fn_to_numeric_cast_any: Do not warn cast to raw pointer

Author: taiki-e

Diff for: clippy_lints/src/casts/fn_to_numeric_cast_any.rs

@@ -8,12 +8,6 @@ use rustc_middle::ty::{self, Ty};
 use super::FN_TO_NUMERIC_CAST_ANY;
 
 pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) {
-    // We allow casts from any function type to any function type.
-    match cast_to.kind() {
-        ty::FnDef(..) | ty::FnPtr(..) => return,
-        _ => { /* continue to checks */ },
-    }
-
     if let ty::FnDef(..) | ty::FnPtr(..) = cast_from.kind() {
         let mut applicability = Applicability::MaybeIncorrect;
         let from_snippet = snippet_with_applicability(cx, cast_expr.span, "..", &mut applicability);

Diff for: clippy_lints/src/casts/mod.rs

@@ -815,9 +815,6 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
             cast_slice_from_raw_parts::check(cx, expr, cast_from_expr, cast_to, &self.msrv);
             ptr_cast_constness::check(cx, expr, cast_from_expr, cast_from, cast_to, &self.msrv);
             as_ptr_cast_mut::check(cx, expr, cast_from_expr, cast_to);
-            fn_to_numeric_cast_any::check(cx, expr, cast_from_expr, cast_from, cast_to);
-            fn_to_numeric_cast::check(cx, expr, cast_from_expr, cast_from, cast_to);
-            fn_to_numeric_cast_with_truncation::check(cx, expr, cast_from_expr, cast_from, cast_to);
             zero_ptr::check(cx, expr, cast_from_expr, cast_to_hir);
 
             if cast_to.is_numeric() {
@@ -831,6 +828,9 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
                 }
                 cast_lossless::check(cx, expr, cast_from_expr, cast_from, cast_to, cast_to_hir, &self.msrv);
                 cast_enum_constructor::check(cx, expr, cast_from_expr, cast_from);
+                fn_to_numeric_cast_any::check(cx, expr, cast_from_expr, cast_from, cast_to);
+                fn_to_numeric_cast::check(cx, expr, cast_from_expr, cast_from, cast_to);
+                fn_to_numeric_cast_with_truncation::check(cx, expr, cast_from_expr, cast_from, cast_to);
             }
 
             as_underscore::check(cx, expr, cast_to_hir);

Diff for: tests/ui/fn_to_numeric_cast_any.rs

@@ -72,7 +72,7 @@ fn closure_to_fn_to_integer() {
 
 fn fn_to_raw_ptr() {
     let _ = foo as *const ();
-    //~^ ERROR: casting function pointer `foo` to `*const ()`
+    let _ = foo as *mut ();
 }
 
 fn cast_fn_to_self() {

Diff for: tests/ui/fn_to_numeric_cast_any.stderr

@@ -176,16 +176,5 @@ help: did you mean to invoke the function?
 LL |     let _ = (clos as fn(u32) -> u32)() as usize;
    |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-error: casting function pointer `foo` to `*const ()`
-  --> tests/ui/fn_to_numeric_cast_any.rs:74:13
-   |
-LL |     let _ = foo as *const ();
-   |             ^^^^^^^^^^^^^^^^
-   |
-help: did you mean to invoke the function?
-   |
-LL |     let _ = foo() as *const ();
-   |             ~~~~~~~~~~~~~~~~~~
-
-error: aborting due to 17 previous errors
+error: aborting due to 16 previous errors