:138:31
+  --> $DIR/concat-usage-errors.rs:146:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
 
 error: integer metavariables of `${concat(..)}` must not be suffixed
-  --> $DIR/concat-usage-errors.rs:138:31
+  --> $DIR/concat-usage-errors.rs:146:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
 
 error: integer metavariables of `${concat(..)}` must not be suffixed
-  --> $DIR/concat-usage-errors.rs:138:31
+  --> $DIR/concat-usage-errors.rs:146:31
    |
 LL |         const ${concat(_foo, $literal)}: () = ();
    |                               ^^^^^^^
@@ -326,7 +347,7 @@ LL |         const ${concat(_foo, $literal)}: () = ();
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/concat-usage-errors.rs:151:31
+  --> $DIR/concat-usage-errors.rs:159:31
    |
 LL |         const ${concat(_foo, $tt)}: () = ();
    |                               ^^
@@ -334,7 +355,7 @@ LL |         const ${concat(_foo, $tt)}: () = ();
    = note: currently only string and integer literals are supported
 
 error: metavariables of `${concat(..)}` must be of type `ident`, `literal` or `tt`
-  --> $DIR/concat-usage-errors.rs:151:31
+  --> $DIR/concat-usage-errors.rs:159:31
    |
 LL |         const ${concat(_foo, $tt)}: () = ();
    |                               ^^