warn for where/return-types that reference regions

This is a step towards fixing #32330. The full fix would be a breaking
change, so we begin by issuing warnings for scenarios that will break.

src/test/compile-fail/associated-types-eq-hr.rs

@@ -40,6 +40,17 @@ impl<'a> TheTrait<&'a isize> for UintStruct {
     }
 }
 
+struct Tuple {
+}
+
+impl<'a> TheTrait<(&'a isize, &'a isize)> for Tuple {
+    type A = &'a isize;
+
+    fn get(&self, t: (&'a isize, &'a isize)) -> &'a isize {
+        t.0
+    }
+}
+
 fn foo<T>()
     where T : for<'x> TheTrait<&'x isize, A = &'x isize>
 {
@@ -52,10 +63,28 @@ fn bar<T>()
     // ok for UintStruct, but not IntStruct
 }
 
-fn baz<T>()
-    where T : for<'x,'y> TheTrait<&'x isize, A = &'y isize>
+fn tuple_one<T>()
+    where T : for<'x,'y> TheTrait<(&'x isize, &'y isize), A = &'x isize>
 {
-    // not ok for either struct, due to the use of two lifetimes
+    // not ok for tuple, two lifetimes and we pick first
+}
+
+fn tuple_two<T>()
+    where T : for<'x,'y> TheTrait<(&'x isize, &'y isize), A = &'y isize>
+{
+    // not ok for tuple, two lifetimes and we pick second
+}
+
+fn tuple_three<T>()
+    where T : for<'x> TheTrait<(&'x isize, &'x isize), A = &'x isize>
+{
+    // ok for tuple
+}
+
+fn tuple_four<T>()
+    where T : for<'x,'y> TheTrait<(&'x isize, &'y isize)>
+{
+    // not ok for tuple, two lifetimes, and lifetime matching is invariant
 }
 
 pub fn main() {
@@ -65,6 +94,16 @@ pub fn main() {
     bar::<IntStruct>(); //~ ERROR type mismatch
     bar::<UintStruct>();
 
-    baz::<IntStruct>(); //~ ERROR type mismatch
-    baz::<UintStruct>(); //~ ERROR type mismatch
+    tuple_one::<Tuple>();
+    //~^ ERROR E0277
+    //~| ERROR type mismatch
+
+    tuple_two::<Tuple>();
+    //~^ ERROR E0277
+    //~| ERROR type mismatch
+
+    tuple_three::<Tuple>();
+
+    tuple_four::<Tuple>();
+    //~^ ERROR E0277
 }

src/test/compile-fail/associated-types/bound-lifetime-constrained.rs

@@ -0,0 +1,66 @@
+// 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.
+
+// revisions: func object clause
+
+#![allow(dead_code)]
+#![feature(rustc_attrs)]
+#![feature(unboxed_closures)]
+#![deny(hr_lifetime_in_assoc_type)]
+
+trait Foo<'a> {
+    type Item;
+}
+
+impl<'a> Foo<'a> for() {
+    type Item = ();
+}
+
+// Check that appearing in a projection input in the argument is not enough:
+#[cfg(func)]
+fn func1(_: for<'a> fn(<() as Foo<'a>>::Item) -> &'a i32) {
+    //[func]~^ ERROR return type references lifetime `'a`
+    //[func]~| WARNING previously accepted
+}
+
+// Check that appearing in a projection input in the return still
+// causes an error:
+#[cfg(func)]
+fn func2(_: for<'a> fn() -> <() as Foo<'a>>::Item) {
+    //[func]~^ ERROR return type references lifetime `'a`
+    //[func]~| WARNING previously accepted
+}
+
+#[cfg(object)]
+fn object1(_: Box<for<'a> Fn(<() as Foo<'a>>::Item) -> &'a i32>) {
+    //[object]~^ ERROR `Output` references lifetime `'a`
+    //[object]~| WARNING previously accepted
+}
+
+#[cfg(object)]
+fn object2(_: Box<for<'a> Fn() -> <() as Foo<'a>>::Item>) {
+    //[object]~^ ERROR `Output` references lifetime `'a`
+    //[object]~| WARNING previously accepted
+}
+
+#[cfg(clause)]
+fn clause1<T>() where T: for<'a> Fn(<() as Foo<'a>>::Item) -> &'a i32 {
+    //[clause]~^ ERROR `Output` references lifetime `'a`
+    //[clause]~| WARNING previously accepted
+}
+
+#[cfg(clause)]
+fn clause2<T>() where T: for<'a> Fn() -> <() as Foo<'a>>::Item {
+    //[clause]~^ ERROR `Output` references lifetime `'a`
+    //[clause]~| WARNING previously accepted
+}
+
+#[rustc_error]
+fn main() { } //[ok]~ ERROR compilation successful

