Improve suggestions for cfg_attr

Signed-off-by: Jonathan Brouwer <jonathantbrouwer@gmail.com>

compiler/rustc_attr_parsing/src/attributes/cfg.rs

@@ -389,6 +389,7 @@ fn parse_cfg_attr_internal<'a>(
     let cfg_predicate = AttributeParser::parse_single_args(
         sess,
         attribute.span,
+        attribute.get_normal_item().span(),
         attribute.style,
         AttrPath {
             segments: attribute

compiler/rustc_attr_parsing/src/context.rs

@@ -337,8 +337,16 @@ pub struct Early {
 /// Gives [`AttributeParser`]s enough information to create errors, for example.
 pub struct AcceptContext<'f, 'sess, S: Stage> {
     pub(crate) shared: SharedContext<'f, 'sess, S>,
-    /// The span of the attribute currently being parsed
+
+    /// The outer span of the attribute currently being parsed
+    /// #[attribute(...)]
+    /// ^^^^^^^^^^^^^^^^^ outer span
+    /// For attributes in `cfg_attr`, the outer span and inner spans are equal.
     pub(crate) attr_span: Span,
+    /// The inner span of the attribute currently being parsed
+    /// #[attribute(...)]
+    ///   ^^^^^^^^^^^^^^  inner span
+    pub(crate) inner_span: Span,
 
     /// Whether it is an inner or outer attribute
     pub(crate) attr_style: AttrStyle,
@@ -607,7 +615,10 @@ pub(crate) fn warn_empty_attribute(&mut self, span: Span) {
     }
 
     pub(crate) fn suggestions(&self) -> Vec<String> {
-        self.template.suggestions(Some(self.attr_style), &self.attr_path)
+        // If the outer and inner spans are equal, we are parsing an attribute from `cfg_attr`,
+        // So don't display an attribute style in the suggestions
+        let style = (self.attr_span != self.inner_span).then_some(self.attr_style);
+        self.template.suggestions(style, &self.attr_path)
     }
 }
 

compiler/rustc_attr_parsing/src/interface.rs

@@ -142,6 +142,7 @@ pub fn parse_single<T>(
         Self::parse_single_args(
             sess,
             attr.span,
+            normal_attr.item.span(),
             attr.style,
             path.get_attribute_path(),
             target_span,
@@ -159,6 +160,7 @@ pub fn parse_single<T>(
     pub fn parse_single_args<T, I>(
         sess: &'sess Session,
         attr_span: Span,
+        inner_span: Span,
         attr_style: AttrStyle,
         attr_path: AttrPath,
         target_span: Span,
@@ -186,6 +188,7 @@ pub fn parse_single_args<T, I>(
                 },
             },
             attr_span,
+            inner_span,
             attr_style,
             template,
             attr_path,
@@ -305,6 +308,7 @@ pub fn parse_attribute_list(
                                     emit_lint: &mut emit_lint,
                                 },
                                 attr_span: lower_span(attr.span),
+                                inner_span: lower_span(attr.get_normal_item().span()),
                                 attr_style: attr.style,
                                 template: &accept.template,
                                 attr_path: path.get_attribute_path(),

tests/ui/conditional-compilation/cfg_attr-attr-syntax-validation.stderr

@@ -113,7 +113,7 @@ error[E0539]: malformed `link_section` attribute input
   --> $DIR/cfg_attr-attr-syntax-validation.rs:44:18
    |
 LL | #[cfg_attr(true, link_section)]
-   |                  ^^^^^^^^^^^^ help: must be of the form: `#[link_section = "name"]`
+   |                  ^^^^^^^^^^^^ help: must be of the form: `link_section = "name"`
    |
    = note: for more information, visit <https://doc.rust-lang.org/reference/abi.html#the-link_section-attribute>
 
@@ -129,14 +129,12 @@ LL | #[cfg_attr(true, inline())]
 help: try changing it to one of the following valid forms of the attribute
    |
 LL - #[cfg_attr(true, inline())]
-LL + #[cfg_attr(true, #[inline(always)])]
-   |
-LL - #[cfg_attr(true, inline())]
-LL + #[cfg_attr(true, #[inline(never)])]
-   |
-LL - #[cfg_attr(true, inline())]
-LL + #[cfg_attr(true, #[inline])]
+LL + #[cfg_attr(true, inline)]
    |
+LL | #[cfg_attr(true, inline(always))]
+   |                         ++++++
+LL | #[cfg_attr(true, inline(never))]
+   |                         +++++
 
 warning: `#[link_section]` attribute cannot be used on structs
   --> $DIR/cfg_attr-attr-syntax-validation.rs:44:18