Use Display rather than Debug printing for const mismatch

Author: varkor

src/librustc/ty/error.rs

@@ -159,7 +159,7 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
                                        &format!("trait `{}`", values.found))
             }
             ConstMismatch(ref values) => {
-                write!(f, "expected `{:?}`, found `{:?}`", values.expected, values.found)
+                write!(f, "expected `{}`, found `{}`", values.expected, values.found)
             }
         }
     }

src/test/ui/const-generics/cannot-infer-type-for-const-param.stderr

@@ -14,7 +14,7 @@ error[E0308]: mismatched types
   --> $DIR/cannot-infer-type-for-const-param.rs:10:22
    |
 LL |     let _ = Foo::<3>([1, 2, 3]);
-   |                      ^^^^^^^^^ expected `Const { ty: usize, val: Unevaluated(DefId(0:18 ~ cannot_infer_type_for_const_param[317d]::main[0]::{{constant}}[0]), []) }`, found `Const { ty: usize, val: Scalar(0x0000000000000003) }`
+   |                      ^^^^^^^^^ expected `3`, found `3usize`
    |
    = note: expected type `[u8; _]`
               found type `[u8; 3]`

src/test/ui/consts/const-array-oob-arith.stderr

@@ -2,7 +2,7 @@ error[E0308]: mismatched types
   --> $DIR/const-array-oob-arith.rs:7:45
    |
 LL | const BLUB: [i32; (ARR[0] - 40) as usize] = [5];
-   |                                             ^^^ expected `Const { ty: usize, val: Scalar(0x0000000000000002) }`, found `Const { ty: usize, val: Scalar(0x0000000000000001) }`
+   |                                             ^^^ expected `2usize`, found `1usize`
    |
    = note: expected type `[i32; 2]`
               found type `[i32; 1]`
@@ -11,7 +11,7 @@ error[E0308]: mismatched types
   --> $DIR/const-array-oob-arith.rs:8:44
    |
 LL | const BOO: [i32; (ARR[0] - 41) as usize] = [5, 99];
-   |                                            ^^^^^^^ expected `Const { ty: usize, val: Scalar(0x0000000000000001) }`, found `Const { ty: usize, val: Scalar(0x0000000000000002) }`
+   |                                            ^^^^^^^ expected `1usize`, found `2usize`
    |
    = note: expected type `[i32; 1]`
               found type `[i32; 2]`