Auto merge of #77015 - davidtwco:check-attr-variant-closure-expr, r=lcnr

passes: `check_attr` on more targets

This PR modifies `check_attr` so that:

- Enum variants are now checked (some attributes would not have been prohibited on variants previously).
- `check_expr_attributes` and `check_stmt_attributes` are removed as `check_attributes` can perform the same checks. This means that codegen attribute errors aren't shown if there are other errors first (e.g. from other attributes, as shown in `src/test/ui/macros/issue-68060.rs` changes below).

src/test/ui/issues/issue-31769.rs

@@ -1,4 +1,4 @@
 fn main() {
     #[inline] struct Foo;  //~ ERROR attribute should be applied to function or closure
-    #[repr(C)] fn foo() {} //~ ERROR attribute should be applied to struct, enum, or union
+    #[repr(C)] fn foo() {} //~ ERROR attribute should be applied to a struct, enum, or union
 }

src/test/ui/issues/issue-31769.stderr

@@ -4,7 +4,7 @@ error[E0518]: attribute should be applied to function or closure
 LL |     #[inline] struct Foo;
    |     ^^^^^^^^^ ----------- not a function or closure
 
-error[E0517]: attribute should be applied to struct, enum, or union
+error[E0517]: attribute should be applied to a struct, enum, or union
   --> $DIR/issue-31769.rs:3:12
    |
 LL |     #[repr(C)] fn foo() {}

src/test/ui/issues/issue-43988.rs

@@ -13,18 +13,17 @@ fn main() {
 
     #[repr(nothing)]
     let _x = 0;
-    //~^^ ERROR attribute should not be applied to a statement
+    //~^^ ERROR attribute should be applied to a struct, enum, or union
 
     #[repr(something_not_real)]
     loop {
         ()
     };
-    //~^^^^ ERROR attribute should not be applied to an expression
+    //~^^^^ ERROR attribute should be applied to a struct, enum, or union
 
     #[repr]
     let _y = "123";
-    //~^^ ERROR attribute should not be applied to a statement
-    //~| ERROR malformed `repr` attribute
+    //~^^ ERROR malformed `repr` attribute
 
     fn foo() {}
 
@@ -33,6 +32,5 @@ fn main() {
     //~^^ ERROR attribute should be applied to function or closure
 
     let _z = #[repr] 1;
-    //~^ ERROR attribute should not be applied to an expression
-    //~| ERROR malformed `repr` attribute
+    //~^ ERROR malformed `repr` attribute
 }

src/test/ui/issues/issue-43988.stderr

@@ -5,7 +5,7 @@ LL |     #[repr]
    |     ^^^^^^^ help: must be of the form: `#[repr(C)]`
 
 error: malformed `repr` attribute input
-  --> $DIR/issue-43988.rs:35:14
+  --> $DIR/issue-43988.rs:34:14
    |
 LL |     let _z = #[repr] 1;
    |              ^^^^^^^ help: must be of the form: `#[repr(C)]`
@@ -26,47 +26,33 @@ LL |     #[inline(XYZ)]
 LL |     let _b = 4;
    |     ----------- not a function or closure
 
-error[E0517]: attribute should not be applied to a statement
-  --> $DIR/issue-43988.rs:14:5
+error[E0517]: attribute should be applied to a struct, enum, or union
+  --> $DIR/issue-43988.rs:14:12
    |
 LL |     #[repr(nothing)]
-   |     ^^^^^^^^^^^^^^^^
+   |            ^^^^^^^
 LL |     let _x = 0;
    |     ----------- not a struct, enum, or union
 
-error[E0517]: attribute should not be applied to an expression
-  --> $DIR/issue-43988.rs:18:5
+error[E0517]: attribute should be applied to a struct, enum, or union
+  --> $DIR/issue-43988.rs:18:12
    |
 LL |       #[repr(something_not_real)]
-   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^
 LL | /     loop {
 LL | |         ()
 LL | |     };
-   | |_____- not defining a struct, enum, or union
-
-error[E0517]: attribute should not be applied to a statement
-  --> $DIR/issue-43988.rs:24:5
-   |
-LL |     #[repr]
-   |     ^^^^^^^
-LL |     let _y = "123";
-   |     --------------- not a struct, enum, or union
+   | |_____- not a struct, enum, or union
 
 error[E0518]: attribute should be applied to function or closure
-  --> $DIR/issue-43988.rs:31:5
+  --> $DIR/issue-43988.rs:30:5
    |
 LL |     #[inline(ABC)]
    |     ^^^^^^^^^^^^^^
 LL |     foo();
    |     ----- not a function or closure
 
-error[E0517]: attribute should not be applied to an expression
-  --> $DIR/issue-43988.rs:35:14
-   |
-LL |     let _z = #[repr] 1;
-   |              ^^^^^^^ - not defining a struct, enum, or union
-
-error: aborting due to 9 previous errors
+error: aborting due to 7 previous errors
 
 Some errors have detailed explanations: E0517, E0518.
 For more information about an error, try `rustc --explain E0517`.

src/test/ui/issues/issue-74082.rs

@@ -1,9 +1,9 @@
 #![allow(dead_code)]
 
-#[repr(i128)] //~ ERROR: attribute should be applied to enum
+#[repr(i128)] //~ ERROR: attribute should be applied to an enum
 struct Foo;
 
-#[repr(u128)] //~ ERROR: attribute should be applied to enum
+#[repr(u128)] //~ ERROR: attribute should be applied to an enum
 struct Bar;
 
 fn main() {}

src/test/ui/issues/issue-74082.stderr

@@ -1,4 +1,4 @@
-error[E0517]: attribute should be applied to enum
+error[E0517]: attribute should be applied to an enum
   --> $DIR/issue-74082.rs:3:8
    |
 LL | #[repr(i128)]
@@ -6,7 +6,7 @@ LL | #[repr(i128)]
 LL | struct Foo;
    | ----------- not an enum
 
-error[E0517]: attribute should be applied to enum
+error[E0517]: attribute should be applied to an enum
   --> $DIR/issue-74082.rs:6:8
    |
 LL | #[repr(u128)]