Restrict transmute intrinsicck to just rust-intrinsic fn's.

src/librustc/middle/intrinsicck.rs

@@ -73,21 +73,25 @@ struct IntrinsicCheckingVisitor<'a> {
 
 impl<'a> IntrinsicCheckingVisitor<'a> {
     fn def_id_is_transmute(&self, def_id: DefId) -> bool {
+        let intrinsic = match ty::get(ty::lookup_item_type(self.tcx, def_id).ty).sty {
+            ty::ty_bare_fn(ref bfty) => bfty.abi == RustIntrinsic,
+            _ => return false
+        };
         if def_id.krate == ast::LOCAL_CRATE {
             match self.tcx.map.get(def_id.node) {
-                NodeForeignItem(ref item) => {
+                NodeForeignItem(ref item) if intrinsic => {
                     token::get_ident(item.ident) ==
                         token::intern_and_get_ident("transmute")
                 }
                 _ => false,
             }
         } else {
             match csearch::get_item_path(self.tcx, def_id).last() {
-                None => false,
-                Some(ref last) => {
+                Some(ref last) if intrinsic => {
                     token::get_name(last.name()) ==
                         token::intern_and_get_ident("transmute")
                 }
+                _ => false,
             }
         }
     }

src/test/auxiliary/issue-15562.rs

@@ -0,0 +1,15 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![crate_type = "lib"]
+
+extern {
+    pub fn transmute();
+}

src/test/run-pass/issue-15562.rs

@@ -0,0 +1,29 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// aux-build:issue-15562.rs
+
+extern crate i = "issue-15562";
+
+pub fn main() {
+    extern {
+        fn transmute();
+    }
+    unsafe {
+        transmute();
+        i::transmute();
+    }
+}
+
+// We declare this so we don't run into unresolved symbol errors
+// The above extern is NOT `extern "rust-intrinsic"` and thus
+// means it'll try to find a corresponding symbol to link to.
+#[no_mangle]
+pub extern fn transmute() {}