Suggest explicit lifetime parameter on some errors

Some types of error are caused by missing lifetime parameter on function
or method declaration. In such cases, this commit generates some
suggestion about what the function declaration could be. This does not
support method declaration yet.

src/test/compile-fail/lifetime-inference-give-expl-lifetime-param.rs

@@ -0,0 +1,58 @@
+// 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.
+
+// ignore-tidy-linelength
+
+struct Foo<'x> { bar: int }
+fn foo1(x: &Foo) -> &int {
+//~^ NOTE: consider using an explicit lifetime parameter as shown: fn foo1<'a>(x: &'a Foo) -> &'a int
+    &x.bar //~ ERROR: cannot infer
+}
+
+fn foo2<'a, 'b>(x: &'a Foo) -> &'b int {
+//~^ NOTE: consider using an explicit lifetime parameter as shown: fn foo2<'c>(x: &'c Foo) -> &'c int
+    &x.bar //~ ERROR: cannot infer
+}
+
+fn foo3(x: &Foo) -> (&int, &int) {
+//~^ NOTE: consider using an explicit lifetime parameter as shown: fn foo3<'a>(x: &'a Foo) -> (&'a int, &'a int)
+    (&x.bar, &x.bar) //~ ERROR: cannot infer
+    //~^ ERROR: cannot infer
+}
+
+fn foo4<'a, 'b>(x: &'a Foo) -> (&'b int, &'a int, &int) {
+//~^ NOTE: consider using an explicit lifetime parameter as shown: fn foo4<'c>(x: &'c Foo) -> (&'c int, &'c int, &'c int)
+    (&x.bar, &x.bar, &x.bar) //~ ERROR: cannot infer
+    //~^ ERROR: cannot infer
+}
+
+fn foo5(x: &int) -> &int {
+//~^ NOTE: consider using an explicit lifetime parameter as shown: fn foo5<'a>(x: &'a int) -> &'a int
+    x //~ ERROR: mismatched types
+    //~^ ERROR: cannot infer
+}
+
+struct Bar<'x, 'y, 'z> { bar: &'y int, baz: int }
+fn bar1(x: &Bar) -> (&int, &int, &int) {
+//~^ NOTE: consider using an explicit lifetime parameter as shown: fn bar1<'a, 'b, 'c, 'd>(x: &'d Bar<'b, 'a, 'c>) -> (&'a int, &'d int, &'d int)
+    (x.bar, &x.baz, &x.baz) //~ ERROR: mismatched types
+    //~^ ERROR: cannot infer
+    //~^^ ERROR: cannot infer
+}
+
+fn bar2<'a, 'b, 'c>(x: &Bar<'a, 'b, 'c>) -> (&int, &int, &int) {
+//~^ NOTE: consider using an explicit lifetime parameter as shown: fn bar2<'d, 'e, 'a, 'c>(x: &'e Bar<'a, 'd, 'c>) -> (&'d int, &'e int, &'e int)
+    (x.bar, &x.baz, &x.baz) //~ ERROR: mismatched types
+    //~^ ERROR: cannot infer
+    //~^^ ERROR: cannot infer
+}
+
+
+fn main() {}