Add a regression test for #87573

src/test/ui/lang-items/issue-87573.rs

@@ -0,0 +1,28 @@
+// Regression test for #87573, ensures that duplicate lang items or invalid generics
+// for lang items doesn't cause ICE.
+
+#![feature(no_core, lang_items)]
+#![no_core]
+#![crate_type = "lib"]
+
+pub static STATIC_BOOL: bool = true;
+
+#[lang = "sized"]
+trait Sized {}
+
+#[lang = "copy"]
+trait Copy {}
+
+#[lang = "sync"]
+trait Sync {}
+impl Sync for bool {}
+
+#[lang = "drop_in_place"]
+//~^ ERROR: `drop_in_place` language item must be applied to a function with at least 1 generic argument
+fn drop_fn() {
+    while false {}
+}
+
+#[lang = "start"]
+//~^ ERROR: `start` language item must be applied to a function with 1 generic argument
+fn start(){}

src/test/ui/lang-items/issue-87573.stderr

@@ -0,0 +1,21 @@
+error[E0718]: `drop_in_place` language item must be applied to a function with at least 1 generic argument
+  --> $DIR/issue-87573.rs:20:1
+   |
+LL | #[lang = "drop_in_place"]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |
+LL | fn drop_fn() {
+   |           - this function has 0 generic arguments
+
+error[E0718]: `start` language item must be applied to a function with 1 generic argument
+  --> $DIR/issue-87573.rs:26:1
+   |
+LL | #[lang = "start"]
+   | ^^^^^^^^^^^^^^^^^
+LL |
+LL | fn start(){}
+   |         - this function has 0 generic arguments
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0718`.