also reset anon-param-mode for fn() types

src/librustc/hir/lowering.rs

@@ -1033,17 +1033,22 @@ impl<'a> LoweringContext<'a> {
                     _ => None,
                 }),
                 |this| {
-                    hir::TyBareFn(P(hir::BareFnTy {
-                        generic_params: this.lower_generic_params(
-                            &f.generic_params,
-                            &NodeMap(),
-                            ImplTraitContext::Disallowed,
-                        ),
-                        unsafety: this.lower_unsafety(f.unsafety),
-                        abi: f.abi,
-                        decl: this.lower_fn_decl(&f.decl, None, false),
-                        arg_names: this.lower_fn_args_to_names(&f.decl),
-                    }))
+                    this.with_anonymous_lifetime_mode(
+                        AnonymousLifetimeMode::PassThrough,
+                        |this| {
+                            hir::TyBareFn(P(hir::BareFnTy {
+                                generic_params: this.lower_generic_params(
+                                    &f.generic_params,
+                                    &NodeMap(),
+                                    ImplTraitContext::Disallowed,
+                                ),
+                                unsafety: this.lower_unsafety(f.unsafety),
+                                abi: f.abi,
+                                decl: this.lower_fn_decl(&f.decl, None, false),
+                                arg_names: this.lower_fn_args_to_names(&f.decl),
+                            }))
+                        },
+                    )
                 },
             ),
             TyKind::Never => hir::TyNever,

src/test/ui/rust-2018/issue-51008-1.rs

@@ -0,0 +1,25 @@
+// Copyright 2018 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.
+
+// Regression test for #51008 -- the anonymous lifetime in `&i32` was
+// being incorrectly considered part of the "elided lifetimes" from
+// the impl.
+//
+// run-pass
+
+#![feature(rust_2018_preview)]
+
+trait A {
+
+}
+
+impl<F> A for F where F: PartialEq<fn(&i32)> { }
+
+fn main() {}