Fixes for suggestion message, tests and lint explanation.

clippy_lints/src/types.rs

@@ -679,9 +679,9 @@ declare_clippy_lint! {
     "cast to the same type, e.g. `x as i32` where `x: i32`"
 }
 
-/// **What it does:** Checks for casts function pointer to the numeric type.
+/// **What it does:** Checks for casts of a function pointer to a numeric type except `usize`.
 ///
-/// **Why is this bad?** Cast pointer not to usize truncate value.
+/// **Why is this bad?** Casting a function pointer to something other than `usize` could truncate the address value.
 ///
 /// **Known problems:** None.
 ///
@@ -1003,8 +1003,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CastPass {
                             FN_TO_NUMERIC_CAST,
                             expr.span,
                             &format!("casting a `{}` to `{}` may truncate the function address value.", cast_from, cast_to),
-                            //   &format!("if you need address of function, use cast zz `usize`:"),
-                            &format!("if you need the address of the function, z consider:"),
+                            "if you need the address of the function, consider :",
                             format!("{} as usize", &snippet(cx, ex.span, "x"))
                         );
                     }

tests/ui/types_fn_to_int.rs

@@ -12,7 +12,4 @@ fn main() {
     let y = x as i32;
 
     let z = bar as u32;
-
-    //let c = || {0i32};
-    //let ac = c as u32;
 }

tests/ui/types_fn_to_int.stderr

@@ -1,14 +1,24 @@
-error: casting a Fn to i32 may truncate the function address value.
- --> $DIR/types_fn_to_int.rs:8:13
-  |
-8 |     let y = x as i32;
-  |             ^^^^^^^^
-  |
-  = note: #[deny(fn_to_numeric_cast)] on by default
-help: if you need address of function, use cast to `usize` instead:
-  |
-8 |     let y = x as usize;
-  |             ^^^^^^^^^^
+error: casting a `fn(usize) -> Foo {Foo::A}` to `i32` may truncate the function address value.
+  --> $DIR/types_fn_to_int.rs:12:13
+   |
+12 |     let y = x as i32;
+   |             ^^^^^^^^
+   |
+   = note: #[deny(fn_to_numeric_cast)] on by default
+help: if you need the address of the function, consider :
+   |
+12 |     let y = x as usize;
+   |             ^^^^^^^^^^
 
-error: aborting due to previous error
+error: casting a `fn() -> i32 {bar}` to `u32` may truncate the function address value.
+  --> $DIR/types_fn_to_int.rs:14:13
+   |
+14 |     let z = bar as u32;
+   |             ^^^^^^^^^^
+help: if you need the address of the function, consider :
+   |
+14 |     let z = bar as usize;
+   |             ^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors