Use into for casting when possible

Author: estebank

src/librustc/hir/mod.rs

@@ -1173,37 +1173,6 @@ impl fmt::Debug for Expr {
     }
 }
 
-impl Expr {
-
-    /// If casting this expression to a given numeric type would be appropriate in case of a type
-    /// mismatch.
-    ///
-    /// We want to minimize the amount of casting operations that are suggested, as it can be a
-    /// lossy operation with potentially bad side effects, so we only suggest when encountering an
-    /// expression that indicates that the original type couldn't be directly changed.
-    pub fn could_cast_in_type_mismatch(&self) -> bool {
-        match self.node {
-            ExprCall(..) |
-            ExprMethodCall(..) |
-            ExprBinary(..) |
-            ExprField(..) |
-            ExprTupField(..) |
-            ExprIndex(..) |
-            ExprPath(..) => true,
-            _ => false,
-        }
-    }
-
-    pub fn needs_parens_around_cast(&self) -> bool {
-        match self.node {
-            ExprBinary(..) |
-            ExprCast(..) |
-            ExprType(..) => true,
-            _ => false,
-        }
-    }
-}
-
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum Expr_ {
     /// A `box x` expression.

src/librustc_typeck/check/demand.rs

@@ -8,7 +8,7 @@ error[E0308]: mismatched types
    |     -------------- in this macro invocation
 help: you can cast an `usize` to `u64`, which will truncate or zero-extend depending on the bit width of `usize`
    |
-26 |                   ($arr.len() * size_of($arr[0]) as )u64); //~ ERROR mismatched types
+26 |                   ($arr.len() * size_of($arr[0])) as u64); //~ ERROR mismatched types
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0605]: non-primitive cast: `{integer}` as `()`

src/test/ui/mismatched_types/issue-26480.stderr

@@ -13,5 +13,7 @@ fn foo() -> i32 {
 }
 fn main() {
     let x: u32 = foo();
+    //~^ ERROR mismatched types
     let z: i32 = x + x;
+    //~^ ERROR mismatched types
 }

src/test/ui/suggestions/numeric-cast-2.rs

@@ -9,13 +9,13 @@ help: you can cast an `i32` to `u32`, which will sign-extend the source value
    |                  ^^^^^^^^^^^^
 
 error[E0308]: mismatched types
-  --> $DIR/numeric-cast-2.rs:16:18
+  --> $DIR/numeric-cast-2.rs:17:18
    |
-16 |     let z: i32 = x + x;
+17 |     let z: i32 = x + x;
    |                  ^^^^^ expected i32, found u32
 help: you can cast an `u32` to `i32`, which will truncate the source value
    |
-16 |     let z: i32 = (x + x as )i32;
+17 |     let z: i32 = (x + x) as i32;
    |                  ^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors

src/test/ui/suggestions/numeric-cast-2.stderr

@@ -331,6 +331,6 @@ fn main() {
     //~^ ERROR mismatched types
     foo::<f32>(x_f64);
     //~^ ERROR mismatched types
-    //~| WARN casting here will cause Undefined Behavior
+    //~| WARN casting here will cause undefined behavior
     foo::<f32>(x_f32);
 }