cleaned up some tests

cleaned up cast-enum-const.rs

cleaned up ufcs-trait-object-format.rs

add comment to cast-to-box-arr.rs

add comment to shadow-primitives.rs

add comment to associated-type-const-nomalization.rs

add comment to fn-trait-explicit-call.rs

add comment to call-unit-struct-impl-fn-once.rs

add comment to cast-to-char-compare.rs

add comment to self-in-method-body-resolves.rs

add comment to derive-debug-newtype-unsized-slice.rs

add comment to tuple-ref-order-distinct-impls.rs

add comment to derive-debug-generic-with-lifetime.rs

add comment to recursive-trait-bound-on-type-param.rs

cleaned up const-static-ref-to-closure.rs

add comment to const-iter-no-conflict-for-loop.rs

tests/ui/associated-types/associated-type-const-nomalization.rs

@@ -1,3 +1,4 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/26614>
 //@ check-pass
 
 trait Mirror {

tests/ui/cast/cast-enum-const.rs

@@ -1,14 +1,12 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/2428>
 //@ run-pass
-#![allow(non_upper_case_globals)]
 
-
-pub fn main() {
-    let _foo = 100;
-    const quux: isize = 5;
+fn main() {
+    const QUUX: isize = 5;
 
     enum Stuff {
-        Bar = quux
+        Bar = QUUX,
     }
 
-    assert_eq!(Stuff::Bar as isize, quux);
+    assert_eq!(Stuff::Bar as isize, QUUX);
 }

tests/ui/cast/cast-to-box-arr.rs

@@ -1,3 +1,4 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/22403>
 //@ run-pass
 fn main() {
     let x = Box::new([1, 2, 3]);

tests/ui/cast/cast-to-char-compare.rs

@@ -1,6 +1,6 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/41998>
 //@ check-pass
 
-
 fn main() {
     if ('x' as char) < ('y' as char) {
         print!("x");

tests/ui/consts/const-static-ref-to-closure.rs

@@ -1,7 +1,7 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/25180>
 //@ check-pass
 #![allow(dead_code)]
-#![allow(non_upper_case_globals)]
 
-const x: &'static dyn Fn() = &|| println!("ICE here");
+const X: &'static dyn Fn() = &|| println!("ICE here");
 
 fn main() {}

tests/ui/derives/derive-debug-generic-with-lifetime.rs

@@ -1,3 +1,4 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/29030>
 //@ check-pass
 #![allow(dead_code)]
 #[derive(Debug)]

tests/ui/derives/derive-debug-newtype-unsized-slice.rs

@@ -1,3 +1,4 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/25394>
 //@ check-pass
 #![allow(dead_code)]
 #[derive(Debug)]

tests/ui/fn_traits/call-unit-struct-impl-fn-once.rs

@@ -1,3 +1,4 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/33687>
 //@ run-pass
 #![feature(unboxed_closures)]
 #![feature(fn_traits)]

tests/ui/fn_traits/fn-trait-explicit-call.rs

@@ -1,3 +1,4 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/20847>
 //@ run-pass
 #![feature(fn_traits)]
 

tests/ui/resolve/const-iter-no-conflict-for-loop.rs

@@ -1,3 +1,7 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/27639>
+//! Ensure that a constant named `iter` does not
+//! interfere with the name resolution of the `iter` methods used internally
+//! by `for` loops
 //@ run-pass
 #![allow(dead_code)]
 #![allow(non_upper_case_globals)]

tests/ui/resolve/shadow-primitives.rs

@@ -1,3 +1,4 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/20427>
 //@ run-pass
 #![allow(dead_code)]
 #![allow(unused_variables)]
@@ -31,17 +32,10 @@ mod char {
     mod char_ {}
 
     mod str {
-        use super::i8 as i8;
-        use super::i32_ as i32;
-        use super::i64_ as i64;
-        use super::u8_ as u8;
-        use super::f_ as f64;
-        use super::u16_ as u16;
-        use super::u32_ as u32;
-        use super::u64_ as u64;
-        use super::bool_ as bool;
-        use super::{bool_ as str};
-        use super::char_ as char;
+        use super::{
+            bool_ as bool, bool_ as str, char_ as char, f_ as f64, i8, i32_ as i32, i64_ as i64,
+            u8_ as u8, u16_ as u16, u32_ as u32, u64_ as u64,
+        };
     }
 }
 
@@ -49,7 +43,9 @@ trait isize_ {
     type isize;
 }
 
-fn usize<'usize>(usize: &'usize usize) -> &'usize usize { usize }
+fn usize<'usize>(usize: &'usize usize) -> &'usize usize {
+    usize
+}
 
 mod reuse {
     use std::mem::size_of;
@@ -68,9 +64,10 @@ mod reuse {
 mod guard {
     pub fn check() {
         use std::u8; // bring module u8 in scope
-        fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
+        fn f() -> u8 {
+            // OK, resolves to primitive u8, not to std::u8
             u8::max_value() // OK, resolves to associated function <u8>::max_value,
-                            // not to non-existent std::u8::max_value
+            // not to non-existent std::u8::max_value
         }
         assert_eq!(f(), u8::MAX); // OK, resolves to std::u8::MAX
     }
@@ -79,7 +76,13 @@ mod guard {
 fn main() {
     let bool = true;
     let _ = match bool {
-        str @ true => if str { i32 as i64 } else { i64 },
+        str @ true => {
+            if str {
+                i32 as i64
+            } else {
+                i64
+            }
+        }
         false => i64,
     };
 

tests/ui/self/self-in-method-body-resolves.rs

@@ -1,11 +1,16 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/24389>
 //@ check-pass
 #![allow(dead_code)]
 
 struct Foo;
 
 impl Foo {
-    fn new() -> Self { Foo }
-    fn bar() { Self::new(); }
+    fn new() -> Self {
+        Foo
+    }
+    fn bar() {
+        Self::new();
+    }
 }
 
 fn main() {}

tests/ui/traits/bound/recursive-trait-bound-on-type-param.rs

@@ -1,6 +1,12 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/19601>
 //@ check-pass
 
 trait A<T> {}
-struct B<T> where B<T>: A<B<T>> { t: T }
+struct B<T>
+where
+    B<T>: A<B<T>>,
+{
+    t: T,
+}
 
 fn main() {}

tests/ui/typeck/tuple-ref-order-distinct-impls.rs

@@ -1,6 +1,9 @@
+//! regression test for <https://github.com/rust-lang/rust/issues/11384>
 //@ check-pass
 
-trait Common { fn dummy(&self) { } }
+trait Common {
+    fn dummy(&self) {}
+}
 
 impl<'t, T> Common for (T, &'t T) {}
 

tests/ui/ufcs/ufcs-trait-object-format.rs

@@ -1,8 +1,9 @@
 //@ run-pass
-// Regression test for #20676. Error was that we didn't support
-// UFCS-style calls to a method in `Trait` where `Self` was bound to a
-// trait object of type `Trait`. See also `ufcs-trait-object.rs`.
-
+//! Regression test for <https://github.com/rust-lang/rust/issues/20676>.
+//! Error was that we didn't support
+//! UFCS-style calls to a method in `Trait` where `Self` was bound to a
+//! trait object of type `Trait`.
+//! See also <https://github.com/rust-lang/rust/blob/ec2cc76/tests/ui/traits/ufcs-object.rs>.
 
 use std::fmt;