src/test/compile-fail/associated-types/bound-lifetime-in-binding-only.rs

@@ -0,0 +1,90 @@
+// 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.
+
+// revisions: angle paren ok elision
+
+#![allow(dead_code)]
+#![feature(rustc_attrs)]
+#![feature(unboxed_closures)]
+#![deny(hr_lifetime_in_assoc_type)]
+
+trait Foo {
+    type Item;
+}
+
+#[cfg(angle)]
+fn angle<T: for<'a> Foo<Item=&'a i32>>() {
+    //[angle]~^ ERROR binding for associated type `Item` references lifetime `'a`
+    //[angle]~| WARNING previously accepted
+}
+
+#[cfg(angle)]
+fn angle1<T>() where T: for<'a> Foo<Item=&'a i32> {
+    //[angle]~^ ERROR binding for associated type `Item` references lifetime `'a`
+    //[angle]~| WARNING previously accepted
+}
+
+#[cfg(angle)]
+fn angle2<T>() where for<'a> T: Foo<Item=&'a i32> {
+    //[angle]~^ ERROR binding for associated type `Item` references lifetime `'a`
+    //[angle]~| WARNING previously accepted
+}
+
+#[cfg(angle)]
+fn angle3(_: &for<'a> Foo<Item=&'a i32>) {
+    //[angle]~^ ERROR binding for associated type `Item` references lifetime `'a`
+    //[angle]~| WARNING previously accepted
+}
+
+#[cfg(paren)]
+fn paren<T: for<'a> Fn() -> &'a i32>() {
+    //[paren]~^ ERROR binding for associated type `Output` references lifetime `'a`
+    //[paren]~| WARNING previously accepted
+}
+
+#[cfg(paren)]
+fn paren1<T>() where T: for<'a> Fn() -> &'a i32 {
+    //[paren]~^ ERROR binding for associated type `Output` references lifetime `'a`
+    //[paren]~| WARNING previously accepted
+}
+
+#[cfg(paren)]
+fn paren2<T>() where for<'a> T: Fn() -> &'a i32 {
+    //[paren]~^ ERROR binding for associated type `Output` references lifetime `'a`
+    //[paren]~| WARNING previously accepted
+}
+
+#[cfg(paren)]
+fn paren3(_: &for<'a> Fn() -> &'a i32) {
+    //[paren]~^ ERROR binding for associated type `Output` references lifetime `'a`
+    //[paren]~| WARNING previously accepted
+}
+
+#[cfg(elision)]
+fn elision<T: Fn() -> &i32>() {
+    //[elision]~^ ERROR E0106
+}
+
+struct Parameterized<'a> { x: &'a str }
+
+#[cfg(ok)]
+fn ok1<T: for<'a> Fn(&Parameterized<'a>) -> &'a i32>() {
+}
+
+#[cfg(ok)]
+fn ok2<T: for<'a,'b> Fn<(&'b Parameterized<'a>,), Output=&'a i32>>() {
+}
+
+#[cfg(ok)]
+fn ok3<T>() where for<'a> Parameterized<'a>: Foo<Item=&'a i32> {
+}
+
+#[rustc_error]
+fn main() { } //[ok]~ ERROR compilation successful

src/test/compile-fail/associated-types/bound-lifetime-in-return-only.rs

@@ -0,0 +1,64 @@
+// 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.
+
+// revisions: sig local structure ok elision
+
+#![allow(dead_code)]
+#![feature(rustc_attrs)]
+#![feature(unboxed_closures)]
+#![deny(hr_lifetime_in_assoc_type)]
+
+trait Foo {
+    type Item;
+}
+
+#[cfg(sig)]
+fn sig1(_: for<'a> fn() -> &'a i32) {
+    //[sig]~^ ERROR return type references lifetime `'a`
+    //[sig]~| WARNING previously accepted
+}
+
+#[cfg(sig)]
+fn sig2(_: for<'a, 'b> fn(&'b i32) -> &'a i32) {
+    //[sig]~^ ERROR return type references lifetime `'a`
+    //[sig]~| WARNING previously accepted
+}
+
+#[cfg(local)]
+fn local1() {
+    let _: for<'a> fn() -> &'a i32 = loop { };
+    //[local]~^ ERROR return type references lifetime `'a`
+    //[local]~| WARNING previously accepted
+}
+
+#[cfg(structure)]
+struct Struct1 {
+    x: for<'a> fn() -> &'a i32
+    //[structure]~^ ERROR return type references lifetime `'a`
+    //[structure]~| WARNING previously accepted
+}
+
+#[cfg(elision)]
+fn elision(_: fn() -> &i32) {
+    //[elision]~^ ERROR E0106
+}
+
+struct Parameterized<'a> { x: &'a str }
+
+#[cfg(ok)]
+fn ok1(_: &for<'a> Fn(&Parameterized<'a>) -> &'a i32) {
+}
+
+#[cfg(ok)]
+fn ok2(_: &for<'a,'b> Fn<(&'b Parameterized<'a>,), Output=&'a i32>) {
+}
+
+#[rustc_error]
+fn main() { } //[ok]~ ERROR compilation successful