Add context span showing item that can't be annotated

compiler/rustc_attr_parsing/src/diagnostics.rs

@@ -1389,6 +1389,8 @@ pub(crate) struct InvalidTarget {
     pub attr_span: Span,
     pub name: AttrPath,
     pub target: &'static str,
+    #[context]
+    pub target_span: Span,
     pub applied: DiagArgValue,
     pub only: &'static str,
     pub attribute_args: String,

compiler/rustc_attr_parsing/src/target_checking.rs

@@ -131,23 +131,31 @@ impl<'sess> AttributeParser<'sess> {
         let (applied, only) = allowed_targets_applied(allowed_targets, cx.target, cx.features);
         let is_diagnostic_attr = cx.attr_path.segments[0] == sym::diagnostic;
 
+        let span = if attribute_args.is_empty() {
+            // Example: for the attribute `#[inline]`, name+attribute_args gives "inline",
+            // and the path span covers `inline` which is just what we want.
+            cx.attr_path.span
+        } else {
+            // Example 1: for the attribute `#[repr(C)]`, name+attribute_args gives
+            // "repr(C)", and the inner span covers `repr(C)` which is just what we want.
+            //
+            // Example 2: for the attribute `#[repr(C, packed)]`, name+attribute_args gives
+            // "repr(C)", and the inner span covers `repr(C, packed)` which doesn't match
+            // exactly but is as close as we can get.
+            cx.inner_span
+        };
+        let target_span = if span.eq_ctxt(cx.target_span) && cx.target != Target::Crate {
+            cx.target_span.shrink_to_lo()
+        } else {
+            span
+        };
+
         let diag = InvalidTarget {
-            span: if attribute_args.is_empty() {
-                // Example: for the attribute `#[inline]`, name+attribute_args gives "inline",
-                // and the path span covers `inline` which is just what we want.
-                cx.attr_path.span
-            } else {
-                // Example 1: for the attribute `#[repr(C)]`, name+attribute_args gives
-                // "repr(C)", and the inner span covers `repr(C)` which is just what we want.
-                //
-                // Example 2: for the attribute `#[repr(C, packed)]`, name+attribute_args gives
-                // "repr(C)", and the inner span covers `repr(C, packed)` which doesn't match
-                // exactly but is as close as we can get.
-                cx.inner_span
-            },
+            span,
             attr_span: cx.attr_span,
             name: cx.attr_path.clone(),
             target: cx.target.plural_name(),
+            target_span,
             only: if only { "only " } else { "" },
             applied: DiagArgValue::StrListSepByAnd(applied.into_iter().map(Cow::Owned).collect()),
             attribute_args: attribute_args.to_string(),

tests/ui/abi/debug.generic.stderr

@@ -3,6 +3,7 @@ error: the `rustc_abi` attribute cannot be used on constants
    |
 LL | #[rustc_abi(debug)]
    |   ^^^^^^^^^
+LL | const C: () = ();
    |
    = help: the `rustc_abi` attribute can be applied to functions and type aliases
 
@@ -11,6 +12,7 @@ error: the `rustc_abi` attribute cannot be used on associated consts
    |
 LL |     #[rustc_abi(debug)]
    |       ^^^^^^^^^
+LL |     const C: () = ();
    |
    = help: the `rustc_abi` attribute can be applied to functions and type aliases
 

tests/ui/abi/debug.loongarch64.stderr

@@ -3,6 +3,7 @@ error: the `rustc_abi` attribute cannot be used on constants
    |
 LL | #[rustc_abi(debug)]
    |   ^^^^^^^^^
+LL | const C: () = ();
    |
    = help: the `rustc_abi` attribute can be applied to functions and type aliases
 
@@ -11,6 +12,7 @@ error: the `rustc_abi` attribute cannot be used on associated consts
    |
 LL |     #[rustc_abi(debug)]
    |       ^^^^^^^^^
+LL |     const C: () = ();
    |
    = help: the `rustc_abi` attribute can be applied to functions and type aliases
 

tests/ui/abi/debug.riscv64.stderr

@@ -3,6 +3,7 @@ error: the `rustc_abi` attribute cannot be used on constants
    |
 LL | #[rustc_abi(debug)]
    |   ^^^^^^^^^
+LL | const C: () = ();
    |
    = help: the `rustc_abi` attribute can be applied to functions and type aliases
 
