Improve wording of "cannot multiply" type error

For example, if you had this code:

    fn foo(x: i32, y: f32) -> f32 {
        x * y
    }

You would get this error:

    error[E0277]: cannot multiply `f32` to `i32`
     --> src/lib.rs:2:7
      |
    2 |     x * y
      |       ^ no implementation for `i32 * f32`
      |
      = help: the trait `Mul<f32>` is not implemented for `i32`

However, that's not usually how people describe multiplication. People
usually describe multiplication like how the division error words it:

    error[E0277]: cannot divide `i32` by `f32`
     --> src/lib.rs:2:7
      |
    2 |     x / y
      |       ^ no implementation for `i32 / f32`
      |
      = help: the trait `Div<f32>` is not implemented for `i32`

So that's what this change does. It changes this:

    error[E0277]: cannot multiply `f32` to `i32`
     --> src/lib.rs:2:7
      |
    2 |     x * y
      |       ^ no implementation for `i32 * f32`
      |
      = help: the trait `Mul<f32>` is not implemented for `i32`

To this:

    error[E0277]: cannot multiply `i32` by `f32`
     --> src/lib.rs:2:7
      |
    2 |     x * y
      |       ^ no implementation for `i32 * f32`
      |
      = help: the trait `Mul<f32>` is not implemented for `i32`

2 files changed, 2 insertions, 2 deletions

diff --git a/src/test/ui/pattern/pattern-tyvar-2.rs b/src/test/ui/pattern/pattern-tyvar-2.rs
index 532df4fa0cb..7647c766ef9 100644
--- a/src/test/ui/pattern/pattern-tyvar-2.rs
+++ b/src/test/ui/pattern/pattern-tyvar-2.rs
@@ -1,6 +1,6 @@
 enum Bar { T1((), Option<Vec<isize>>), T2, }
 
 fn foo(t: Bar) -> isize { match t { Bar::T1(_, Some(x)) => { return x * 3; } _ => { panic!(); } } }
-//~^ ERROR cannot multiply `{integer}` to `Vec<isize>`
+//~^ ERROR cannot multiply `Vec<isize>` by `{integer}`
 
 fn main() { }
diff --git a/src/test/ui/pattern/pattern-tyvar-2.stderr b/src/test/ui/pattern/pattern-tyvar-2.stderr
index e205cd9015e..121817e7056 100644
--- a/src/test/ui/pattern/pattern-tyvar-2.stderr
+++ b/src/test/ui/pattern/pattern-tyvar-2.stderr
@@ -1,4 +1,4 @@
-error[E0369]: cannot multiply `{integer}` to `Vec<isize>`
+error[E0369]: cannot multiply `Vec<isize>` by `{integer}`
   --> $DIR/pattern-tyvar-2.rs:3:71
    |
 LL | fn foo(t: Bar) -> isize { match t { Bar::T1(_, Some(x)) => { return x * 3; } _ => { panic!(); } } }