Auto merge of #44516 - gaurikholkar:fns, r=arielb1

Extend E0623 for fn items

This fixes #44516
The below example now gives
```
error[E0623]: lifetime mismatch
 --> gg.rs:3:10
  |
2 | fn foo(x:fn(&u8, &u8), y: Vec<&u8>, z: &u8) {
  |                               ---      --- these two types are declared with different lifetimes...
3 |   y.push(z);
  |          ^ ...but data from `z` flows into `y` here

error: aborting due to previous error
```

r? @nikomatsakis
cc @arielb1

9 files changed, 124 insertions, 0 deletions

diff --git a/src/test/ui/lifetime-errors/ex3-both-anon-regions-4.stderr b/src/test/ui/lifetime-errors/ex3-both-anon-regions-4.stderr
new file mode 100644
index 00000000000..b159e147869
--- /dev/null
+++ b/src/test/ui/lifetime-errors/ex3-both-anon-regions-4.stderr
@@ -0,0 +1,18 @@
+error[E0623]: lifetime mismatch
+  --> $DIR/ex3-both-anon-regions-4.rs:12:13
+   |
+11 | fn foo(z: &mut Vec<(&u8,&u8)>, (x, y): (&u8, &u8)) {
+   |                     ---                 --- these references are declared with different lifetimes...
+12 |     z.push((x,y));
+   |             ^ ...but data flows into `z` here
+
+error[E0623]: lifetime mismatch
+  --> $DIR/ex3-both-anon-regions-4.rs:12:15
+   |
+11 | fn foo(z: &mut Vec<(&u8,&u8)>, (x, y): (&u8, &u8)) {
+   |                         ---                  --- these references are declared with different lifetimes...
+12 |     z.push((x,y));
+   |               ^ ...but data flows into `z` here
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/lifetime-errors/ex3-both-anon-regions-both-are-structs-4.rs b/src/test/ui/lifetime-errors/ex3-both-anon-regions-both-are-structs-4.rs
new file mode 100644
index 00000000000..606e611865f
--- /dev/null
+++ b/src/test/ui/lifetime-errors/ex3-both-anon-regions-both-are-structs-4.rs
@@ -0,0 +1,19 @@
+// Copyright 2017 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.
+struct Ref<'a, 'b> {
+    a: &'a u32,
+    b: &'b u32,
+}
+
+fn foo(mut x: Ref) {
+    x.a = x.b;
+}
+
+fn main() {}
diff --git a/src/test/ui/lifetime-errors/ex3-both-anon-regions-both-are-structs-4.stderr b/src/test/ui/lifetime-errors/ex3-both-anon-regions-both-are-structs-4.stderr
new file mode 100644
index 00000000000..689a1ac292b
--- /dev/null
+++ b/src/test/ui/lifetime-errors/ex3-both-anon-regions-both-are-structs-4.stderr
@@ -0,0 +1,12 @@
+error[E0623]: lifetime mismatch
+  --> $DIR/ex3-both-anon-regions-both-are-structs-4.rs:16:11
+   |
+15 | fn foo(mut x: Ref) {
+   |               ---
+   |               |
+   |               this type was declared with multiple lifetimes...
+16 |     x.a = x.b;
+   |           ^^^ ...but data with one lifetime flows into the other here
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.rs b/src/test/ui/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.rs
new file mode 100644
index 00000000000..4933dbb7e7a
--- /dev/null
+++ b/src/test/ui/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.rs
@@ -0,0 +1,17 @@
+// Copyright 2017 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.
+
+struct Ref<'a, 'b> { a: &'a u32, b: &'b u32 }
+
+fn foo(mut y: Ref, x: &u32) {
+    y.b = x;
+}
+
+fn main() { }
diff --git a/src/test/ui/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.stderr b/src/test/ui/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.stderr
new file mode 100644
index 00000000000..40f026bcb1b
--- /dev/null
+++ b/src/test/ui/lifetime-errors/ex3-both-anon-regions-one-is-struct-4.stderr
@@ -0,0 +1,10 @@
+error[E0623]: lifetime mismatch
+  --> $DIR/ex3-both-anon-regions-one-is-struct-4.rs:14:11
+   |
+13 | fn foo(mut y: Ref, x: &u32) {
+   |               ---     ---- these two types are declared with different lifetimes...
+14 |     y.b = x;
+   |           ^ ...but data from `x` flows into `y` here
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-fn-items.rs b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-fn-items.rs
new file mode 100644
index 00000000000..9220c34489f
--- /dev/null
+++ b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-fn-items.rs
@@ -0,0 +1,14 @@
+// Copyright 2017 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.
+fn foo(x:fn(&u8, &u8), y: Vec<&u8>, z: &u8) {
+  y.push(z);
+}
+
+fn main() { }
diff --git a/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-fn-items.stderr b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-fn-items.stderr
new file mode 100644
index 00000000000..adfc4dc0c27
--- /dev/null
+++ b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-fn-items.stderr
@@ -0,0 +1,10 @@
+error[E0623]: lifetime mismatch
+  --> $DIR/ex3-both-anon-regions-using-fn-items.rs:11:10
+   |
+10 | fn foo(x:fn(&u8, &u8), y: Vec<&u8>, z: &u8) {
+   |                               ---      --- these two types are declared with different lifetimes...
+11 |   y.push(z);
+   |          ^ ...but data from `z` flows into `y` here
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-trait-objects.rs b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-trait-objects.rs
new file mode 100644
index 00000000000..78a6ad54eae
--- /dev/null
+++ b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-trait-objects.rs
@@ -0,0 +1,14 @@
+// Copyright 2017 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.
+fn foo(x:Box<Fn(&u8, &u8)> , y: Vec<&u8>, z: &u8) {
+  y.push(z);
+}
+
+fn main() { }
diff --git a/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-trait-objects.stderr b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-trait-objects.stderr
new file mode 100644
index 00000000000..ce766b2e406
--- /dev/null
+++ b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-trait-objects.stderr
@@ -0,0 +1,10 @@
+error[E0623]: lifetime mismatch
+  --> $DIR/ex3-both-anon-regions-using-trait-objects.rs:11:10
+   |
+10 | fn foo(x:Box<Fn(&u8, &u8)> , y: Vec<&u8>, z: &u8) {
+   |                 ---  --- these two types are declared with different lifetimes...
+11 |   y.push(z);
+   |          ^ ...but data from `z` flows into `y` here
+
+error: aborting due to previous error
+