2 files changed, 31 insertions, 0 deletions
diff --git a/tests/ui/macros/macro-metavar-expr-concat/empty-input.rs b/tests/ui/macros/macro-metavar-expr-concat/empty-input.rs
new file mode 100644
index 00000000000..caad63c5f6b
--- /dev/null
+++ b/tests/ui/macros/macro-metavar-expr-concat/empty-input.rs
@@ -0,0 +1,12 @@
+// Issue 50403
+// Ensure that `concat` can't create empty identifiers
+// FIXME(macro_metavar_expr_concat): this error message could be improved
+
+macro_rules! empty {
+    () => { ${concat()} } //~ ERROR expected identifier or string literal
+                          //~^ERROR expected expression
+}
+
+fn main() {
+    let x = empty!();
+}
diff --git a/tests/ui/macros/macro-metavar-expr-concat/empty-input.stderr b/tests/ui/macros/macro-metavar-expr-concat/empty-input.stderr
new file mode 100644
index 00000000000..e95032dd247
--- /dev/null
+++ b/tests/ui/macros/macro-metavar-expr-concat/empty-input.stderr
@@ -0,0 +1,19 @@
+error: expected identifier or string literal
+  --> $DIR/empty-input.rs:6:14
+   |
+LL |     () => { ${concat()} }
+   |              ^^^^^^^^^^
+
+error: expected expression, found `$`
+  --> $DIR/empty-input.rs:6:13
+   |
+LL |     () => { ${concat()} }
+   |             ^ expected expression
+...
+LL |     let x = empty!();
+   |             -------- in this macro invocation
+   |
+   = note: this error originates in the macro `empty` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 2 previous errors
+