Improve &-ptr printing

Author: Jonathan Turner

src/librustc/ty/error.rs

@@ -222,7 +222,24 @@ impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
             ty::TyArray(_, n) => format!("array of {} elements", n),
             ty::TySlice(_) => "slice".to_string(),
             ty::TyRawPtr(_) => "*-ptr".to_string(),
-            ty::TyRef(_, _) => "&-ptr".to_string(),
+            ty::TyRef(region, tymut) => {
+                let tymut_string = tymut.to_string();
+                if tymut_string == "_" ||         //unknown type name,
+                   tymut_string.len() > 10 ||     //name longer than saying "reference",
+                   region.to_string() != ""       //... or a complex type
+                {
+                    match tymut {
+                        ty::TypeAndMut{mutbl, ..} => {
+                            format!("{}reference", match mutbl {
+                                hir::Mutability::MutMutable => "mutable ",
+                                _ => ""
+                            })
+                        }
+                    }
+                } else {
+                    format!("&{}", tymut_string)
+                }
+            }
             ty::TyFnDef(..) => format!("fn item"),
             ty::TyFnPtr(_) => "fn pointer".to_string(),
             ty::TyTrait(ref inner) => {

src/test/compile-fail/coercion-slice.rs

@@ -15,5 +15,5 @@ fn main() {
     //~^ ERROR mismatched types
     //~| expected type `&[i32]`
     //~| found type `[{integer}; 1]`
-    //~| expected &-ptr, found array of 1 elements
+    //~| expected &[i32], found array of 1 elements
 }

src/test/compile-fail/cross-borrow-trait.rs

@@ -21,5 +21,5 @@ pub fn main() {
     let _y: &Trait = x; //~  ERROR mismatched types
                         //~| expected type `&Trait`
                         //~| found type `Box<Trait>`
-                        //~| expected &-ptr, found box
+                        //~| expected &Trait, found box
 }

src/test/compile-fail/destructure-trait-ref.rs

@@ -42,12 +42,12 @@ fn main() {
     //~^ ERROR mismatched types
     //~| expected type `T`
     //~| found type `&_`
-    //~| expected trait T, found &-ptr
+    //~| expected trait T, found reference
     let &&&x = &(&1isize as &T);
     //~^ ERROR mismatched types
     //~| expected type `T`
     //~| found type `&_`
-    //~| expected trait T, found &-ptr
+    //~| expected trait T, found reference
     let box box x = box 1isize as Box<T>;
     //~^ ERROR mismatched types
     //~| expected type `T`

src/test/compile-fail/dst-bad-coercions.rs

@@ -19,12 +19,12 @@ struct Foo<T: ?Sized> {
 }
 
 pub fn main() {
-    // Test that we cannot convert from *-ptr to &-ptr
+    // Test that we cannot convert from *-ptr to &S and &T
     let x: *const S = &S;
     let y: &S = x; //~ ERROR mismatched types
     let y: &T = x; //~ ERROR mismatched types
 
-    // Test that we cannot convert from *-ptr to &-ptr (mut version)
+    // Test that we cannot convert from *-ptr to &S and &T (mut version)
     let x: *mut S = &mut S;
     let y: &S = x; //~ ERROR mismatched types
     let y: &T = x; //~ ERROR mismatched types

src/test/compile-fail/issue-12997-2.rs

@@ -17,4 +17,4 @@ fn bar(x: isize) { }
 //~^ ERROR mismatched types
 //~| expected type `fn(&mut __test::test::Bencher)`
 //~| found type `fn(isize) {bar}`
-//~| expected &-ptr, found isize
+//~| expected mutable reference, found isize

src/test/compile-fail/issue-16338.rs

@@ -18,5 +18,5 @@ fn main() {
     //~^ ERROR mismatched types
     //~| expected type `&str`
     //~| found type `Slice<_>`
-    //~| expected &-ptr, found struct `Slice`
+    //~| expected &str, found struct `Slice`
 }

src/test/compile-fail/issue-17033.rs

@@ -12,7 +12,7 @@ fn f<'r>(p: &'r mut fn(p: &mut ())) {
     (*p)(()) //~  ERROR mismatched types
              //~| expected type `&mut ()`
              //~| found type `()`
-             //~| expected &-ptr, found ()
+             //~| expected &mut (), found ()
 }
 
 fn main() {}

src/test/compile-fail/issue-20225.rs

@@ -15,21 +15,21 @@ struct Foo;
 impl<'a, T> Fn<(&'a T,)> for Foo {
   extern "rust-call" fn call(&self, (_,): (T,)) {}
   //~^ ERROR: has an incompatible type for trait
-  //~| expected &-ptr
+  //~| expected reference
 }
 
 impl<'a, T> FnMut<(&'a T,)> for Foo {
   extern "rust-call" fn call_mut(&mut self, (_,): (T,)) {}
   //~^ ERROR: has an incompatible type for trait
-  //~| expected &-ptr
+  //~| expected reference
 }
 
 impl<'a, T> FnOnce<(&'a T,)> for Foo {
   type Output = ();
 
   extern "rust-call" fn call_once(self, (_,): (T,)) {}
   //~^ ERROR: has an incompatible type for trait
-  //~| expected &-ptr
+  //~| expected reference
 }
 
 fn main() {}

src/test/compile-fail/issue-29084.rs

@@ -13,7 +13,7 @@ macro_rules! foo {
         fn bar(d: u8) { }
         bar(&mut $d);
         //~^ ERROR mismatched types
-        //~| expected u8, found &-ptr
+        //~| expected u8, found &mut u8
         //~| expected type `u8`
         //~| found type `&mut u8`
     }}