Rollup merge of #75885 - jumbatm:issue75739-clashing-extern-declarations-transparent-nonzero, r=lcnr

Fix another clashing_extern_declarations false positive.

Fixes #75739.

Fix another clashing_extern_declarations false positive, this time for transparent newtype with a non-zero member.

r? @lcnr

2 files changed, 89 insertions, 14 deletions

diff --git a/src/test/ui/lint/clashing-extern-fn.rs b/src/test/ui/lint/clashing-extern-fn.rs
index 44cef19b0d3..41f0baecf24 100644
--- a/src/test/ui/lint/clashing-extern-fn.rs
+++ b/src/test/ui/lint/clashing-extern-fn.rs
@@ -182,7 +182,9 @@ mod same_sized_members_clash {
             y: f32,
             z: f32,
         }
-        extern "C" { fn origin() -> Point3; }
+        extern "C" {
+            fn origin() -> Point3;
+        }
     }
     mod b {
         #[repr(C)]
@@ -191,8 +193,9 @@ mod same_sized_members_clash {
             y: i32,
             z: i32, // NOTE: Incorrectly redeclared as i32
         }
-        extern "C" { fn origin() -> Point3; }
-        //~^ WARN `origin` redeclared with a different signature
+        extern "C" {
+            fn origin() -> Point3; //~ WARN `origin` redeclared with a different signature
+        }
     }
 }
 
@@ -258,6 +261,78 @@ mod non_zero_and_non_null {
     }
 }
 
+// See #75739
+mod non_zero_transparent {
+    mod a1 {
+        use std::num::NonZeroUsize;
+        extern "C" {
+            fn f1() -> NonZeroUsize;
+        }
+    }
+
+    mod b1 {
+        #[repr(transparent)]
+        struct X(NonZeroUsize);
+        use std::num::NonZeroUsize;
+        extern "C" {
+            fn f1() -> X;
+        }
+    }
+
+    mod a2 {
+        use std::num::NonZeroUsize;
+        extern "C" {
+            fn f2() -> NonZeroUsize;
+        }
+    }
+
+    mod b2 {
+        #[repr(transparent)]
+        struct X1(NonZeroUsize);
+
+        #[repr(transparent)]
+        struct X(X1);
+
+        use std::num::NonZeroUsize;
+        extern "C" {
+            // Same case as above, but with two layers of newtyping.
+            fn f2() -> X;
+        }
+    }
+
+    mod a3 {
+        #[repr(transparent)]
+        struct X(core::ptr::NonNull<i32>);
+
+        use std::num::NonZeroUsize;
+        extern "C" {
+            fn f3() -> X;
+        }
+    }
+
+    mod b3 {
+        extern "C" {
+            fn f3() -> core::ptr::NonNull<i32>;
+        }
+    }
+
+    mod a4 {
+        #[repr(transparent)]
+        enum E {
+            X(std::num::NonZeroUsize),
+        }
+        extern "C" {
+            fn f4() -> E;
+        }
+    }
+
+    mod b4 {
+        extern "C" {
+            fn f4() -> std::num::NonZeroUsize;
+        }
+    }
+}
+
 mod null_optimised_enums {
     mod a {
         extern "C" {
diff --git a/src/test/ui/lint/clashing-extern-fn.stderr b/src/test/ui/lint/clashing-extern-fn.stderr
index cca0c4c59eb..0a18f05ba29 100644
--- a/src/test/ui/lint/clashing-extern-fn.stderr
+++ b/src/test/ui/lint/clashing-extern-fn.stderr
@@ -106,19 +106,19 @@ LL |             fn draw_point(p: Point);
               found `unsafe extern "C" fn(sameish_members::b::Point)`
 
 warning: `origin` redeclared with a different signature
-  --> $DIR/clashing-extern-fn.rs:194:22
+  --> $DIR/clashing-extern-fn.rs:197:13
    |
-LL |         extern "C" { fn origin() -> Point3; }
-   |                      ---------------------- `origin` previously declared here
+LL |             fn origin() -> Point3;
+   |             ---------------------- `origin` previously declared here
 ...
-LL |         extern "C" { fn origin() -> Point3; }
-   |                      ^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
+LL |             fn origin() -> Point3;
+   |             ^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
    |
    = note: expected `unsafe extern "C" fn() -> same_sized_members_clash::a::Point3`
               found `unsafe extern "C" fn() -> same_sized_members_clash::b::Point3`
 
 warning: `transparent_incorrect` redeclared with a different signature
-  --> $DIR/clashing-extern-fn.rs:217:13
+  --> $DIR/clashing-extern-fn.rs:220:13
    |
 LL |             fn transparent_incorrect() -> T;
    |             -------------------------------- `transparent_incorrect` previously declared here
@@ -130,7 +130,7 @@ LL |             fn transparent_incorrect() -> isize;
               found `unsafe extern "C" fn() -> isize`
 
 warning: `missing_return_type` redeclared with a different signature
-  --> $DIR/clashing-extern-fn.rs:235:13
+  --> $DIR/clashing-extern-fn.rs:238:13
    |
 LL |             fn missing_return_type() -> usize;
    |             ---------------------------------- `missing_return_type` previously declared here
@@ -142,7 +142,7 @@ LL |             fn missing_return_type();
               found `unsafe extern "C" fn()`
 
 warning: `non_zero_usize` redeclared with a different signature
-  --> $DIR/clashing-extern-fn.rs:253:13
+  --> $DIR/clashing-extern-fn.rs:256:13
    |
 LL |             fn non_zero_usize() -> core::num::NonZeroUsize;
    |             ----------------------------------------------- `non_zero_usize` previously declared here
@@ -154,7 +154,7 @@ LL |             fn non_zero_usize() -> usize;
               found `unsafe extern "C" fn() -> usize`
 
 warning: `non_null_ptr` redeclared with a different signature
-  --> $DIR/clashing-extern-fn.rs:255:13
+  --> $DIR/clashing-extern-fn.rs:258:13
    |
 LL |             fn non_null_ptr() -> core::ptr::NonNull<usize>;
    |             ----------------------------------------------- `non_null_ptr` previously declared here
@@ -166,7 +166,7 @@ LL |             fn non_null_ptr() -> *const usize;
               found `unsafe extern "C" fn() -> *const usize`
 
 warning: `option_non_zero_usize_incorrect` redeclared with a different signature
-  --> $DIR/clashing-extern-fn.rs:281:13
+  --> $DIR/clashing-extern-fn.rs:356:13
    |
 LL |             fn option_non_zero_usize_incorrect() -> usize;
    |             ---------------------------------------------- `option_non_zero_usize_incorrect` previously declared here
@@ -178,7 +178,7 @@ LL |             fn option_non_zero_usize_incorrect() -> isize;
               found `unsafe extern "C" fn() -> isize`
 
 warning: `option_non_null_ptr_incorrect` redeclared with a different signature
-  --> $DIR/clashing-extern-fn.rs:283:13
+  --> $DIR/clashing-extern-fn.rs:358:13
    |
 LL |             fn option_non_null_ptr_incorrect() -> *const usize;
    |             --------------------------------------------------- `option_non_null_ptr_incorrect` previously declared here