add source type for invalid bool casts

compiler/rustc_hir_typeck/src/cast.rs

@@ -321,8 +321,13 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                 .emit();
             }
             CastError::CastToBool => {
-                let mut err =
-                    struct_span_err!(fcx.tcx.sess, self.span, E0054, "cannot cast as `bool`");
+                let mut err = struct_span_err!(
+                    fcx.tcx.sess,
+                    self.span,
+                    E0054,
+                    "cannot cast `{}` as `bool`",
+                    self.expr_ty
+                );
 
                 if self.expr_ty.is_numeric() {
                     match fcx.tcx.sess.source_map().span_to_snippet(self.expr_span) {

tests/ui/cast/cast-as-bool.rs

@@ -1,12 +1,48 @@
 fn main() {
-    let u = 5 as bool; //~ ERROR cannot cast as `bool`
+    let u = 5 as bool; //~ ERROR cannot cast `i32` as `bool`
                        //~| HELP compare with zero instead
                        //~| SUGGESTION 5 != 0
 
-    let t = (1 + 2) as bool; //~ ERROR cannot cast as `bool`
+    let t = (1 + 2) as bool; //~ ERROR cannot cast `i32` as `bool`
                              //~| HELP compare with zero instead
                              //~| SUGGESTION (1 + 2) != 0
 
+    let _ = 5_u32 as bool; //~ ERROR cannot cast `u32` as `bool`
+                           //~| HELP compare with zero instead
+
+    let _ = 64.0_f64 as bool; //~ ERROR cannot cast `f64` as `bool`
+                              //~| HELP compare with zero instead
+
+    // Enums that can normally be cast to integers can't be cast to `bool`, just like integers.
+    // Note that enums that cannot be cast to integers can't be cast to anything at *all*
+    // so that's not tested here.
+    enum IntEnum {
+        Zero,
+        One,
+        Two
+    }
+    let _ = IntEnum::One as bool; //~ ERROR cannot cast `IntEnum` as `bool`
+
+    fn uwu(_: u8) -> String {
+        todo!()
+    }
+
+    unsafe fn owo() {}
+
+    // fn item to bool
+    let _ = uwu as bool; //~ ERROR cannot cast `fn(u8) -> String {uwu}` as `bool`
+    // unsafe fn item
+    let _ = owo as bool; //~ ERROR cannot cast `unsafe fn() {owo}` as `bool`
+
+    // fn ptr to bool
+    let _ = uwu as fn(u8) -> String as bool; //~ ERROR cannot cast `fn(u8) -> String` as `bool`
+
+    let _ = 'x' as bool; //~ ERROR cannot cast `char` as `bool`
+
+    let ptr = 1 as *const ();
+
+    let _ = ptr as bool; //~ ERROR cannot cast `*const ()` as `bool`
+
     let v = "hello" as bool;
     //~^ ERROR casting `&'static str` as `bool` is invalid
     //~| HELP consider using the `is_empty` method on `&'static str` to determine if it contains anything

tests/ui/cast/cast-as-bool.stderr

@@ -1,18 +1,66 @@
-error[E0054]: cannot cast as `bool`
+error[E0054]: cannot cast `i32` as `bool`
   --> $DIR/cast-as-bool.rs:2:13
    |
 LL |     let u = 5 as bool;
    |             ^^^^^^^^^ help: compare with zero instead: `5 != 0`
 
-error[E0054]: cannot cast as `bool`
+error[E0054]: cannot cast `i32` as `bool`
   --> $DIR/cast-as-bool.rs:6:13
    |
 LL |     let t = (1 + 2) as bool;
    |             ^^^^^^^^^^^^^^^ help: compare with zero instead: `(1 + 2) != 0`
 