@@ -11,6 +12,7 @@ error: the `rustc_abi` attribute cannot be used on associated consts
    |
 LL |     #[rustc_abi(debug)]
    |       ^^^^^^^^^
+LL |     const C: () = ();
    |
    = help: the `rustc_abi` attribute can be applied to functions and type aliases
 

tests/ui/asm/invalid-repr-simd-on-enum-148634.stderr

@@ -3,6 +3,8 @@ error: the `repr(simd)` attribute cannot be used on enums
    |
 LL | #[repr(simd)]
    |   ^^^^^^^^^^
+...
+LL | enum Es {}
    |
    = help: the `repr(simd)` attribute can only be applied to structs
 

tests/ui/asm/naked-functions/invalid-attr.stderr

@@ -17,6 +17,7 @@ error: the `naked` attribute cannot be used on foreign functions
    |
 LL |     #[unsafe(naked)]
    |              ^^^^^
+LL |     fn f();
    |
    = help: the `naked` attribute can only be applied to functions with a body
 
@@ -25,6 +26,8 @@ error: the `naked` attribute cannot be used on structs
    |
 LL | #[unsafe(naked)]
    |          ^^^^^
+LL | #[repr(C)]
+LL | struct S {
    |
    = help: the `naked` attribute can only be applied to functions
 
@@ -33,6 +36,7 @@ error: the `naked` attribute cannot be used on struct fields
    |
 LL |     #[unsafe(naked)]
    |              ^^^^^
+LL |     a: u32,
    |
    = help: the `naked` attribute can only be applied to functions
 
@@ -41,6 +45,7 @@ error: the `naked` attribute cannot be used on required trait methods
    |
 LL |     #[unsafe(naked)]
    |              ^^^^^
+LL |     extern "C" fn invoke(&self);
    |
    = help: the `naked` attribute can only be applied to functions with a body
 
@@ -49,6 +54,7 @@ error: the `naked` attribute cannot be used on closures
    |
 LL |     #[unsafe(naked)]
    |              ^^^^^
+LL |     || {};
    |
    = help: the `naked` attribute can be applied to functions and methods
 

tests/ui/asm/naked-functions/invalid-repr-attr.stderr

@@ -3,6 +3,8 @@ error: the `repr(C)` attribute cannot be used on functions
    |
 LL | #[repr(C)]
    |   ^^^^^^^
+...
+LL | extern "C" fn example1() {
    |
    = help: the `repr(C)` attribute can only be applied to data types
 
@@ -11,6 +13,8 @@ error: the `repr(transparent)` attribute cannot be used on functions
    |
 LL | #[repr(transparent)]
    |   ^^^^^^^^^^^^^^^^^
+...
+LL | extern "C" fn example2() {
    |
    = help: the `repr(transparent)` attribute can only be applied to data types
 
@@ -19,6 +23,8 @@ error: the `repr(C)` attribute cannot be used on functions
    |
 LL | #[repr(C)]
    |   ^^^^^^^
+...
+LL | extern "C" fn example3() {
    |
    = help: the `repr(C)` attribute can only be applied to data types
 
@@ -27,6 +33,8 @@ error: the `repr(C)` attribute cannot be used on functions
    |
 LL | #[repr(C, packed)]
    |   ^^^^^^^^^^^^^^^
+...
+LL | extern "C" fn example4() {
    |
    = help: the `repr(C)` attribute can only be applied to data types
 
@@ -35,6 +43,8 @@ error: the `repr(packed)` attribute cannot be used on functions
    |
 LL | #[repr(C, packed)]
    |   ^^^^^^^^^^^^^^^
+...
+LL | extern "C" fn example4() {
    |
    = help: the `repr(packed)` attribute can only be applied to data types
 
@@ -43,6 +53,8 @@ error: the `repr(u8)` attribute cannot be used on functions
    |
 LL | #[repr(u8)]
    |   ^^^^^^^^
+...
+LL | extern "C" fn example5() {
    |
    = help: the `repr(u8)` attribute can only be applied to enums
 

tests/ui/attributes/align-on-fields-143987.stderr

@@ -15,6 +15,7 @@ error: the `rustc_align` attribute cannot be used on struct fields
    |
 LL |     #[rustc_align(8)]
    |       ^^^^^^^^^^^
+LL |     x: usize,
    |
    = help: the `rustc_align` attribute can only be applied to functions
 
@@ -23,6 +24,7 @@ error: the `rustc_align` attribute cannot be used on struct fields
    |
 LL |     #[rustc_align(8)]
    |       ^^^^^^^^^^^
+LL |     x: usize8,
    |
    = help: the `rustc_align` attribute can only be applied to functions
 
@@ -31,6 +33,7 @@ error: the `rustc_align` attribute cannot be used on struct fields
    |
 LL |     #[rustc_align(32)]
    |       ^^^^^^^^^^^
+LL |     u32
    |
    = help: the `rustc_align` attribute can only be applied to functions