Don't report UB for #[no_mangle] on associated functions

src/shims/foreign_items.rs

@@ -177,7 +177,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                                 second_crate: tcx.crate_name(cnum),
                             });
                         }
-                        if tcx.def_kind(def_id) != DefKind::Fn {
+                        if !matches!(tcx.def_kind(def_id), DefKind::Fn | DefKind::AssocFn) {
                             throw_ub_format!(
                                 "attempt to call an exported symbol that is not defined as a function"
                             );

test-cargo-miri/exported-symbol-dep/src/lib.rs

@@ -2,3 +2,12 @@
 fn exported_symbol() -> i32 {
     123456
 }
+
+pub struct AssocFn;
+
+impl AssocFn {
+    #[no_mangle]
+    pub fn assoc_fn_as_exported_symbol() -> i32 {
+        -123456
+    }
+}

test-cargo-miri/src/main.rs

@@ -62,15 +62,22 @@ mod test {
     fn exported_symbol() {
         extern crate cargo_miri_test;
         extern crate exported_symbol;
+        extern crate issue_rust_86261;
         // Test calling exported symbols in (transitive) dependencies.
         // Repeat calls to make sure the `Instance` cache is not broken.
         for _ in 0..3 {
             extern "Rust" {
                 fn exported_symbol() -> i32;
+                fn assoc_fn_as_exported_symbol() -> i32;
                 fn make_true() -> bool;
+                fn NoMangleStruct();
+                fn no_mangle_generic();
             }
             assert_eq!(unsafe { exported_symbol() }, 123456);
+            assert_eq!(unsafe { assoc_fn_as_exported_symbol() }, -123456);
             assert!(unsafe { make_true() });
+            unsafe { NoMangleStruct() }
+            unsafe { no_mangle_generic() }
         }
     }
 }