From c92c183ed9c965c79df3592dffc4c23f3711815e Mon Sep 17 00:00:00 2001
From: jumbatm <30644300+jumbatm@users.noreply.github.com>
Date: Tue, 4 Aug 2020 22:01:06 +1000
Subject: [PATCH 1/3] Deny clashing_extern_declarations by default.

---
 src/librustc_lint/builtin.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index 6515708e115a5..2bf43b86c7c15 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -2067,7 +2067,7 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
 
 declare_lint! {
     pub CLASHING_EXTERN_DECLARATIONS,
-    Warn,
+    Deny,
     "detects when an extern fn has been declared with the same name but different types"
 }
 

From c2db0de4290c8dc0802af8f3b290cd57c330dec8 Mon Sep 17 00:00:00 2001
From: jumbatm <30644300+jumbatm@users.noreply.github.com>
Date: Wed, 5 Aug 2020 22:41:12 +1000
Subject: [PATCH 2/3] Fix test failure.

---
 src/test/ui/abi/foreign/auxiliary/foreign_lib.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/test/ui/abi/foreign/auxiliary/foreign_lib.rs b/src/test/ui/abi/foreign/auxiliary/foreign_lib.rs
index de6b0e2118a58..1822822deb26c 100644
--- a/src/test/ui/abi/foreign/auxiliary/foreign_lib.rs
+++ b/src/test/ui/abi/foreign/auxiliary/foreign_lib.rs
@@ -25,6 +25,9 @@ pub mod rustrt3 {
     // importing the same symbol under different types.
     // See https://github.com/rust-lang/rust/issues/32740.
     extern {
+        // NOTE: Allow clashing decl here as we want this test case to catch ICE or LLVM assert
+        // failures if the lint has been allowed.
+        #[allow(clashing_extern_declarations)]
         pub fn rust_get_test_int() -> *const u8;
     }
 }

From 40db56cd76ae38514151e8b6a7cac5a43e2fe8c0 Mon Sep 17 00:00:00 2001
From: jumbatm <30644300+jumbatm@users.noreply.github.com>
Date: Wed, 5 Aug 2020 23:12:05 +1000
Subject: [PATCH 3/3] Move invoke extern test to dedupe foreign_lib.rs

---
 src/test/ui/abi/auxiliary/foreign_lib.rs      | 38 -------------------
 .../{ => foreign}/invoke-external-foreign.rs  |  0
 2 files changed, 38 deletions(-)
 delete mode 100644 src/test/ui/abi/auxiliary/foreign_lib.rs
 rename src/test/ui/abi/{ => foreign}/invoke-external-foreign.rs (100%)

diff --git a/src/test/ui/abi/auxiliary/foreign_lib.rs b/src/test/ui/abi/auxiliary/foreign_lib.rs
deleted file mode 100644
index de6b0e2118a58..0000000000000
--- a/src/test/ui/abi/auxiliary/foreign_lib.rs
+++ /dev/null
@@ -1,38 +0,0 @@
-#![crate_name="foreign_lib"]
-
-#![feature(rustc_private)]
-
-pub mod rustrt {
-    extern crate libc;
-
-    #[link(name = "rust_test_helpers", kind = "static")]
-    extern {
-        pub fn rust_get_test_int() -> libc::intptr_t;
-    }
-}
-
-pub mod rustrt2 {
-    extern crate libc;
-
-    extern {
-        pub fn rust_get_test_int() -> libc::intptr_t;
-    }
-}
-
-pub mod rustrt3 {
-    // Different type, but same ABI (on all supported platforms).
-    // Ensures that we don't ICE or trigger LLVM asserts when
-    // importing the same symbol under different types.
-    // See https://github.com/rust-lang/rust/issues/32740.
-    extern {
-        pub fn rust_get_test_int() -> *const u8;
-    }
-}
-
-pub fn local_uses() {
-    unsafe {
-        let x = rustrt::rust_get_test_int();
-        assert_eq!(x, rustrt2::rust_get_test_int());
-        assert_eq!(x as *const _, rustrt3::rust_get_test_int());
-    }
-}
diff --git a/src/test/ui/abi/invoke-external-foreign.rs b/src/test/ui/abi/foreign/invoke-external-foreign.rs
similarity index 100%
rename from src/test/ui/abi/invoke-external-foreign.rs
rename to src/test/ui/abi/foreign/invoke-external-foreign.rs