-error[E0606]: casting `&'static str` as `bool` is invalid
+error[E0054]: cannot cast `u32` as `bool`
   --> $DIR/cast-as-bool.rs:10:13
    |
+LL |     let _ = 5_u32 as bool;
+   |             ^^^^^^^^^^^^^ help: compare with zero instead: `5_u32 != 0`
+
+error[E0054]: cannot cast `f64` as `bool`
+  --> $DIR/cast-as-bool.rs:13:13
+   |
+LL |     let _ = 64.0_f64 as bool;
+   |             ^^^^^^^^^^^^^^^^ help: compare with zero instead: `64.0_f64 != 0`
+
+error[E0054]: cannot cast `IntEnum` as `bool`
+  --> $DIR/cast-as-bool.rs:24:13
+   |
+LL |     let _ = IntEnum::One as bool;
+   |             ^^^^^^^^^^^^^^^^^^^^ unsupported cast
+
+error[E0054]: cannot cast `fn(u8) -> String {uwu}` as `bool`
+  --> $DIR/cast-as-bool.rs:33:13
+   |
+LL |     let _ = uwu as bool;
+   |             ^^^^^^^^^^^ unsupported cast
+
+error[E0054]: cannot cast `unsafe fn() {owo}` as `bool`
+  --> $DIR/cast-as-bool.rs:35:13
+   |
+LL |     let _ = owo as bool;
+   |             ^^^^^^^^^^^ unsupported cast
+
+error[E0054]: cannot cast `fn(u8) -> String` as `bool`
+  --> $DIR/cast-as-bool.rs:38:13
+   |
+LL |     let _ = uwu as fn(u8) -> String as bool;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unsupported cast
+
+error[E0054]: cannot cast `char` as `bool`
+  --> $DIR/cast-as-bool.rs:40:13
+   |
+LL |     let _ = 'x' as bool;
+   |             ^^^^^^^^^^^ unsupported cast
+
+error[E0054]: cannot cast `*const ()` as `bool`
+  --> $DIR/cast-as-bool.rs:44:13
+   |
+LL |     let _ = ptr as bool;
+   |             ^^^^^^^^^^^ unsupported cast
+
+error[E0606]: casting `&'static str` as `bool` is invalid
+  --> $DIR/cast-as-bool.rs:46:13
+   |
 LL |     let v = "hello" as bool;
    |             ^^^^^^^^^^^^^^^
    |
@@ -21,7 +69,7 @@ help: consider using the `is_empty` method on `&'static str` to determine if it
 LL |     let v = !"hello".is_empty();
    |             +       ~~~~~~~~~~~
 
-error: aborting due to 3 previous errors
+error: aborting due to 11 previous errors
 
 Some errors have detailed explanations: E0054, E0606.
 For more information about an error, try `rustc --explain E0054`.

tests/ui/cast/cast-rfc0401-2.rs

@@ -4,5 +4,5 @@
 
 fn main() {
     let _ = 3 as bool;
-    //~^ ERROR cannot cast as `bool`
+    //~^ ERROR cannot cast `i32` as `bool`
 }

tests/ui/cast/cast-rfc0401-2.stderr

@@ -1,4 +1,4 @@
-error[E0054]: cannot cast as `bool`
+error[E0054]: cannot cast `i32` as `bool`
   --> $DIR/cast-rfc0401-2.rs:6:13
    |
 LL |     let _ = 3 as bool;

tests/ui/error-codes/E0054.stderr

@@ -1,4 +1,4 @@
-error[E0054]: cannot cast as `bool`
+error[E0054]: cannot cast `i32` as `bool`
   --> $DIR/E0054.rs:3:24
    |
 LL |     let x_is_nonzero = x as bool;

tests/ui/error-festival.stderr

@@ -59,7 +59,7 @@ error[E0605]: non-primitive cast: `u8` as `Vec<u8>`
 LL |     x as Vec<u8>;
    |     ^^^^^^^^^^^^ an `as` expression can only be used to convert between primitive types or to coerce to a specific trait object
 
-error[E0054]: cannot cast as `bool`
+error[E0054]: cannot cast `{integer}` as `bool`
   --> $DIR/error-festival.rs:33:24
    |
 LL |     let x_is_nonzero = x as bool;

tests/ui/mismatched_types/cast-rfc0401.stderr

@@ -82,13 +82,13 @@ error[E0606]: casting `f32` as `*const u8` is invalid
 LL |     let _ = f as *const u8;
    |             ^^^^^^^^^^^^^^
 
-error[E0054]: cannot cast as `bool`
+error[E0054]: cannot cast `i32` as `bool`
   --> $DIR/cast-rfc0401.rs:39:13
    |
 LL |     let _ = 3_i32 as bool;
    |             ^^^^^^^^^^^^^ help: compare with zero instead: `3_i32 != 0`
 
-error[E0054]: cannot cast as `bool`
+error[E0054]: cannot cast `E` as `bool`
   --> $DIR/cast-rfc0401.rs:40:13
    |
 LL |     let _ = E::A as bool;