Add regression test for #18501

src/test/auxiliary/issue-18501.rs

+// 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 = "rlib"]
+struct Foo;
+
+trait Tr {
+    fn tr(&self);
+}
+
+impl Tr for Foo {
+    fn tr(&self) {}
+}
+
+fn take_method<T>(f: fn(&T), t: &T) {}
+
+#[inline]
+pub fn pass_method() {
+    take_method(Tr::tr, &Foo);
+}

src/test/run-pass/issue-18501.rs

+// 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.
+
+// Test that we don't ICE when inlining a function from another
+// crate that uses a trait method as a value due to incorrectly
+// translating the def ID of the trait during AST decoding.
+
+// aux-build:issue-18501.rs
+extern crate "issue-18501" as issue;
+
+fn main() {
+    issue::pass_method();
+}