improves duplicate lang item test

tests/ui/duplicate_entry_error.rs

@@ -1,18 +0,0 @@
-//@ normalize-stderr: "loaded from .*libstd-.*.rlib" -> "loaded from SYSROOT/libstd-*.rlib"
-// note-pattern: first defined in crate `std`.
-
-// Test for issue #31788 and E0152
-
-#![feature(lang_items)]
-
-extern crate core;
-
-use core::panic::PanicInfo;
-
-#[lang = "panic_impl"]
-fn panic_impl(info: &PanicInfo) -> ! {
-//~^ ERROR: found duplicate lang item `panic_impl`
-    loop {}
-}
-
-fn main() {}

tests/ui/error-codes/E0152-duplicate-lang-items.rs

@@ -0,0 +1,20 @@
+//! Validates the correct printing of E0152 in the case of duplicate "lang_item" function
+//! definitions.
+//!
+//! Issue: <https://github.com/rust-lang/rust/issues/31788>
+
+//@ error-pattern: first defined in crate `std`
+//@ normalize-stderr: "loaded from .*libstd-.*.rlib" -> "loaded from SYSROOT/libstd-*.rlib"
+#![feature(lang_items)]
+
+extern crate core;
+
+use core::panic::PanicInfo;
+
+#[lang = "panic_impl"]
+fn panic_impl(info: &PanicInfo) -> ! {
+    //~^ ERROR: found duplicate lang item `panic_impl`
+    loop {}
+}
+
+fn main() {}

tests/ui/error-codes/E0152-duplicate-lang-items.stderr

@@ -1,5 +1,5 @@
 error[E0152]: found duplicate lang item `panic_impl`
-  --> $DIR/duplicate_entry_error.rs:13:1
+  --> $DIR/E0152-duplicate-lang-items.rs:15:1
    |
 LL | / fn panic_impl(info: &PanicInfo) -> ! {
 LL | |
@@ -7,9 +7,9 @@ LL | |     loop {}
 LL | | }
    | |_^
    |
-   = note: the lang item is first defined in crate `std` (which `duplicate_entry_error` depends on)
+   = note: the lang item is first defined in crate `std` (which `E0152_duplicate_lang_items` depends on)
    = note: first definition in `std` loaded from SYSROOT/libstd-*.rlib
-   = note: second definition in the local crate (`duplicate_entry_error`)
+   = note: second definition in the local crate (`E0152_duplicate_lang_items`)
 
 error: aborting due to 1 previous error