first attempt at implementing RFC 1623. This fixes #35897.

This is a work in progress. In particular, I want to add more tests,
especially the compile-fail test is very bare-bones.

Author: llogiq

src/librustc_typeck/collect.rs

@@ -1554,7 +1554,7 @@ fn type_of_def_id<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
             NodeItem(item) => {
                 match item.node {
                     ItemStatic(ref t, _, _) | ItemConst(ref t, _) => {
-                        ccx.icx(&()).to_ty(&ExplicitRscope, &t)
+                        ccx.icx(&()).to_ty(&ElidableRscope::new(ty::ReStatic), &t)
                     }
                     ItemFn(ref decl, unsafety, _, abi, ref generics, _) => {
                         let tofd = AstConv::ty_of_bare_fn(&ccx.icx(generics), unsafety, abi, &decl,

src/test/compile-fail/rfc1623.rs

@@ -0,0 +1,21 @@
+// Copyright 2012 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.
+
+#![allow(dead_code)]
+
+fn non_elidable<'a, 'b>(a: &'a u8, b: &'b u8) -> &'a u8 { a }
+
+// the boundaries of elision
+static NON_ELIDABLE_FN : &fn(&u8, &u8) -> &u8 = non_elidable;
+//~^ERROR: missing lifetime specifier
+
+fn main() {
+    // nothing to do here
+}

src/test/run-pass/rfc1623.rs

@@ -0,0 +1,52 @@
+// Copyright 2012 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.
+
+#![allow(dead_code)]
+
+// very simple test for a 'static static with default lifetime
+static SOME_STATIC_STR : &str = "&'static str";
+const SOME_CONST_STR : &str = "&'static str";
+
+// this should be the same as without default:
+static SOME_EXPLICIT_STATIC_STR : &'static str = "&'static str";
+const SOME_EXPLICIT_CONST_STR : &'static str = "&'static str";
+
+// a function that elides to an unbound lifetime for both in- and output
+fn id_u8_slice(arg: &[u8]) -> &[u8] { arg }
+
+// one with a function, argument elided
+static SOME_STATIC_SIMPLE_FN : &fn(&[u8]) -> &[u8] = id_u8_slice;
+const SOME_CONST_SIMPLE_FN : &fn(&[u8]) -> &[u8] = id_u8_slice;
+
+// this should be the same as without elision
+static SOME_STATIC_NON_ELIDED_fN : &fn<'a>(&'a [u8]) -> &'a [u8] = id_u8_slice;
+const SOME_CONST_NON_ELIDED_fN : &fn<'a>(&'a [u8]) -> &'a [u8] = id_u8_slice;
+
+// another function that elides, each to a different unbound lifetime
+fn multi_args(a: &u8, b: &u8, c: &u8) { }
+
+static SOME_STATIC_MULTI_FN : &fn(&u8, &u8, &u8) = multi_args;
+const SOME_CONST_MULTI_FN : &fn(&u8, &u8, &u8) = multi_args;
+
+
+fn main() {
+    // make sure that the lifetime is actually elided (and not defaulted)
+    let x = &[1u8, 2, 3];
+    SOME_STATIC_SIMPLE_FN(x);
+    SOME_CONST_SIMPLE_FN(x);
+    
+    // make sure this works with different lifetimes
+    let a = &1;
+    {
+        let b = &2;
+        let c = &3;
+        SOME_CONST_MULTI_FN(a, b, c);
+    }
+}